diff --git a/documentation/content/en/books/handbook/advanced-networking/_index.adoc b/documentation/content/en/books/handbook/advanced-networking/_index.adoc index 8d30e5e8a0..743e6d03a0 100644 --- a/documentation/content/en/books/handbook/advanced-networking/_index.adoc +++ b/documentation/content/en/books/handbook/advanced-networking/_index.adoc @@ -1,3238 +1,3238 @@ --- title: Chapter 32. Advanced Networking part: IV. Network Communication prev: books/handbook/firewalls next: books/handbook/partv description: "Advanced networking in FreeBSD: basics of gateways and routes, CARP, how to configure multiple VLANs on FreeBSD, etc" tags: ["Advanced Networking", "Handbook", "gateway", "routes", "wireless", "tethering", "bluetooth", "bridging", "ipv6", "CARP", "VLAN"] showBookMenu: true weight: 37 path: "/books/handbook/" --- [[advanced-networking]] = Advanced Networking :doctype: book :toc: macro :toclevels: 1 :icons: font :sectnums: :sectnumlevels: 6 :sectnumoffset: 32 :partnums: :source-highlighter: rouge :experimental: :images-path: books/handbook/advanced-networking/ ifdef::env-beastie[] ifdef::backend-html5[] :imagesdir: ../../../../images/{images-path} endif::[] ifndef::book[] include::shared/authors.adoc[] include::shared/mirrors.adoc[] include::shared/releases.adoc[] include::shared/attributes/attributes-{{% lang %}}.adoc[] include::shared/{{% lang %}}/teams.adoc[] include::shared/{{% lang %}}/mailing-lists.adoc[] include::shared/{{% lang %}}/urls.adoc[] toc::[] endif::[] ifdef::backend-pdf,backend-epub3[] include::../../../../../shared/asciidoctor.adoc[] endif::[] endif::[] ifndef::env-beastie[] toc::[] include::../../../../../shared/asciidoctor.adoc[] endif::[] [[advanced-networking-synopsis]] == Synopsis This chapter covers a number of advanced networking topics. After reading this chapter, you will know: * The basics of gateways and routes. * How to set up USB tethering. * How to set up IEEE(R) 802.11 and Bluetooth(R) devices. * How to make FreeBSD act as a bridge. * How to set up network PXE booting. * How to set up IPv6 on a FreeBSD machine. * How to enable and utilize the features of the Common Address Redundancy Protocol (CARP) in FreeBSD. * How to configure multiple VLANs on FreeBSD. * Configure bluetooth headset. Before reading this chapter, you should: * Understand the basics of the [.filename]#/etc/rc# scripts. * Be familiar with basic network terminology. * Know how to configure and install a new FreeBSD kernel (crossref:kernelconfig[kernelconfig,Configuring the FreeBSD Kernel]). * Know how to install additional third-party software (crossref:ports[ports,Installing Applications: Packages and Ports]). [[network-routing]] == Gateways and Routes _Routing_ is the mechanism that allows a system to find the network path to another system. A _route_ is a defined pair of addresses which represent the "destination" and a "gateway". The route indicates that when trying to get to the specified destination, send the packets through the specified gateway. There are three types of destinations: individual hosts, subnets, and "default". The "default route" is used if no other routes apply. There are also three types of gateways: individual hosts, interfaces, also called links, and Ethernet hardware (MAC) addresses. Known routes are stored in a routing table. This section provides an overview of routing basics. It then demonstrates how to configure a FreeBSD system as a router and offers some troubleshooting tips. [[network-routing-default]] === Routing Basics To view the routing table of a FreeBSD system, use man:netstat[1]: [source,shell] .... % netstat -r Routing tables Internet: Destination Gateway Flags Refs Use Netif Expire default outside-gw UGS 37 418 em0 localhost localhost UH 0 181 lo0 test0 0:e0:b5:36:cf:4f UHLW 5 63288 re0 77 10.20.30.255 link#1 UHLW 1 2421 example.com link#1 UC 0 0 host1 0:e0:a8:37:8:1e UHLW 3 4601 lo0 host2 0:e0:a8:37:8:1e UHLW 0 5 lo0 => host2.example.com link#1 UC 0 0 224 link#1 UC 0 0 .... The entries in this example are as follows: default:: The first route in this table specifies the `default` route. When the local system needs to make a connection to a remote host, it checks the routing table to determine if a known path exists. If the remote host matches an entry in the table, the system checks to see if it can connect using the interface specified in that entry. + If the destination does not match an entry, or if all known paths fail, the system uses the entry for the default route. For hosts on a local area network, the `Gateway` field in the default route is set to the system which has a direct connection to the Internet. When reading this entry, verify that the `Flags` column indicates that the gateway is usable (`UG`). + The default route for a machine which itself is functioning as the gateway to the outside world will be the gateway machine at the Internet Service Provider (ISP). localhost:: The second route is the `localhost` route. The interface specified in the `Netif` column for `localhost` is [.filename]#lo0#, also known as the loopback device. This indicates that all traffic for this destination should be internal, rather than sending it out over the network. MAC address:: The addresses beginning with `0:e0:` are MAC addresses. FreeBSD will automatically identify any hosts, `test0` in the example, on the local Ethernet and add a route for that host over the Ethernet interface, [.filename]#re0#. This type of route has a timeout, seen in the `Expire` column, which is used if the host does not respond in a specific amount of time. When this happens, the route to this host will be automatically deleted. These hosts are identified using the Routing Information Protocol (RIP), which calculates routes to local hosts based upon a shortest path determination. subnet:: FreeBSD will automatically add subnet routes for the local subnet. In this example, `10.20.30.255` is the broadcast address for the subnet `10.20.30` and `example.com` is the domain name associated with that subnet. The designation `link#1` refers to the first Ethernet card in the machine. + Local network hosts and local subnets have their routes automatically configured by a daemon called man:routed[8]. If it is not running, only routes which are statically defined by the administrator will exist. host:: The `host1` line refers to the host by its Ethernet address. Since it is the sending host, FreeBSD knows to use the loopback interface ([.filename]#lo0#) rather than the Ethernet interface. + The two `host2` lines represent aliases which were created using man:ifconfig[8]. The `=>` symbol after the [.filename]#lo0# interface says that an alias has been set in addition to the loopback address. Such routes only show up on the host that supports the alias and all other hosts on the local network will have a `link#1` line for such routes. 224:: The final line (destination subnet `224`) deals with multicasting. Various attributes of each route can be seen in the `Flags` column. <> summarizes some of these flags and their meanings: [[routeflags]] .Commonly Seen Routing Table Flags [cols="1,1", frame="none", options="header"] |=== | Command | Purpose |U |The route is active (up). |H |The route destination is a single host. |G |Send anything for this destination on to this gateway, which will figure out from there where to send it. |S |This route was statically configured. |C |Clones a new route based upon this route for machines to connect to. This type of route is normally used for local networks. |W |The route was auto-configured based upon a local area network (clone) route. |L |Route involves references to Ethernet (link) hardware. |=== On a FreeBSD system, the default route can defined in [.filename]#/etc/rc.conf# by specifying the IP address of the default gateway: [.programlisting] .... defaultrouter="10.20.30.1" .... It is also possible to manually add the route using `route`: [source,shell] .... # route add default 10.20.30.1 .... Note that manually added routes will not survive a reboot. For more information on manual manipulation of network routing tables, refer to man:route[8]. [[network-static-routes]] === Configuring a Router with Static Routes A FreeBSD system can be configured as the default gateway, or router, for a network if it is a dual-homed system. A dual-homed system is a host which resides on at least two different networks. Typically, each network is connected to a separate network interface, though IP aliasing can be used to bind multiple addresses, each on a different subnet, to one physical interface. In order for the system to forward packets between interfaces, FreeBSD must be configured as a router. Internet standards and good engineering practice prevent the FreeBSD Project from enabling this feature by default, but it can be configured to start at boot by adding this line to [.filename]#/etc/rc.conf#: [.programlisting] .... gateway_enable="YES" # Set to YES if this host will be a gateway .... To enable routing now, set the man:sysctl[8] variable `net.inet.ip.forwarding` to `1`. To stop routing, reset this variable to `0`. The routing table of a router needs additional routes so it knows how to reach other networks. Routes can be either added manually using static routes or routes can be automatically learned using a routing protocol. Static routes are appropriate for small networks and this section describes how to add a static routing entry for a small network. [NOTE] ==== For large networks, static routes quickly become unscalable. FreeBSD comes with the standard BSD routing daemon man:routed[8], which provides the routing protocols RIP, versions 1 and 2, and IRDP. Support for the BGP and OSPF routing protocols can be installed using the package:net/zebra[] package or port. ==== Consider the following network: image::static-routes.png[] In this scenario, `RouterA` is a FreeBSD machine that is acting as a router to the rest of the Internet. It has a default route set to `10.0.0.1` which allows it to connect with the outside world. `RouterB` is already configured to use `192.168.1.1` as its default gateway. Before adding any static routes, the routing table on `RouterA` looks like this: [source,shell] .... % netstat -nr Routing tables Internet: Destination Gateway Flags Refs Use Netif Expire default 10.0.0.1 UGS 0 49378 xl0 127.0.0.1 127.0.0.1 UH 0 6 lo0 10.0.0.0/24 link#1 UC 0 0 xl0 192.168.1.0/24 link#2 UC 0 0 xl1 .... With the current routing table, `RouterA` does not have a route to the `192.168.2.0/24` network. The following command adds the `Internal Net 2` network to ``RouterA``'s routing table using `192.168.1.2` as the next hop: [source,shell] .... # route add -net 192.168.2.0/24 192.168.1.2 .... Now, `RouterA` can reach any host on the `192.168.2.0/24` network. However, the routing information will not persist if the FreeBSD system reboots. If a static route needs to be persistent, add it to [.filename]#/etc/rc.conf#: [.programlisting] .... # Add Internal Net 2 as a persistent static route static_routes="internalnet2" route_internalnet2="-net 192.168.2.0/24 192.168.1.2" .... The `static_routes` configuration variable is a list of strings separated by a space, where each string references a route name. The variable `route_internalnet2` contains the static route for that route name. Using more than one string in `static_routes` creates multiple static routes. The following shows an example of adding static routes for the `192.168.0.0/24` and `192.168.1.0/24` networks: [.programlisting] .... static_routes="net1 net2" route_net1="-net 192.168.0.0/24 192.168.0.1" route_net2="-net 192.168.1.0/24 192.168.1.1" .... [[network-routing-troubleshooting]] === Troubleshooting When an address space is assigned to a network, the service provider configures their routing tables so that all traffic for the network will be sent to the link for the site. But how do external sites know to send their packets to the network's ISP? There is a system that keeps track of all assigned address spaces and defines their point of connection to the Internet backbone, or the main trunk lines that carry Internet traffic across the country and around the world. Each backbone machine has a copy of a master set of tables, which direct traffic for a particular network to a specific backbone carrier, and from there down the chain of service providers until it reaches a particular network. It is the task of the service provider to advertise to the backbone sites that they are the point of connection, and thus the path inward, for a site. This is known as route propagation. Sometimes, there is a problem with route propagation and some sites are unable to connect. Perhaps the most useful command for trying to figure out where routing is breaking down is `traceroute`. It is useful when `ping` fails. When using `traceroute`, include the address of the remote host to connect to. The output will show the gateway hosts along the path of the attempt, eventually either reaching the target host, or terminating because of a lack of connection. For more information, refer to man:traceroute[8]. [[network-routing-multicast]] === Multicast Considerations FreeBSD natively supports both multicast applications and multicast routing. Multicast applications do not require any special configuration in order to run on FreeBSD. Support for multicast routing requires that the following option be compiled into a custom kernel: [.programlisting] .... options MROUTING .... The multicast routing daemon, mrouted can be installed using the package:net/mrouted[] package or port. This daemon implements the DVMRP multicast routing protocol and is configured by editing [.filename]#/usr/local/etc/mrouted.conf# in order to set up the tunnels and DVMRP. The installation of mrouted also installs map-mbone and mrinfo, as well as their associated man pages. Refer to these for configuration examples. [NOTE] ==== DVMRP has largely been replaced by the PIM protocol in many multicast installations. Refer to man:pim[4] for more information. ==== [[network-wireless]] == Wireless Networking === Wireless Networking Basics Most wireless networks are based on the IEEE(R) 802.11 standards. A basic wireless network consists of multiple stations communicating with radios that broadcast in either the 2.4GHz or 5GHz band, though this varies according to the locale and is also changing to enable communication in the 2.3GHz and 4.9GHz ranges. 802.11 networks are organized in two ways. In _infrastructure mode_, one station acts as a master with all the other stations associating to it, the network is known as a BSS, and the master station is termed an access point (AP). In a BSS, all communication passes through the AP; even when one station wants to communicate with another wireless station, messages must go through the AP. In the second form of network, there is no master and stations communicate directly. This form of network is termed an IBSS and is commonly known as an _ad-hoc network_. 802.11 networks were first deployed in the 2.4GHz band using protocols defined by the IEEE(R) 802.11 and 802.11b standard. These specifications include the operating frequencies and the MAC layer characteristics, including framing and transmission rates, as communication can occur at various rates. Later, the 802.11a standard defined operation in the 5GHz band, including different signaling mechanisms and higher transmission rates. Still later, the 802.11g standard defined the use of 802.11a signaling and transmission mechanisms in the 2.4GHz band in such a way as to be backwards compatible with 802.11b networks. Separate from the underlying transmission techniques, 802.11 networks have a variety of security mechanisms. The original 802.11 specifications defined a simple security protocol called WEP. This protocol uses a fixed pre-shared key and the RC4 cryptographic cipher to encode data transmitted on a network. Stations must all agree on the fixed key in order to communicate. This scheme was shown to be easily broken and is now rarely used except to discourage transient users from joining networks. Current security practice is given by the IEEE(R) 802.11i specification that defines new cryptographic ciphers and an additional protocol to authenticate stations to an access point and exchange keys for data communication. Cryptographic keys are periodically refreshed and there are mechanisms for detecting and countering intrusion attempts. Another security protocol specification commonly used in wireless networks is termed WPA, which was a precursor to 802.11i. WPA specifies a subset of the requirements found in 802.11i and is designed for implementation on legacy hardware. Specifically, WPA requires only the TKIP cipher that is derived from the original WEP cipher. 802.11i permits use of TKIP but also requires support for a stronger cipher, AES-CCM, for encrypting data. The AES cipher was not required in WPA because it was deemed too computationally costly to be implemented on legacy hardware. The other standard to be aware of is 802.11e. It defines protocols for deploying multimedia applications, such as streaming video and voice over IP (VoIP), in an 802.11 network. Like 802.11i, 802.11e also has a precursor specification termed WME (later renamed WMM) that has been defined by an industry group as a subset of 802.11e that can be deployed now to enable multimedia applications while waiting for the final ratification of 802.11e. The most important thing to know about 802.11e and WME/WMM is that it enables prioritized traffic over a wireless network through Quality of Service (QoS) protocols and enhanced media access protocols. Proper implementation of these protocols enables high speed bursting of data and prioritized traffic flow. FreeBSD supports networks that operate using 802.11a, 802.11b, and 802.11g. The WPA and 802.11i security protocols are likewise supported (in conjunction with any of 11a, 11b, and 11g) and QoS and traffic prioritization required by the WME/WMM protocols are supported for a limited set of wireless devices. [[network-wireless-quick-start]] === Quick Start Connecting a computer to an existing wireless network is a very common situation. This procedure shows the steps required. [.procedure] . Obtain the SSID (Service Set Identifier) and PSK (Pre-Shared Key) for the wireless network from the network administrator. . Identify the wireless adapter. The FreeBSD [.filename]#GENERIC# kernel includes drivers for many common wireless adapters. If the wireless adapter is one of those models, it will be listed in the man:sysctl[8] `net.wlan.devices` variable: + [source,shell] .... % sysctl net.wlan.devices .... + If a wireless adapter is not listed, an additional kernel module might be required, or it might be a model not supported by FreeBSD. + This example shows the Atheros `ath0` wireless adapter. . Add an entry for this network to [.filename]#/etc/wpa_supplicant.conf#. If the file does not exist, create it. Replace _myssid_ and _mypsk_ with the SSID and PSK provided by the network administrator. + [.programlisting] .... network={ ssid="myssid" psk="mypsk" } .... . Add entries to [.filename]#/etc/rc.conf# to configure the network on startup: + [.programlisting] .... wlans_ath0="wlan0" ifconfig_wlan0="WPA SYNCDHCP" .... . Restart the computer, or restart the network service to connect to the network: + [source,shell] .... # service netif restart .... [[network-wireless-basic]] === Basic Setup ==== Kernel Configuration To use wireless networking, a wireless networking card is needed and the kernel needs to be configured with the appropriate wireless networking support. The kernel is separated into multiple modules so that only the required support needs to be configured. The most commonly used wireless devices are those that use parts made by Atheros. These devices are supported by man:ath[4] and require the following line to be added to [.filename]#/boot/loader.conf#: [.programlisting] .... if_ath_load="YES" .... The Atheros driver is split up into three separate pieces: the driver (man:ath[4]), the hardware support layer that handles chip-specific functions (man:ath_hal[4]), and an algorithm for selecting the rate for transmitting frames. When this support is loaded as kernel modules, any dependencies are automatically handled. To load support for a different type of wireless device, specify the module for that device. This example is for devices based on the Intersil Prism parts (man:wi[4]) driver: [.programlisting] .... if_wi_load="YES" .... [NOTE] ==== The examples in this section use an man:ath[4] device and the device name in the examples must be changed according to the configuration. A list of available wireless drivers and supported adapters can be found in the FreeBSD Hardware Notes, available on the https://www.FreeBSD.org/releases/[Release Information] page of the FreeBSD website. If a native FreeBSD driver for the wireless device does not exist, it may be possible to use the Windows(R) driver with the help of the crossref:config[config-network-ndis,NDIS] driver wrapper. ==== In addition, the modules that implement cryptographic support for the security protocols to use must be loaded. These are intended to be dynamically loaded on demand by the man:wlan[4] module, but for now they must be manually configured. The following modules are available: man:wlan_wep[4], man:wlan_ccmp[4], and man:wlan_tkip[4]. The man:wlan_ccmp[4] and man:wlan_tkip[4] drivers are only needed when using the WPA or 802.11i security protocols. If the network does not use encryption, man:wlan_wep[4] support is not needed. To load these modules at boot time, add the following lines to [.filename]#/boot/loader.conf#: [.programlisting] .... wlan_wep_load="YES" wlan_ccmp_load="YES" wlan_tkip_load="YES" .... Once this information has been added to [.filename]#/boot/loader.conf#, reboot the FreeBSD box. Alternately, load the modules by hand using man:kldload[8]. [NOTE] ==== For users who do not want to use modules, it is possible to compile these drivers into the kernel by adding the following lines to a custom kernel configuration file: [.programlisting] .... -device wlan # 802.11 support -device wlan_wep # 802.11 WEP support -device wlan_ccmp # 802.11 CCMP support -device wlan_tkip # 802.11 TKIP support -device wlan_amrr # AMRR transmit rate control algorithm -device ath # Atheros pci/cardbus NIC's -device ath_hal # pci/cardbus chip support -options AH_SUPPORT_AR5416 # enable AR5416 tx/rx descriptors -device ath_rate_sample # SampleRate tx rate control for ath +device wlan # 802.11 support +device wlan_wep # 802.11 WEP support +device wlan_ccmp # 802.11 CCMP support +device wlan_tkip # 802.11 TKIP support +device wlan_amrr # AMRR transmit rate control algorithm +device ath # Atheros pci/cardbus NIC's +device ath_hal # pci/cardbus chip support +options AH_SUPPORT_AR5416 # enable AR5416 tx/rx descriptors +device ath_rate_sample # SampleRate tx rate control for ath .... With this information in the kernel configuration file, recompile the kernel and reboot the FreeBSD machine. ==== Information about the wireless device should appear in the boot messages, like this: [source,shell] .... ath0: mem 0x88000000-0x8800ffff irq 11 at device 0.0 on cardbus1 ath0: [ITHREAD] ath0: AR2413 mac 7.9 RF2413 phy 4.5 .... ==== Setting the Correct Region Since the regulatory situation is different in various parts of the world, it is necessary to correctly set the domains that apply to your location to have the correct information about what channels can be used. The available region definitions can be found in [.filename]#/etc/regdomain.xml#. To set the data at runtime, use `ifconfig`: [source,shell] .... # ifconfig wlan0 regdomain ETSI country AT .... To persist the settings, add it to [.filename]#/etc/rc.conf#: [source,shell] .... # sysrc create_args_wlan0="country AT regdomain ETSI" .... === Infrastructure Mode Infrastructure (BSS) mode is the mode that is typically used. In this mode, a number of wireless access points are connected to a wired network. Each wireless network has its own name, called the SSID. Wireless clients connect to the wireless access points. ==== FreeBSD Clients ===== How to Find Access Points To scan for available networks, use man:ifconfig[8]. This request may take a few moments to complete as it requires the system to switch to each available wireless frequency and probe for available access points. Only the superuser can initiate a scan: [source,shell] .... # ifconfig wlan0 create wlandev ath0 # ifconfig wlan0 up scan SSID/MESH ID BSSID CHAN RATE S:N INT CAPS dlinkap 00:13:46:49:41:76 11 54M -90:96 100 EPS WPA WME freebsdap 00:11:95:c3:0d:ac 1 54M -83:96 100 EPS WPA .... [NOTE] ==== The interface must be `up` before it can scan. Subsequent scan requests do not require the interface to be marked as up again. ==== The output of a scan request lists each BSS/IBSS network found. Besides listing the name of the network, the `SSID`, the output also shows the `BSSID`, which is the MAC address of the access point. The `CAPS` field identifies the type of each network and the capabilities of the stations operating there (see the definition of `list scan` in man:ifconfig[8] for more details). One can also display the current list of known networks with: [source,shell] .... # ifconfig wlan0 list scan .... This information may be updated automatically by the adapter or manually with a `scan` request. Old data is automatically removed from the cache, so over time this list may shrink unless more scans are done. ===== Basic Settings This section provides a simple example of how to make the wireless network adapter work in FreeBSD without encryption. Once familiar with these concepts, it is strongly recommend to use <> to set up the wireless network. There are three basic steps to configure a wireless network: select an access point, authenticate the station, and configure an IP address. The following sections discuss each step. ====== Selecting an Access Point Most of the time, it is sufficient to let the system choose an access point using the builtin heuristics. This is the default behavior when an interface is marked as up or it is listed in [.filename]#/etc/rc.conf#: [.programlisting] .... wlans_ath0="wlan0" ifconfig_wlan0="DHCP" .... If there are multiple access points, a specific one can be selected by its SSID: [.programlisting] .... wlans_ath0="wlan0" ifconfig_wlan0="ssid your_ssid_here DHCP" .... In an environment where there are multiple access points with the same SSID, which is often done to simplify roaming, it may be necessary to associate to one specific device. In this case, the BSSID of the access point can be specified, with or without the SSID: [.programlisting] .... wlans_ath0="wlan0" ifconfig_wlan0="ssid your_ssid_here bssid xx:xx:xx:xx:xx:xx DHCP" .... There are other ways to constrain the choice of an access point, such as limiting the set of frequencies the system will scan on. This may be useful for a multi-band wireless card as scanning all the possible channels can be time-consuming. To limit operation to a specific band, use the `mode` parameter: [.programlisting] .... wlans_ath0="wlan0" ifconfig_wlan0="mode 11g ssid your_ssid_here DHCP" .... This example will force the card to operate in 802.11g, which is defined only for 2.4GHz frequencies so any 5GHz channels will not be considered. This can also be achieved with the `channel` parameter, which locks operation to one specific frequency, and the `chanlist` parameter, to specify a list of channels for scanning. More information about these parameters can be found in man:ifconfig[8]. ====== Authentication Once an access point is selected, the station needs to authenticate before it can pass data. Authentication can happen in several ways. The most common scheme, open authentication, allows any station to join the network and communicate. This is the authentication to use for test purposes the first time a wireless network is setup. Other schemes require cryptographic handshakes to be completed before data traffic can flow, either using pre-shared keys or secrets, or more complex schemes that involve backend services such as RADIUS. Open authentication is the default setting. The next most common setup is WPA-PSK, also known as WPA Personal, which is described in <>. [NOTE] ==== If using an Apple(R) AirPort(R) Extreme base station for an access point, shared-key authentication together with a WEP key needs to be configured. This can be configured in [.filename]#/etc/rc.conf# or by using man:wpa_supplicant[8]. For a single AirPort(R) base station, access can be configured with: [.programlisting] .... wlans_ath0="wlan0" ifconfig_wlan0="authmode shared wepmode on weptxkey 1 wepkey 01234567 DHCP" .... In general, shared key authentication should be avoided because it uses the WEP key material in a highly-constrained manner, making it even easier to crack the key. If WEP must be used for compatibility with legacy devices, it is better to use WEP with `open` authentication. More information regarding WEP can be found in <>. ==== ====== Getting an IP Address with DHCP Once an access point is selected and the authentication parameters are set, an IP address must be obtained in order to communicate. Most of the time, the IP address is obtained via DHCP. To achieve that, edit [.filename]#/etc/rc.conf# and add `DHCP` to the configuration for the device: [.programlisting] .... wlans_ath0="wlan0" ifconfig_wlan0="DHCP" .... The wireless interface is now ready to bring up: [source,shell] .... # service netif start .... Once the interface is running, use man:ifconfig[8] to see the status of the interface [.filename]#ath0#: [source,shell] .... # ifconfig wlan0 wlan0: flags=8843 mtu 1500 ether 00:11:95:d5:43:62 inet 192.168.1.100 netmask 0xffffff00 broadcast 192.168.1.255 media: IEEE 802.11 Wireless Ethernet OFDM/54Mbps mode 11g status: associated ssid dlinkap channel 11 (2462 Mhz 11g) bssid 00:13:46:49:41:76 country US ecm authmode OPEN privacy OFF txpower 21.5 bmiss 7 scanvalid 60 bgscan bgscanintvl 300 bgscanidle 250 roam:rssi 7 roam:rate 5 protmode CTS wme burst .... The `status: associated` line means that it is connected to the wireless network. The `bssid 00:13:46:49:41:76` is the MAC address of the access point and `authmode OPEN` indicates that the communication is not encrypted. ====== Static IP Address If an IP address cannot be obtained from a DHCP server, set a fixed IP address. Replace the `DHCP` keyword shown above with the address information. Be sure to retain any other parameters for selecting the access point: [.programlisting] .... wlans_ath0="wlan0" ifconfig_wlan0="inet 192.168.1.100 netmask 255.255.255.0 ssid your_ssid_here" .... [[network-wireless-wpa]] ===== WPA Wi-Fi Protected Access (WPA) is a security protocol used together with 802.11 networks to address the lack of proper authentication and the weakness of WEP. WPA leverages the 802.1X authentication protocol and uses one of several ciphers instead of WEP for data integrity. The only cipher required by WPA is the Temporary Key Integrity Protocol (TKIP). TKIP is a cipher that extends the basic RC4 cipher used by WEP by adding integrity checking, tamper detection, and measures for responding to detected intrusions. TKIP is designed to work on legacy hardware with only software modification. It represents a compromise that improves security but is still not entirely immune to attack. WPA also specifies the AES-CCMP cipher as an alternative to TKIP, and that is preferred when possible. For this specification, the term WPA2 or RSN is commonly used. WPA defines authentication and encryption protocols. Authentication is most commonly done using one of two techniques: by 802.1X and a backend authentication service such as RADIUS, or by a minimal handshake between the station and the access point using a pre-shared secret. The former is commonly termed WPA Enterprise and the latter is known as WPA Personal. Since most people will not set up a RADIUS backend server for their wireless network, WPA-PSK is by far the most commonly encountered configuration for WPA. The control of the wireless connection and the key negotiation or authentication with a server is done using man:wpa_supplicant[8]. This program requires a configuration file, [.filename]#/etc/wpa_supplicant.conf#, to run. More information regarding this file can be found in man:wpa_supplicant.conf[5]. [[network-wireless-wpa-wpa-psk]] ====== WPA-PSK WPA-PSK, also known as WPA Personal, is based on a pre-shared key (PSK) which is generated from a given password and used as the master key in the wireless network. This means every wireless user will share the same key. WPA-PSK is intended for small networks where the use of an authentication server is not possible or desired. [WARNING] ==== Always use strong passwords that are sufficiently long and made from a rich alphabet so that they will not be easily guessed or attacked. ==== The first step is the configuration of [.filename]#/etc/wpa_supplicant.conf# with the SSID and the pre-shared key of the network: [.programlisting] .... network={ ssid="freebsdap" psk="freebsdmall" } .... Then, in [.filename]#/etc/rc.conf#, indicate that the wireless device configuration will be done with WPA and the IP address will be obtained with DHCP: [.programlisting] .... wlans_ath0="wlan0" ifconfig_wlan0="WPA DHCP" .... Then, bring up the interface: [source,shell] .... # service netif start Starting wpa_supplicant. DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 5 DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 6 DHCPOFFER from 192.168.0.1 DHCPREQUEST on wlan0 to 255.255.255.255 port 67 DHCPACK from 192.168.0.1 bound to 192.168.0.254 -- renewal in 300 seconds. wlan0: flags=8843 mtu 1500 ether 00:11:95:d5:43:62 inet 192.168.0.254 netmask 0xffffff00 broadcast 192.168.0.255 media: IEEE 802.11 Wireless Ethernet OFDM/36Mbps mode 11g status: associated ssid freebsdap channel 1 (2412 Mhz 11g) bssid 00:11:95:c3:0d:ac country US ecm authmode WPA2/802.11i privacy ON deftxkey UNDEF AES-CCM 3:128-bit txpower 21.5 bmiss 7 scanvalid 450 bgscan bgscanintvl 300 bgscanidle 250 roam:rssi 7 roam:rate 5 protmode CTS wme burst roaming MANUAL .... Or, try to configure the interface manually using the information in [.filename]#/etc/wpa_supplicant.conf#: [source,shell] .... # wpa_supplicant -i wlan0 -c /etc/wpa_supplicant.conf Trying to associate with 00:11:95:c3:0d:ac (SSID='freebsdap' freq=2412 MHz) Associated with 00:11:95:c3:0d:ac WPA: Key negotiation completed with 00:11:95:c3:0d:ac [PTK=CCMP GTK=CCMP] CTRL-EVENT-CONNECTED - Connection to 00:11:95:c3:0d:ac completed (auth) [id=0 id_str=] .... The next operation is to launch man:dhclient[8] to get the IP address from the DHCP server: [source,shell] .... # dhclient wlan0 DHCPREQUEST on wlan0 to 255.255.255.255 port 67 DHCPACK from 192.168.0.1 bound to 192.168.0.254 -- renewal in 300 seconds. # ifconfig wlan0 wlan0: flags=8843 mtu 1500 ether 00:11:95:d5:43:62 inet 192.168.0.254 netmask 0xffffff00 broadcast 192.168.0.255 media: IEEE 802.11 Wireless Ethernet OFDM/36Mbps mode 11g status: associated ssid freebsdap channel 1 (2412 Mhz 11g) bssid 00:11:95:c3:0d:ac country US ecm authmode WPA2/802.11i privacy ON deftxkey UNDEF AES-CCM 3:128-bit txpower 21.5 bmiss 7 scanvalid 450 bgscan bgscanintvl 300 bgscanidle 250 roam:rssi 7 roam:rate 5 protmode CTS wme burst roaming MANUAL .... [NOTE] ==== If [.filename]#/etc/rc.conf# has an `ifconfig_wlan0="DHCP"` entry, man:dhclient[8] will be launched automatically after man:wpa_supplicant[8] associates with the access point. ==== If DHCP is not possible or desired, set a static IP address after man:wpa_supplicant[8] has authenticated the station: [source,shell] .... # ifconfig wlan0 inet 192.168.0.100 netmask 255.255.255.0 # ifconfig wlan0 wlan0: flags=8843 mtu 1500 ether 00:11:95:d5:43:62 inet 192.168.0.100 netmask 0xffffff00 broadcast 192.168.0.255 media: IEEE 802.11 Wireless Ethernet OFDM/36Mbps mode 11g status: associated ssid freebsdap channel 1 (2412 Mhz 11g) bssid 00:11:95:c3:0d:ac country US ecm authmode WPA2/802.11i privacy ON deftxkey UNDEF AES-CCM 3:128-bit txpower 21.5 bmiss 7 scanvalid 450 bgscan bgscanintvl 300 bgscanidle 250 roam:rssi 7 roam:rate 5 protmode CTS wme burst roaming MANUAL .... When DHCP is not used, the default gateway and the nameserver also have to be manually set: [source,shell] .... # route add default your_default_router # echo "nameserver your_DNS_server" >> /etc/resolv.conf .... [[network-wireless-wpa-eap-tls]] ====== WPA with EAP-TLS The second way to use WPA is with an 802.1X backend authentication server. In this case, WPA is called WPA Enterprise to differentiate it from the less secure WPA Personal. Authentication in WPA Enterprise is based on the Extensible Authentication Protocol (EAP). EAP does not come with an encryption method. Instead, EAP is embedded inside an encrypted tunnel. There are many EAP authentication methods, but EAP-TLS, EAP-TTLS, and EAP-PEAP are the most common. EAP with Transport Layer Security (EAP-TLS) is a well-supported wireless authentication protocol since it was the first EAP method to be certified by the http://www.wi-fi.org/[Wi-Fi Alliance]. EAP-TLS requires three certificates to run: the certificate of the Certificate Authority (CA) installed on all machines, the server certificate for the authentication server, and one client certificate for each wireless client. In this EAP method, both the authentication server and wireless client authenticate each other by presenting their respective certificates, and then verify that these certificates were signed by the organization's CA. As previously, the configuration is done via [.filename]#/etc/wpa_supplicant.conf#: [.programlisting] .... network={ ssid="freebsdap" <.> proto=RSN <.> key_mgmt=WPA-EAP <.> eap=TLS <.> identity="loader" <.> ca_cert="/etc/certs/cacert.pem" <.> client_cert="/etc/certs/clientcert.pem" <.> private_key="/etc/certs/clientkey.pem" <.> private_key_passwd="freebsdmallclient" <.> } .... <.> This field indicates the network name (SSID). <.> This example uses the RSN IEEE(R) 802.11i protocol, also known as WPA2. <.> The `key_mgmt` line refers to the key management protocol to use. In this example, it is WPA using EAP authentication. <.> This field indicates the EAP method for the connection. <.> The `identity` field contains the identity string for EAP. <.> The `ca_cert` field indicates the pathname of the CA certificate file. This file is needed to verify the server certificate. <.> The `client_cert` line gives the pathname to the client certificate file. This certificate is unique to each wireless client of the network. <.> The `private_key` field is the pathname to the client certificate private key file. <.> The `private_key_passwd` field contains the passphrase for the private key. Then, add the following lines to [.filename]#/etc/rc.conf#: [.programlisting] .... wlans_ath0="wlan0" ifconfig_wlan0="WPA DHCP" .... The next step is to bring up the interface: [source,shell] .... # service netif start Starting wpa_supplicant. DHCPREQUEST on wlan0 to 255.255.255.255 port 67 interval 7 DHCPREQUEST on wlan0 to 255.255.255.255 port 67 interval 15 DHCPACK from 192.168.0.20 bound to 192.168.0.254 -- renewal in 300 seconds. wlan0: flags=8843 mtu 1500 ether 00:11:95:d5:43:62 inet 192.168.0.254 netmask 0xffffff00 broadcast 192.168.0.255 media: IEEE 802.11 Wireless Ethernet DS/11Mbps mode 11g status: associated ssid freebsdap channel 1 (2412 Mhz 11g) bssid 00:11:95:c3:0d:ac country US ecm authmode WPA2/802.11i privacy ON deftxkey UNDEF AES-CCM 3:128-bit txpower 21.5 bmiss 7 scanvalid 450 bgscan bgscanintvl 300 bgscanidle 250 roam:rssi 7 roam:rate 5 protmode CTS wme burst roaming MANUAL .... It is also possible to bring up the interface manually using man:wpa_supplicant[8] and man:ifconfig[8]. [[network-wireless-wpa-eap-ttls]] ====== WPA with EAP-TTLS With EAP-TLS, both the authentication server and the client need a certificate. With EAP-TTLS, a client certificate is optional. This method is similar to a web server which creates a secure SSL tunnel even if visitors do not have client-side certificates. EAP-TTLS uses an encrypted TLS tunnel for safe transport of the authentication data. The required configuration can be added to [.filename]#/etc/wpa_supplicant.conf#: [.programlisting] .... network={ ssid="freebsdap" proto=RSN key_mgmt=WPA-EAP eap=TTLS <.> identity="test" <.> password="test" <.> ca_cert="/etc/certs/cacert.pem" <.> phase2="auth=MD5" <.> } .... <.> This field specifies the EAP method for the connection. <.> The `identity` field contains the identity string for EAP authentication inside the encrypted TLS tunnel. <.> The `password` field contains the passphrase for the EAP authentication. <.> The `ca_cert` field indicates the pathname of the CA certificate file. This file is needed to verify the server certificate. <.> This field specifies the authentication method used in the encrypted TLS tunnel. In this example, EAP with MD5-Challenge is used. The "inner authentication" phase is often called "phase2". Next, add the following lines to [.filename]#/etc/rc.conf#: [.programlisting] .... wlans_ath0="wlan0" ifconfig_wlan0="WPA DHCP" .... The next step is to bring up the interface: [source,shell] .... # service netif start Starting wpa_supplicant. DHCPREQUEST on wlan0 to 255.255.255.255 port 67 interval 7 DHCPREQUEST on wlan0 to 255.255.255.255 port 67 interval 15 DHCPREQUEST on wlan0 to 255.255.255.255 port 67 interval 21 DHCPACK from 192.168.0.20 bound to 192.168.0.254 -- renewal in 300 seconds. wlan0: flags=8843 mtu 1500 ether 00:11:95:d5:43:62 inet 192.168.0.254 netmask 0xffffff00 broadcast 192.168.0.255 media: IEEE 802.11 Wireless Ethernet DS/11Mbps mode 11g status: associated ssid freebsdap channel 1 (2412 Mhz 11g) bssid 00:11:95:c3:0d:ac country US ecm authmode WPA2/802.11i privacy ON deftxkey UNDEF AES-CCM 3:128-bit txpower 21.5 bmiss 7 scanvalid 450 bgscan bgscanintvl 300 bgscanidle 250 roam:rssi 7 roam:rate 5 protmode CTS wme burst roaming MANUAL .... [[network-wireless-wpa-eap-peap]] ====== WPA with EAP-PEAP [NOTE] ==== PEAPv0/EAP-MSCHAPv2 is the most common PEAP method. In this chapter, the term PEAP is used to refer to that method. ==== Protected EAP (PEAP) is designed as an alternative to EAP-TTLS and is the most used EAP standard after EAP-TLS. In a network with mixed operating systems, PEAP should be the most supported standard after EAP-TLS. PEAP is similar to EAP-TTLS as it uses a server-side certificate to authenticate clients by creating an encrypted TLS tunnel between the client and the authentication server, which protects the ensuing exchange of authentication information. PEAP authentication differs from EAP-TTLS as it broadcasts the username in the clear and only the password is sent in the encrypted TLS tunnel. EAP-TTLS will use the TLS tunnel for both the username and password. Add the following lines to [.filename]#/etc/wpa_supplicant.conf# to configure the EAP-PEAP related settings: [.programlisting] .... network={ ssid="freebsdap" proto=RSN key_mgmt=WPA-EAP eap=PEAP <.> identity="test" <.> password="test" <.> ca_cert="/etc/certs/cacert.pem" <.> phase1="peaplabel=0" <.> phase2="auth=MSCHAPV2" <.> } .... <.> This field specifies the EAP method for the connection. <.> The `identity` field contains the identity string for EAP authentication inside the encrypted TLS tunnel. <.> The `password` field contains the passphrase for the EAP authentication. <.> The `ca_cert` field indicates the pathname of the CA certificate file. This file is needed to verify the server certificate. <.> This field contains the parameters for the first phase of authentication, the TLS tunnel. According to the authentication server used, specify a specific label for authentication. Most of the time, the label will be "client EAP encryption" which is set by using `peaplabel=0`. More information can be found in man:wpa_supplicant.conf[5]. <.> This field specifies the authentication protocol used in the encrypted TLS tunnel. In the case of PEAP, it is `auth=MSCHAPV2`. Add the following to [.filename]#/etc/rc.conf#: [.programlisting] .... wlans_ath0="wlan0" ifconfig_wlan0="WPA DHCP" .... Then, bring up the interface: [source,shell] .... # service netif start Starting wpa_supplicant. DHCPREQUEST on wlan0 to 255.255.255.255 port 67 interval 7 DHCPREQUEST on wlan0 to 255.255.255.255 port 67 interval 15 DHCPREQUEST on wlan0 to 255.255.255.255 port 67 interval 21 DHCPACK from 192.168.0.20 bound to 192.168.0.254 -- renewal in 300 seconds. wlan0: flags=8843 mtu 1500 ether 00:11:95:d5:43:62 inet 192.168.0.254 netmask 0xffffff00 broadcast 192.168.0.255 media: IEEE 802.11 Wireless Ethernet DS/11Mbps mode 11g status: associated ssid freebsdap channel 1 (2412 Mhz 11g) bssid 00:11:95:c3:0d:ac country US ecm authmode WPA2/802.11i privacy ON deftxkey UNDEF AES-CCM 3:128-bit txpower 21.5 bmiss 7 scanvalid 450 bgscan bgscanintvl 300 bgscanidle 250 roam:rssi 7 roam:rate 5 protmode CTS wme burst roaming MANUAL .... [[network-wireless-wep]] ===== WEP Wired Equivalent Privacy (WEP) is part of the original 802.11 standard. There is no authentication mechanism, only a weak form of access control which is easily cracked. WEP can be set up using man:ifconfig[8]: [source,shell] .... # ifconfig wlan0 create wlandev ath0 # ifconfig wlan0 inet 192.168.1.100 netmask 255.255.255.0 \ ssid my_net wepmode on weptxkey 3 wepkey 3:0x3456789012 .... * The `weptxkey` specifies which WEP key will be used in the transmission. This example uses the third key. This must match the setting on the access point. When unsure which key is used by the access point, try `1` (the first key) for this value. * The `wepkey` selects one of the WEP keys. It should be in the format _index:key_. Key `1` is used by default; the index only needs to be set when using a key other than the first key. + [NOTE] ==== Replace the `0x3456789012` with the key configured for use on the access point. ==== Refer to man:ifconfig[8] for further information. The man:wpa_supplicant[8] facility can be used to configure a wireless interface with WEP. The example above can be set up by adding the following lines to [.filename]#/etc/wpa_supplicant.conf#: [.programlisting] .... network={ ssid="my_net" key_mgmt=NONE wep_key3=3456789012 wep_tx_keyidx=3 } .... Then: [source,shell] .... # wpa_supplicant -i wlan0 -c /etc/wpa_supplicant.conf Trying to associate with 00:13:46:49:41:76 (SSID='dlinkap' freq=2437 MHz) Associated with 00:13:46:49:41:76 .... === Ad-hoc Mode IBSS mode, also called ad-hoc mode, is designed for point to point connections. For example, to establish an ad-hoc network between the machines `A` and `B`, choose two IP addresses and a SSID. On `A`: [source,shell] .... # ifconfig wlan0 create wlandev ath0 wlanmode adhoc # ifconfig wlan0 inet 192.168.0.1 netmask 255.255.255.0 ssid freebsdap # ifconfig wlan0 wlan0: flags=8843 metric 0 mtu 1500 ether 00:11:95:c3:0d:ac inet 192.168.0.1 netmask 0xffffff00 broadcast 192.168.0.255 media: IEEE 802.11 Wireless Ethernet autoselect mode 11g status: running ssid freebsdap channel 2 (2417 Mhz 11g) bssid 02:11:95:c3:0d:ac country US ecm authmode OPEN privacy OFF txpower 21.5 scanvalid 60 protmode CTS wme burst .... The `adhoc` parameter indicates that the interface is running in IBSS mode. `B` should now be able to detect `A`: [source,shell] .... # ifconfig wlan0 create wlandev ath0 wlanmode adhoc # ifconfig wlan0 up scan SSID/MESH ID BSSID CHAN RATE S:N INT CAPS freebsdap 02:11:95:c3:0d:ac 2 54M -64:-96 100 IS WME .... The `I` in the output confirms that `A` is in ad-hoc mode. Now, configure `B` with a different IP address: [source,shell] .... # ifconfig wlan0 inet 192.168.0.2 netmask 255.255.255.0 ssid freebsdap # ifconfig wlan0 wlan0: flags=8843 metric 0 mtu 1500 ether 00:11:95:d5:43:62 inet 192.168.0.2 netmask 0xffffff00 broadcast 192.168.0.255 media: IEEE 802.11 Wireless Ethernet autoselect mode 11g status: running ssid freebsdap channel 2 (2417 Mhz 11g) bssid 02:11:95:c3:0d:ac country US ecm authmode OPEN privacy OFF txpower 21.5 scanvalid 60 protmode CTS wme burst .... Both `A` and `B` are now ready to exchange information. [[network-wireless-ap]] === FreeBSD Host Access Points FreeBSD can act as an Access Point (AP) which eliminates the need to buy a hardware AP or run an ad-hoc network. This can be particularly useful when a FreeBSD machine is acting as a gateway to another network such as the Internet. [[network-wireless-ap-basic]] ==== Basic Settings Before configuring a FreeBSD machine as an AP, the kernel must be configured with the appropriate networking support for the wireless card as well as the security protocols being used. For more details, see <>. [NOTE] ==== The NDIS driver wrapper for Windows(R) drivers does not currently support AP operation. Only native FreeBSD wireless drivers support AP mode. ==== Once wireless networking support is loaded, check if the wireless device supports the host-based access point mode, also known as hostap mode: [source,shell] .... # ifconfig wlan0 create wlandev ath0 # ifconfig wlan0 list caps drivercaps=6f85edc1 cryptocaps=1f .... This output displays the card's capabilities. The `HOSTAP` word confirms that this wireless card can act as an AP. Various supported ciphers are also listed: WEP, TKIP, and AES. This information indicates which security protocols can be used on the AP. The wireless device can only be put into hostap mode during the creation of the network pseudo-device, so a previously created device must be destroyed first: [source,shell] .... # ifconfig wlan0 destroy .... then regenerated with the correct option before setting the other parameters: [source,shell] .... # ifconfig wlan0 create wlandev ath0 wlanmode hostap # ifconfig wlan0 inet 192.168.0.1 netmask 255.255.255.0 ssid freebsdap mode 11g channel 1 .... Use man:ifconfig[8] again to see the status of the [.filename]#wlan0# interface: [source,shell] .... # ifconfig wlan0 wlan0: flags=8843 metric 0 mtu 1500 ether 00:11:95:c3:0d:ac inet 192.168.0.1 netmask 0xffffff00 broadcast 192.168.0.255 media: IEEE 802.11 Wireless Ethernet autoselect mode 11g status: running ssid freebsdap channel 1 (2412 Mhz 11g) bssid 00:11:95:c3:0d:ac country US ecm authmode OPEN privacy OFF txpower 21.5 scanvalid 60 protmode CTS wme burst dtimperiod 1 -dfs .... The `hostap` parameter indicates the interface is running in the host-based access point mode. The interface configuration can be done automatically at boot time by adding the following lines to [.filename]#/etc/rc.conf#: [.programlisting] .... wlans_ath0="wlan0" create_args_wlan0="wlanmode hostap" ifconfig_wlan0="inet 192.168.0.1 netmask 255.255.255.0 ssid freebsdap mode 11g channel 1" .... ==== Host-based Access Point Without Authentication or Encryption Although it is not recommended to run an AP without any authentication or encryption, this is a simple way to check if the AP is working. This configuration is also important for debugging client issues. Once the AP is configured, initiate a scan from another wireless machine to find the AP: [source,shell] .... # ifconfig wlan0 create wlandev ath0 # ifconfig wlan0 up scan SSID/MESH ID BSSID CHAN RATE S:N INT CAPS freebsdap 00:11:95:c3:0d:ac 1 54M -66:-96 100 ES WME .... The client machine found the AP and can be associated with it: [source,shell] .... # ifconfig wlan0 inet 192.168.0.2 netmask 255.255.255.0 ssid freebsdap # ifconfig wlan0 wlan0: flags=8843 metric 0 mtu 1500 ether 00:11:95:d5:43:62 inet 192.168.0.2 netmask 0xffffff00 broadcast 192.168.0.255 media: IEEE 802.11 Wireless Ethernet OFDM/54Mbps mode 11g status: associated ssid freebsdap channel 1 (2412 Mhz 11g) bssid 00:11:95:c3:0d:ac country US ecm authmode OPEN privacy OFF txpower 21.5 bmiss 7 scanvalid 60 bgscan bgscanintvl 300 bgscanidle 250 roam:rssi 7 roam:rate 5 protmode CTS wme burst .... [[network-wireless-ap-wpa]] ==== WPA2 Host-based Access Point This section focuses on setting up a FreeBSD access point using the WPA2 security protocol. More details regarding WPA and the configuration of WPA-based wireless clients can be found in <>. The man:hostapd[8] daemon is used to deal with client authentication and key management on the WPA2-enabled AP. The following configuration operations are performed on the FreeBSD machine acting as the AP. Once the AP is correctly working, man:hostapd[8] can be automatically started at boot with this line in [.filename]#/etc/rc.conf#: [.programlisting] .... hostapd_enable="YES" .... Before trying to configure man:hostapd[8], first configure the basic settings introduced in <>. ===== WPA2-PSK WPA2-PSK is intended for small networks where the use of a backend authentication server is not possible or desired. The configuration is done in [.filename]#/etc/hostapd.conf#: [.programlisting] .... interface=wlan0 <.> debug=1 <.> ctrl_interface=/var/run/hostapd <.> ctrl_interface_group=wheel <.> ssid=freebsdap <.> wpa=2 <.> wpa_passphrase=freebsdmall <.> wpa_key_mgmt=WPA-PSK <.> wpa_pairwise=CCMP <.> .... <.> Wireless interface used for the access point. <.> Level of verbosity used during the execution of man:hostapd[8]. A value of `1` represents the minimal level. <.> Pathname of the directory used by man:hostapd[8] to store domain socket files for communication with external programs such as man:hostapd_cli[8]. The default value is used in this example. <.> The group allowed to access the control interface files. <.> The wireless network name, or SSID, that will appear in wireless scans. <.> Enable WPA and specify which WPA authentication protocol will be required. A value of `2` configures the AP for WPA2 and is recommended. Set to `1` only if the obsolete WPA is required. <.> ASCII passphrase for WPA authentication. <.> The key management protocol to use. This example sets WPA-PSK. <.> Encryption algorithms accepted by the access point. In this example, only the CCMP (AES) cipher is accepted. CCMP is an alternative to TKIP and is strongly preferred when possible. TKIP should be allowed only when there are stations incapable of using CCMP. The next step is to start man:hostapd[8]: [source,shell] .... # service hostapd forcestart .... [source,shell] .... # ifconfig wlan0 wlan0: flags=8943 metric 0 mtu 1500 ether 04:f0:21:16:8e:10 inet6 fe80::6f0:21ff:fe16:8e10%wlan0 prefixlen 64 scopeid 0x9 nd6 options=21 media: IEEE 802.11 Wireless Ethernet autoselect mode 11na status: running ssid No5ignal channel 36 (5180 MHz 11a ht/40+) bssid 04:f0:21:16:8e:10 country US ecm authmode WPA2/802.11i privacy MIXED deftxkey 2 AES-CCM 2:128-bit AES-CCM 3:128-bit txpower 17 mcastrate 6 mgmtrate 6 scanvalid 60 ampdulimit 64k ampdudensity 8 shortgi wme burst dtimperiod 1 -dfs groups: wlan .... Once the AP is running, the clients can associate with it. See <> for more details. It is possible to see the stations associated with the AP using `ifconfig _wlan0_ list sta`. ==== WEP Host-based Access Point It is not recommended to use WEP for setting up an AP since there is no authentication mechanism and the encryption is easily cracked. Some legacy wireless cards only support WEP and these cards will only support an AP without authentication or encryption. The wireless device can now be put into hostap mode and configured with the correct SSID and IP address: [source,shell] .... # ifconfig wlan0 create wlandev ath0 wlanmode hostap # ifconfig wlan0 inet 192.168.0.1 netmask 255.255.255.0 \ ssid freebsdap wepmode on weptxkey 3 wepkey 3:0x3456789012 mode 11g .... * The `weptxkey` indicates which WEP key will be used in the transmission. This example uses the third key as key numbering starts with `1`. This parameter must be specified in order to encrypt the data. * The `wepkey` sets the selected WEP key. It should be in the format _index:key_. If the index is not given, key `1` is set. The index needs to be set when using keys other than the first key. Use man:ifconfig[8] to see the status of the [.filename]#wlan0# interface: [source,shell] .... # ifconfig wlan0 wlan0: flags=8843 metric 0 mtu 1500 ether 00:11:95:c3:0d:ac inet 192.168.0.1 netmask 0xffffff00 broadcast 192.168.0.255 media: IEEE 802.11 Wireless Ethernet autoselect mode 11g status: running ssid freebsdap channel 4 (2427 Mhz 11g) bssid 00:11:95:c3:0d:ac country US ecm authmode OPEN privacy ON deftxkey 3 wepkey 3:40-bit txpower 21.5 scanvalid 60 protmode CTS wme burst dtimperiod 1 -dfs .... From another wireless machine, it is now possible to initiate a scan to find the AP: [source,shell] .... # ifconfig wlan0 create wlandev ath0 # ifconfig wlan0 up scan SSID BSSID CHAN RATE S:N INT CAPS freebsdap 00:11:95:c3:0d:ac 1 54M 22:1 100 EPS .... In this example, the client machine found the AP and can associate with it using the correct parameters. See <> for more details. === Using Both Wired and Wireless Connections A wired connection provides better performance and reliability, while a wireless connection provides flexibility and mobility. Laptop users typically want to roam seamlessly between the two types of connections. On FreeBSD, it is possible to combine two or even more network interfaces together in a "failover" fashion. This type of configuration uses the most preferred and available connection from a group of network interfaces, and the operating system switches automatically when the link state changes. Link aggregation and failover is covered in <> and an example for using both wired and wireless connections is provided at <>. === Troubleshooting This section describes a number of steps to help troubleshoot common wireless networking problems. * If the access point is not listed when scanning, check that the configuration has not limited the wireless device to a limited set of channels. * If the device cannot associate with an access point, verify that the configuration matches the settings on the access point. This includes the authentication scheme and any security protocols. Simplify the configuration as much as possible. If using a security protocol such as WPA or WEP, configure the access point for open authentication and no security to see if traffic will pass. + Debugging support is provided by man:wpa_supplicant[8]. Try running this utility manually with `-dd` and look at the system logs. * Once the system can associate with the access point, diagnose the network configuration using tools like man:ping[8]. * There are many lower-level debugging tools. Debugging messages can be enabled in the 802.11 protocol support layer using man:wlandebug[8]. For example, to enable console messages related to scanning for access points and the 802.11 protocol handshakes required to arrange communication: + [source,shell] .... # wlandebug -i wlan0 +scan+auth+debug+assoc net.wlan.0.debug: 0 => 0xc80000 .... + -Many useful statistics are maintained by the 802.11 layer and `wlanstats`, found in [.filename]#/usr/src/tools/tools/net80211#, will dump this information. +Many useful statistics are maintained by the 802.11 layer and `wlanstats`, found in [.filename]#/usr/src/tools/tools/net80211#, will dump this information. These statistics should display all errors identified by the 802.11 layer. However, some errors are identified in the device drivers that lie below the 802.11 layer so they may not show up. -To diagnose device-specific problems, refer to the drivers' documentation. +To diagnose device-specific problems, refer to the driver documentation. If the above information does not help to clarify the problem, submit a problem report and include output from the above tools. [[network-usb-tethering]] == USB Tethering Many cellphones provide the option to share their data connection over USB (often called "tethering"). This feature uses one of RNDIS, CDC, or a custom Apple(R) iPhone(R)/iPad(R) protocol. * Android(TM) devices generally use the man:urndis[4] driver. * Apple(R) devices use the man:ipheth[4] driver. * Older devices will often use the man:cdce[4] driver. Before attaching a device, load the appropriate driver into the kernel: [source,shell] .... # kldload if_urndis # kldload if_cdce # kldload if_ipheth .... Once the device is attached ``ue``_0_ will be available for use like a normal network device. Be sure that the "USB tethering" option is enabled on the device. To make this change permanent and load the driver as a module at boot time, place the appropriate line of the following in [.filename]#/boot/loader.conf#: [source,shell] .... if_urndis_load="YES" if_cdce_load="YES" if_ipheth_load="YES" .... [[network-bluetooth]] == Bluetooth Bluetooth is a wireless technology for creating personal networks operating in the 2.4 GHz unlicensed band, with a range of 10 meters. Networks are usually formed ad-hoc from portable devices such as cellular phones, handhelds, and laptops. Unlike Wi-Fi wireless technology, Bluetooth offers higher level service profiles, such as FTP-like file servers, file pushing, voice transport, serial line emulation, and more. This section describes the use of a USB Bluetooth dongle on a FreeBSD system. It then describes the various Bluetooth protocols and utilities. === Loading Bluetooth Support The Bluetooth stack in FreeBSD is implemented using the man:netgraph[4] framework. A broad variety of Bluetooth USB dongles is supported by man:ng_ubt[4]. Broadcom BCM2033 based Bluetooth devices are supported by the man:ubtbcmfw[4] and man:ng_ubt[4] drivers. The 3Com Bluetooth PC Card 3CRWB60-A is supported by the man:ng_bt3c[4] driver. Serial and UART based Bluetooth devices are supported by man:sio[4], man:ng_h4[4], and man:hcseriald[8]. Before attaching a device, determine which of the above drivers it uses, then load the driver. For example, if the device uses the man:ng_ubt[4] driver: [source,shell] .... # kldload ng_ubt .... If the Bluetooth device will be attached to the system during system startup, the system can be configured to load the module at boot time by adding the driver to [.filename]#/boot/loader.conf#: [.programlisting] .... ng_ubt_load="YES" .... Once the driver is loaded, plug in the USB dongle. If the driver load was successful, output similar to the following should appear on the console and in [.filename]#/var/log/messages#: [source,shell] .... ubt0: vendor 0x0a12 product 0x0001, rev 1.10/5.25, addr 2 ubt0: Interface 0 endpoints: interrupt=0x81, bulk-in=0x82, bulk-out=0x2 ubt0: Interface 1 (alt.config 5) endpoints: isoc-in=0x83, isoc-out=0x3, wMaxPacketSize=49, nframes=6, buffer size=294 .... To start and stop the Bluetooth stack, use its startup script. It is a good idea to stop the stack before unplugging the device. Starting the bluetooth stack might require man:hcsecd[8] to be started. When starting the stack, the output should be similar to the following: [source,shell] .... # service bluetooth start ubt0 BD_ADDR: 00:02:72:00:d4:1a Features: 0xff 0xff 0xf 00 00 00 00 00 <3-Slot> <5-Slot> Max. ACL packet size: 192 bytes Number of ACL packets: 8 Max. SCO packet size: 64 bytes Number of SCO packets: 8 .... === Finding Other Bluetooth Devices The Host Controller Interface (HCI) provides a uniform method for accessing Bluetooth baseband capabilities. In FreeBSD, a netgraph HCI node is created for each Bluetooth device. For more details, refer to man:ng_hci[4]. One of the most common tasks is discovery of Bluetooth devices within RF proximity. This operation is called _inquiry_. Inquiry and other HCI related operations are done using man:hccontrol[8]. The example below shows how to find out which Bluetooth devices are in range. The list of devices should be displayed in a few seconds. Note that a remote device will only answer the inquiry if it is set to _discoverable_ mode. [source,shell] .... % hccontrol -n ubt0hci inquiry Inquiry result, num_responses=1 Inquiry result #0 BD_ADDR: 00:80:37:29:19:a4 Page Scan Rep. Mode: 0x1 Page Scan Period Mode: 00 Page Scan Mode: 00 Class: 52:02:04 Clock offset: 0x78ef Inquiry complete. Status: No error [00] .... The `BD_ADDR` is the unique address of a Bluetooth device, similar to the MAC address of a network card. This address is needed for further communication with a device and it is possible to assign a human readable name to a `BD_ADDR`. Information regarding the known Bluetooth hosts is contained in [.filename]#/etc/bluetooth/hosts#. The following example shows how to obtain the human readable name that was assigned to the remote device: [source,shell] .... % hccontrol -n ubt0hci remote_name_request 00:80:37:29:19:a4 BD_ADDR: 00:80:37:29:19:a4 Name: Pav's T39 .... If an inquiry is performed on a remote Bluetooth device, it will find the computer as "your.host.name (ubt0)". The name assigned to the local device can be changed at any time. Remote devices can be assigned aliases in [.filename]#/etc/bluetooth/hosts#. More information about [.filename]#/etc/bluetooth/hosts# file might be found in man:bluetooth.hosts[5]. The Bluetooth system provides a point-to-point connection between two Bluetooth units, or a point-to-multipoint connection which is shared among several Bluetooth devices. The following example shows how to create a connection to a remote device: [source,shell] .... % hccontrol -n ubt0hci create_connection BT_ADDR .... `create_connection` accepts `BT_ADDR` as well as host aliases in [.filename]#/etc/bluetooth/hosts#. The following example shows how to obtain the list of active baseband connections for the local device: [source,shell] .... % hccontrol -n ubt0hci read_connection_list Remote BD_ADDR Handle Type Mode Role Encrypt Pending Queue State 00:80:37:29:19:a4 41 ACL 0 MAST NONE 0 0 OPEN .... A _connection handle_ is useful when termination of the baseband connection is required, though it is normally not required to do this by hand. The stack will automatically terminate inactive baseband connections. [source,shell] .... # hccontrol -n ubt0hci disconnect 41 Connection handle: 41 Reason: Connection terminated by local host [0x16] .... Type `hccontrol help` for a complete listing of available HCI commands. Most of the HCI commands do not require superuser privileges. === Device Pairing By default, Bluetooth communication is not authenticated, and any device can talk to any other device. A Bluetooth device, such as a cellular phone, may choose to require authentication to provide a particular service. Bluetooth authentication is normally done with a _PIN code_, an ASCII string up to 16 characters in length. The user is required to enter the same PIN code on both devices. Once the user has entered the PIN code, both devices will generate a _link key_. After that, the link key can be stored either in the devices or in a persistent storage. Next time, both devices will use the previously generated link key. This procedure is called _pairing_. Note that if the link key is lost by either device, the pairing must be repeated. The man:hcsecd[8] daemon is responsible for handling Bluetooth authentication requests. The default configuration file is [.filename]#/etc/bluetooth/hcsecd.conf#. An example section for a cellular phone with the PIN code set to `1234` is shown below: [.programlisting] .... device { bdaddr 00:80:37:29:19:a4; name "Pav's T39"; key nokey; pin "1234"; } .... The only limitation on PIN codes is length. Some devices, such as Bluetooth headsets, may have a fixed PIN code built in. The `-d` switch forces man:hcsecd[8] to stay in the foreground, so it is easy to see what is happening. Set the remote device to receive pairing and initiate the Bluetooth connection to the remote device. The remote device should indicate that pairing was accepted and request the PIN code. Enter the same PIN code listed in [.filename]#hcsecd.conf#. Now the computer and the remote device are paired. Alternatively, pairing can be initiated on the remote device. The following line can be added to [.filename]#/etc/rc.conf# to configure man:hcsecd[8] to start automatically on system start: [.programlisting] .... hcsecd_enable="YES" .... The following is a sample of the man:hcsecd[8] daemon output: [.programlisting] .... hcsecd[16484]: Got Link_Key_Request event from 'ubt0hci', remote bdaddr 0:80:37:29:19:a4 hcsecd[16484]: Found matching entry, remote bdaddr 0:80:37:29:19:a4, name 'Pav's T39', link key doesn't exist hcsecd[16484]: Sending Link_Key_Negative_Reply to 'ubt0hci' for remote bdaddr 0:80:37:29:19:a4 hcsecd[16484]: Got PIN_Code_Request event from 'ubt0hci', remote bdaddr 0:80:37:29:19:a4 hcsecd[16484]: Found matching entry, remote bdaddr 0:80:37:29:19:a4, name 'Pav's T39', PIN code exists hcsecd[16484]: Sending PIN_Code_Reply to 'ubt0hci' for remote bdaddr 0:80:37:29:19:a4 .... === Network Access with PPP Profiles A Dial-Up Networking (DUN) profile can be used to configure a cellular phone as a wireless modem for connecting to a dial-up Internet access server. It can also be used to configure a computer to receive data calls from a cellular phone. Network access with a PPP profile can be used to provide LAN access for a single Bluetooth device or multiple Bluetooth devices. It can also provide PC to PC connection using PPP networking over serial cable emulation. In FreeBSD, these profiles are implemented with man:ppp[8] and the man:rfcomm_pppd[8] wrapper which converts a Bluetooth connection into something PPP can use. Before a profile can be used, a new PPP label must be created in [.filename]#/etc/ppp/ppp.conf#. Consult man:rfcomm_pppd[8] for examples. In this example, man:rfcomm_pppd[8] is used to open a connection to a remote device with a `BD_ADDR` of `00:80:37:29:19:a4` on a DUNRFCOMM channel: [source,shell] .... # rfcomm_pppd -a 00:80:37:29:19:a4 -c -C dun -l rfcomm-dialup .... The actual channel number will be obtained from the remote device using the SDP protocol. It is possible to specify the RFCOMM channel by hand, and in this case man:rfcomm_pppd[8] will not perform the SDP query. Use man:sdpcontrol[8] to find out the RFCOMM channel on the remote device. In order to provide network access with the PPPLAN service, man:sdpd[8] must be running and a new entry for LAN clients must be created in [.filename]#/etc/ppp/ppp.conf#. Consult man:rfcomm_pppd[8] for examples. Finally, start the RFCOMMPPP server on a valid RFCOMM channel number. The RFCOMMPPP server will automatically register the Bluetooth LAN service with the local SDP daemon. The example below shows how to start the RFCOMMPPP server. [source,shell] .... # rfcomm_pppd -s -C 7 -l rfcomm-server .... === Bluetooth Protocols This section provides an overview of the various Bluetooth protocols, their function, and associated utilities. ==== Logical Link Control and Adaptation Protocol (L2CAP) The Logical Link Control and Adaptation Protocol (L2CAP) provides connection-oriented and connectionless data services to upper layer protocols. L2CAP permits higher level protocols and applications to transmit and receive L2CAP data packets up to 64 kilobytes in length. L2CAP is based around the concept of _channels_. A channel is a logical connection on top of a baseband connection, where each channel is bound to a single protocol in a many-to-one fashion. Multiple channels can be bound to the same protocol, but a channel cannot be bound to multiple protocols. Each L2CAP packet received on a channel is directed to the appropriate higher level protocol. Multiple channels can share the same baseband connection. In FreeBSD, a netgraph L2CAP node is created for each Bluetooth device. This node is normally connected to the downstream Bluetooth HCI node and upstream Bluetooth socket nodes. The default name for the L2CAP node is "devicel2cap". For more details refer to man:ng_l2cap[4]. A useful command is man:l2ping[8], which can be used to ping other devices. Some Bluetooth implementations might not return all of the data sent to them, so `0 bytes` in the following example is normal. [source,shell] .... # l2ping -a 00:80:37:29:19:a4 0 bytes from 0:80:37:29:19:a4 seq_no=0 time=48.633 ms result=0 0 bytes from 0:80:37:29:19:a4 seq_no=1 time=37.551 ms result=0 0 bytes from 0:80:37:29:19:a4 seq_no=2 time=28.324 ms result=0 0 bytes from 0:80:37:29:19:a4 seq_no=3 time=46.150 ms result=0 .... The man:l2control[8] utility is used to perform various operations on L2CAP nodes. This example shows how to obtain the list of logical connections (channels) and the list of baseband connections for the local device: [source,shell] .... % l2control -a 00:02:72:00:d4:1a read_channel_list L2CAP channels: Remote BD_ADDR SCID/ DCID PSM IMTU/ OMTU State 00:07:e0:00:0b:ca 66/ 64 3 132/ 672 OPEN % l2control -a 00:02:72:00:d4:1a read_connection_list L2CAP connections: Remote BD_ADDR Handle Flags Pending State 00:07:e0:00:0b:ca 41 O 0 OPEN .... Another diagnostic tool is man:btsockstat[1]. It is similar to man:netstat[1], but for Bluetooth network-related data structures. The example below shows the same logical connection as man:l2control[8] above. [source,shell] .... % btsockstat Active L2CAP sockets PCB Recv-Q Send-Q Local address/PSM Foreign address CID State c2afe900 0 0 00:02:72:00:d4:1a/3 00:07:e0:00:0b:ca 66 OPEN Active RFCOMM sessions L2PCB PCB Flag MTU Out-Q DLCs State c2afe900 c2b53380 1 127 0 Yes OPEN Active RFCOMM sockets PCB Recv-Q Send-Q Local address Foreign address Chan DLCI State c2e8bc80 0 250 00:02:72:00:d4:1a 00:07:e0:00:0b:ca 3 6 OPEN .... ==== Radio Frequency Communication (RFCOMM) The RFCOMM protocol provides emulation of serial ports over the L2CAP protocol. RFCOMM is a simple transport protocol, with additional provisions for emulating the 9 circuits of RS-232 (EIATIA-232-E) serial ports. It supports up to 60 simultaneous connections (RFCOMM channels) between two Bluetooth devices. For the purposes of RFCOMM, a complete communication path involves two applications running on the communication endpoints with a communication segment between them. RFCOMM is intended to cover applications that make use of the serial ports of the devices in which they reside. The communication segment is a direct connect Bluetooth link from one device to another. RFCOMM is only concerned with the connection between the devices in the direct connect case, or between the device and a modem in the network case. RFCOMM can support other configurations, such as modules that communicate via Bluetooth wireless technology on one side and provide a wired interface on the other side. In FreeBSD, RFCOMM is implemented at the Bluetooth sockets layer. ==== Service Discovery Protocol (SDP) The Service Discovery Protocol (SDP) provides the means for client applications to discover the existence of services provided by server applications as well as the attributes of those services. The attributes of a service include the type or class of service offered and the mechanism or protocol information needed to utilize the service. SDP involves communication between a SDP server and a SDP client. The server maintains a list of service records that describe the characteristics of services associated with the server. Each service record contains information about a single service. A client may retrieve information from a service record maintained by the SDP server by issuing a SDP request. If the client, or an application associated with the client, decides to use a service, it must open a separate connection to the service provider in order to utilize the service. SDP provides a mechanism for discovering services and their attributes, but it does not provide a mechanism for utilizing those services. Normally, a SDP client searches for services based on some desired characteristics of the services. However, there are times when it is desirable to discover which types of services are described by an SDP server's service records without any prior information about the services. This process of looking for any offered services is called _browsing_. The Bluetooth SDP server, man:sdpd[8], and command line client, man:sdpcontrol[8], are included in the standard FreeBSD installation. The following example shows how to perform a SDP browse query. [source,shell] .... % sdpcontrol -a 00:01:03:fc:6e:ec browse Record Handle: 00000000 Service Class ID List: Service Discovery Server (0x1000) Protocol Descriptor List: L2CAP (0x0100) Protocol specific parameter #1: u/int/uuid16 1 Protocol specific parameter #2: u/int/uuid16 1 Record Handle: 0x00000001 Service Class ID List: Browse Group Descriptor (0x1001) Record Handle: 0x00000002 Service Class ID List: LAN Access Using PPP (0x1102) Protocol Descriptor List: L2CAP (0x0100) RFCOMM (0x0003) Protocol specific parameter #1: u/int8/bool 1 Bluetooth Profile Descriptor List: LAN Access Using PPP (0x1102) ver. 1.0 .... Note that each service has a list of attributes, such as the RFCOMM channel. Depending on the service, the user might need to make note of some of the attributes. Some Bluetooth implementations do not support service browsing and may return an empty list. In this case, it is possible to search for the specific service. The example below shows how to search for the OBEX Object Push (OPUSH) service: [source,shell] .... % sdpcontrol -a 00:01:03:fc:6e:ec search OPUSH .... Offering services on FreeBSD to Bluetooth clients is done with the man:sdpd[8] server. The following line can be added to [.filename]#/etc/rc.conf#: [.programlisting] .... sdpd_enable="YES" .... Then the man:sdpd[8] daemon can be started with: [source,shell] .... # service sdpd start .... The local server application that wants to provide a Bluetooth service to remote clients will register the service with the local SDP daemon. An example of such an application is man:rfcomm_pppd[8]. Once started, it will register the Bluetooth LAN service with the local SDP daemon. The list of services registered with the local SDP server can be obtained by issuing a SDP browse query via the local control channel: [source,shell] .... # sdpcontrol -l browse .... ==== OBEX Object Push (OPUSH) Object Exchange (OBEX) is a widely used protocol for simple file transfers between mobile devices. Its main use is in infrared communication, where it is used for generic file transfers between notebooks or PDAs, and for sending business cards or calendar entries between cellular phones and other devices with Personal Information Manager (PIM) applications. The OBEX server and client are implemented by obexapp, which can be installed using the package:comms/obexapp[] package or port. The OBEX client is used to push and/or pull objects from the OBEX server. An example object is a business card or an appointment. The OBEX client can obtain the RFCOMM channel number from the remote device via SDP. This can be done by specifying the service name instead of the RFCOMM channel number. Supported service names are: `IrMC`, `FTRN`, and `OPUSH`. It is also possible to specify the RFCOMM channel as a number. Below is an example of an OBEX session where the device information object is pulled from the cellular phone, and a new object, the business card, is pushed into the phone's directory. [source,shell] .... % obexapp -a 00:80:37:29:19:a4 -C IrMC obex> get telecom/devinfo.txt devinfo-t39.txt Success, response: OK, Success (0x20) obex> put new.vcf Success, response: OK, Success (0x20) obex> di Success, response: OK, Success (0x20) .... In order to provide the OPUSH service, man:sdpd[8] must be running and a root folder, where all incoming objects will be stored, must be created. The default path to the root folder is [.filename]#/var/spool/obex#. Finally, start the OBEX server on a valid RFCOMM channel number. The OBEX server will automatically register the OPUSH service with the local SDP daemon. The example below shows how to start the OBEX server. [source,shell] .... # obexapp -s -C 10 .... ==== Serial Port Profile (SPP) The Serial Port Profile (SPP) allows Bluetooth devices to perform serial cable emulation. This profile allows legacy applications to use Bluetooth as a cable replacement, through a virtual serial port abstraction. In FreeBSD, man:rfcomm_sppd[1] implements SPP and a pseudo tty is used as a virtual serial port abstraction. The example below shows how to connect to a remote device's serial port service. A RFCOMM channel does not have to be specified as man:rfcomm_sppd[1] can obtain it from the remote device via SDP. To override this, specify a RFCOMM channel on the command line. [source,shell] .... # rfcomm_sppd -a 00:07:E0:00:0B:CA -t rfcomm_sppd[94692]: Starting on /dev/pts/6... /dev/pts/6 .... Once connected, the pseudo tty can be used as serial port: [source,shell] .... # cu -l /dev/pts/6 .... The pseudo tty is printed on stdout and can be read by wrapper scripts: [.programlisting] .... PTS=`rfcomm_sppd -a 00:07:E0:00:0B:CA -t` cu -l $PTS .... === Troubleshooting By default, when FreeBSD is accepting a new connection, it tries to perform a role switch and become master. Some older Bluetooth devices which do not support role switching will not be able to connect. Since role switching is performed when a new connection is being established, it is not possible to ask the remote device if it supports role switching. However, there is a HCI option to disable role switching on the local side: [source,shell] .... # hccontrol -n ubt0hci write_node_role_switch 0 .... To display Bluetooth packets, use the third-party package hcidump, which can be installed using the package:comms/hcidump[] package or port. This utility is similar to man:tcpdump[1] and can be used to display the contents of Bluetooth packets on the terminal and to dump the Bluetooth packets to a file. [[network-bridging]] == Bridging It is sometimes useful to divide a network, such as an Ethernet segment, into network segments without having to create IP subnets and use a router to connect the segments together. A device that connects two networks together in this fashion is called a "bridge". A bridge works by learning the MAC addresses of the devices on each of its network interfaces. It forwards traffic between networks only when the source and destination MAC addresses are on different networks. In many respects, a bridge is like an Ethernet switch with very few ports. A FreeBSD system with multiple network interfaces can be configured to act as a bridge. Bridging can be useful in the following situations: Connecting Networks:: The basic operation of a bridge is to join two or more network segments. There are many reasons to use a host-based bridge instead of networking equipment, such as cabling constraints or firewalling. A bridge can also connect a wireless interface running in hostap mode to a wired network and act as an access point. Filtering/Traffic Shaping Firewall:: A bridge can be used when firewall functionality is needed without routing or Network Address Translation (NAT). + An example is a small company that is connected via DSL or ISDN to an ISP. There are thirteen public IP addresses from the ISP and ten computers on the network. In this situation, using a router-based firewall is difficult because of subnetting issues. A bridge-based firewall can be configured without any IP addressing issues. Network Tap:: -A bridge can join two network segments in order to inspect all Ethernet frames that pass between them using man:bpf[4] and man:tcpdump[1] on the bridge interface or by sending a copy of all frames out an additional interface known as a span port. +A bridge can join two network segments in order to inspect all Ethernet frames that pass between them using man:bpf[4] and man:tcpdump[1] on the bridge interface, or by sending a copy of all frames out on an additional interface known as a span port. Layer 2 VPN:: Two Ethernet networks can be joined across an IP link by bridging the networks to an EtherIP tunnel or a man:tap[4] based solution such as OpenVPN. Layer 2 Redundancy:: A network can be connected together with multiple links and use the Spanning Tree Protocol (STP) to block redundant paths. This section describes how to configure a FreeBSD system as a bridge using man:if_bridge[4]. A netgraph bridging driver is also available, and is described in man:ng_bridge[4]. [NOTE] ==== Packet filtering can be used with any firewall package that hooks into the man:pfil[9] framework. The bridge can be used as a traffic shaper with man:altq[4] or man:dummynet[4]. ==== === Enabling the Bridge In FreeBSD, man:if_bridge[4] is a kernel module which is automatically loaded by man:ifconfig[8] when creating a bridge interface. It is also possible to compile bridge support into a custom kernel by adding `device if_bridge` to the custom kernel configuration file. The bridge is created using interface cloning. To create the bridge interface: [source,shell] .... # ifconfig bridge create bridge0 # ifconfig bridge0 bridge0: flags=8802 metric 0 mtu 1500 ether 96:3d:4b:f1:79:7a id 00:00:00:00:00:00 priority 32768 hellotime 2 fwddelay 15 maxage 20 holdcnt 6 proto rstp maxaddr 100 timeout 1200 root id 00:00:00:00:00:00 priority 0 ifcost 0 port 0 .... When a bridge interface is created, it is automatically assigned a randomly generated Ethernet address. The `maxaddr` and `timeout` parameters control how many MAC addresses the bridge will keep in its forwarding table and how many seconds before each entry is removed after it is last seen. The other parameters control how STP operates. Next, specify which network interfaces to add as members of the bridge. For the bridge to forward packets, all member interfaces and the bridge need to be up: [source,shell] .... # ifconfig bridge0 addm fxp0 addm fxp1 up # ifconfig fxp0 up # ifconfig fxp1 up .... The bridge can now forward Ethernet frames between [.filename]#fxp0# and [.filename]#fxp1#. Add the following lines to [.filename]#/etc/rc.conf# so the bridge is created at startup: [.programlisting] .... cloned_interfaces="bridge0" ifconfig_bridge0="addm fxp0 addm fxp1 up" ifconfig_fxp0="up" ifconfig_fxp1="up" .... If the bridge host needs an IP address, set it on the bridge interface, not on the member interfaces. The address can be set statically or via DHCP. This example sets a static IP address: [source,shell] .... # ifconfig bridge0 inet 192.168.0.1/24 .... It is also possible to assign an IPv6 address to a bridge interface. To make the changes permanent, add the addressing information to [.filename]#/etc/rc.conf#. [NOTE] ==== When packet filtering is enabled, bridged packets will pass through the filter inbound on the originating interface on the bridge interface, and outbound on the appropriate interfaces. Either stage can be disabled. When direction of the packet flow is important, it is best to firewall on the member interfaces rather than the bridge itself. The bridge has several configurable settings for passing non-IP and IP packets, and layer2 firewalling with man:ipfw[8]. See man:if_bridge[4] for more information. ==== === Enabling Spanning Tree For an Ethernet network to function properly, only one active path can exist between two devices. The STP protocol detects loops and puts redundant links into a blocked state. Should one of the active links fail, STP calculates a different tree and enables one of the blocked paths to restore connectivity to all points in the network. The Rapid Spanning Tree Protocol (RSTP or 802.1w) provides backwards compatibility with legacy STP. RSTP provides faster convergence and exchanges information with neighboring switches to quickly transition to forwarding mode without creating loops. FreeBSD supports RSTP and STP as operating modes, with RSTP being the default mode. STP can be enabled on member interfaces using man:ifconfig[8]. For a bridge with [.filename]#fxp0# and [.filename]#fxp1# as the current interfaces, enable STP with: [source,shell] .... # ifconfig bridge0 stp fxp0 stp fxp1 bridge0: flags=8843 metric 0 mtu 1500 ether d6:cf:d5:a0:94:6d id 00:01:02:4b:d4:50 priority 32768 hellotime 2 fwddelay 15 maxage 20 holdcnt 6 proto rstp maxaddr 100 timeout 1200 root id 00:01:02:4b:d4:50 priority 32768 ifcost 0 port 0 member: fxp0 flags=1c7 port 3 priority 128 path cost 200000 proto rstp role designated state forwarding member: fxp1 flags=1c7 port 4 priority 128 path cost 200000 proto rstp role designated state forwarding .... This bridge has a spanning tree ID of `00:01:02:4b:d4:50` and a priority of `32768`. As the `root id` is the same, it indicates that this is the root bridge for the tree. Another bridge on the network also has STP enabled: [source,shell] .... bridge0: flags=8843 metric 0 mtu 1500 ether 96:3d:4b:f1:79:7a id 00:13:d4:9a:06:7a priority 32768 hellotime 2 fwddelay 15 maxage 20 holdcnt 6 proto rstp maxaddr 100 timeout 1200 root id 00:01:02:4b:d4:50 priority 32768 ifcost 400000 port 4 member: fxp0 flags=1c7 port 4 priority 128 path cost 200000 proto rstp role root state forwarding member: fxp1 flags=1c7 port 5 priority 128 path cost 200000 proto rstp role designated state forwarding .... The line `root id 00:01:02:4b:d4:50 priority 32768 ifcost 400000 port 4` shows that the root bridge is `00:01:02:4b:d4:50` and has a path cost of `400000` from this bridge. The path to the root bridge is via `port 4` which is [.filename]#fxp0#. === Bridge Interface Parameters Several `ifconfig` parameters are unique to bridge interfaces. This section summarizes some common uses for these parameters. The complete list of available parameters is described in man:ifconfig[8]. private:: A private interface does not forward any traffic to any other port that is also designated as a private interface. The traffic is blocked unconditionally so no Ethernet frames will be forwarded, including ARP packets. If traffic needs to be selectively blocked, a firewall should be used instead. span:: A span port transmits a copy of every Ethernet frame received by the bridge. The number of span ports configured on a bridge is unlimited, but if an interface is designated as a span port, it cannot also be used as a regular bridge port. This is most useful for snooping a bridged network passively on another host connected to one of the span ports of the bridge. For example, to send a copy of all frames out the interface named [.filename]#fxp4#: + [source,shell] .... # ifconfig bridge0 span fxp4 .... sticky:: If a bridge member interface is marked as sticky, dynamically learned address entries are treated as static entries in the forwarding cache. Sticky entries are never aged out of the cache or replaced, even if the address is seen on a different interface. This gives the benefit of static address entries without the need to pre-populate the forwarding table. Clients learned on a particular segment of the bridge cannot roam to another segment. + An example of using sticky addresses is to combine the bridge with VLANs in order to isolate customer networks without wasting IP address space. Consider that `CustomerA` is on `vlan100`, `CustomerB` is on `vlan101`, and the bridge has the address `192.168.0.1`: + [source,shell] .... # ifconfig bridge0 addm vlan100 sticky vlan100 addm vlan101 sticky vlan101 # ifconfig bridge0 inet 192.168.0.1/24 .... + In this example, both clients see `192.168.0.1` as their default gateway. Since the bridge cache is sticky, one host cannot spoof the MAC address of the other customer in order to intercept their traffic. + Any communication between the VLANs can be blocked using a firewall or, as seen in this example, private interfaces: + [source,shell] .... # ifconfig bridge0 private vlan100 private vlan101 .... + The customers are completely isolated from each other and the full `/24` address range can be allocated without subnetting. + The number of unique source MAC addresses behind an interface can be limited. Once the limit is reached, packets with unknown source addresses are dropped until an existing host cache entry expires or is removed. + The following example sets the maximum number of Ethernet devices for `CustomerA` on `vlan100` to 10: + [source,shell] .... # ifconfig bridge0 ifmaxaddr vlan100 10 .... Bridge interfaces also support monitor mode, where the packets are discarded after man:bpf[4] processing and are not processed or forwarded further. This can be used to multiplex the input of two or more interfaces into a single man:bpf[4] stream. This is useful for reconstructing the traffic for network taps that transmit the RX/TX signals out through two separate interfaces. For example, to read the input from four network interfaces as one stream: [source,shell] .... # ifconfig bridge0 addm fxp0 addm fxp1 addm fxp2 addm fxp3 monitor up # tcpdump -i bridge0 .... === SNMP Monitoring The bridge interface and STP parameters can be monitored via man:bsnmpd[1] which is included in the FreeBSD base system. The exported bridge MIBs conform to IETF standards so any SNMP client or monitoring package can be used to retrieve the data. To enable monitoring on the bridge, uncomment this line in [.filename]#/etc/snmpd.config# by removing the beginning `#` symbol: [.programlisting] .... begemotSnmpdModulePath."bridge" = "/usr/lib/snmp_bridge.so" .... Other configuration settings, such as community names and access lists, may need to be modified in this file. See man:bsnmpd[1] and man:snmp_bridge[3] for more information. Once these edits are saved, add this line to [.filename]#/etc/rc.conf#: [.programlisting] .... bsnmpd_enable="YES" .... Then, start man:bsnmpd[1]: [source,shell] .... # service bsnmpd start .... The following examples use the Net-SNMP software (package:net-mgmt/net-snmp[]) to query a bridge from a client system. The package:net-mgmt/bsnmptools[] port can also be used. From the SNMP client which is running Net-SNMP, add the following lines to [.filename]#$HOME/.snmp/snmp.conf# in order to import the bridge MIB definitions: [.programlisting] .... mibdirs +/usr/share/snmp/mibs mibs +BRIDGE-MIB:RSTP-MIB:BEGEMOT-MIB:BEGEMOT-BRIDGE-MIB .... To monitor a single bridge using the IETF BRIDGE-MIB (RFC4188): [source,shell] .... % snmpwalk -v 2c -c public bridge1.example.com mib-2.dot1dBridge BRIDGE-MIB::dot1dBaseBridgeAddress.0 = STRING: 66:fb:9b:6e:5c:44 BRIDGE-MIB::dot1dBaseNumPorts.0 = INTEGER: 1 ports BRIDGE-MIB::dot1dStpTimeSinceTopologyChange.0 = Timeticks: (189959) 0:31:39.59 centi-seconds BRIDGE-MIB::dot1dStpTopChanges.0 = Counter32: 2 BRIDGE-MIB::dot1dStpDesignatedRoot.0 = Hex-STRING: 80 00 00 01 02 4B D4 50 ... BRIDGE-MIB::dot1dStpPortState.3 = INTEGER: forwarding(5) BRIDGE-MIB::dot1dStpPortEnable.3 = INTEGER: enabled(1) BRIDGE-MIB::dot1dStpPortPathCost.3 = INTEGER: 200000 BRIDGE-MIB::dot1dStpPortDesignatedRoot.3 = Hex-STRING: 80 00 00 01 02 4B D4 50 BRIDGE-MIB::dot1dStpPortDesignatedCost.3 = INTEGER: 0 BRIDGE-MIB::dot1dStpPortDesignatedBridge.3 = Hex-STRING: 80 00 00 01 02 4B D4 50 BRIDGE-MIB::dot1dStpPortDesignatedPort.3 = Hex-STRING: 03 80 BRIDGE-MIB::dot1dStpPortForwardTransitions.3 = Counter32: 1 RSTP-MIB::dot1dStpVersion.0 = INTEGER: rstp(2) .... The `dot1dStpTopChanges.0` value is two, indicating that the STP bridge topology has changed twice. A topology change means that one or more links in the network have changed or failed and a new tree has been calculated. The `dot1dStpTimeSinceTopologyChange.0` value will show when this happened. To monitor multiple bridge interfaces, the private BEGEMOT-BRIDGE-MIB can be used: [source,shell] .... % snmpwalk -v 2c -c public bridge1.example.com enterprises.fokus.begemot.begemotBridge BEGEMOT-BRIDGE-MIB::begemotBridgeBaseName."bridge0" = STRING: bridge0 BEGEMOT-BRIDGE-MIB::begemotBridgeBaseName."bridge2" = STRING: bridge2 BEGEMOT-BRIDGE-MIB::begemotBridgeBaseAddress."bridge0" = STRING: e:ce:3b:5a:9e:13 BEGEMOT-BRIDGE-MIB::begemotBridgeBaseAddress."bridge2" = STRING: 12:5e:4d:74:d:fc BEGEMOT-BRIDGE-MIB::begemotBridgeBaseNumPorts."bridge0" = INTEGER: 1 BEGEMOT-BRIDGE-MIB::begemotBridgeBaseNumPorts."bridge2" = INTEGER: 1 ... BEGEMOT-BRIDGE-MIB::begemotBridgeStpTimeSinceTopologyChange."bridge0" = Timeticks: (116927) 0:19:29.27 centi-seconds BEGEMOT-BRIDGE-MIB::begemotBridgeStpTimeSinceTopologyChange."bridge2" = Timeticks: (82773) 0:13:47.73 centi-seconds BEGEMOT-BRIDGE-MIB::begemotBridgeStpTopChanges."bridge0" = Counter32: 1 BEGEMOT-BRIDGE-MIB::begemotBridgeStpTopChanges."bridge2" = Counter32: 1 BEGEMOT-BRIDGE-MIB::begemotBridgeStpDesignatedRoot."bridge0" = Hex-STRING: 80 00 00 40 95 30 5E 31 BEGEMOT-BRIDGE-MIB::begemotBridgeStpDesignatedRoot."bridge2" = Hex-STRING: 80 00 00 50 8B B8 C6 A9 .... To change the bridge interface being monitored via the `mib-2.dot1dBridge` subtree: [source,shell] .... % snmpset -v 2c -c private bridge1.example.com BEGEMOT-BRIDGE-MIB::begemotBridgeDefaultBridgeIf.0 s bridge2 .... [[network-aggregation]] == Link Aggregation and Failover FreeBSD provides the man:lagg[4] interface which can be used to aggregate multiple network interfaces into one virtual interface in order to provide failover and link aggregation. Failover allows traffic to continue to flow as long as at least one aggregated network interface has an established link. Link aggregation works best on switches which support LACP, as this protocol distributes traffic bi-directionally while responding to the failure of individual links. The aggregation protocols supported by the lagg interface determine which ports are used for outgoing traffic and whether or not a specific port accepts incoming traffic. The following protocols are supported by man:lagg[4]: failover:: This mode sends and receives traffic only through the master port. If the master port becomes unavailable, the next active port is used. The first interface added to the virtual interface is the master port and all subsequently added interfaces are used as failover devices. If failover to a non-master port occurs, the original port becomes master once it becomes available again. loadbalance:: This provides a static setup and does not negotiate aggregation with the peer or exchange frames to monitor the link. If the switch supports LACP, that should be used instead. lacp:: The IEEE(R) 802.3ad Link Aggregation Control Protocol (LACP) negotiates a set of aggregable links with the peer into one or more Link Aggregated Groups (LAGs). Each LAG is composed of ports of the same speed, set to full-duplex operation, and traffic is balanced across the ports in the LAG with the greatest total speed. Typically, there is only one LAG which contains all the ports. In the event of changes in physical connectivity, LACP will quickly converge to a new configuration. + LACP balances outgoing traffic across the active ports based on hashed protocol header information and accepts incoming traffic from any active port. The hash includes the Ethernet source and destination address and, if available, the VLAN tag, and the IPv4 or IPv6 source and destination address. roundrobin:: This mode distributes outgoing traffic using a round-robin scheduler through all active ports and accepts incoming traffic from any active port. Since this mode violates Ethernet frame ordering, it should be used with caution. broadcast:: This mode sends outgoing traffic to all ports configured on the lagg interface, and receives frames on any port. === Configuration Examples This section demonstrates how to configure a Cisco(R) switch and a FreeBSD system for LACP load balancing. It then shows how to configure two Ethernet interfaces in failover mode as well as how to configure failover mode between an Ethernet and a wireless interface. [[networking-lacp-aggregation-cisco]] .LACP Aggregation with a Cisco(R) Switch [example] ==== This example connects two man:fxp[4] Ethernet interfaces on a FreeBSD machine to the first two Ethernet ports on a Cisco(R) switch as a single load balanced and fault tolerant link. More interfaces can be added to increase throughput and fault tolerance. Replace the names of the Cisco(R) ports, Ethernet devices, channel group number, and IP address shown in the example to match the local configuration. Frame ordering is mandatory on Ethernet links and any traffic between two stations always flows over the same physical link, limiting the maximum speed to that of one interface. The transmit algorithm attempts to use as much information as it can to distinguish different traffic flows and balance the flows across the available interfaces. On the Cisco(R) switch, add the _FastEthernet0/1_ and _FastEthernet0/2_ interfaces to channel group _1_: [source,shell] .... interface FastEthernet0/1 channel-group 1 mode active channel-protocol lacp ! interface FastEthernet0/2 channel-group 1 mode active channel-protocol lacp .... On the FreeBSD system, create the man:lagg[4] interface using the physical interfaces _fxp0_ and _fxp1_ and bring the interfaces up with an IP address of _10.0.0.3/24_: [source,shell] .... # ifconfig fxp0 up # ifconfig fxp1 up # ifconfig lagg0 create # ifconfig lagg0 up laggproto lacp laggport fxp0 laggport fxp1 10.0.0.3/24 .... Next, verify the status of the virtual interface: [source,shell] .... # ifconfig lagg0 lagg0: flags=8843 metric 0 mtu 1500 options=8 ether 00:05:5d:71:8d:b8 inet 10.0.0.3 netmask 0xffffff00 broadcast 10.0.0.255 media: Ethernet autoselect status: active laggproto lacp laggport: fxp1 flags=1c laggport: fxp0 flags=1c .... Ports marked as `ACTIVE` are part of the LAG that has been negotiated with the remote switch. Traffic will be transmitted and received through these active ports. Add `-v` to the above command to view the LAG identifiers. To see the port status on the Cisco(R) switch: [source,shell] .... switch# show lacp neighbor Flags: S - Device is requesting Slow LACPDUs F - Device is requesting Fast LACPDUs A - Device is in Active mode P - Device is in Passive mode Channel group 1 neighbors Partner's information: LACP port Oper Port Port Port Flags Priority Dev ID Age Key Number State Fa0/1 SA 32768 0005.5d71.8db8 29s 0x146 0x3 0x3D Fa0/2 SA 32768 0005.5d71.8db8 29s 0x146 0x4 0x3D .... For more detail, type `show lacp neighbor detail`. To retain this configuration across reboots, add the following entries to [.filename]#/etc/rc.conf# on the FreeBSD system: [.programlisting] .... ifconfig_fxp0="up" ifconfig_fxp1="up" cloned_interfaces="lagg0" ifconfig_lagg0="laggproto lacp laggport fxp0 laggport fxp1 10.0.0.3/24" .... ==== [[networking-lagg-failover]] .Failover Mode [example] ==== Failover mode can be used to switch over to a secondary interface if the link is lost on the master interface. To configure failover, make sure that the underlying physical interfaces are up, then create the man:lagg[4] interface. In this example, _fxp0_ is the master interface, _fxp1_ is the secondary interface, and the virtual interface is assigned an IP address of _10.0.0.15/24_: [source,shell] .... # ifconfig fxp0 up # ifconfig fxp1 up # ifconfig lagg0 create # ifconfig lagg0 up laggproto failover laggport fxp0 laggport fxp1 10.0.0.15/24 .... The virtual interface should look something like this: [source,shell] .... # ifconfig lagg0 lagg0: flags=8843 metric 0 mtu 1500 options=8 ether 00:05:5d:71:8d:b8 inet 10.0.0.15 netmask 0xffffff00 broadcast 10.0.0.255 media: Ethernet autoselect status: active laggproto failover laggport: fxp1 flags=0<> laggport: fxp0 flags=5 .... Traffic will be transmitted and received on _fxp0_. If the link is lost on _fxp0_, _fxp1_ will become the active link. If the link is restored on the master interface, it will once again become the active link. To retain this configuration across reboots, add the following entries to [.filename]#/etc/rc.conf#: [.programlisting] .... ifconfig_fxp0="up" ifconfig_fxp1="up" cloned_interfaces="lagg0" ifconfig_lagg0="laggproto failover laggport fxp0 laggport fxp1 10.0.0.15/24" .... ==== [[networking-lagg-wired-and-wireless]] .Failover Mode Between Ethernet and Wireless Interfaces [example] ==== For laptop users, it is usually desirable to configure the wireless device as a secondary which is only used when the Ethernet connection is not available. With man:lagg[4], it is possible to configure a failover which prefers the Ethernet connection for both performance and security reasons, while maintaining the ability to transfer data over the wireless connection. This is achieved by overriding the Ethernet interface's MAC address with that of the wireless interface. [NOTE] **** In theory, either the Ethernet or wireless MAC address can be changed to match the other. However, some popular wireless interfaces lack support for overriding the MAC address. We therefore recommend overriding the Ethernet MAC address for this purpose. **** [NOTE] **** If the driver for the wireless interface is not loaded in the `GENERIC` or custom kernel, and the computer is running FreeBSD {rel121-current}, load the corresponding [.filename]#.ko# in [.filename]#/boot/loader.conf# by adding `*driver_load="YES"*` to that file and rebooting. Another, better way is to load the driver in [.filename]#/etc/rc.conf# by adding it to `kld_list` (see man:rc.conf[5] for details) in that file and rebooting. This is needed because otherwise the driver is not loaded yet at the time the man:lagg[4] interface is set up. **** In this example, the Ethernet interface, _re0_, is the master and the wireless interface, _wlan0_, is the failover. The _wlan0_ interface was created from the _ath0_ physical wireless interface, and the Ethernet interface will be configured with the MAC address of the wireless interface. First, bring the wireless interface up (replacing _FR_ with your own 2-letter country code), but do not set an IP address. Replace _wlan0_ to match the system's wireless interface name: [source,shell] .... # ifconfig wlan0 create wlandev ath0 country FR ssid my_router up .... Now you can determine the MAC address of the wireless interface: [source,shell] .... # ifconfig wlan0 wlan0: flags=8843 metric 0 mtu 1500 ether b8:ee:65:5b:32:59 groups: wlan ssid Bbox-A3BD2403 channel 6 (2437 MHz 11g ht/20) bssid 00:37:b7:56:4b:60 regdomain ETSI country FR indoor ecm authmode WPA2/802.11i privacy ON deftxkey UNDEF AES-CCM 2:128-bit txpower 30 bmiss 7 scanvalid 60 protmode CTS ampdulimit 64k ampdudensity 8 shortgi -stbctx stbcrx -ldpc wme burst roaming MANUAL media: IEEE 802.11 Wireless Ethernet MCS mode 11ng status: associated nd6 options=29 .... The `ether` line will contain the MAC address of the specified interface. Now, change the MAC address of the Ethernet interface to match: [source,shell] .... # ifconfig re0 ether b8:ee:65:5b:32:59 .... Make sure the _re0_ interface is up, then create the man:lagg[4] interface with _re0_ as master with failover to _wlan0_: [source,shell] .... # ifconfig re0 up # ifconfig lagg0 create # ifconfig lagg0 up laggproto failover laggport re0 laggport wlan0 .... The virtual interface should look something like this: [source,shell] .... # ifconfig lagg0 lagg0: flags=8843 metric 0 mtu 1500 options=8 ether b8:ee:65:5b:32:59 laggproto failover lagghash l2,l3,l4 laggport: re0 flags=5 laggport: wlan0 flags=0<> groups: lagg media: Ethernet autoselect status: active .... Then, start the DHCP client to obtain an IP address: [source,shell] .... # dhclient lagg0 .... To retain this configuration across reboots, add the following entries to [.filename]#/etc/rc.conf#: [.programlisting] .... ifconfig_re0="ether b8:ee:65:5b:32:59" wlans_ath0="wlan0" ifconfig_wlan0="WPA" create_args_wlan0="country FR" cloned_interfaces="lagg0" ifconfig_lagg0="up laggproto failover laggport re0 laggport wlan0 DHCP" .... ==== [[network-diskless]] == Diskless Operation with PXE The Intel(R) Preboot eXecution Environment (PXE) allows an operating system to boot over the network. For example, a FreeBSD system can boot over the network and operate without a local disk, using file systems mounted from an NFS server. PXE support is usually available in the BIOS. To use PXE when the machine starts, select the `Boot from network` option in the BIOS setup or type a function key during system initialization. In order to provide the files needed for an operating system to boot over the network, a PXE setup also requires properly configured DHCP, TFTP, and NFS servers, where: * Initial parameters, such as an IP address, executable boot filename and location, server name, and root path are obtained from the DHCP server. * The operating system loader file is booted using TFTP. * The file systems are loaded using NFS. When a computer PXE boots, it receives information over DHCP about where to obtain the initial boot loader file. After the host computer receives this information, it downloads the boot loader via TFTP and then executes the boot loader. In FreeBSD, the boot loader file is [.filename]#/boot/pxeboot#. After [.filename]#/boot/pxeboot# executes, the FreeBSD kernel is loaded and the rest of the FreeBSD bootup sequence proceeds, as described in crossref:boot[boot,The FreeBSD Booting Process]. This section describes how to configure these services on a FreeBSD system so that other systems can PXE boot into FreeBSD. Refer to man:diskless[8] for more information. [CAUTION] ==== As described, the system providing these services is insecure. It should live in a protected area of a network and be untrusted by other hosts. ==== [[network-pxe-nfs]] === Setting Up the PXE Environment The steps shown in this section configure the built-in NFS and TFTP servers. The next section demonstrates how to install and configure the DHCP server. In this example, the directory which will contain the files used by PXE users is [.filename]#/b/tftpboot/FreeBSD/install#. It is important that this directory exists and that the same directory name is set in both [.filename]#/etc/inetd.conf# and [.filename]#/usr/local/etc/dhcpd.conf#. [NOTE] ==== The command examples below assume use of the man:sh[1] shell. man:csh[1] and man:tcsh[1] users will need to start a man:sh[1] shell or adapt the commands to man:csh[1] syntax. ==== [.procedure] . Create the root directory which will contain a FreeBSD installation to be NFS mounted: + [source,shell] .... # export NFSROOTDIR=/b/tftpboot/FreeBSD/install # mkdir -p ${NFSROOTDIR} .... . Enable the NFS server by adding this line to [.filename]#/etc/rc.conf#: + [.programlisting] .... nfs_server_enable="YES" .... . Export the diskless root directory via NFS by adding the following to [.filename]#/etc/exports#: + [.programlisting] .... /b -ro -alldirs -maproot=root .... . Start the NFS server: + [source,shell] .... # service nfsd start .... . Enable man:inetd[8] by adding the following line to [.filename]#/etc/rc.conf#: + [.programlisting] .... inetd_enable="YES" .... . Uncomment the following line in [.filename]#/etc/inetd.conf# by making sure it does not start with a `#` symbol: + [.programlisting] .... tftp dgram udp wait root /usr/libexec/tftpd tftpd -l -s /b/tftpboot .... + [NOTE] ==== Some PXE versions require the TCP version of TFTP. In this case, uncomment the second `tftp` line which contains `stream tcp`. ==== . Start man:inetd[8]: + [source,shell] .... # service inetd start .... . Install the base system into [.filename]#${NFSROOTDIR}#, either by decompressing the official archives or by rebuilding the FreeBSD kernel and userland (refer to crossref:cutting-edge[makeworld,“Updating FreeBSD from Source”] for more detailed instructions, but do not forget to add `DESTDIR=_${NFSROOTDIR}_` when running the `make installkernel` and `make installworld` commands. . Test that the TFTP server works and can download the boot loader which will be obtained via PXE: + [source,shell] .... # tftp localhost tftp> get FreeBSD/install/boot/pxeboot Received 264951 bytes in 0.1 seconds .... . Edit [.filename]#${NFSROOTDIR}/etc/fstab# and create an entry to mount the root file system over NFS: + [.programlisting] .... # Device Mountpoint FSType Options Dump Pass myhost.example.com:/b/tftpboot/FreeBSD/install / nfs ro 0 0 .... + Replace _myhost.example.com_ with the hostname or IP address of the NFS server. In this example, the root file system is mounted read-only in order to prevent NFS clients from potentially deleting the contents of the root file system. . Set the root password in the PXE environment for client machines which are PXE booting : + [source,shell] .... # chroot ${NFSROOTDIR} # passwd .... . If needed, enable man:ssh[1] root logins for client machines which are PXE booting by editing [.filename]#${NFSROOTDIR}/etc/ssh/sshd_config# and enabling `PermitRootLogin`. This option is documented in man:sshd_config[5]. . Perform any other needed customizations of the PXE environment in [.filename]#${NFSROOTDIR}#. These customizations could include things like installing packages or editing the password file with man:vipw[8]. When booting from an NFS root volume, [.filename]#/etc/rc# detects the NFS boot and runs [.filename]#/etc/rc.initdiskless#. In this case, [.filename]#/etc# and [.filename]#/var# need to be memory backed file systems so that these directories are writable but the NFS root directory is read-only: [source,shell] .... # chroot ${NFSROOTDIR} # mkdir -p conf/base # tar -c -v -f conf/base/etc.cpio.gz --format cpio --gzip etc # tar -c -v -f conf/base/var.cpio.gz --format cpio --gzip var .... When the system boots, memory file systems for [.filename]#/etc# and [.filename]#/var# will be created and mounted and the contents of the [.filename]#cpio.gz# files will be copied into them. By default, these file systems have a maximum capacity of 5 megabytes. If your archives do not fit, which is usually the case for [.filename]#/var# when binary packages have been installed, request a larger size by putting the number of 512 byte sectors needed (e.g., 5 megabytes is 10240 sectors) in [.filename]#${NFSROOTDIR}/conf/base/etc/md_size# and [.filename]#${NFSROOTDIR}/conf/base/var/md_size# files for [.filename]#/etc# and [.filename]#/var# file systems respectively. [[network-pxe-setting-up-dhcp]] === Configuring the DHCP Server The DHCP server does not need to be the same machine as the TFTP and NFS server, but it needs to be accessible in the network. DHCP is not part of the FreeBSD base system but can be installed using the package:net/isc-dhcp44-server[] port or package. Once installed, edit the configuration file, [.filename]#/usr/local/etc/dhcpd.conf#. Configure the `next-server`, `filename`, and `root-path` settings as seen in this example: [.programlisting] .... subnet 192.168.0.0 netmask 255.255.255.0 { range 192.168.0.2 192.168.0.3 ; option subnet-mask 255.255.255.0 ; option routers 192.168.0.1 ; option broadcast-address 192.168.0.255 ; option domain-name-servers 192.168.35.35, 192.168.35.36 ; option domain-name "example.com"; # IP address of TFTP server next-server 192.168.0.1 ; # path of boot loader obtained via tftp filename "FreeBSD/install/boot/pxeboot" ; # pxeboot boot loader will try to NFS mount this directory for root FS option root-path "192.168.0.1:/b/tftpboot/FreeBSD/install/" ; } .... The `next-server` directive is used to specify the IP address of the TFTP server. The `filename` directive defines the path to [.filename]#/boot/pxeboot#. A relative filename is used, meaning that [.filename]#/b/tftpboot# is not included in the path. The `root-path` option defines the path to the NFS root file system. Once the edits are saved, enable DHCP at boot time by adding the following line to [.filename]#/etc/rc.conf#: [.programlisting] .... dhcpd_enable="YES" .... Then start the DHCP service: [source,shell] .... # service isc-dhcpd start .... === Debugging PXE Problems Once all of the services are configured and started, PXE clients should be able to automatically load FreeBSD over the network. If a particular client is unable to connect, when that client machine boots up, enter the BIOS configuration menu and confirm that it is set to boot from the network. This section describes some troubleshooting tips for isolating the source of the configuration problem should no clients be able to PXE boot. [.procedure] **** . Use the package:net/wireshark[] package or port to debug the network traffic involved during the PXE booting process, which is illustrated in the diagram below. + .PXE Booting Process with NFS Root Mount image::pxe-nfs.png[] + 1. Client broadcasts a DHCPDISCOVER message. + 2. The DHCP server responds with the IP address, next-server, filename, and root-path values. + 3. The client sends a TFTP request to next-server, asking to retrieve filename. + 4. The TFTP server responds and sends filename to client. + 5. The client executes filename, which is pxeboot(8), which then loads the kernel. When the kernel executes, the root file system specified by root-path is mounted over NFS. + . On the TFTP server, read [.filename]#/var/log/xferlog# to ensure that [.filename]#pxeboot# is being retrieved from the correct location. To test this example configuration: + [source,shell] .... # tftp 192.168.0.1 tftp> get FreeBSD/install/boot/pxeboot Received 264951 bytes in 0.1 seconds .... + The `BUGS` sections in man:tftpd[8] and man:tftp[1] document some limitations with TFTP. . Make sure that the root file system can be mounted via NFS. To test this example configuration: + [source,shell] .... # mount -t nfs 192.168.0.1:/b/tftpboot/FreeBSD/install /mnt .... **** [[network-ipv6]] == IPv6 IPv6 is the new version of the well known IP protocol, also known as IPv4. IPv6 provides several advantages over IPv4 as well as many new features: * Its 128-bit address space allows for 340,282,366,920,938,463,463,374,607,431,768,211,456 addresses. This addresses the IPv4 address shortage and eventual IPv4 address exhaustion. * Routers only store network aggregation addresses in their routing tables, thus reducing the average space of a routing table to 8192 entries. This addresses the scalability issues associated with IPv4, which required every allocated block of IPv4 addresses to be exchanged between Internet routers, causing their routing tables to become too large to allow efficient routing. * Address autoconfiguration (http://www.ietf.org/rfc/rfc2462.txt[RFC2462]). * Mandatory multicast addresses. * Built-in IPsec (IP security). * Simplified header structure. * Support for mobile IP. * IPv6-to-IPv4 transition mechanisms. FreeBSD includes the http://www.kame.net/[http://www.kame.net/] IPv6 reference implementation and comes with everything needed to use IPv6. This section focuses on getting IPv6 configured and running. === Background on IPv6 Addresses There are three different types of IPv6 addresses: Unicast:: A packet sent to a unicast address arrives at the interface belonging to the address. Anycast:: These addresses are syntactically indistinguishable from unicast addresses but they address a group of interfaces. The packet destined for an anycast address will arrive at the nearest router interface. Anycast addresses are only used by routers. Multicast:: These addresses identify a group of interfaces. A packet destined for a multicast address will arrive at all interfaces belonging to the multicast group. The IPv4 broadcast address, usually `xxx.xxx.xxx.255`, is expressed by multicast addresses in IPv6. When reading an IPv6 address, the canonical form is represented as `x:x:x:x:x:x:x:x`, where each `x` represents a 16 bit hex value. An example is `FEBC:A574:382B:23C1:AA49:4592:4EFE:9982`. Often, an address will have long substrings of all zeros. A `::` (double colon) can be used to replace one substring per address. Also, up to three leading ``0``s per hex value can be omitted. For example, `fe80::1` corresponds to the canonical form `fe80:0000:0000:0000:0000:0000:0000:0001`. A third form is to write the last 32 bits using the well known IPv4 notation. For example, `2002::10.0.0.1` corresponds to the hexadecimal canonical representation `2002:0000:0000:0000:0000:0000:0a00:0001`, which in turn is equivalent to `2002::a00:1`. To view a FreeBSD system's IPv6 address, use man:ifconfig[8]: [source,shell] .... # ifconfig .... [.programlisting] .... rl0: flags=8943 mtu 1500 inet 10.0.0.10 netmask 0xffffff00 broadcast 10.0.0.255 inet6 fe80::200:21ff:fe03:8e1%rl0 prefixlen 64 scopeid 0x1 ether 00:00:21:03:08:e1 media: Ethernet autoselect (100baseTX ) status: active .... In this example, the [.filename]#rl0# interface is using `fe80::200:21ff:fe03:8e1%rl0`, an auto-configured link-local address which was automatically generated from the MAC address. Some IPv6 addresses are reserved. A summary of these reserved addresses is seen in <>: [[reservedip6]] .Reserved IPv6 Addresses [cols="1,1,1,1", frame="none", options="header"] |=== | IPv6 address | Prefixlength (Bits) | Description | Notes |`::` |128 bits |unspecified |Equivalent to `0.0.0.0` in IPv4. |`::1` |128 bits |loopback address |Equivalent to `127.0.0.1` in IPv4. |`::00:xx:xx:xx:xx` |96 bits |embedded IPv4 |The lower 32 bits are the compatible IPv4 address. |`::ff:xx:xx:xx:xx` |96 bits |IPv4 mapped IPv6 address |The lower 32 bits are the IPv4 address for hosts which do not support IPv6. |`fe80::/10` |10 bits |link-local |Equivalent to 169.254.0.0/16 in IPv4. |`fc00::/7` |7 bits |unique-local |Unique local addresses are intended for local communication and are only routable within a set of cooperating sites. |`ff00::` |8 bits |multicast | |``2000::-3fff::`` |3 bits |global unicast |All global unicast addresses are assigned from this pool. The first 3 bits are `001`. |=== For further information on the structure of IPv6 addresses, refer to http://www.ietf.org/rfc/rfc3513.txt[RFC3513]. === Configuring IPv6 To configure a FreeBSD system as an IPv6 client, add these two lines to [.filename]#rc.conf#: [.programlisting] .... ifconfig_rl0_ipv6="inet6 accept_rtadv" rtsold_enable="YES" .... The first line enables the specified interface to receive router advertisement messages. The second line enables the router solicitation daemon, man:rtsol[8]. If the interface needs a statically assigned IPv6 address, add an entry to specify the static address and associated prefix length: [.programlisting] .... ifconfig_rl0_ipv6="inet6 2001:db8:4672:6565:2026:5043:2d42:5344 prefixlen 64" .... To assign a default router, specify its address: [.programlisting] .... ipv6_defaultrouter="2001:db8:4672:6565::1" .... === Connecting to a Provider In order to connect to other IPv6 networks, one must have a provider or a tunnel that supports IPv6: * Contact an Internet Service Provider to see if they offer IPv6. * http://www.tunnelbroker.net[Hurricane Electric] offers tunnels with end-points all around the globe. [NOTE] ==== Install the package:net/freenet6[] package or port for a dial-up connection. ==== This section demonstrates how to take the directions from a tunnel provider and convert them into [.filename]#/etc/rc.conf# settings that will persist through reboots. The first [.filename]#/etc/rc.conf# entry creates the generic tunneling interface [.filename]#gif0#: [.programlisting] .... cloned_interfaces="gif0" .... Next, configure that interface with the IPv4 addresses of the local and remote endpoints. Replace `_MY_IPv4_ADDR_` and `_REMOTE_IPv4_ADDR_` with the actual IPv4 addresses: [.programlisting] .... create_args_gif0="tunnel MY_IPv4_ADDR REMOTE_IPv4_ADDR" .... To apply the IPv6 address that has been assigned for use as the IPv6 tunnel endpoint, add this line, replacing `_MY_ASSIGNED_IPv6_TUNNEL_ENDPOINT_ADDR_` with the assigned address: [.programlisting] .... ifconfig_gif0_ipv6="inet6 MY_ASSIGNED_IPv6_TUNNEL_ENDPOINT_ADDR" .... Then, set the default route for the other side of the IPv6 tunnel. Replace `_MY_IPv6_REMOTE_TUNNEL_ENDPOINT_ADDR_` with the default gateway address assigned by the provider: [.programlisting] .... ipv6_defaultrouter="MY_IPv6_REMOTE_TUNNEL_ENDPOINT_ADDR" .... If the FreeBSD system will route IPv6 packets between the rest of the network and the world, enable the gateway using this line: [.programlisting] .... ipv6_gateway_enable="YES" .... === Router Advertisement and Host Auto Configuration This section demonstrates how to setup man:rtadvd[8] to advertise the IPv6 default route. To enable man:rtadvd[8], add the following to [.filename]#/etc/rc.conf#: [.programlisting] .... rtadvd_enable="YES" .... It is important to specify the interface on which to do IPv6 router advertisement. For example, to tell man:rtadvd[8] to use [.filename]#rl0#: [.programlisting] .... rtadvd_interfaces="rl0" .... Next, create the configuration file, [.filename]#/etc/rtadvd.conf# as seen in this example: [.programlisting] .... rl0:\ :addrs#1:addr="2001:db8:1f11:246::":prefixlen#64:tc=ether: .... Replace [.filename]#rl0# with the interface to be used and `2001:db8:1f11:246::` with the prefix of the allocation. For a dedicated `/64` subnet, nothing else needs to be changed. Otherwise, change the `prefixlen#` to the correct value. === IPv6 and IPv6 Address Mapping When IPv6 is enabled on a server, there may be a need to enable IPv4 mapped IPv6 address communication. This compatibility option allows for IPv4 addresses to be represented as IPv6 addresses. Permitting IPv6 applications to communicate with IPv4 and vice versa may be a security issue. This option may not be required in most cases and is available only for compatibility. This option will allow IPv6-only applications to work with IPv4 in a dual stack environment. This is most useful for third party applications which may not support an IPv6-only environment. To enable this feature, add the following to [.filename]#/etc/rc.conf#: [.programlisting] .... ipv6_ipv4mapping="YES" .... Reviewing the information in RFC 3493, section 3.6 and 3.7 as well as RFC 4038 section 4.2 may be useful to some administrators. [[carp]] == Common Address Redundancy Protocol (CARP) The Common Address Redundancy Protocol (CARP) allows multiple hosts to share the same IP address and Virtual Host ID (VHID) in order to provide _high availability_ for one or more services. This means that one or more hosts can fail, and the other hosts will transparently take over so that users do not see a service failure. In addition to the shared IP address, each host has its own IP address for management and configuration. All of the machines that share an IP address have the same VHID. The VHID for each virtual IP address must be unique across the broadcast domain of the network interface. High availability using CARP is built into FreeBSD, though the steps to configure it vary slightly depending upon the FreeBSD version. This section provides the same example configuration for versions before and equal to or after FreeBSD 10. This example configures failover support with three hosts, all with unique IP addresses, but providing the same web content. It has two different masters named `hosta.example.org` and `hostb.example.org`, with a shared backup named `hostc.example.org`. These machines are load balanced with a Round Robin DNS configuration. The master and backup machines are configured identically except for their hostnames and management IP addresses. These servers must have the same configuration and run the same services. When the failover occurs, requests to the service on the shared IP address can only be answered correctly if the backup server has access to the same content. The backup machine has two additional CARP interfaces, one for each of the master content server's IP addresses. When a failure occurs, the backup server will pick up the failed master machine's IP address. [[carp-10x]] === Using CARP on FreeBSD 10 and Later Enable boot-time support for CARP by adding an entry for the [.filename]#carp.ko# kernel module in [.filename]#/boot/loader.conf#: [.programlisting] .... carp_load="YES" .... To load the module now without rebooting: [source,shell] .... # kldload carp .... For users who prefer to use a custom kernel, include the following line in the custom kernel configuration file and compile the kernel as described in crossref:kernelconfig[kernelconfig,Configuring the FreeBSD Kernel]: [.programlisting] .... device carp .... The hostname, management IP address and subnet mask, shared IP address, and VHID are all set by adding entries to [.filename]#/etc/rc.conf#. This example is for `hosta.example.org`: [.programlisting] .... hostname="hosta.example.org" ifconfig_em0="inet 192.168.1.3 netmask 255.255.255.0" ifconfig_em0_alias0="inet vhid 1 pass testpass alias 192.168.1.50/32" .... The next set of entries are for `hostb.example.org`. Since it represents a second master, it uses a different shared IP address and VHID. However, the passwords specified with `pass` must be identical as CARP will only listen to and accept advertisements from machines with the correct password. [.programlisting] .... hostname="hostb.example.org" ifconfig_em0="inet 192.168.1.4 netmask 255.255.255.0" ifconfig_em0_alias0="inet vhid 2 pass testpass alias 192.168.1.51/32" .... The third machine, `hostc.example.org`, is configured to handle failover from either master. This machine is configured with two CARPVHIDs, one to handle the virtual IP address for each of the master hosts. The CARP advertising skew, `advskew`, is set to ensure that the backup host advertises later than the master, since `advskew` controls the order of precedence when there are multiple backup servers. [.programlisting] .... hostname="hostc.example.org" ifconfig_em0="inet 192.168.1.5 netmask 255.255.255.0" ifconfig_em0_alias0="inet vhid 1 advskew 100 pass testpass alias 192.168.1.50/32" ifconfig_em0_alias1="inet vhid 2 advskew 100 pass testpass alias 192.168.1.51/32" .... Having two CARPVHIDs configured means that `hostc.example.org` will notice if either of the master servers becomes unavailable. If a master fails to advertise before the backup server, the backup server will pick up the shared IP address until the master becomes available again. [NOTE] ==== If the original master server becomes available again, `hostc.example.org` will not release the virtual IP address back to it automatically. For this to happen, preemption has to be enabled. The feature is disabled by default, it is controlled via the man:sysctl[8] variable `net.inet.carp.preempt`. The administrator can force the backup server to return the IP address to the master: [source,shell] .... # ifconfig em0 vhid 1 state backup .... ==== Once the configuration is complete, either restart networking or reboot each system. High availability is now enabled. CARP functionality can be controlled via several man:sysctl[8] variables documented in the man:carp[4] manual pages. Other actions can be triggered from CARP events by using man:devd[8]. [[carp-9x]] === Using CARP on FreeBSD 9 and Earlier The configuration for these versions of FreeBSD is similar to the one described in the previous section, except that a CARP device must first be created and referred to in the configuration. Enable boot-time support for CARP by loading the [.filename]#if_carp.ko# kernel module in [.filename]#/boot/loader.conf#: [.programlisting] .... if_carp_load="YES" .... To load the module now without rebooting: [source,shell] .... # kldload carp .... For users who prefer to use a custom kernel, include the following line in the custom kernel configuration file and compile the kernel as described in crossref:kernelconfig[kernelconfig,Configuring the FreeBSD Kernel]: [.programlisting] .... device carp .... Next, on each host, create a CARP device: [source,shell] .... # ifconfig carp0 create .... Set the hostname, management IP address, the shared IP address, and VHID by adding the required lines to [.filename]#/etc/rc.conf#. Since a virtual CARP device is used instead of an alias, the actual subnet mask of `/24` is used instead of `/32`. Here are the entries for `hosta.example.org`: [.programlisting] .... hostname="hosta.example.org" ifconfig_fxp0="inet 192.168.1.3 netmask 255.255.255.0" cloned_interfaces="carp0" ifconfig_carp0="vhid 1 pass testpass 192.168.1.50/24" .... On `hostb.example.org`: [.programlisting] .... hostname="hostb.example.org" ifconfig_fxp0="inet 192.168.1.4 netmask 255.255.255.0" cloned_interfaces="carp0" ifconfig_carp0="vhid 2 pass testpass 192.168.1.51/24" .... The third machine, `hostc.example.org`, is configured to handle failover from either of the master hosts: [.programlisting] .... hostname="hostc.example.org" ifconfig_fxp0="inet 192.168.1.5 netmask 255.255.255.0" cloned_interfaces="carp0 carp1" ifconfig_carp0="vhid 1 advskew 100 pass testpass 192.168.1.50/24" ifconfig_carp1="vhid 2 advskew 100 pass testpass 192.168.1.51/24" .... [NOTE] ==== Preemption is disabled in the [.filename]#GENERIC# FreeBSD kernel. If preemption has been enabled with a custom kernel, `hostc.example.org` may not release the IP address back to the original content server. The administrator can force the backup server to return the IP address to the master with the command: [source,shell] .... # ifconfig carp0 down && ifconfig carp0 up .... This should be done on the [.filename]#carp# interface which corresponds to the correct host. ==== Once the configuration is complete, either restart networking or reboot each system. High availability is now enabled. [[network-vlan]] == VLANs VLANs are a way of virtually dividing up a network into many different subnetworks, also referred to as segmenting. Each segment will have its own broadcast domain and be isolated from other VLANs. On FreeBSD, VLANs must be supported by the network card driver. To see which drivers support vlans, refer to the man:vlan[4] manual page. When configuring a VLAN, a couple pieces of information must be known. First, which network interface? Second, what is the VLAN tag? To configure VLANs at run time, with a NIC of `em0` and a VLAN tag of `5` the command would look like this: [source,shell] .... # ifconfig em0.5 create vlan 5 vlandev em0 inet 192.168.20.20/24 .... [NOTE] ==== See how the interface name includes the NIC driver name and the VLAN tag, separated by a period? This is a best practice to make maintaining the VLAN configuration easy when many VLANs are present on a machine. ==== To configure VLANs at boot time, [.filename]#/etc/rc.conf# must be updated. To duplicate the configuration above, the following will need to be added: [.programlisting] .... vlans_em0="5" ifconfig_em0_5="inet 192.168.20.20/24" .... Additional VLANs may be added, by simply adding the tag to the `vlans_em0` field and adding an additional line configuring the network on that VLAN tag's interface. It is useful to assign a symbolic name to an interface so that when the associated hardware is changed, only a few configuration variables need to be updated. For example, security cameras need to be run over VLAN 1 on `em0`. Later, if the `em0` card is replaced with a card that uses the man:ixgb[4] driver, all references to `em0.1` will not have to change to `ixgb0.1`. To configure VLAN `5`, on the NIC `em0`, assign the interface name `cameras`, and assign the interface an IP address of `_192.168.20.20_` with a `24`-bit prefix, use this command: [source,shell] .... # ifconfig em0.5 create vlan 5 vlandev em0 name cameras inet 192.168.20.20/24 .... For an interface named `video`, use the following: [source,shell] .... # ifconfig video.5 create vlan 5 vlandev video name cameras inet 192.168.20.20/24 .... To apply the changes at boot time, add the following lines to [.filename]#/etc/rc.conf#: [.programlisting] .... vlans_video="cameras" create_args_cameras="vlan 5" ifconfig_cameras="inet 192.168.20.20/24" .... diff --git a/documentation/content/en/books/handbook/bibliography/_index.adoc b/documentation/content/en/books/handbook/bibliography/_index.adoc index db52ba4fff..b5373676ae 100644 --- a/documentation/content/en/books/handbook/bibliography/_index.adoc +++ b/documentation/content/en/books/handbook/bibliography/_index.adoc @@ -1,172 +1,173 @@ --- title: Appendix B. Bibliography part: Part V. Appendices prev: books/handbook/mirrors next: books/handbook/eresources description: FreeBSD Handbook Bibliography tags: ["appendix", "bibliography", "handbook", "books", "guides", "security", "periodicals", "journals", "magazines"] showBookMenu: true weight: 40 path: "/books/handbook/" --- [appendix] [[bibliography]] = Bibliography :doctype: book :toc: macro :toclevels: 1 :icons: font :sectnums: :sectnumlevels: 6 :sectnumoffset: B :partnums: :source-highlighter: rouge :experimental: :images-path: books/handbook/bibliography/ ifdef::env-beastie[] ifdef::backend-html5[] :imagesdir: ../../../../images/{images-path} endif::[] ifndef::book[] include::shared/authors.adoc[] include::shared/mirrors.adoc[] include::shared/releases.adoc[] include::shared/attributes/attributes-{{% lang %}}.adoc[] include::shared/{{% lang %}}/teams.adoc[] include::shared/{{% lang %}}/mailing-lists.adoc[] include::shared/{{% lang %}}/urls.adoc[] toc::[] endif::[] ifdef::backend-pdf,backend-epub3[] include::../../../../../shared/asciidoctor.adoc[] endif::[] endif::[] ifndef::env-beastie[] toc::[] include::../../../../../shared/asciidoctor.adoc[] endif::[] While manual pages provide a definitive reference for individual pieces of the FreeBSD operating system, they seldom illustrate how to put the pieces together to make the whole operating system run smoothly. For this, there is no substitute for a good book or users' manual on UNIX(R) system administration. [[bibliography-freebsd]] == Books Specific to FreeBSD International books: * http://jdli.tw.FreeBSD.org/publication/book/freebsd2/index.htm[Using FreeBSD] (in Traditional Chinese), published by http://www.drmaster.com.tw/[Drmaster], 1997. ISBN 9-578-39435-7. * FreeBSD Unleashed (Simplified Chinese translation), published by http://www.hzbook.com/[China Machine Press]. ISBN 7-111-10201-0. * FreeBSD From Scratch Second Edition (in Simplified Chinese), published by China Machine Press. ISBN 7-111-10286-X. * FreeBSD Handbook Second Edition (Simplified Chinese translation), published by http://www.ptpress.com.cn/[Posts & Telecom Press]. ISBN 7-115-10541-3. * FreeBSD & Windows (in Simplified Chinese), published by http://www.tdpress.com/[China Railway Publishing House]. ISBN 7-113-03845-X * FreeBSD Internet Services HOWTO (in Simplified Chinese), published by China Railway Publishing House. ISBN 7-113-03423-3 * FreeBSD (in Japanese), published by CUTT. ISBN 4-906391-22-2 C3055 P2400E. * http://www.shoeisha.com/book/Detail.asp?bid=650[Complete Introduction to FreeBSD] (in Japanese), published by http://www.shoeisha.co.jp/[Shoeisha Co., Ltd]. ISBN 4-88135-473-6 P3600E. * http://www.ascii.co.jp/pb/book1/shinkan/detail/1322785.html[Personal UNIX Starter Kit FreeBSD] (in Japanese), published by http://www.ascii.co.jp/[ASCII]. ISBN 4-7561-1733-3 P3000E. * FreeBSD Handbook (Japanese translation), published by http://www.ascii.co.jp/[ASCII]. ISBN 4-7561-1580-2 P3800E. * FreeBSD mit Methode (in German), published by http://www.cul.de[Computer und Literatur Verlag]/Vertrieb Hanser, 1998. ISBN 3-932311-31-0. * http://www.mitp.de/vmi/mitp/detail/pWert/1343/[FreeBSD de Luxe] (in German), published by http://www.mitp.de[Verlag Modere Industrie], 2003. ISBN 3-8266-1343-0. * http://www.pc.mycom.co.jp/FreeBSD/install-manual.html[FreeBSD Install and Utilization Manual] (in Japanese), published by http://www.pc.mycom.co.jp/[Mainichi Communications Inc.], 1998. ISBN 4-8399-0112-0. * Onno W Purbo, Dodi Maryanto, Syahrial Hubbany, Widjil Widodo _http://maxwell.itb.ac.id/[Building Internet Server with FreeBSD]_ (in Indonesia Language), published by http://www.elexmedia.co.id/[Elex Media Komputindo]. * Absolute BSD: The Ultimate Guide to FreeBSD (Traditional Chinese translation), published by http://www.grandtech.com.tw/[GrandTech Press], 2003. ISBN 986-7944-92-5. * http://www.twbsd.org/cht/book/[The FreeBSD 6.0 Book] (in Traditional Chinese), published by Drmaster, 2006. ISBN 9-575-27878-X. English language books: -* http://www.absoluteFreeBSD.com/[Absolute FreeBSD, 2nd Edition: The Complete Guide to FreeBSD], published by http://www.nostarch.com/[No Starch Press], 2007. ISBN: 978-1-59327-151-0 +* Absolute FreeBSD: The Complete Guide To FreeBSD, Third Edition, published by http://www.nostarch.com/[No Starch Press], 2018. ISBN: 9781593278922 +* The Complete FreeBSD, published by http://www.oreilly.com/[O'Reilly], 2003. ISBN: 0596005164 * http://www.freebsdmall.com/cgi-bin/fm/bsdcomp[The Complete FreeBSD], published by http://www.oreilly.com/[O'Reilly], 2003. ISBN: 0596005164 * http://www.freebsd-corp-net-guide.com/[The FreeBSD Corporate Networker's Guide], published by http://www.awl.com/aw/[Addison-Wesley], 2000. ISBN: 0201704811 -* http://andrsn.stanford.edu/FreeBSD/introbook/[FreeBSD: An Open-Source Operating System for Your Personal Computer], published by The Bit Tree Press, 2001. ISBN: 0971204500 +* FreeBSD: An Open-Source Operating System for Your Personal Computer, published by The Bit Tree Press, 2001. ISBN: 0971204500 * Teach Yourself FreeBSD in 24 Hours, published by http://www.samspublishing.com/[Sams], 2002. ISBN: 0672324245 * FreeBSD 6 Unleashed, published by http://www.samspublishing.com/[Sams], 2006. ISBN: 0672328755 * FreeBSD: The Complete Reference, published by http://books.mcgraw-hill.com[McGrawHill], 2003. ISBN: 0072224096 [[bibliography-userguides]] == Users' Guides * Ohio State University has written a http://www.cs.duke.edu/csl/docs/unix_course/[UNIX Introductory Course] which is available online in HTML and PostScript format. + An Italian https://www.FreeBSD.org/doc/it_IT.ISO8859-15/books/unix-introduction/[translation] of this document is available as part of the FreeBSD Italian Documentation Project. * http://www.jp.FreeBSD.org/[Jpman Project, Japan FreeBSD Users Group]. FreeBSD User's Reference Manual (Japanese translation). http://www.pc.mycom.co.jp/[Mainichi Communications Inc.], 1998. ISBN4-8399-0088-4 P3800E. * http://www.ed.ac.uk/[Edinburgh University] has written an http://www.ed.ac.uk/information-services/help-consultancy/is-skills/catalogue/program-op-sys-catalogue/unix1[Online Guide] for newcomers to the UNIX environment. [[bibliography-adminguides]] == Administrators' Guides * http://www.jp.FreeBSD.org/[Jpman Project, Japan FreeBSD Users Group]. FreeBSD System Administrator's Manual (Japanese translation). http://www.pc.mycom.co.jp/[Mainichi Communications Inc.], 1998. ISBN4-8399-0109-0 P3300E. * Dreyfus, Emmanuel. http://www.eyrolles.com/Informatique/Livre/9782212114638/[Cahiers de l'Admin: BSD] 2nd Ed. (in French), Eyrolles, 2004. ISBN 2-212-11463-X [[bibliography-programmers]] == Programmers' Guides * Computer Systems Research Group, UC Berkeley. _4.4BSD Programmer's Reference Manual_. O'Reilly & Associates, Inc., 1994. ISBN 1-56592-078-3 * Computer Systems Research Group, UC Berkeley. _4.4BSD Programmer's Supplementary Documents_. O'Reilly & Associates, Inc., 1994. ISBN 1-56592-079-1 * Harbison, Samuel P. and Steele, Guy L. Jr. _C: A Reference Manual_. 4th Ed. Prentice Hall, 1995. ISBN 0-13-326224-3 * Kernighan, Brian and Dennis M. Ritchie. _The C Programming Language_. 2nd Ed. PTR Prentice Hall, 1988. ISBN 0-13-110362-8 * Lehey, Greg. _Porting UNIX Software_. O'Reilly & Associates, Inc., 1995. ISBN 1-56592-126-7 * Plauger, P. J. _The Standard C Library_. Prentice Hall, 1992. ISBN 0-13-131509-9 * Spinellis, Diomidis. http://www.spinellis.gr/codereading/[Code Reading: The Open Source Perspective]. Addison-Wesley, 2003. ISBN 0-201-79940-5 * Spinellis, Diomidis. http://www.spinellis.gr/codequality/[Code Quality: The Open Source Perspective]. Addison-Wesley, 2006. ISBN 0-321-16607-8 * Stevens, W. Richard and Stephen A. Rago. _Advanced Programming in the UNIX Environment_. 2nd Ed. Reading, Mass. : Addison-Wesley, 2005. ISBN 0-201-43307-9 * Stevens, W. Richard. _UNIX Network Programming_. 2nd Ed, PTR Prentice Hall, 1998. ISBN 0-13-490012-X [[bibliography-osinternals]] == Operating System Internals * Andleigh, Prabhat K. _UNIX System Architecture_. Prentice-Hall, Inc., 1990. ISBN 0-13-949843-5 * Jolitz, William. "Porting UNIX to the 386". _Dr. Dobb's Journal_. January 1991-July 1992. * Leffler, Samuel J., Marshall Kirk McKusick, Michael J Karels and John Quarterman _The Design and Implementation of the 4.3BSD UNIX Operating System_. Reading, Mass. : Addison-Wesley, 1989. ISBN 0-201-06196-1 * Leffler, Samuel J., Marshall Kirk McKusick, _The Design and Implementation of the 4.3BSD UNIX Operating System: Answer Book_. Reading, Mass. : Addison-Wesley, 1991. ISBN 0-201-54629-9 * McKusick, Marshall Kirk, Keith Bostic, Michael J Karels, and John Quarterman. _The Design and Implementation of the 4.4BSD Operating System_. Reading, Mass. : Addison-Wesley, 1996. ISBN 0-201-54979-4 + (Chapter 2 of this book is available extref:{design-44bsd}[online] as part of the FreeBSD Documentation Project.) * Marshall Kirk McKusick, George V. Neville-Neil _The Design and Implementation of the FreeBSD Operating System_. Boston, Mass. : Addison-Wesley, 2004. ISBN 0-201-70245-2 * Marshall Kirk McKusick, George V. Neville-Neil, Robert N. M. Watson _The Design and Implementation of the FreeBSD Operating System, 2nd Ed._. Westford, Mass. : Pearson Education, Inc., 2014. ISBN 0-321-96897-2 * Stevens, W. Richard. _TCP/IP Illustrated, Volume 1: The Protocols_. Reading, Mass. : Addison-Wesley, 1996. ISBN 0-201-63346-9 * Schimmel, Curt. _Unix Systems for Modern Architectures_. Reading, Mass. : Addison-Wesley, 1994. ISBN 0-201-63338-8 * Stevens, W. Richard. _TCP/IP Illustrated, Volume 3: TCP for Transactions, HTTP, NNTP and the UNIX Domain Protocols_. Reading, Mass. : Addison-Wesley, 1996. ISBN 0-201-63495-3 * Vahalia, Uresh. _UNIX Internals -- The New Frontiers_. Prentice Hall, 1996. ISBN 0-13-101908-2 * Wright, Gary R. and W. Richard Stevens. _TCP/IP Illustrated, Volume 2: The Implementation_. Reading, Mass. : Addison-Wesley, 1995. ISBN 0-201-63354-X [[bibliography-security]] == Security Reference * Cheswick, William R. and Steven M. Bellovin. _Firewalls and Internet Security: Repelling the Wily Hacker_. Reading, Mass. : Addison-Wesley, 1995. ISBN 0-201-63357-4 * Garfinkel, Simson. _PGP Pretty Good Privacy_ O'Reilly & Associates, Inc., 1995. ISBN 1-56592-098-8 [[bibliography-hardware]] == Hardware Reference * Anderson, Don and Tom Shanley. _Pentium Processor System Architecture_. 2nd Ed. Reading, Mass. : Addison-Wesley, 1995. ISBN 0-201-40992-5 * Ferraro, Richard F. _Programmer's Guide to the EGA, VGA, and Super VGA Cards_. 3rd ed. Reading, Mass. : Addison-Wesley, 1995. ISBN 0-201-62490-7 * Intel Corporation publishes documentation on their CPUs, chipsets and standards on their http://developer.intel.com/[developer web site], usually as PDF files. * Shanley, Tom. _80486 System Architecture_. 3rd Ed. Reading, Mass. : Addison-Wesley, 1995. ISBN 0-201-40994-1 * Shanley, Tom. _ISA System Architecture_. 3rd Ed. Reading, Mass. : Addison-Wesley, 1995. ISBN 0-201-40996-8 * Shanley, Tom. _PCI System Architecture_. 4th Ed. Reading, Mass. : Addison-Wesley, 1999. ISBN 0-201-30974-2 * Van Gilluwe, Frank. _The Undocumented PC_, 2nd Ed. Reading, Mass: Addison-Wesley Pub. Co., 1996. ISBN 0-201-47950-8 * Messmer, Hans-Peter. _The Indispensable PC Hardware Book_, 4th Ed. Reading, Mass : Addison-Wesley Pub. Co., 2002. ISBN 0-201-59616-4 [[bibliography-history]] == UNIX(R) History * Lion, John _Lion's Commentary on UNIX, 6th Ed. With Source Code_. ITP Media Group, 1996. ISBN 1573980137 * Raymond, Eric S. _The New Hacker's Dictionary, 3rd edition_. MIT Press, 1996. ISBN 0-262-68092-0. Also known as the http://www.catb.org/~esr/jargon/html/index.html[Jargon File] * Salus, Peter H. _A quarter century of UNIX_. Addison-Wesley Publishing Company, Inc., 1994. ISBN 0-201-54777-5 * Simon Garfinkel, Daniel Weise, Steven Strassmann. _The UNIX-HATERS Handbook_. IDG Books Worldwide, Inc., 1994. ISBN 1-56884-203-1. Out of print, but available http://www.simson.net/ref/ugh.pdf[online]. * Don Libes, Sandy Ressler _Life with UNIX_ - special edition. Prentice-Hall, Inc., 1989. ISBN 0-13-536657-7 * _The BSD family tree_. https://cgit.freebsd.org/src/tree/share/misc/bsd-family-tree[https://cgit.freebsd.org/src/tree/share/misc/bsd-family-tree] or link:file://localhost/usr/share/misc/bsd-family-tree[/usr/share/misc/bsd-family-tree] on a FreeBSD machine. * _Networked Computer Science Technical Reports Library_. * _Old BSD releases from the Computer Systems Research group (CSRG)_. http://www.mckusick.com/csrg/[http://www.mckusick.com/csrg/]: The 4CD set covers all BSD versions from 1BSD to 4.4BSD and 4.4BSD-Lite2 (but not 2.11BSD, unfortunately). The last disk also holds the final sources plus the SCCS files. * Kernighan, Brian _Unix: A History and a Memoir_. Kindle Direct Publishing, 2020. ISBN 978-169597855-3 [[bibliography-journals]] == Periodicals, Journals, and Magazines * http://www.admin-magazin.de/[Admin Magazin] (in German), published by Medialinx AG. ISSN: 2190-1066 * http://www.bsdmag.org/[BSD Magazine], published by Software Press Sp. z o.o. SK. ISSN: 1898-9144 * http://www.bsdnow.tv/[BSD Now - Video Podcast], published by Jupiter Broadcasting LLC * http://bsdtalk.blogspot.com/[BSD Talk Podcast], by Will Backman * http://freebsdjournal.com/[FreeBSD Journal], published by S&W Publishing, sponsored by The FreeBSD Foundation. ISBN: 978-0-615-88479-0 diff --git a/documentation/content/en/books/handbook/firewalls/_index.adoc b/documentation/content/en/books/handbook/firewalls/_index.adoc index ec3bc64543..0d77039b67 100644 --- a/documentation/content/en/books/handbook/firewalls/_index.adoc +++ b/documentation/content/en/books/handbook/firewalls/_index.adoc @@ -1,2685 +1,2690 @@ --- title: Chapter 31. Firewalls part: IV. Network Communication prev: books/handbook/network-servers next: books/handbook/advanced-networking description: "FreeBSD has three firewalls built into the base system: PF, IPFW, and IPFILTER. This chapter covers how to define packet filtering rules, the differences between the firewalls built into FreeBSD and how to use them" tags: ["firewall", "pf", "ipfw", "ipfilter", "blacklistd", "filtering"] showBookMenu: true weight: 36 path: "/books/handbook/" --- [[firewalls]] = Firewalls :doctype: book :toc: macro :toclevels: 1 :icons: font :sectnums: :sectnumlevels: 6 :sectnumoffset: 31 :partnums: :source-highlighter: rouge :experimental: :images-path: books/handbook/firewalls/ ifdef::env-beastie[] ifdef::backend-html5[] :imagesdir: ../../../../images/{images-path} endif::[] ifndef::book[] include::shared/authors.adoc[] include::shared/mirrors.adoc[] include::shared/releases.adoc[] include::shared/attributes/attributes-{{% lang %}}.adoc[] include::shared/{{% lang %}}/teams.adoc[] include::shared/{{% lang %}}/mailing-lists.adoc[] include::shared/{{% lang %}}/urls.adoc[] toc::[] endif::[] ifdef::backend-pdf,backend-epub3[] include::../../../../../shared/asciidoctor.adoc[] endif::[] endif::[] ifndef::env-beastie[] toc::[] include::../../../../../shared/asciidoctor.adoc[] endif::[] [[firewalls-intro]] == Synopsis Firewalls make it possible to filter the incoming and outgoing traffic that flows through a system. A firewall can use one or more sets of "rules" to inspect network packets as they come in or go out of network connections and either allows the traffic through or blocks it. The rules of a firewall can inspect one or more characteristics of the packets such as the protocol type, source or destination host address, and source or destination port. Firewalls can enhance the security of a host or a network. They can be used to do one or more of the following: * Protect and insulate the applications, services, and machines of an internal network from unwanted traffic from the public Internet. * Limit or disable access from hosts of the internal network to services of the public Internet. * Support network address translation (NAT), which allows an internal network to use private IP addresses and share a single connection to the public Internet using either a single IP address or a shared pool of automatically assigned public addresses. FreeBSD has three firewalls built into the base system: PF, IPFW, and IPFILTER, also known as IPF. FreeBSD also provides two traffic shapers for controlling bandwidth usage: man:altq[4] and man:dummynet[4]. ALTQ has traditionally been closely tied with PF and dummynet with IPFW. Each firewall uses rules to control the access of packets to and from a FreeBSD system, although they go about it in different ways and each has a different rule syntax. FreeBSD provides multiple firewalls in order to meet the different requirements and preferences for a wide variety of users. Each user should evaluate which firewall best meets their needs. After reading this chapter, you will know: * How to define packet filtering rules. * The differences between the firewalls built into FreeBSD. * How to use and configure the PF firewall. * How to use and configure the IPFW firewall. * How to use and configure the IPFILTER firewall. Before reading this chapter, you should: * Understand basic FreeBSD and Internet concepts. [NOTE] ==== Since all firewalls are based on inspecting the values of selected packet control fields, the creator of the firewall ruleset must have an understanding of how TCP/IP works, what the different values in the packet control fields are, and how these values are used in a normal session conversation. For a good introduction, refer to http://www.ipprimer.com[Daryl's TCP/IP Primer]. ==== [[firewalls-concepts]] == Firewall Concepts A ruleset contains a group of rules which pass or block packets based on the values contained in the packet. The bi-directional exchange of packets between hosts comprises a session conversation. The firewall ruleset processes both the packets arriving from the public Internet, as well as the packets produced by the system as a response to them. Each TCP/IP service is predefined by its protocol and listening port. Packets destined for a specific service originate from the source address using an unprivileged port and target the specific service port on the destination address. All the above parameters can be used as selection criteria to create rules which will pass or block services. To lookup unknown port numbers, refer to [.filename]#/etc/services#. Alternatively, visit http://en.wikipedia.org/wiki/List_of_TCP_and_UDP_port_numbers[http://en.wikipedia.org/wiki/List_of_TCP_and_UDP_port_numbers] and do a port number lookup to find the purpose of a particular port number. Check out this link for http://web.archive.org/web/20150803024617/http://www.sans.org/security-resources/idfaq/oddports.php[port numbers used by Trojans]. FTP has two modes: active mode and passive mode. The difference is in how the data channel is acquired. Passive mode is more secure as the data channel is acquired by the ordinal ftp session requester. For a good explanation of FTP and the different modes, see http://www.slacksite.com/other/ftp.html[http://www.slacksite.com/other/ftp.html]. A firewall ruleset can be either "exclusive" or "inclusive". An exclusive firewall allows all traffic through except for the traffic matching the ruleset. An inclusive firewall does the reverse as it only allows traffic matching the rules through and blocks everything else. An inclusive firewall offers better control of the outgoing traffic, making it a better choice for systems that offer services to the public Internet. It also controls the type of traffic originating from the public Internet that can gain access to a private network. All traffic that does not match the rules is blocked and logged. Inclusive firewalls are generally safer than exclusive firewalls because they significantly reduce the risk of allowing unwanted traffic. [NOTE] ==== Unless noted otherwise, all configuration and example rulesets in this chapter create inclusive firewall rulesets. ==== Security can be tightened further using a "stateful firewall". This type of firewall keeps track of open connections and only allows traffic which either matches an existing connection or opens a new, allowed connection. Stateful filtering treats traffic as a bi-directional exchange of packets comprising a session. When state is specified on a matching rule the firewall dynamically generates internal rules for each anticipated packet being exchanged during the session. It has sufficient matching capabilities to determine if a packet is valid for a session. Any packets that do not properly fit the session template are automatically rejected. When the session completes, it is removed from the dynamic state table. Stateful filtering allows one to focus on blocking/passing new sessions. If the new session is passed, all its subsequent packets are allowed automatically and any impostor packets are automatically rejected. If a new session is blocked, none of its subsequent packets are allowed. Stateful filtering provides advanced matching abilities capable of defending against the flood of different attack methods employed by attackers. NAT stands for _Network Address Translation_. NAT function enables the private LAN behind the firewall to share a single ISP-assigned IP address, even if that address is dynamically assigned. NAT allows each computer in the LAN to have Internet access, without having to pay the ISP for multiple Internet accounts or IP addresses. NAT will automatically translate the private LAN IP address for each system on the LAN to the single public IP address as packets exit the firewall bound for the public Internet. It also performs the reverse translation for returning packets. According to RFC 1918, the following IP address ranges are reserved for private networks which will never be routed directly to the public Internet, and therefore are available for use with NAT: * `10.0.0.0/8`. * `172.16.0.0/12`. * `192.168.0.0/16`. [WARNING] ==== When working with the firewall rules, be _very careful_. Some configurations _can lock the administrator out_ of the server. To be on the safe side, consider performing the initial firewall configuration from the local console rather than doing it remotely over ssh. ==== [[firewalls-pf]] == PF Since FreeBSD 5.3, a ported version of OpenBSD's PF firewall has been included as an integrated part of the base system. PF is a complete, full-featured firewall that has optional support for ALTQ (Alternate Queuing), which provides Quality of Service (QoS). The OpenBSD Project maintains the definitive reference for PF in the http://www.openbsd.org/faq/pf/[PF FAQ]. Peter Hansteen maintains a thorough PF tutorial at http://home.nuug.no/\~peter/pf/[http://home.nuug.no/~peter/pf/]. [WARNING] ==== When reading the http://www.openbsd.org/faq/pf/[PF FAQ], keep in mind that FreeBSD's version of PF has diverged substantially from the upstream OpenBSD version over the years. Not all features work the same way on FreeBSD as they do in OpenBSD and vice versa. ==== The {freebsd-pf} is a good place to ask questions about configuring and running the PF firewall. Check the mailing list archives before asking a question as it may have already been answered. This section of the Handbook focuses on PF as it pertains to FreeBSD. It demonstrates how to enable PF and ALTQ. It also provides several examples for creating rulesets on a FreeBSD system. === Enabling PF To use PF, its kernel module must be first loaded. This section describes the entries that can be added to [.filename]#/etc/rc.conf# to enable PF. Start by adding `pf_enable=yes` to [.filename]#/etc/rc.conf#: [source,shell] .... # sysrc pf_enable=yes .... Additional options, described in man:pfctl[8], can be passed to PF when it is started. Add or change this entry in [.filename]#/etc/rc.conf# and specify any required flags between the two quotes (`""`): [.programlisting] .... pf_flags="" # additional flags for pfctl startup .... PF will not start if it cannot find its ruleset configuration file. By default, FreeBSD does not ship with a ruleset and there is no [.filename]#/etc/pf.conf#. Example rulesets can be found in [.filename]#/usr/share/examples/pf/#. If a custom ruleset has been saved somewhere else, add a line to [.filename]#/etc/rc.conf# which specifies the full path to the file: [.programlisting] .... pf_rules="/path/to/pf.conf" .... Logging support for PF is provided by man:pflog[4]. To enable logging support, add `pflog_enable=yes` to [.filename]#/etc/rc.conf#: [source,shell] .... # sysrc pflog_enable=yes .... The following lines can also be added to change the default location of the log file or to specify any additional flags to pass to man:pflog[4] when it is started: [.programlisting] .... pflog_logfile="/var/log/pflog" # where pflogd should store the logfile pflog_flags="" # additional flags for pflogd startup .... Finally, if there is a LAN behind the firewall and packets need to be forwarded for the computers on the LAN, or NAT is required, enable the following option: [.programlisting] .... gateway_enable="YES" # Enable as LAN gateway .... After saving the needed edits, PF can be started with logging support by typing: [source,shell] .... # service pf start # service pflog start .... By default, PF reads its configuration rules from [.filename]#/etc/pf.conf# and modifies, drops, or passes packets according to the rules or definitions specified in this file. The FreeBSD installation includes several sample files located in [.filename]#/usr/share/examples/pf/#. Refer to the http://www.openbsd.org/faq/pf/[PF FAQ] for complete coverage of PF rulesets. To control PF, use `pfctl`. <> summarizes some useful options to this command. Refer to man:pfctl[8] for a description of all available options: [[pfctl]] .Useful `pfctl` Options [cols="1,1", frame="none", options="header"] |=== | Command | Purpose |`pfctl -e` |Enable PF. |`pfctl -d` |Disable PF. |`pfctl -F all -f /etc/pf.conf` |Flush all NAT, filter, state, and table rules and reload [.filename]#/etc/pf.conf#. |`pfctl -s [ rules \| nat \| states ]` |Report on the filter rules, NAT rules, or state table. |`pfctl -vnf /etc/pf.conf` |Check [.filename]#/etc/pf.conf# for errors, but do not load ruleset. |=== [TIP] ==== package:security/sudo[] is useful for running commands like `pfctl` that require elevated privileges. It can be installed from the Ports Collection. ==== To keep an eye on the traffic that passes through the PF firewall, consider installing the package:sysutils/pftop[] package or port. Once installed, pftop can be run to view a running snapshot of traffic in a format which is similar to man:top[1]. [[pf-tutorial]] === PF Rulesets This section demonstrates how to create a customized ruleset. It starts with the simplest of rulesets and builds upon its concepts using several examples to demonstrate real-world usage of PF's many features. The simplest possible ruleset is for a single machine that does not run any services and which needs access to one network, which may be the Internet. To create this minimal ruleset, edit [.filename]#/etc/pf.conf# so it looks like this: [.programlisting] .... block in all pass out all keep state .... The first rule denies all incoming traffic by default. The second rule allows connections created by this system to pass out, while retaining state information on those connections. This state information allows return traffic for those connections to pass back and should only be used on machines that can be trusted. The ruleset can be loaded with: [source,shell] .... # pfctl -e ; pfctl -f /etc/pf.conf .... In addition to keeping state, PF provides _lists_ and _macros_ which can be defined for use when creating rules. Macros can include lists and need to be defined before use. As an example, insert these lines at the very top of the ruleset: [.programlisting] .... tcp_services = "{ ssh, smtp, domain, www, pop3, auth, pop3s }" udp_services = "{ domain }" .... PF understands port names as well as port numbers, as long as the names are listed in [.filename]#/etc/services#. This example creates two macros. The first is a list of seven TCP port names and the second is one UDP port name. Once defined, macros can be used in rules. In this example, all traffic is blocked except for the connections initiated by this system for the seven specified TCP services and the one specified UDP service: [.programlisting] .... tcp_services = "{ ssh, smtp, domain, www, pop3, auth, pop3s }" udp_services = "{ domain }" block all pass out proto tcp to any port $tcp_services keep state pass proto udp to any port $udp_services keep state .... Even though UDP is considered to be a stateless protocol, PF is able to track some state information. For example, when a UDP request is passed which asks a name server about a domain name, PF will watch for the response to pass it back. Whenever an edit is made to a ruleset, the new rules must be loaded so they can be used: [source,shell] .... # pfctl -f /etc/pf.conf .... If there are no syntax errors, `pfctl` will not output any messages during the rule load. Rules can also be tested before attempting to load them: [source,shell] .... # pfctl -nf /etc/pf.conf .... Including `-n` causes the rules to be interpreted only, but not loaded. This provides an opportunity to correct any errors. At all times, the last valid ruleset loaded will be enforced until either PF is disabled or a new ruleset is loaded. [TIP] ==== Adding `-v` to a `pfctl` ruleset verify or load will display the fully parsed rules exactly the way they will be loaded. This is extremely useful when debugging rules. ==== [[pftut-gateway]] ==== A Simple Gateway with NAT This section demonstrates how to configure a FreeBSD system running PF to act as a gateway for at least one other machine. The gateway needs at least two network interfaces, each connected to a separate network. In this example, [.filename]#xl0# is connected to the Internet and [.filename]#xl1# is connected to the internal network. First, enable the gateway to let the machine forward the network traffic it receives on one interface to another interface. This sysctl setting will forward IPv4 packets: [source,shell] .... # sysctl net.inet.ip.forwarding=1 .... To forward IPv6 traffic, use: [source,shell] .... # sysctl net.inet6.ip6.forwarding=1 .... To enable these settings at system boot, use man:sysrc[8] to add them to [.filename]#/etc/rc.conf#: [source,shell] .... # sysrc gateway_enable=yes # sysrc ipv6_gateway_enable=yes .... Verify with `ifconfig` that both of the interfaces are up and running. Next, create the PF rules to allow the gateway to pass traffic. While the following rule allows stateful traffic from hosts of the internal network to pass to the gateway, the `to` keyword does not guarantee passage all the way from source to destination: [.programlisting] .... pass in on xl1 from xl1:network to xl0:network port $ports keep state .... That rule only lets the traffic pass in to the gateway on the internal interface. To let the packets go further, a matching rule is needed: [.programlisting] .... pass out on xl0 from xl1:network to xl0:network port $ports keep state .... While these two rules will work, rules this specific are rarely needed. For a busy network admin, a readable ruleset is a safer ruleset. The remainder of this section demonstrates how to keep the rules as simple as possible for readability. For example, those two rules could be replaced with one rule: [.programlisting] .... pass from xl1:network to any port $ports keep state .... The `interface:network` notation can be replaced with a macro to make the ruleset even more readable. For example, a `$localnet` macro could be defined as the network directly attached to the internal interface (`$xl1:network`). Alternatively, the definition of `$localnet` could be changed to an _IP address/netmask_ notation to denote a network, such as `192.168.100.1/24` for a subnet of private addresses. If required, `$localnet` could even be defined as a list of networks. Whatever the specific needs, a sensible `$localnet` definition could be used in a typical pass rule as follows: [.programlisting] .... pass from $localnet to any port $ports keep state .... The following sample ruleset allows all traffic initiated by machines on the internal network. It first defines two macros to represent the external and internal 3COM interfaces of the gateway. [NOTE] ==== For dialup users, the external interface will use [.filename]#tun0#. For an ADSL connection, specifically those using PPP over Ethernet (PPPoE), the correct external interface is [.filename]#tun0#, not the physical Ethernet interface. ==== [.programlisting] .... ext_if = "xl0" # macro for external interface - use tun0 for PPPoE int_if = "xl1" # macro for internal interface localnet = $int_if:network # ext_if IP address could be dynamic, hence ($ext_if) nat on $ext_if from $localnet to any -> ($ext_if) block all pass from { lo0, $localnet } to any keep state .... This ruleset introduces the `nat` rule which is used to handle the network address translation from the non-routable addresses inside the internal network to the IP address assigned to the external interface. The parentheses surrounding the last part of the nat rule `($ext_if)` is included when the IP address of the external interface is dynamically assigned. It ensures that network traffic runs without serious interruptions even if the external IP address changes. Note that this ruleset probably allows more traffic to pass out of the network than is needed. One reasonable setup could create this macro: [.programlisting] .... client_out = "{ ftp-data, ftp, ssh, domain, pop3, auth, nntp, http, \ https, cvspserver, 2628, 5999, 8000, 8080 }" .... to use in the main pass rule: [.programlisting] .... pass inet proto tcp from $localnet to any port $client_out \ flags S/SA keep state .... A few other pass rules may be needed. This one enables SSH on the external interface: [.programlisting] .... pass in inet proto tcp to $ext_if port ssh .... This macro definition and rule allows DNS and NTP for internal clients: [.programlisting] .... udp_services = "{ domain, ntp }" pass quick inet proto { tcp, udp } to any port $udp_services keep state .... Note the `quick` keyword in this rule. Since the ruleset consists of several rules, it is important to understand the relationships between the rules in a ruleset. Rules are evaluated from top to bottom, in the sequence they are written. For each packet or connection evaluated by PF, _the last matching rule_ in the ruleset is the one which is applied. However, when a packet matches a rule which contains the `quick` keyword, the rule processing stops and the packet is treated according to that rule. This is very useful when an exception to the general rules is needed. [[pftut-ftp]] ==== Creating an FTP Proxy Configuring working FTP rules can be problematic due to the nature of the FTP protocol. FTP pre-dates firewalls by several decades and is insecure in its design. The most common points against using FTP include: * Passwords are transferred in the clear. * The protocol demands the use of at least two TCP connections (control and data) on separate ports. * When a session is established, data is communicated using randomly selected ports. -All of these points present security challenges, even before considering any potential security weaknesses in client or server software. -More secure alternatives for file transfer exist, such as man:sftp[1] or man:scp[1], which both feature authentication and data transfer over encrypted connections.. +All of these points present security challenges, even before considering any potential security weaknesses in client or server software. +More secure alternatives for file transfer exist, such as man:sftp[1] or man:scp[1], which both feature authentication and data transfer over encrypted connections. For those situations when FTP is required, PF provides redirection of FTP traffic to a small proxy program called man:ftp-proxy[8], which is included in the base system of FreeBSD. The role of the proxy is to dynamically insert and delete rules in the ruleset, using a set of anchors, to correctly handle FTP traffic. To enable the FTP proxy, add this line to [.filename]#/etc/rc.conf#: [.programlisting] .... ftpproxy_enable="YES" .... -Then start the proxy by running `service ftp-proxy start`. +Then start the proxy by running: + +[source,bash] +.... +# service ftp-proxy start +.... For a basic configuration, three elements need to be added to [.filename]#/etc/pf.conf#. First, the anchors which the proxy will use to insert the rules it generates for the FTP sessions: [.programlisting] .... nat-anchor "ftp-proxy/*" rdr-anchor "ftp-proxy/*" .... Second, a pass rule is needed to allow FTP traffic in to the proxy. Third, redirection and NAT rules need to be defined before the filtering rules. Insert this `rdr` rule immediately after the `nat` rule: [.programlisting] .... rdr pass on $int_if proto tcp from any to any port ftp -> 127.0.0.1 port 8021 .... Finally, allow the redirected traffic to pass: [.programlisting] .... pass out proto tcp from $proxy to any port ftp .... where `$proxy` expands to the address the proxy daemon is bound to. Save [.filename]#/etc/pf.conf#, load the new rules, and verify from a client that FTP connections are working: [source,shell] .... # pfctl -f /etc/pf.conf .... This example covers a basic setup where the clients in the local network need to contact FTP servers elsewhere. This basic configuration should work well with most combinations of FTP clients and servers. As shown in man:ftp-proxy[8], the proxy's behavior can be changed in various ways by adding options to the `ftpproxy_flags=` line. Some clients or servers may have specific quirks that must be compensated for in the configuration, or there may be a need to integrate the proxy in specific ways such as assigning FTP traffic to a specific queue. For ways to run an FTP server protected by PF and man:ftp-proxy[8], configure a separate `ftp-proxy` in reverse mode, using `-R`, on a separate port with its own redirecting pass rule. [[pftut-icmp]] ==== Managing ICMP Many of the tools used for debugging or troubleshooting a TCP/IP network rely on the Internet Control Message Protocol (ICMP), which was designed specifically with debugging in mind. The ICMP protocol sends and receives _control messages_ between hosts and gateways, mainly to provide feedback to a sender about any unusual or difficult conditions enroute to the target host. Routers use ICMP to negotiate packet sizes and other transmission parameters in a process often referred to as _path MTU discovery_. From a firewall perspective, some ICMP control messages are vulnerable to known attack vectors. Also, letting all diagnostic traffic pass unconditionally makes debugging easier, but it also makes it easier for others to extract information about the network. For these reasons, the following rule may not be optimal: [.programlisting] .... pass inet proto icmp from any to any .... One solution is to let all ICMP traffic from the local network through while stopping all probes from outside the network: [.programlisting] .... pass inet proto icmp from $localnet to any keep state pass inet proto icmp from any to $ext_if keep state .... Additional options are available which demonstrate some of PF's flexibility. For example, rather than allowing all ICMP messages, one can specify the messages used by man:ping[8] and man:traceroute[8]. Start by defining a macro for that type of message: [.programlisting] .... icmp_types = "echoreq" .... and a rule which uses the macro: [.programlisting] .... pass inet proto icmp all icmp-type $icmp_types keep state .... If other types of ICMP packets are needed, expand `icmp_types` to a list of those packet types. Type `more /usr/src/sbin/pfctl/pfctl_parser.c` to see the list of ICMP message types supported by PF. Refer to http://www.iana.org/assignments/icmp-parameters/icmp-parameters.xhtml[http://www.iana.org/assignments/icmp-parameters/icmp-parameters.xhtml] for an explanation of each message type. Since Unix `traceroute` uses UDP by default, another rule is needed to allow Unix `traceroute`: [.programlisting] .... # allow out the default range for traceroute(8): pass out on $ext_if inet proto udp from any to any port 33433 >< 33626 keep state .... Since `TRACERT.EXE` on Microsoft Windows systems uses ICMP echo request messages, only the first rule is needed to allow network traces from those systems. Unix `traceroute` can be instructed to use other protocols as well, and will use ICMP echo request messages if `-I` is used. Check the man:traceroute[8] man page for details. [[pftut-pathmtudisc]] ===== Path MTU Discovery Internet protocols are designed to be device independent, and one consequence of device independence is that the optimal packet size for a given connection cannot always be predicted reliably. The main constraint on packet size is the _Maximum Transmission Unit_ (MTU) which sets the upper limit on the packet size for an interface. Type `ifconfig` to view the MTUs for a system's network interfaces. TCP/IP uses a process known as path MTU discovery to determine the right packet size for a connection. This process sends packets of varying sizes with the "Do not fragment" flag set, expecting an ICMP return packet of "type 3, code 4" when the upper limit has been reached. Type 3 means "destination unreachable", and code 4 is short for "fragmentation needed, but the do-not-fragment flag is set". To allow path MTU discovery in order to support connections to other MTUs, add the `destination unreachable` type to the `icmp_types` macro: [.programlisting] .... icmp_types = "{ echoreq, unreach }" .... Since the pass rule already uses that macro, it does not need to be modified to support the new ICMP type: [.programlisting] .... pass inet proto icmp all icmp-type $icmp_types keep state .... PF allows filtering on all variations of ICMP types and codes. The list of possible types and codes are documented in man:icmp[4] and man:icmp6[4]. [[pftut-tables]] ==== Using Tables Some types of data are relevant to filtering and redirection at a given time, but their definition is too long to be included in the ruleset file. PF supports the use of tables, which are defined lists that can be manipulated without needing to reload the entire ruleset, and which can provide fast lookups. Table names are always enclosed within `< >`, like this: [.programlisting] .... table { 192.168.2.0/24, !192.168.2.5 } .... In this example, the `192.168.2.0/24` network is part of the table, except for the address `192.168.2.5`, which is excluded using the `!` operator. It is also possible to load tables from files where each item is on a separate line, as seen in this example [.filename]#/etc/clients#: [.programlisting] .... 192.168.2.0/24 !192.168.2.5 .... To refer to the file, define the table like this: [.programlisting] .... table persist file "/etc/clients" .... Once the table is defined, it can be referenced by a rule: [.programlisting] .... pass inet proto tcp from to any port $client_out flags S/SA keep state .... A table's contents can be manipulated live, using `pfctl`. This example adds another network to the table: [source,shell] .... # pfctl -t clients -T add 192.168.1.0/16 .... Note that any changes made this way will take affect now, making them ideal for testing, but will not survive a power failure or reboot. To make the changes permanent, modify the definition of the table in the ruleset or edit the file that the table refers to. One can maintain the on-disk copy of the table using a man:cron[8] job which dumps the table's contents to disk at regular intervals, using a command such as `pfctl -t clients -T show >/etc/clients`. Alternatively, [.filename]#/etc/clients# can be updated with the in-memory table contents: [source,shell] .... # pfctl -t clients -T replace -f /etc/clients .... [[pftut-overload]] ==== Using Overload Tables to Protect SSH Those who run SSH on an external interface have probably seen something like this in the authentication logs: [.programlisting] .... Sep 26 03:12:34 skapet sshd[25771]: Failed password for root from 200.72.41.31 port 40992 ssh2 Sep 26 03:12:34 skapet sshd[5279]: Failed password for root from 200.72.41.31 port 40992 ssh2 Sep 26 03:12:35 skapet sshd[5279]: Received disconnect from 200.72.41.31: 11: Bye Bye Sep 26 03:12:44 skapet sshd[29635]: Invalid user admin from 200.72.41.31 Sep 26 03:12:44 skapet sshd[24703]: input_userauth_request: invalid user admin Sep 26 03:12:44 skapet sshd[24703]: Failed password for invalid user admin from 200.72.41.31 port 41484 ssh2 .... This is indicative of a brute force attack where somebody or some program is trying to discover the user name and password which will let them into the system. If external SSH access is needed for legitimate users, changing the default port used by SSH can offer some protection. However, PF provides a more elegant solution. Pass rules can contain limits on what connecting hosts can do and violators can be banished to a table of addresses which are denied some or all access. It is even possible to drop all existing connections from machines which overreach the limits. To configure this, create this table in the tables section of the ruleset: [.programlisting] .... table persist .... Then, somewhere early in the ruleset, add rules to block brute access while allowing legitimate access: [.programlisting] .... block quick from pass inet proto tcp from any to $localnet port $tcp_services \ flags S/SA keep state \ (max-src-conn 100, max-src-conn-rate 15/5, \ overload flush global) .... The part in parentheses defines the limits and the numbers should be changed to meet local requirements. It can be read as follows: `max-src-conn` is the number of simultaneous connections allowed from one host. `max-src-conn-rate` is the rate of new connections allowed from any single host (_15_) per number of seconds (_5_). `overload ` means that any host which exceeds these limits gets its address added to the `bruteforce` table. The ruleset blocks all traffic from addresses in the `bruteforce` table. Finally, `flush global` says that when a host reaches the limit, that all (`global`) of that host's connections will be terminated (`flush`). [NOTE] ==== These rules will _not_ block slow bruteforcers, as described in http://home.nuug.no/\~peter/hailmary2013/[http://home.nuug.no/~peter/hailmary2013/]. ==== This example ruleset is intended mainly as an illustration. For example, if a generous number of connections in general are wanted, but the desire is to be more restrictive when it comes to ssh, supplement the rule above with something like the one below, early on in the rule set: [.programlisting] .... pass quick proto { tcp, udp } from any to any port ssh \ flags S/SA keep state \ (max-src-conn 15, max-src-conn-rate 5/3, \ overload flush global) .... [NOTE] ==== *It May Not be Necessary to Block All Overloaders:* + It is worth noting that the overload mechanism is a general technique which does not apply exclusively to SSH, and it is not always optimal to entirely block all traffic from offenders. For example, an overload rule could be used to protect a mail service or a web service, and the overload table could be used in a rule to assign offenders to a queue with a minimal bandwidth allocation or to redirect to a specific web page. ==== Over time, tables will be filled by overload rules and their size will grow incrementally, taking up more memory. Sometimes an IP address that is blocked is a dynamically assigned one, which has since been assigned to a host who has a legitimate reason to communicate with hosts in the local network. For situations like these, pfctl provides the ability to expire table entries. For example, this command will remove `` table entries which have not been referenced for `86400` seconds: [source,shell] .... # pfctl -t bruteforce -T expire 86400 .... Similar functionality is provided by package:security/expiretable[], which removes table entries which have not been accessed for a specified period of time. Once installed, expiretable can be run to remove `` table entries older than a specified age. This example removes all entries older than 24 hours: [.programlisting] .... /usr/local/sbin/expiretable -v -d -t 24h bruteforce .... [[pftut-spamd]] ==== Protecting Against SPAM Not to be confused with the spamd daemon which comes bundled with spamassassin, package:mail/spamd[] can be configured with PF to provide an outer defense against SPAM. This spamd hooks into the PF configuration using a set of redirections. Spammers tend to send a large number of messages, and SPAM is mainly sent from a few spammer friendly networks and a large number of hijacked machines, both of which are reported to _blocklists_ fairly quickly. When an SMTP connection from an address in a blocklist is received, spamd presents its banner and immediately switches to a mode where it answers SMTP traffic one byte at a time. This technique, which is intended to waste as much time as possible on the spammer's end, is called _tarpitting_. The specific implementation which uses one byte SMTP replies is often referred to as _stuttering_. This example demonstrates the basic procedure for setting up spamd with automatically updated blocklists. Refer to the man pages which are installed with package:mail/spamd[] for more information. [.procedure] **** .Procedure: Configuring spamd . Install the package:mail/spamd[] package or port. To use spamd's greylisting features, man:fdescfs[5] must be mounted at [.filename]#/dev/fd#. Add the following line to [.filename]#/etc/fstab#: + [.programlisting] .... fdescfs /dev/fd fdescfs rw 0 0 .... + Then, mount the filesystem: + [.programlisting] .... # mount fdescfs .... . Next, edit the PF ruleset to include: + [.programlisting] .... table persist table persist rdr pass on $ext_if inet proto tcp from to \ { $ext_if, $localnet } port smtp -> 127.0.0.1 port 8025 rdr pass on $ext_if inet proto tcp from ! to \ { $ext_if, $localnet } port smtp -> 127.0.0.1 port 8025 .... + The two tables `` and `` are essential. SMTP traffic from an address listed in `` but not in `` is redirected to the spamd daemon listening at port 8025. . The next step is to configure spamd in [.filename]#/usr/local/etc/spamd.conf# and to add some [.filename]#rc.conf# parameters. + The installation of package:mail/spamd[] includes a sample configuration file ([.filename]#/usr/local/etc/spamd.conf.sample#) and a man page for [.filename]#spamd.conf#. Refer to these for additional configuration options beyond those shown in this example. + One of the first lines in the configuration file that does not begin with a `#` comment sign contains the block which defines the `all` list, which specifies the lists to use: + [.programlisting] .... all:\ :traplist:allowlist: .... + This entry adds the desired blocklists, separated by colons (`:`). To use an allowlist to subtract addresses from a blocklist, add the name of the allowlist _immediately_ after the name of that blocklist. For example: `:blocklist:allowlist:`. + This is followed by the specified blocklist's definition: + [.programlisting] .... traplist:\ :black:\ :msg="SPAM. Your address %A has sent spam within the last 24 hours":\ :method=http:\ :file=www.openbsd.org/spamd/traplist.gz .... + where the first line is the name of the blocklist and the second line specifies the list type. The `msg` field contains the message to display to blocklisted senders during the SMTP dialogue. The `method` field specifies how spamd-setup fetches the list data; supported methods are `http`, `ftp`, from a `file` in a mounted file system, and via `exec` of an external program. Finally, the `file` field specifies the name of the file spamd expects to receive. + The definition of the specified allowlist is similar, but omits the `msg` field since a message is not needed: + [.programlisting] .... allowlist:\ :white:\ :method=file:\ :file=/var/mail/allowlist.txt .... + [TIP] ==== *Choose Data Sources with Care:* + Using all the blocklists in the sample [.filename]#spamd.conf# will block large blocks of the Internet. Administrators need to edit the file to create an optimal configuration which uses applicable data sources and, when necessary, uses custom lists. ==== + Next, add this entry to [.filename]#/etc/rc.conf#. Additional flags are described in the man page specified by the comment: + [.programlisting] .... spamd_flags="-v" # use "" and see spamd-setup(8) for flags .... + When finished, reload the ruleset, start spamd by typing `service obspamd start`, and complete the configuration using `spamd-setup`. Finally, create a man:cron[8] job which calls `spamd-setup` to update the tables at reasonable intervals. **** On a typical gateway in front of a mail server, hosts will soon start getting trapped within a few seconds to several minutes. PF also supports _greylisting_, which temporarily rejects messages from unknown hosts with _45n_ codes. Messages from greylisted hosts which try again within a reasonable time are let through. Traffic from senders which are set up to behave within the limits set by RFC 1123 and RFC 2821 are immediately let through. More information about greylisting as a technique can be found at the http://www.greylisting.org/[greylisting.org] web site. The most amazing thing about greylisting, apart from its simplicity, is that it still works. Spammers and malware writers have been very slow to adapt to bypass this technique. The basic procedure for configuring greylisting is as follows: [.procedure] .Procedure: Configuring Greylisting . Make sure that man:fdescfs[5] is mounted as described in Step 1 of the previous Procedure. . To run spamd in greylisting mode, add this line to [.filename]#/etc/rc.conf#: + [.programlisting] .... spamd_grey="YES" # use spamd greylisting if YES .... + Refer to the spamd man page for descriptions of additional related parameters. . To complete the greylisting setup: + [.programlisting] .... # service obspamd restart # service obspamlogd start .... Behind the scenes, the spamdb database tool and the spamlogd whitelist updater perform essential functions for the greylisting feature. spamdb is the administrator's main interface to managing the block, grey, and allow lists via the contents of the [.filename]#/var/db/spamdb# database. [[pftut-hygiene]] ==== Network Hygiene This section describes how `block-policy`, `scrub`, and `antispoof` can be used to make the ruleset behave sanely. The `block-policy` is an option which can be set in the `options` part of the ruleset, which precedes the redirection and filtering rules. This option determines which feedback, if any, PF sends to hosts that are blocked by a rule. The option has two possible values: `drop` drops blocked packets with no feedback, and `return` returns a status code such as `Connection refused`. If not set, the default policy is `drop`. To change the `block-policy`, specify the desired value: [.programlisting] .... set block-policy return .... In PF, `scrub` is a keyword which enables network packet normalization. This process reassembles fragmented packets and drops TCP packets that have invalid flag combinations. Enabling `scrub` provides a measure of protection against certain kinds of attacks based on incorrect handling of packet fragments. A number of options are available, but the simplest form is suitable for most configurations: [.programlisting] .... scrub in all .... Some services, such as NFS, require specific fragment handling options. Refer to https://home.nuug.no/\~peter/pf/en/scrub.html[https://home.nuug.no/~peter/pf/en/scrub.html] for more information. This example reassembles fragments, clears the "do not fragment" bit, and sets the maximum segment size to 1440 bytes: [.programlisting] .... scrub in all fragment reassemble no-df max-mss 1440 .... The `antispoof` mechanism protects against activity from spoofed or forged IP addresses, mainly by blocking packets appearing on interfaces and in directions which are logically not possible. These rules weed out spoofed traffic coming in from the rest of the world as well as any spoofed packets which originate in the local network: [.programlisting] .... antispoof for $ext_if antispoof for $int_if .... [[pftut-unrouteables]] ==== Handling Non-Routable Addresses Even with a properly configured gateway to handle network address translation, one may have to compensate for other people's misconfigurations. A common misconfiguration is to let traffic with non-routable addresses out to the Internet. Since traffic from non-routeable addresses can play a part in several DoS attack techniques, consider explicitly blocking traffic from non-routeable addresses from entering the network through the external interface. In this example, a macro containing non-routable addresses is defined, then used in blocking rules. Traffic to and from these addresses is quietly dropped on the gateway's external interface. [.programlisting] .... martians = "{ 127.0.0.0/8, 192.168.0.0/16, 172.16.0.0/12, \ 10.0.0.0/8, 169.254.0.0/16, 192.0.2.0/24, \ 0.0.0.0/8, 240.0.0.0/4 }" block drop in quick on $ext_if from $martians to any block drop out quick on $ext_if from any to $martians .... === Enabling ALTQ On FreeBSD, ALTQ can be used with PF to provide Quality of Service (QOS). Once ALTQ is enabled, queues can be defined in the ruleset which determine the processing priority of outbound packets. Before enabling ALTQ, refer to man:altq[4] to determine if the drivers for the network cards installed on the system support it. ALTQ is not available as a loadable kernel module. If the system's interfaces support ALTQ, create a custom kernel using the instructions in crossref:kernelconfig[kernelconfig,Configuring the FreeBSD Kernel]. The following kernel options are available. The first is needed to enable ALTQ. At least one of the other options is necessary to specify the queueing scheduler algorithm: [.programlisting] .... options ALTQ options ALTQ_CBQ # Class Based Queuing (CBQ) options ALTQ_RED # Random Early Detection (RED) options ALTQ_RIO # RED In/Out options ALTQ_HFSC # Hierarchical Packet Scheduler (HFSC) options ALTQ_PRIQ # Priority Queuing (PRIQ) .... The following scheduler algorithms are available: CBQ:: Class Based Queuing (CBQ) is used to divide a connection's bandwidth into different classes or queues to prioritize traffic based on filter rules. RED:: Random Early Detection (RED) is used to avoid network congestion by measuring the length of the queue and comparing it to the minimum and maximum thresholds for the queue. When the queue is over the maximum, all new packets are randomly dropped. RIO:: In Random Early Detection In and Out (RIO) mode, RED maintains multiple average queue lengths and multiple threshold values, one for each QOS level. HFSC:: Hierarchical Fair Service Curve Packet Scheduler (HFSC) is described in http://www-2.cs.cmu.edu/\~hzhang/HFSC/main.html[http://www-2.cs.cmu.edu/~hzhang/HFSC/main.html]. PRIQ:: Priority Queuing (PRIQ) always passes traffic that is in a higher queue first. More information about the scheduling algorithms and example rulesets are available at the https://web.archive.org/web/20151109213426/http://www.openbsd.org/faq/pf/queueing.html[OpenBSD's web archive]. [[firewalls-ipfw]] == IPFW IPFW is a stateful firewall written for FreeBSD which supports both IPv4 and IPv6. It is comprised of several components: the kernel firewall filter rule processor and its integrated packet accounting facility, the logging facility, NAT, the man:dummynet[4] traffic shaper, a forward facility, a bridge facility, and an ipstealth facility. FreeBSD provides a sample ruleset in [.filename]#/etc/rc.firewall# which defines several firewall types for common scenarios to assist novice users in generating an appropriate ruleset. IPFW provides a powerful syntax which advanced users can use to craft customized rulesets that meet the security requirements of a given environment. This section describes how to enable IPFW, provides an overview of its rule syntax, and demonstrates several rulesets for common configuration scenarios. [[firewalls-ipfw-enable]] === Enabling IPFW IPFW is included in the basic FreeBSD install as a kernel loadable module, meaning that a custom kernel is not needed in order to enable IPFW. For those users who wish to statically compile IPFW support into a custom kernel, see <>. To configure the system to enable IPFW at boot time, add `firewall_enable="YES"` to [.filename]#/etc/rc.conf#: [source,shell] .... # sysrc firewall_enable="YES" .... To use one of the default firewall types provided by FreeBSD, add another line which specifies the type: [source,shell] .... # sysrc firewall_type="open" .... The available types are: * `open`: passes all traffic. * `client`: protects only this machine. * `simple`: protects the whole network. * `closed`: entirely disables IP traffic except for the loopback interface. * `workstation`: protects only this machine using stateful rules. * `UNKNOWN`: disables the loading of firewall rules. * [.filename]#filename#: full path of the file containing the firewall ruleset. If `firewall_type` is set to either `client` or `simple`, modify the default rules found in [.filename]#/etc/rc.firewall# to fit the configuration of the system. Note that the `filename` type is used to load a custom ruleset. An alternate way to load a custom ruleset is to set the `firewall_script` variable to the absolute path of an _executable script_ that includes IPFW commands. The examples used in this section assume that the `firewall_script` is set to [.filename]#/etc/ipfw.rules#: [source,shell] .... # sysrc firewall_script="/etc/ipfw.rules" .... To enable logging through man:syslogd[8], include this line: [source,shell] .... # sysrc firewall_logging="YES" .... [WARNING] ==== Only firewall rules with the `log` option will be logged. The default rules do not include this option and it must be manually added. Therefore it is advisable that the default ruleset is edited for logging. In addition, log rotation may be desired if the logs are stored in a separate file. ==== There is no [.filename]#/etc/rc.conf# variable to set logging limits. To limit the number of times a rule is logged per connection attempt, specify the number using this line in [.filename]#/etc/sysctl.conf#: [source,shell] .... # echo "net.inet.ip.fw.verbose_limit=5" >> /etc/sysctl.conf .... To enable logging through a dedicated interface named `ipfw0`, add this line to [.filename]#/etc/rc.conf# instead: [source,shell] .... # sysrc firewall_logif="YES" .... Then use tcpdump to see what is being logged: [source,shell] .... # tcpdump -t -n -i ipfw0 .... [TIP] ==== There is no overhead due to logging unless tcpdump is attached. ==== After saving the needed edits, start the firewall. To enable logging limits now, also set the `sysctl` value specified above: [source,shell] .... # service ipfw start # sysctl net.inet.ip.fw.verbose_limit=5 .... [[firewalls-ipfw-rules]] === IPFW Rule Syntax When a packet enters the IPFW firewall, it is compared against the first rule in the ruleset and progresses one rule at a time, moving from top to bottom in sequence. When the packet matches the selection parameters of a rule, the rule's action is executed and the search of the ruleset terminates for that packet. This is referred to as "first match wins". If the packet does not match any of the rules, it gets caught by the mandatory IPFW default rule number 65535, which denies all packets and silently discards them. However, if the packet matches a rule that contains the `count`, `skipto`, or `tee` keywords, the search continues. Refer to man:ipfw[8] for details on how these keywords affect rule processing. When creating an IPFW rule, keywords must be written in the following order. Some keywords are mandatory while other keywords are optional. The words shown in uppercase represent a variable and the words shown in lowercase must precede the variable that follows it. The `#` symbol is used to mark the start of a comment and may appear at the end of a rule or on its own line. Blank lines are ignored. `_CMD RULE_NUMBER set SET_NUMBER ACTION log LOG_AMOUNT PROTO from SRC SRC_PORT to DST DST_PORT OPTIONS_` This section provides an overview of these keywords and their options. It is not an exhaustive list of every possible option. Refer to man:ipfw[8] for a complete description of the rule syntax that can be used when creating IPFW rules. CMD:: Every rule must start with `ipfw add`. RULE_NUMBER:: Each rule is associated with a number from `1` to `65534`. The number is used to indicate the order of rule processing. Multiple rules can have the same number, in which case they are applied according to the order in which they have been added. SET_NUMBER:: Each rule is associated with a set number from `0` to `31`. Sets can be individually disabled or enabled, making it possible to quickly add or delete a set of rules. If a SET_NUMBER is not specified, the rule will be added to set `0`. ACTION:: A rule can be associated with one of the following actions. The specified action will be executed when the packet matches the selection criterion of the rule. + `allow | accept | pass | permit`: these keywords are equivalent and allow packets that match the rule. + `check-state`: checks the packet against the dynamic state table. If a match is found, execute the action associated with the rule which generated this dynamic rule, otherwise move to the next rule. A `check-state` rule does not have selection criterion. If no `check-state` rule is present in the ruleset, the dynamic rules table is checked at the first `keep-state` or `limit` rule. + `count`: updates counters for all packets that match the rule. The search continues with the next rule. + `deny | drop`: either word silently discards packets that match this rule. + Additional actions are available. Refer to man:ipfw[8] for details. LOG_AMOUNT:: When a packet matches a rule with the `log` keyword, a message will be logged to man:syslogd[8] with a facility name of `SECURITY`. Logging only occurs if the number of packets logged for that particular rule does not exceed a specified LOG_AMOUNT. If no LOG_AMOUNT is specified, the limit is taken from the value of `net.inet.ip.fw.verbose_limit`. A value of zero removes the logging limit. Once the limit is reached, logging can be re-enabled by clearing the logging counter or the packet counter for that rule, using `ipfw resetlog`. + [NOTE] ==== Logging is done after all other packet matching conditions have been met, and before performing the final action on the packet. The administrator decides which rules to enable logging on. ==== PROTO:: This optional value can be used to specify any protocol name or number found in [.filename]#/etc/protocols#. SRC:: The `from` keyword must be followed by the source address or a keyword that represents the source address. An address can be represented by `any`, `me` (any address configured on an interface on this system), `me6`, (any IPv6 address configured on an interface on this system), or `table` followed by the number of a lookup table which contains a list of addresses. When specifying an IP address, it can be optionally followed by its CIDR mask or subnet mask. For example, `1.2.3.4/25` or `1.2.3.4:255.255.255.128`. SRC_PORT:: An optional source port can be specified using the port number or name from [.filename]#/etc/services#. DST:: The `to` keyword must be followed by the destination address or a keyword that represents the destination address. The same keywords and addresses described in the SRC section can be used to describe the destination. DST_PORT:: An optional destination port can be specified using the port number or name from [.filename]#/etc/services#. OPTIONS:: Several keywords can follow the source and destination. As the name suggests, OPTIONS are optional. Commonly used options include `in` or `out`, which specify the direction of packet flow, `icmptypes` followed by the type of ICMP message, and `keep-state`. + When a `keep-state` rule is matched, the firewall will create a dynamic rule which matches bidirectional traffic between the source and destination addresses and ports using the same protocol. + The dynamic rules facility is vulnerable to resource depletion from a SYN-flood attack which would open a huge number of dynamic rules. To counter this type of attack with IPFW, use `limit`. This option limits the number of simultaneous sessions by checking the open dynamic rules, counting the number of times this rule and IP address combination occurred. If this count is greater than the value specified by `limit`, the packet is discarded. + Dozens of OPTIONS are available. Refer to man:ipfw[8] for a description of each available option. === Example Ruleset This section demonstrates how to create an example stateful firewall ruleset script named [.filename]#/etc/ipfw.rules#. In this example, all connection rules use `in` or `out` to clarify the direction. They also use `via` _interface-name_ to specify the interface the packet is traveling over. [NOTE] ==== When first creating or testing a firewall ruleset, consider temporarily setting this tunable: [.programlisting] .... net.inet.ip.fw.default_to_accept="1" .... This sets the default policy of man:ipfw[8] to be more permissive than the default `deny ip from any to any`, making it slightly more difficult to get locked out of the system right after a reboot. ==== The firewall script begins by indicating that it is a Bourne shell script and flushes any existing rules. It then creates the `cmd` variable so that `ipfw add` does not have to be typed at the beginning of every rule. It also defines the `pif` variable which represents the name of the interface that is attached to the Internet. [.programlisting] .... #!/bin/sh # Flush out the list before we begin. ipfw -q -f flush # Set rules command prefix cmd="ipfw -q add" pif="dc0" # interface name of NIC attached to Internet .... The first two rules allow all traffic on the trusted internal interface and on the loopback interface: [.programlisting] .... # Change xl0 to LAN NIC interface name $cmd 00005 allow all from any to any via xl0 # No restrictions on Loopback Interface $cmd 00010 allow all from any to any via lo0 .... The next rule allows the packet through if it matches an existing entry in the dynamic rules table: [.programlisting] .... $cmd 00101 check-state .... The next set of rules defines which stateful connections internal systems can create to hosts on the Internet: [.programlisting] .... # Allow access to public DNS # Replace x.x.x.x with the IP address of a public DNS server # and repeat for each DNS server in /etc/resolv.conf $cmd 00110 allow tcp from any to x.x.x.x 53 out via $pif setup keep-state $cmd 00111 allow udp from any to x.x.x.x 53 out via $pif keep-state # Allow access to ISP's DHCP server for cable/DSL configurations. # Use the first rule and check log for IP address. # Then, uncomment the second rule, input the IP address, and delete the first rule $cmd 00120 allow log udp from any to any 67 out via $pif keep-state #$cmd 00120 allow udp from any to x.x.x.x 67 out via $pif keep-state # Allow outbound HTTP and HTTPS connections $cmd 00200 allow tcp from any to any 80 out via $pif setup keep-state $cmd 00220 allow tcp from any to any 443 out via $pif setup keep-state # Allow outbound email connections $cmd 00230 allow tcp from any to any 25 out via $pif setup keep-state $cmd 00231 allow tcp from any to any 110 out via $pif setup keep-state # Allow outbound ping $cmd 00250 allow icmp from any to any out via $pif keep-state # Allow outbound NTP $cmd 00260 allow udp from any to any 123 out via $pif keep-state # Allow outbound SSH $cmd 00280 allow tcp from any to any 22 out via $pif setup keep-state # deny and log all other outbound connections $cmd 00299 deny log all from any to any out via $pif .... The next set of rules controls connections from Internet hosts to the internal network. It starts by denying packets typically associated with attacks and then explicitly allows specific types of connections. All the authorized services that originate from the Internet use `limit` to prevent flooding. [.programlisting] .... # Deny all inbound traffic from non-routable reserved address spaces $cmd 00300 deny all from 192.168.0.0/16 to any in via $pif #RFC 1918 private IP $cmd 00301 deny all from 172.16.0.0/12 to any in via $pif #RFC 1918 private IP $cmd 00302 deny all from 10.0.0.0/8 to any in via $pif #RFC 1918 private IP $cmd 00303 deny all from 127.0.0.0/8 to any in via $pif #loopback $cmd 00304 deny all from 0.0.0.0/8 to any in via $pif #loopback $cmd 00305 deny all from 169.254.0.0/16 to any in via $pif #DHCP auto-config $cmd 00306 deny all from 192.0.2.0/24 to any in via $pif #reserved for docs $cmd 00307 deny all from 204.152.64.0/23 to any in via $pif #Sun cluster interconnect $cmd 00308 deny all from 224.0.0.0/3 to any in via $pif #Class D & E multicast # Deny public pings $cmd 00310 deny icmp from any to any in via $pif # Deny ident $cmd 00315 deny tcp from any to any 113 in via $pif # Deny all Netbios services. $cmd 00320 deny tcp from any to any 137 in via $pif $cmd 00321 deny tcp from any to any 138 in via $pif $cmd 00322 deny tcp from any to any 139 in via $pif $cmd 00323 deny tcp from any to any 81 in via $pif # Deny fragments $cmd 00330 deny all from any to any frag in via $pif # Deny ACK packets that did not match the dynamic rule table $cmd 00332 deny tcp from any to any established in via $pif # Allow traffic from ISP's DHCP server. # Replace x.x.x.x with the same IP address used in rule 00120. #$cmd 00360 allow udp from any to x.x.x.x 67 in via $pif keep-state # Allow HTTP connections to internal web server $cmd 00400 allow tcp from any to me 80 in via $pif setup limit src-addr 2 # Allow inbound SSH connections $cmd 00410 allow tcp from any to me 22 in via $pif setup limit src-addr 2 # Reject and log all other incoming connections $cmd 00499 deny log all from any to any in via $pif .... The last rule logs all packets that do not match any of the rules in the ruleset: [.programlisting] .... # Everything else is denied and logged $cmd 00999 deny log all from any to any .... [[in-kernel-nat]] === In-kernel NAT FreeBSD's IPFW firewall has two implementations of NAT: the userland implementation man:natd[8], and the more recent in-kernel NAT implementation. Both work in conjunction with IPFW to provide network address translation. This can be used to provide an Internet Connection Sharing solution so that several internal computers can connect to the Internet using a single public IP address. To do this, the FreeBSD machine connected to the Internet must act as a gateway. This system must have two NICs, where one is connected to the Internet and the other is connected to the internal LAN. Each machine connected to the LAN should be assigned an IP address in the private network space, as defined by https://www.ietf.org/rfc/rfc1918.txt[RFC 1918]. Some additional configuration is needed in order to enable the in-kernel NAT facility of IPFW. To enable in-kernel NAT support at boot time, the following must be set in [.filename]#/etc/rc.conf#: [.programlisting] .... gateway_enable="YES" firewall_enable="YES" firewall_nat_enable="YES" .... [NOTE] ==== When `firewall_nat_enable` is set but `firewall_enable` is not, it will have no effect and do nothing. This is because the in-kernel NAT implementation is only compatible with IPFW. ==== When the ruleset contains stateful rules, the positioning of the NAT rule is critical and the `skipto` action is used. The `skipto` action requires a rule number so that it knows which rule to jump to. The example below builds upon the firewall ruleset shown in the previous section. It adds some additional entries and modifies some existing rules in order to configure the firewall for in-kernel NAT. It starts by adding some additional variables which represent the rule number to skip to, the `keep-state` option, and a list of TCP ports which will be used to reduce the number of rules. [.programlisting] .... #!/bin/sh ipfw -q -f flush cmd="ipfw -q add" skip="skipto 1000" pif=dc0 ks="keep-state" good_tcpo="22,25,37,53,80,443,110" .... With in-kernel NAT it is necessary to disable TCP segmentation offloading (TSO) due to the architecture of man:libalias[3], a library implemented as a kernel module to provide the in-kernel NAT facility of IPFW. TSO can be disabled on a per network interface basis using man:ifconfig[8] or on a system wide basis using man:sysctl[8]. To disable TSO system wide, the following must be set it [.filename]#/etc/sysctl.conf#: [.programlisting] .... net.inet.tcp.tso="0" .... A NAT instance will also be configured. It is possible to have multiple NAT instances each with their own configuration. For this example only one NAT instance is needed, NAT instance number 1. -The configuration can take a few options such as: `if` which indicates the public interface, `same_ports` which takes care that alliased ports and local port numbers are mapped the same, `unreg_only` will result in only unregistered (private) address spaces to be processed by the NAT instance, and `reset` which will help to keep a functioning NAT instance even when the public IP address of the IPFW machine changes. +The configuration can take a few options such as: `if` which indicates the public interface, `same_ports` which takes care that aliased ports and local port numbers are mapped the same, `unreg_only` will result in only unregistered (private) address spaces to be processed by the NAT instance, and `reset` which will help to keep a functioning NAT instance even when the public IP address of the IPFW machine changes. For all possible options that can be passed to a single NAT instance configuration consult man:ipfw[8]. When configuring a stateful NATing firewall, it is necessary to allow translated packets to be reinjected in the firewall for further processing. This can be achieved by disabling `one_pass` behavior at the start of the firewall script. [.programlisting] .... ipfw disable one_pass ipfw -q nat 1 config if $pif same_ports unreg_only reset .... The inbound NAT rule is inserted _after_ the two rules which allow all traffic on the trusted and loopback interfaces and after the reassemble rule but _before_ the `check-state` rule. It is important that the rule number selected for this NAT rule, in this example `100`, is higher than the first three rules and lower than the `check-state` rule. Furthermore, because of the behavior of in-kernel NAT it is advised to place a reassemble rule just before the first NAT rule and after the rules that allow traffic on trusted interface. Normally, IP fragmentation should not happen, but when dealing with IPSEC/ESP/GRE tunneling traffic it might and the reassembling of fragments is necessary before handing the complete packet over to the in-kernel NAT facility. [NOTE] ==== The reassemble rule was not needed with userland man:natd[8] because the internal workings of the IPFW `divert` action already takes care of reassembling packets before delivery to the socket as also stated in man:ipfw[8]. The NAT instance and rule number used in this example does not match with the default NAT instance and rule number created by [.filename]#rc.firewall#. [.filename]#rc.firewall# is a script that sets up the default firewall rules present in FreeBSD. ==== [.programlisting] .... $cmd 005 allow all from any to any via xl0 # exclude LAN traffic $cmd 010 allow all from any to any via lo0 # exclude loopback traffic $cmd 099 reass all from any to any in # reassemble inbound packets $cmd 100 nat 1 ip from any to any in via $pif # NAT any inbound packets # Allow the packet through if it has an existing entry in the dynamic rules table $cmd 101 check-state .... The outbound rules are modified to replace the `allow` action with the `$skip` variable, indicating that rule processing will continue at rule `1000`. The seven `tcp` rules have been replaced by rule `125` as the `$good_tcpo` variable contains the seven allowed outbound ports. [NOTE] ==== Remember that IPFW's performance is largely determined by the number of rules present in the ruleset. ==== [.programlisting] .... # Authorized outbound packets $cmd 120 $skip udp from any to x.x.x.x 53 out via $pif $ks $cmd 121 $skip udp from any to x.x.x.x 67 out via $pif $ks $cmd 125 $skip tcp from any to any $good_tcpo out via $pif setup $ks $cmd 130 $skip icmp from any to any out via $pif $ks .... The inbound rules remain the same, except for the very last rule which removes the `via $pif` in order to catch both inbound and outbound rules. The NAT rule must follow this last outbound rule, must have a higher number than that last rule, and the rule number must be referenced by the `skipto` action. In this ruleset, rule number `1000` handles passing all packets to our configured instance for NAT processing. The next rule allows any packet which has undergone NAT processing to pass. [.programlisting] .... $cmd 999 deny log all from any to any $cmd 1000 nat 1 ip from any to any out via $pif # skipto location for outbound stateful rules $cmd 1001 allow ip from any to any .... In this example, rules `100`, `101`, `125`, `1000`, and `1001` control the address translation of the outbound and inbound packets so that the entries in the dynamic state table always register the private LANIP address. Consider an internal web browser which initializes a new outbound HTTP session over port 80. When the first outbound packet enters the firewall, it does not match rule `100` because it is headed out rather than in. It passes rule `101` because this is the first packet and it has not been posted to the dynamic state table yet. The packet finally matches rule `125` as it is outbound on an allowed port and has a source IP address from the internal LAN. On matching this rule, two actions take place. First, the `keep-state` action adds an entry to the dynamic state table and the specified action, `skipto rule 1000`, is executed. Next, the packet undergoes NAT and is sent out to the Internet. This packet makes its way to the destination web server, where a response packet is generated and sent back. This new packet enters the top of the ruleset. It matches rule `100` and has its destination IP address mapped back to the original internal address. It then is processed by the `check-state` rule, is found in the table as an existing session, and is released to the LAN. On the inbound side, the ruleset has to deny bad packets and allow only authorized services. A packet which matches an inbound rule is posted to the dynamic state table and the packet is released to the LAN. The packet generated as a response is recognized by the `check-state` rule as belonging to an existing session. It is then sent to rule `1000` to undergo NAT before being released to the outbound interface. [NOTE] ==== Transitioning from userland man:natd[8] to in-kernel NAT might appear seamless at first but there is small catch. When using the GENERIC kernel, IPFW will load the [.filename]#libalias.ko# kernel module, when `firewall_nat_enable` is enabled in [.filename]#/etc/rc.conf#. The [.filename]#libalias.ko# kernel module only provides basic NAT functionality, whereas the userland implementation man:natd[8] has all NAT functionality available in its userland library without any extra configuration. All functionality refers to the following kernel modules that can additionally be loaded when needed besides the standard [.filename]#libalias.ko# kernel module: [.filename]#alias_ftp.ko#, [.filename]#alias_bbt.ko#, [.filename]#skinny.ko#, [.filename]#irc.ko#, [.filename]#alias_pptp.ko# and [.filename]#alias_smedia.ko# using the `kld_list` directive in [.filename]#/etc/rc.conf#. If a custom kernel is used, the full functionality of the userland library can be compiled in, in the kernel, using the `options LIBALIAS`. ==== ==== Port Redirection The drawback with NAT in general is that the LAN clients are not accessible from the Internet. Clients on the LAN can make outgoing connections to the world but cannot receive incoming ones. This presents a problem if trying to run Internet services on one of the LAN client machines. A simple way around this is to redirect selected Internet ports on the NAT providing machine to a LAN client. For example, an IRC server runs on client `A` and a web server runs on client `B`. For this to work properly, connections received on ports 6667 (IRC) and 80 (HTTP) must be redirected to the respective machines. With in-kernel NAT all configuration is done in the NAT instance configuration. For a full list of options that an in-kernel NAT instance can use, consult man:ipfw[8]. The IPFW syntax follows the syntax of natd. The syntax for `redirect_port` is as follows: [.programlisting] .... redirect_port proto targetIP:targetPORT[-targetPORT] [aliasIP:]aliasPORT[-aliasPORT] [remoteIP[:remotePORT[-remotePORT]]] .... To configure the above example setup, the arguments should be: [.programlisting] .... redirect_port tcp 192.168.0.2:6667 6667 redirect_port tcp 192.168.0.3:80 80 .... After adding these arguments to the configuration of NAT instance 1 in the above ruleset, the TCP ports will be port forwarded to the LAN client machines running the IRC and HTTP services. [.programlisting] .... ipfw -q nat 1 config if $pif same_ports unreg_only reset \ redirect_port tcp 192.168.0.2:6667 6667 \ redirect_port tcp 192.168.0.3:80 80 .... Port ranges over individual ports can be indicated with `redirect_port`. For example, _tcp 192.168.0.2:2000-3000 2000-3000_ would redirect all connections received on ports 2000 to 3000 to ports 2000 to 3000 on client `A`. ==== Address Redirection Address redirection is useful if more than one IP address is available. Each LAN client can be assigned its own external IP address by man:ipfw[8], which will then rewrite outgoing packets from the LAN clients with the proper external IP address and redirects all traffic incoming on that particular IP address back to the specific LAN client. This is also known as static NAT. For example, if IP addresses `128.1.1.1`, `128.1.1.2`, and `128.1.1.3` are available, `128.1.1.1` can be used as the man:ipfw[8] machine's external IP address, while `128.1.1.2` and `128.1.1.3` are forwarded back to LAN clients `A` and `B`. The `redirect_address` syntax is as below, where `localIP` is the internal IP address of the LAN client, and `publicIP` the external IP address corresponding to the LAN client. [.programlisting] .... redirect_address localIP publicIP .... In the example, the arguments would read: [.programlisting] .... redirect_address 192.168.0.2 128.1.1.2 redirect_address 192.168.0.3 128.1.1.3 .... Like `redirect_port`, these arguments are placed in a NAT instance configuration. With address redirection, there is no need for port redirection, as all data received on a particular IP address is redirected. The external IP addresses on the man:ipfw[8] machine must be active and aliased to the external interface. Refer to man:rc.conf[5] for details. ==== Userspace NAT Let us start with a statement: the userspace NAT implementation: man:natd[8], has more overhead than in-kernel NAT. For man:natd[8] to translate packets, the packets have to be copied from the kernel to userspace and back which brings in extra overhead that is not present with in-kernel NAT. To enable the userpace NAT daemon man:natd[8] at boot time, the following is a minimum configuration in [.filename]#/etc/rc.conf#. Where `natd_interface` is set to the name of the NIC attached to the Internet. The man:rc[8] script of man:natd[8] will automatically check if a dynamic IP address is used and configure itself to handle that. [.programlisting] .... gateway_enable="YES" natd_enable="YES" natd_interface="rl0" .... In general, the above ruleset as explained for in-kernel NAT can also be used together with man:natd[8]. The exceptions are the configuration of the in-kernel NAT instance `(ipfw -q nat 1 config ...)` which is not needed together with reassemble rule 99 because its functionality is included in the `divert` action. Rule number 100 and 1000 will have to change sligthly as shown below. [.programlisting] .... $cmd 100 divert natd ip from any to any in via $pif $cmd 1000 divert natd ip from any to any out via $pif .... To configure port or address redirection, a similar syntax as with in-kernel NAT is used. Although, now, instead of specifying the configuration in our ruleset script like with in-kernel NAT, configuration of man:natd[8] is best done in a configuration file. To do this, an extra flag must be passed via [.filename]#/etc/rc.conf# which specifies the path of the configuration file. [.programlisting] .... natd_flags="-f /etc/natd.conf" .... [NOTE] ==== The specified file must contain a list of configuration options, one per line. For more information about the configuration file and possible variables, consult man:natd[8]. Below are two example entries, one per line: [.programlisting] .... redirect_port tcp 192.168.0.2:6667 6667 redirect_address 192.168.0.3 128.1.1.3 .... ==== [[firewalls-ipfw-cmd]] === The IPFW Command `ipfw` can be used to make manual, single rule additions or deletions to the active firewall while it is running. The problem with using this method is that all the changes are lost when the system reboots. It is recommended to instead write all the rules in a file and to use that file to load the rules at boot time and to replace the currently running firewall rules whenever that file changes. `ipfw` is a useful way to display the running firewall rules to the console screen. The IPFW accounting facility dynamically creates a counter for each rule that counts each packet that matches the rule. During the process of testing a rule, listing the rule with its counter is one way to determine if the rule is functioning as expected. To list all the running rules in sequence: [source,shell] .... # ipfw list .... To list all the running rules with a time stamp of when the last time the rule was matched: [source,shell] .... # ipfw -t list .... The next example lists accounting information and the packet count for matched rules along with the rules themselves. The first column is the rule number, followed by the number of matched packets and bytes, followed by the rule itself. [source,shell] .... # ipfw -a list .... To list dynamic rules in addition to static rules: [source,shell] .... # ipfw -d list .... To also show the expired dynamic rules: [source,shell] .... # ipfw -d -e list .... To zero the counters: [source,shell] .... # ipfw zero .... To zero the counters for just the rule with number _NUM_: [source,shell] .... # ipfw zero NUM .... ==== Logging Firewall Messages Even with the logging facility enabled, IPFW will not generate any rule logging on its own. The firewall administrator decides which rules in the ruleset will be logged, and adds the `log` keyword to those rules. Normally only deny rules are logged. It is customary to duplicate the "ipfw default deny everything" rule with the `log` keyword included as the last rule in the ruleset. This way, it is possible to see all the packets that did not match any of the rules in the ruleset. Logging is a two edged sword. If one is not careful, an over abundance of log data or a DoS attack can fill the disk with log files. Log messages are not only written to syslogd, but also are displayed on the root console screen and soon become annoying. The `IPFIREWALL_VERBOSE_LIMIT=5` kernel option limits the number of consecutive messages sent to man:syslogd[8], concerning the packet matching of a given rule. When this option is enabled in the kernel, the number of consecutive messages concerning a particular rule is capped at the number specified. There is nothing to be gained from 200 identical log messages. With this option set to five, five consecutive messages concerning a particular rule would be logged to syslogd and the remainder identical consecutive messages would be counted and posted to syslogd with a phrase like the following: [.programlisting] .... last message repeated 45 times .... All logged packets messages are written by default to [.filename]#/var/log/security#, which is defined in [.filename]#/etc/syslog.conf#. [[firewalls-ipfw-rules-script]] ==== Building a Rule Script Most experienced IPFW users create a file containing the rules and code them in a manner compatible with running them as a script. The major benefit of doing this is the firewall rules can be refreshed in mass without the need of rebooting the system to activate them. This method is convenient in testing new rules as the procedure can be executed as many times as needed. Being a script, symbolic substitution can be used for frequently used values to be substituted into multiple rules. This example script is compatible with the syntax used by the man:sh[1], man:csh[1], and man:tcsh[1] shells. Symbolic substitution fields are prefixed with a dollar sign ($). Symbolic fields do not have the $ prefix. The value to populate the symbolic field must be enclosed in double quotes (""). Start the rules file like this: [.programlisting] .... ############### start of example ipfw rules script ############# # ipfw -q -f flush # Delete all rules # Set defaults oif="tun0" # out interface odns="192.0.2.11" # ISP's DNS server IP address cmd="ipfw -q add " # build rule prefix ks="keep-state" # just too lazy to key this each time $cmd 00500 check-state $cmd 00502 deny all from any to any frag $cmd 00501 deny tcp from any to any established $cmd 00600 allow tcp from any to any 80 out via $oif setup $ks $cmd 00610 allow tcp from any to $odns 53 out via $oif setup $ks $cmd 00611 allow udp from any to $odns 53 out via $oif $ks ################### End of example ipfw rules script ############ .... The rules are not important as the focus of this example is how the symbolic substitution fields are populated. If the above example was in [.filename]#/etc/ipfw.rules#, the rules could be reloaded by the following command: [source,shell] .... # sh /etc/ipfw.rules .... [.filename]#/etc/ipfw.rules# can be located anywhere and the file can have any name. The same thing could be accomplished by running these commands by hand: [source,shell] .... # ipfw -q -f flush # ipfw -q add check-state # ipfw -q add deny all from any to any frag # ipfw -q add deny tcp from any to any established # ipfw -q add allow tcp from any to any 80 out via tun0 setup keep-state # ipfw -q add allow tcp from any to 192.0.2.11 53 out via tun0 setup keep-state # ipfw -q add 00611 allow udp from any to 192.0.2.11 53 out via tun0 keep-state .... [[firewalls-ipfw-kernelconfig]] === IPFW Kernel Options In order to statically compile IPFW support into a custom kernel, refer to the instructions in crossref:kernelconfig[kernelconfig,Configuring the FreeBSD Kernel]. The following options are available for the custom kernel configuration file: [.programlisting] .... options IPFIREWALL # enables IPFW options IPFIREWALL_VERBOSE # enables logging for rules with log keyword to syslogd(8) options IPFIREWALL_VERBOSE_LIMIT=5 # limits number of logged packets per-entry options IPFIREWALL_DEFAULT_TO_ACCEPT # sets default policy to pass what is not explicitly denied options IPFIREWALL_NAT # enables basic in-kernel NAT support options LIBALIAS # enables full in-kernel NAT support options IPFIREWALL_NAT64 # enables in-kernel NAT64 support options IPFIREWALL_NPTV6 # enables in-kernel IPv6 NPT support options IPFIREWALL_PMOD # enables protocols modification module support options IPDIVERT # enables NAT through natd(8) .... [NOTE] ==== IPFW can be loaded as a kernel module: options above are built by default as modules or can be set at runtime using tunables. ==== [[firewalls-ipf]] == IPFILTER (IPF) IPFILTER, also known as IPF, is a cross-platform, open source firewall which has been ported to several operating systems, including FreeBSD, NetBSD, OpenBSD, and Solaris(TM). IPFILTER is a kernel-side firewall and NAT mechanism that can be controlled and monitored by userland programs. Firewall rules can be set or deleted using ipf, NAT rules can be set or deleted using ipnat, run-time statistics for the kernel parts of IPFILTER can be printed using ipfstat, and ipmon can be used to log IPFILTER actions to the system log files. IPF was originally written using a rule processing logic of "the last matching rule wins" and only used stateless rules. Since then, IPF has been enhanced to include the `quick` and `keep state` options. The IPF FAQ is at http://www.phildev.net/ipf/index.html[http://www.phildev.net/ipf/index.html]. A searchable archive of the IPFilter mailing list is available at http://marc.info/?l=ipfilter[http://marc.info/?l=ipfilter]. This section of the Handbook focuses on IPF as it pertains to FreeBSD. It provides examples of rules that contain the `quick` and `keep state` options. === Enabling IPF IPF is included in the basic FreeBSD install as a kernel loadable module, meaning that a custom kernel is not needed in order to enable IPF. For users who prefer to statically compile IPF support into a custom kernel, refer to the instructions in crossref:kernelconfig[kernelconfig,Configuring the FreeBSD Kernel]. The following kernel options are available: [.programlisting] .... options IPFILTER options IPFILTER_LOG options IPFILTER_LOOKUP options IPFILTER_DEFAULT_BLOCK .... where `options IPFILTER` enables support for IPFILTER, `options IPFILTER_LOG` enables IPF logging using the [.filename]#ipl# packet logging pseudo-device for every rule that has the `log` keyword, `IPFILTER_LOOKUP` enables IP pools in order to speed up IP lookups, and `options IPFILTER_DEFAULT_BLOCK` changes the default behavior so that any packet not matching a firewall `pass` rule gets blocked. To configure the system to enable IPF at boot time, add the following entries to [.filename]#/etc/rc.conf#. These entries will also enable logging and `default pass all`. To change the default policy to `block all` without compiling a custom kernel, remember to add a `block all` rule at the end of the ruleset. [.programlisting] .... ipfilter_enable="YES" # Start ipf firewall ipfilter_rules="/etc/ipf.rules" # loads rules definition text file ipv6_ipfilter_rules="/etc/ipf6.rules" # loads rules definition text file for IPv6 ipmon_enable="YES" # Start IP monitor log ipmon_flags="-Ds" # D = start as daemon # s = log to syslog # v = log tcp window, ack, seq # n = map IP & port to names .... If NAT functionality is needed, also add these lines: [.programlisting] .... gateway_enable="YES" # Enable as LAN gateway ipnat_enable="YES" # Start ipnat function ipnat_rules="/etc/ipnat.rules" # rules definition file for ipnat .... Then, to start IPF now: [.programlisting] .... # service ipfilter start .... To load the firewall rules, specify the name of the ruleset file using `ipf`. The following command can be used to replace the currently running firewall rules: [source,shell] .... # ipf -Fa -f /etc/ipf.rules .... where `-Fa` flushes all the internal rules tables and `-f` specifies the file containing the rules to load. This provides the ability to make changes to a custom ruleset and update the running firewall with a fresh copy of the rules without having to reboot the system. This method is convenient for testing new rules as the procedure can be executed as many times as needed. Refer to man:ipf[8] for details on the other flags available with this command. === IPF Rule Syntax This section describes the IPF rule syntax used to create stateful rules. When creating rules, keep in mind that unless the `quick` keyword appears in a rule, every rule is read in order, with the _last matching rule_ being the one that is applied. This means that even if the first rule to match a packet is a `pass`, if there is a later matching rule that is a `block`, the packet will be dropped. Sample rulesets can be found in [.filename]#/usr/share/examples/ipfilter#. When creating rules, a `#` character is used to mark the start of a comment and may appear at the end of a rule, to explain that rule's function, or on its own line. Any blank lines are ignored. The keywords which are used in rules must be written in a specific order, from left to right. Some keywords are mandatory while others are optional. Some keywords have sub-options which may be keywords themselves and also include more sub-options. The keyword order is as follows, where the words shown in uppercase represent a variable and the words shown in lowercase must precede the variable that follows it: `_ACTION DIRECTION OPTIONS proto PROTO_TYPE from SRC_ADDR SRC_PORT to DST_ADDR DST_PORT TCP_FLAG|ICMP_TYPE keep state STATE_` This section describes each of these keywords and their options. It is not an exhaustive list of every possible option. Refer to man:ipf[5] for a complete description of the rule syntax that can be used when creating IPF rules and examples for using each keyword. ACTION:: The action keyword indicates what to do with the packet if it matches that rule. Every rule _must_ have an action. The following actions are recognized: + `block`: drops the packet. + `pass`: allows the packet. + `log`: generates a log record. + `count`: counts the number of packets and bytes which can provide an indication of how often a rule is used. + `auth`: queues the packet for further processing by another program. + `call`: provides access to functions built into IPF that allow more complex actions. + `decapsulate`: removes any headers in order to process the contents of the packet. DIRECTION:: Next, each rule must explicitly state the direction of traffic using one of these keywords: + `in`: the rule is applied against an inbound packet. + `out`: the rule is applied against an outbound packet. + `all`: the rule applies to either direction. + If the system has multiple interfaces, the interface can be specified along with the direction. An example would be `in on fxp0`. OPTIONS:: Options are optional. However, if multiple options are specified, they must be used in the order shown here. + `log`: when performing the specified ACTION, the contents of the packet's headers will be written to the man:ipl[4] packet log pseudo-device. + `quick`: if a packet matches this rule, the ACTION specified by the rule occurs and no further processing of any following rules will occur for this packet. + `on`: must be followed by the interface name as displayed by man:ifconfig[8]. The rule will only match if the packet is going through the specified interface in the specified direction. + When using the `log` keyword, the following qualifiers may be used in this order: + `body`: indicates that the first 128 bytes of the packet contents will be logged after the headers. + `first`: if the `log` keyword is being used in conjunction with a `keep state` option, this option is recommended so that only the triggering packet is logged and not every packet which matches the stateful connection. + Additional options are available to specify error return messages. Refer to man:ipf[5] for more details. PROTO_TYPE:: The protocol type is optional. However, it is mandatory if the rule needs to specify a SRC_PORT or a DST_PORT as it defines the type of protocol. When specifying the type of protocol, use the `proto` keyword followed by either a protocol number or name from [.filename]#/etc/protocols#. Example protocol names include `tcp`, `udp`, or `icmp`. If PROTO_TYPE is specified but no SRC_PORT or DST_PORT is specified, all port numbers for that protocol will match that rule. SRC_ADDR:: The `from` keyword is mandatory and is followed by a keyword which represents the source of the packet. The source can be a hostname, an IP address followed by the CIDR mask, an address pool, or the keyword `all`. Refer to man:ipf[5] for examples. + There is no way to match ranges of IP addresses which do not express themselves easily using the dotted numeric form / mask-length notation. The package:net-mgmt/ipcalc[] package or port may be used to ease the calculation of the CIDR mask. Additional information is available at the utility's web page: http://jodies.de/ipcalc[http://jodies.de/ipcalc]. SRC_PORT:: The port number of the source is optional. However, if it is used, it requires PROTO_TYPE to be first defined in the rule. The port number must also be preceded by the `proto` keyword. + A number of different comparison operators are supported: `=` (equal to), `!=` (not equal to), `<` (less than), `>` (greater than), `<=` (less than or equal to), and `>=` (greater than or equal to). + To specify port ranges, place the two port numbers between `<>` (less than and greater than ), `><` (greater than and less than ), or `:` (greater than or equal to and less than or equal to). DST_ADDR:: The `to` keyword is mandatory and is followed by a keyword which represents the destination of the packet. Similar to SRC_ADDR, it can be a hostname, an IP address followed by the CIDR mask, an address pool, or the keyword `all`. DST_PORT:: Similar to SRC_PORT, the port number of the destination is optional. However, if it is used, it requires PROTO_TYPE to be first defined in the rule. The port number must also be preceded by the `proto` keyword. TCP_FLAG|ICMP_TYPE:: If `tcp` is specified as the PROTO_TYPE, flags can be specified as letters, where each letter represents one of the possible TCP flags used to determine the state of a connection. Possible values are: `S` (SYN), `A` (ACK), `P` (PSH), `F` (FIN), `U` (URG), `R` (RST), `C` (CWN), and `E` (ECN). + If `icmp` is specified as the PROTO_TYPE, the ICMP type to match can be specified. Refer to man:ipf[5] for the allowable types. STATE:: If a `pass` rule contains `keep state`, IPF will add an entry to its dynamic state table and allow subsequent packets that match the connection. IPF can track state for TCP, UDP, and ICMP sessions. Any packet that IPF can be certain is part of an active session, even if it is a different protocol, will be allowed. + In IPF, packets destined to go out through the interface connected to the public Internet are first checked against the dynamic state table. If the packet matches the next expected packet comprising an active session conversation, it exits the firewall and the state of the session conversation flow is updated in the dynamic state table. Packets that do not belong to an already active session are checked against the outbound ruleset. Packets coming in from the interface connected to the public Internet are first checked against the dynamic state table. If the packet matches the next expected packet comprising an active session, it exits the firewall and the state of the session conversation flow is updated in the dynamic state table. Packets that do not belong to an already active session are checked against the inbound ruleset. + Several keywords can be added after `keep state`. If used, these keywords set various options that control stateful filtering, such as setting connection limits or connection age. Refer to man:ipf[5] for the list of available options and their descriptions. === Example Ruleset This section demonstrates how to create an example ruleset which only allows services matching `pass` rules and blocks all others. FreeBSD uses the loopback interface ([.filename]#lo0#) and the IP address `127.0.0.1` for internal communication. The firewall ruleset must contain rules to allow free movement of these internally used packets: [.programlisting] .... # no restrictions on loopback interface pass in quick on lo0 all pass out quick on lo0 all .... The public interface connected to the Internet is used to authorize and control access of all outbound and inbound connections. If one or more interfaces are cabled to private networks, those internal interfaces may require rules to allow packets originating from the LAN to flow between the internal networks or to the interface attached to the Internet. The ruleset should be organized into three major sections: any trusted internal interfaces, outbound connections through the public interface, and inbound connections through the public interface. These two rules allow all traffic to pass through a trusted LAN interface named [.filename]#xl0#: [.programlisting] .... # no restrictions on inside LAN interface for private network pass out quick on xl0 all pass in quick on xl0 all .... The rules for the public interface's outbound and inbound sections should have the most frequently matched rules placed before less commonly matched rules, with the last rule in the section blocking and logging all packets for that interface and direction. This set of rules defines the outbound section of the public interface named [.filename]#dc0#. These rules keep state and identify the specific services that internal systems are authorized for public Internet access. All the rules use `quick` and specify the appropriate port numbers and, where applicable, destination addresses. [.programlisting] .... # interface facing Internet (outbound) # Matches session start requests originating from or behind the # firewall, destined for the Internet. # Allow outbound access to public DNS servers. -# Replace x.x.x. with address listed in /etc/resolv.conf. +# Replace x.x.x.x with address listed in /etc/resolv.conf. # Repeat for each DNS server. -pass out quick on dc0 proto tcp from any to x.x.x. port = 53 flags S keep state -pass out quick on dc0 proto udp from any to xxx port = 53 keep state +pass out quick on dc0 proto tcp from any to x.x.x.x port = 53 flags S keep state +pass out quick on dc0 proto udp from any to x.x.x.x port = 53 keep state # Allow access to ISP's specified DHCP server for cable or DSL networks. # Use the first rule, then check log for the IP address of DHCP server. # Then, uncomment the second rule, replace z.z.z.z with the IP address, # and comment out the first rule pass out log quick on dc0 proto udp from any to any port = 67 keep state #pass out quick on dc0 proto udp from any to z.z.z.z port = 67 keep state # Allow HTTP and HTTPS pass out quick on dc0 proto tcp from any to any port = 80 flags S keep state pass out quick on dc0 proto tcp from any to any port = 443 flags S keep state # Allow email pass out quick on dc0 proto tcp from any to any port = 110 flags S keep state pass out quick on dc0 proto tcp from any to any port = 25 flags S keep state # Allow NTP pass out quick on dc0 proto tcp from any to any port = 37 flags S keep state # Allow FTP pass out quick on dc0 proto tcp from any to any port = 21 flags S keep state # Allow SSH pass out quick on dc0 proto tcp from any to any port = 22 flags S keep state # Allow ping pass out quick on dc0 proto icmp from any to any icmp-type 8 keep state # Block and log everything else block out log first quick on dc0 all .... This example of the rules in the inbound section of the public interface blocks all undesirable packets first. This reduces the number of packets that are logged by the last rule. [.programlisting] .... # interface facing Internet (inbound) # Block all inbound traffic from non-routable or reserved address spaces block in quick on dc0 from 192.168.0.0/16 to any #RFC 1918 private IP block in quick on dc0 from 172.16.0.0/12 to any #RFC 1918 private IP block in quick on dc0 from 10.0.0.0/8 to any #RFC 1918 private IP block in quick on dc0 from 127.0.0.0/8 to any #loopback block in quick on dc0 from 0.0.0.0/8 to any #loopback block in quick on dc0 from 169.254.0.0/16 to any #DHCP auto-config block in quick on dc0 from 192.0.2.0/24 to any #reserved for docs block in quick on dc0 from 204.152.64.0/23 to any #Sun cluster interconnect block in quick on dc0 from 224.0.0.0/3 to any #Class D & E multicast # Block fragments and too short tcp packets block in quick on dc0 all with frags block in quick on dc0 proto tcp all with short # block source routed packets block in quick on dc0 all with opt lsrr block in quick on dc0 all with opt ssrr # Block OS fingerprint attempts and log first occurrence block in log first quick on dc0 proto tcp from any to any flags FUP # Block anything with special options block in quick on dc0 all with ipopts # Block public pings and ident block in quick on dc0 proto icmp all icmp-type 8 block in quick on dc0 proto tcp from any to any port = 113 # Block incoming Netbios services block in log first quick on dc0 proto tcp/udp from any to any port = 137 block in log first quick on dc0 proto tcp/udp from any to any port = 138 block in log first quick on dc0 proto tcp/udp from any to any port = 139 block in log first quick on dc0 proto tcp/udp from any to any port = 81 .... Any time there are logged messages on a rule with the `log first` option, run `ipfstat -hio` to evaluate how many times the rule has been matched. A large number of matches may indicate that the system is under attack. The rest of the rules in the inbound section define which connections are allowed to be initiated from the Internet. The last rule denies all connections which were not explicitly allowed by previous rules in this section. [.programlisting] .... # Allow traffic in from ISP's DHCP server. Replace z.z.z.z with # the same IP address used in the outbound section. pass in quick on dc0 proto udp from z.z.z.z to any port = 68 keep state # Allow public connections to specified internal web server pass in quick on dc0 proto tcp from any to x.x.x.x port = 80 flags S keep state # Block and log only first occurrence of all remaining traffic. block in log first quick on dc0 all .... === Configuring NAT To enable NAT, add these statements to [.filename]#/etc/rc.conf# and specify the name of the file containing the NAT rules: [.programlisting] .... gateway_enable="YES" ipnat_enable="YES" ipnat_rules="/etc/ipnat.rules" .... NAT rules are flexible and can accomplish many different things to fit the needs of both commercial and home users. The rule syntax presented here has been simplified to demonstrate common usage. For a complete rule syntax description, refer to man:ipnat[5]. The basic syntax for a NAT rule is as follows, where `map` starts the rule and _IF_ should be replaced with the name of the external interface: [.programlisting] .... map IF LAN_IP_RANGE -> PUBLIC_ADDRESS .... The _LAN_IP_RANGE_ is the range of IP addresses used by internal clients. Usually, it is a private address range such as `192.168.1.0/24`. The _PUBLIC_ADDRESS_ can either be the static external IP address or the keyword `0/32` which represents the IP address assigned to _IF_. In IPF, when a packet arrives at the firewall from the LAN with a public destination, it first passes through the outbound rules of the firewall ruleset. Then, the packet is passed to the NAT ruleset which is read from the top down, where the first matching rule wins. IPF tests each NAT rule against the packet's interface name and source IP address. When a packet's interface name matches a NAT rule, the packet's source IP address in the private LAN is checked to see if it falls within the IP address range specified in _LAN_IP_RANGE_. On a match, the packet has its source IP address rewritten with the public IP address specified by _PUBLIC_ADDRESS_. IPF posts an entry in its internal NAT table so that when the packet returns from the Internet, it can be mapped back to its original private IP address before being passed to the firewall rules for further processing. For networks that have large numbers of internal systems or multiple subnets, the process of funneling every private IP address into a single public IP address becomes a resource problem. Two methods are available to relieve this issue. The first method is to assign a range of ports to use as source ports. By adding the `portmap` keyword, NAT can be directed to only use source ports in the specified range: [.programlisting] .... map dc0 192.168.1.0/24 -> 0/32 portmap tcp/udp 20000:60000 .... Alternately, use the `auto` keyword which tells NAT to determine the ports that are available for use: [.programlisting] .... map dc0 192.168.1.0/24 -> 0/32 portmap tcp/udp auto .... The second method is to use a pool of public addresses. This is useful when there are too many LAN addresses to fit into a single public address and a block of public IP addresses is available. These public addresses can be used as a pool from which NAT selects an IP address as a packet's address is mapped on its way out. The range of public IP addresses can be specified using a netmask or CIDR notation. These two rules are equivalent: [.programlisting] .... map dc0 192.168.1.0/24 -> 204.134.75.0/255.255.255.0 map dc0 192.168.1.0/24 -> 204.134.75.0/24 .... A common practice is to have a publically accessible web server or mail server segregated to an internal network segment. The traffic from these servers still has to undergo NAT, but port redirection is needed to direct inbound traffic to the correct server. For example, to map a web server using the internal address `10.0.10.25` to its public IP address of `20.20.20.5`, use this rule: [.programlisting] .... rdr dc0 20.20.20.5/32 port 80 -> 10.0.10.25 port 80 .... If it is the only web server, this rule would also work as it redirects all external HTTP requests to `10.0.10.25`: [.programlisting] .... rdr dc0 0.0.0.0/0 port 80 -> 10.0.10.25 port 80 .... IPF has a built in FTP proxy which can be used with NAT. It monitors all outbound traffic for active or passive FTP connection requests and dynamically creates temporary filter rules containing the port number used by the FTP data channel. This eliminates the need to open large ranges of high order ports for FTP connections. In this example, the first rule calls the proxy for outbound FTP traffic from the internal LAN. The second rule passes the FTP traffic from the firewall to the Internet, and the third rule handles all non-FTP traffic from the internal LAN: [.programlisting] .... map dc0 10.0.10.0/29 -> 0/32 proxy port 21 ftp/tcp map dc0 0.0.0.0/0 -> 0/32 proxy port 21 ftp/tcp map dc0 10.0.10.0/29 -> 0/32 .... The FTP `map` rules go before the NAT rule so that when a packet matches an FTP rule, the FTP proxy creates temporary filter rules to let the FTP session packets pass and undergo NAT. All LAN packets that are not FTP will not match the FTP rules but will undergo NAT if they match the third rule. Without the FTP proxy, the following firewall rules would instead be needed. Note that without the proxy, all ports above `1024` need to be allowed: [.programlisting] .... # Allow out LAN PC client FTP to public Internet # Active and passive modes pass out quick on rl0 proto tcp from any to any port = 21 flags S keep state # Allow out passive mode data channel high order port numbers pass out quick on rl0 proto tcp from any to any port > 1024 flags S keep state # Active mode let data channel in from FTP server pass in quick on rl0 proto tcp from any to any port = 20 flags S keep state .... Whenever the file containing the NAT rules is edited, run `ipnat` with `-CF` to delete the current NAT rules and flush the contents of the dynamic translation table. Include `-f` and specify the name of the NAT ruleset to load: [source,shell] .... # ipnat -CF -f /etc/ipnat.rules .... To display the NAT statistics: [source,shell] .... # ipnat -s .... To list the NAT table's current mappings: [source,shell] .... # ipnat -l .... To turn verbose mode on and display information relating to rule processing and active rules and table entries: [source,shell] .... # ipnat -v .... === Viewing IPF Statistics IPF includes man:ipfstat[8] which can be used to retrieve and display statistics which are gathered as packets match rules as they go through the firewall. Statistics are accumulated since the firewall was last started or since the last time they were reset to zero using `ipf -Z`. The default `ipfstat` output looks like this: [source,shell] .... input packets: blocked 99286 passed 1255609 nomatch 14686 counted 0 output packets: blocked 4200 passed 1284345 nomatch 14687 counted 0 input packets logged: blocked 99286 passed 0 output packets logged: blocked 0 passed 0 packets logged: input 0 output 0 log failures: input 3898 output 0 fragment state(in): kept 0 lost 0 fragment state(out): kept 0 lost 0 packet state(in): kept 169364 lost 0 packet state(out): kept 431395 lost 0 ICMP replies: 0 TCP RSTs sent: 0 Result cache hits(in): 1215208 (out): 1098963 IN Pullups succeeded: 2 failed: 0 OUT Pullups succeeded: 0 failed: 0 Fastroute successes: 0 failures: 0 TCP cksum fails(in): 0 (out): 0 Packet log flags set: (0) .... Several options are available. When supplied with either `-i` for inbound or `-o` for outbound, the command will retrieve and display the appropriate list of filter rules currently installed and in use by the kernel. To also see the rule numbers, include `-n`. For example, `ipfstat -on` displays the outbound rules table with rule numbers: [source,shell] .... @1 pass out on xl0 from any to any @2 block out on dc0 from any to any @3 pass out quick on dc0 proto tcp/udp from any to any keep state .... Include `-h` to prefix each rule with a count of how many times the rule was matched. For example, `ipfstat -oh` displays the outbound internal rules table, prefixing each rule with its usage count: [source,shell] .... 2451423 pass out on xl0 from any to any 354727 block out on dc0 from any to any 430918 pass out quick on dc0 proto tcp/udp from any to any keep state .... To display the state table in a format similar to man:top[1], use `ipfstat -t`. When the firewall is under attack, this option provides the ability to identify and see the attacking packets. The optional sub-flags give the ability to select the destination or source IP, port, or protocol to be monitored in real time. Refer to man:ipfstat[8] for details. === IPF Logging IPF provides `ipmon`, which can be used to write the firewall's logging information in a human readable format. It requires that `options IPFILTER_LOG` be first added to a custom kernel using the instructions in crossref:kernelconfig[kernelconfig,Configuring the FreeBSD Kernel]. This command is typically run in daemon mode in order to provide a continuous system log file so that logging of past events may be reviewed. Since FreeBSD has a built in man:syslogd[8] facility to automatically rotate system logs, the default [.filename]#rc.conf# `ipmon_flags` statement uses `-Ds`: [.programlisting] .... ipmon_flags="-Ds" # D = start as daemon # s = log to syslog # v = log tcp window, ack, seq # n = map IP & port to names .... Logging provides the ability to review, after the fact, information such as which packets were dropped, what addresses they came from, and where they were going. This information is useful in tracking down attackers. Once the logging facility is enabled in [.filename]#rc.conf# and started with `service ipmon start`, IPF will only log the rules which contain the `log` keyword. The firewall administrator decides which rules in the ruleset should be logged and normally only deny rules are logged. It is customary to include the `log` keyword in the last rule in the ruleset. This makes it possible to see all the packets that did not match any of the rules in the ruleset. By default, `ipmon -Ds` mode uses `local0` as the logging facility. The following logging levels can be used to further segregate the logged data: [source,shell] .... LOG_INFO - packets logged using the "log" keyword as the action rather than pass or block. LOG_NOTICE - packets logged which are also passed LOG_WARNING - packets logged which are also blocked LOG_ERR - packets which have been logged and which can be considered short due to an incomplete header .... In order to setup IPF to log all data to [.filename]#/var/log/ipfilter.log#, first create the empty file: [source,shell] .... # touch /var/log/ipfilter.log .... Then, to write all logged messages to the specified file, add the following statement to [.filename]#/etc/syslog.conf#: [.programlisting] .... local0.* /var/log/ipfilter.log .... To activate the changes and instruct man:syslogd[8] to read the modified [.filename]#/etc/syslog.conf#, run `service syslogd reload`. Do not forget to edit [.filename]#/etc/newsyslog.conf# to rotate the new log file. Messages generated by `ipmon` consist of data fields separated by white space. Fields common to all messages are: . The date of packet receipt. . The time of packet receipt. This is in the form HH:MM:SS.F, for hours, minutes, seconds, and fractions of a second. . The name of the interface that processed the packet. . The group and rule number of the rule in the format `@0:17`. . The action: `p` for passed, `b` for blocked, `S` for a short packet, `n` did not match any rules, and `L` for a log rule. . The addresses written as three fields: the source address and port separated by a comma, the -> symbol, and the destination address and port. For example: `209.53.17.22,80 -> 198.73.220.17,1722`. . `PR` followed by the protocol name or number: for example, `PR tcp`. . `len` followed by the header length and total length of the packet: for example, `len 20 40`. If the packet is a TCP packet, there will be an additional field starting with a hyphen followed by letters corresponding to any flags that were set. Refer to man:ipf[5] for a list of letters and their flags. If the packet is an ICMP packet, there will be two fields at the end: the first always being "icmp" and the next being the ICMP message and sub-message type, separated by a slash. For example: `icmp 3/3` for a port unreachable message. [[firewalls-blacklistd]] == Blacklistd Blacklistd is a daemon listening to sockets to receive notifications from other daemons about connection attempts that failed or were successful. It is most widely used in blocking too many connection attempts on open ports. A prime example is SSH running on the internet getting a lot of requests from bots or scripts trying to guess passwords and gain access. Using blacklistd, the daemon can notify the firewall to create a filter rule to block excessive connection attempts from a single source after a number of tries. Blacklistd was first developed on NetBSD and appeared there in version 7. FreeBSD 11 imported blacklistd from NetBSD. This chapter describes how to set up blacklistd, configure it, and provides examples on how to use it. Readers should be familiar with basic firewall concepts like rules. For details, refer to the firewall chapter. PF is used in the examples, but other firewalls available on FreeBSD should be able to work with blacklistd, too. === Enabling Blacklistd The main configuration for blacklistd is stored in man:blacklistd.conf[5]. Various command line options are also available to change blacklistd's run-time behavior. Persistent configuration across reboots should be stored in [.filename]#/etc/blacklistd.conf#. To enable the daemon during system boot, add a `blacklistd_enable` line to [.filename]#/etc/rc.conf# like this: [source,shell] .... # sysrc blacklistd_enable=yes .... To start the service manually, run this command: [source,shell] .... # service blacklistd start .... === Creating a Blacklistd Ruleset Rules for blacklistd are configured in man:blacklistd.conf[5] with one entry per line. Each rule contains a tuple separated by spaces or tabs. Rules either belong to a `local` or a `remote`, which applies to the machine where blacklistd is running or an outside source, respectively. ==== Local Rules An example blacklistd.conf entry for a local rule looks like this: [.programlisting] .... [local] ssh stream * * * 3 24h .... All rules that follow the `[local]` section are treated as local rules (which is the default), applying to the local machine. When a `[remote]` section is encountered, all rules that follow it are handled as remote machine rules. Seven fields define a rule separated by either tabs or spaces. The first four fields identify the traffic that should be blocklisted. The three fields that follow define backlistd's behavior. Wildcards are denoted as asterisks (`*`), matching anything in this field. The first field defines the location. In local rules, these are the network ports. The syntax for the location field is as follows: [.programlisting] .... [address|interface][/mask][:port] .... Addresses can be specified as IPv4 in numeric format or IPv6 in square brackets. An interface name like `_em0_` can also be used. The socket type is defined by the second field. TCP sockets are of type `stream`, whereas UDP is denoted as `dgram`. The example above uses TCP, since SSH is using that protocol. A protocol can be used in the third field of a blacklistd rule. The following protocols can be used: `tcp`, `udp`, `tcp6`, `udp6`, or numeric. A wildcard, like in the example, is typically used to match all protocols unless there is a reason to distinguish traffic by a certain protocol. In the fourth field, the effective user or owner of the daemon process that is reporting the event is defined. The username or UID can be used here, as well as a wildcard (see example rule above). The packet filter rule name is declared by the fifth field, which starts the behavior part of the rule. By default, blacklistd puts all blocks under a pf anchor called `blacklistd` in [.filename]#pf.conf# like this: [.programlisting] .... anchor "blacklistd/*" in on $ext_if block in pass out .... For separate blocklists, an anchor name can be used in this field. In other cases, the wildcard will suffice. When a name starts with a hyphen (`-`) it means that an anchor with the default rule name prepended should be used. A modified example from the above using the hyphen would look like this: [.programlisting] .... ssh stream * * -ssh 3 24h .... With such a rule, any new blocklist rules are added to an anchor called `blacklistd-ssh`. To block whole subnets for a single rule violation, a `/` in the rule name can be used. This causes the remaining portion of the name to be interpreted as the mask to be applied to the address specified in the rule. For example, this rule would block every address adjoining `/24`. [.programlisting] .... 22 stream tcp * */24 3 24h .... [NOTE] ==== It is important to specify the proper protocol here. IPv4 and IPv6 treat /24 differently, that is the reason why `*` cannot be used in the third field for this rule. ==== This rule defines that if any one host in that network is misbehaving, everything else on that network will be blocked, too. The sixth field, called `nfail`, sets the number of login failures required to blocklist the remote IP in question. When a wildcard is used at this position, it means that blocks will never happen. In the example rule above, a limit of three is defined meaning that after three attempts to log into SSH on one connection, the IP is blocked. The last field in a blacklistd rule definition specifies how long a host is blocklisted. The default unit is seconds, but suffixes like `m`, `h`, and `d` can also be specified for minutes, hours, and days, respectively. The example rule in its entirety means that after three times authenticating to SSH will result in a new PF block rule for that host. Rule matches are performed by first checking local rules one after another, from most specific to least specific. When a match occurs, the `remote` rules are applied and the name, `nfail`, and disable fields are changed by the `remote` rule that matched. ==== Remote Rules Remote rules are used to specify how blacklistd changes its behavior depending on the remote host currently being evaluated. Each field in a remote rule is the same as in a local rule. The only difference is in the way blacklistd is using them. To explain it, this example rule is used: [.programlisting] .... [remote] 203.0.113.128/25 * * * =/25 = 48h .... The address field can be an IP address (either v4 or v6), a port or both. This allows setting special rules for a specific remote address range like in this example. The fields for type, protocol and owner are identically interpreted as in the local rule. The name fields is different though: the equal sign (`=`) in a remote rule tells blacklistd to use the value from the matching local rule. It means that the firewall rule entry is taken and the `/25` prefix (a netmask of `255.255.255.128`) is added. When a connection from that address range is blocklisted, the entire subnet is affected. A PF anchor name can also be used here, in which case blacklistd will add rules for this address block to the anchor of that name. The default table is used when a wildcard is specified. A custom number of failures in the `nfail` column can be defined for an address. This is useful for exceptions to a specific rule, to maybe allow someone a less strict application of rules or a bit more leniency in login tries. Blocking is disabled when an asterisk is used in this sixth field. Remote rules allow a stricter enforcement of limits on attempts to log in compared to attempts coming from a local network like an office. === Blacklistd Client Configuration There are a few software packages in FreeBSD that can utilize blacklistd's functionality. The two most prominent ones are man:ftpd[8] and man:sshd[8] to block excessive connection attempts. To activate blacklistd in the SSH daemon, add the following line to [.filename]#/etc/ssh/sshd_config#: [.programlisting] .... UseBlacklist yes .... Restart sshd afterwards to make these changes take effect. Blacklisting for man:ftpd[8] is enabled using `-B`, either in [.filename]#/etc/inetd.conf# or as a flag in [.filename]#/etc/rc.conf# like this: [.programlisting] .... ftpd_flags="-B" .... That is all that is needed to make these programs talk to blacklistd. === Blacklistd Management Blacklistd provides the user with a management utility called man:blacklistctl[8]. It displays blocked addresses and networks that are blocklisted by the rules defined in man:blacklistd.conf[5]. To see the list of currently blocked hosts, use `dump` combined with `-b` like this. [source,shell] .... # blacklistctl dump -b address/ma:port id nfail last access 213.0.123.128/25:22 OK 6/3 2019/06/08 14:30:19 .... This example shows that there were 6 out of three permitted attempts on port 22 coming from the address range `213.0.123.128/25`. There are more attempts listed than are allowed because SSH allows a client to try multiple logins on a single TCP connection. A connection that is currently going on is not stopped by blacklistd. The last connection attempt is listed in the `last access` column of the output. To see the remaining time that this host will be on the blocklist, add `-r` to the previous command. [source,shell] .... # blacklistctl dump -br address/ma:port id nfail remaining time 213.0.123.128/25:22 OK 6/3 36s .... In this example, there are 36s seconds left until this host will not be blocked any more. === Removing Hosts from the Block List Sometimes it is necessary to remove a host from the block list before the remaining time expires. Unfortunately, there is no functionality in blacklistd to do that. However, it is possible to remove the address from the PF table using pfctl. For each blocked port, there is a child anchor inside the blacklistd anchor defined in [.filename]#/etc/pf.conf#. For example, if there is a child anchor for blocking port 22 it is called `blacklistd/22`. There is a table inside that child anchor that contains the blocked addresses. This table is called port followed by the port number. In this example, it would be called `port22`. With that information at hand, it is now possible to use man:pfctl[8] to display all addresses listed like this: [source,shell] .... # pfctl -a blacklistd/22 -t port22 -T show ... 213.0.123.128/25 ... .... After identifying the address to be unblocked from the list, the following command removes it from the list: [source,shell] .... # pfctl -a blacklistd/22 -t port22 -T delete 213.0.123.128/25 .... -The address is now removed from PF, but will still show up in the blacklistctl list, since it does not know about any changes made in PF. -The entry in blacklistd's database will eventually expire and be removed from its output eventually. +The address is now removed from PF, but will still show up in the blacklistctl list, since it does not know about any changes made in PF. +The entry in blacklistd's database will eventually expire and be removed from its output. The entry will be added again if the host is matching one of the block rules in blacklistd again. diff --git a/documentation/content/en/books/handbook/geom/_index.adoc b/documentation/content/en/books/handbook/geom/_index.adoc index b220487080..01a26d9ae5 100644 --- a/documentation/content/en/books/handbook/geom/_index.adoc +++ b/documentation/content/en/books/handbook/geom/_index.adoc @@ -1,1304 +1,1304 @@ --- title: "Chapter 19. GEOM: Modular Disk Transformation Framework" part: Part III. System Administration prev: books/handbook/disks next: books/handbook/zfs description: In FreeBSD, the GEOM framework permits access and control to classes, such as Master Boot Records and BSD labels, through the use of providers, or the disk devices in /dev. tags: ["GEOM", "RAID", "RAID0", "RAID1", "RAID3", "Striping", "bsdlabel", "newfs", "labelling", "UFS", "journaling"] showBookMenu: true weight: 23 path: "/books/handbook/" --- [[geom]] = GEOM: Modular Disk Transformation Framework :doctype: book :toc: macro :toclevels: 1 :icons: font :sectnums: :sectnumlevels: 6 :sectnumoffset: 19 :partnums: :source-highlighter: rouge :experimental: :images-path: books/handbook/geom/ ifdef::env-beastie[] ifdef::backend-html5[] :imagesdir: ../../../../images/{images-path} endif::[] ifndef::book[] include::shared/authors.adoc[] include::shared/mirrors.adoc[] include::shared/releases.adoc[] include::shared/attributes/attributes-{{% lang %}}.adoc[] include::shared/{{% lang %}}/teams.adoc[] include::shared/{{% lang %}}/mailing-lists.adoc[] include::shared/{{% lang %}}/urls.adoc[] toc::[] endif::[] ifdef::backend-pdf,backend-epub3[] include::../../../../../shared/asciidoctor.adoc[] endif::[] endif::[] ifndef::env-beastie[] toc::[] include::../../../../../shared/asciidoctor.adoc[] endif::[] [[geom-synopsis]] == Synopsis In FreeBSD, the GEOM framework permits access and control to classes, such as Master Boot Records and BSD labels, through the use of providers, or the disk devices in [.filename]#/dev#. By supporting various software RAID configurations, GEOM transparently provides access to the operating system and operating system utilities. This chapter covers the use of disks under the GEOM framework in FreeBSD. This includes the major RAID control utilities which use the framework for configuration. This chapter is not a definitive guide to RAID configurations and only GEOM-supported RAID classifications are discussed. After reading this chapter, you will know: * What type of RAID support is available through GEOM. * How to use the base utilities to configure, maintain, and manipulate the various RAID levels. * How to mirror, stripe, encrypt, and remotely connect disk devices through GEOM. * How to troubleshoot disks attached to the GEOM framework. Before reading this chapter, you should: * Understand how FreeBSD treats disk devices (crossref:disks[disks,Storage]). * Know how to configure and install a new kernel (crossref:kernelconfig[kernelconfig,Configuring the FreeBSD Kernel]). [[geom-striping]] == RAID0 - Striping Striping combines several disk drives into a single volume. Striping can be performed through the use of hardware RAID controllers. The GEOM disk subsystem provides software support for disk striping, also known as RAID0, without the need for a RAID disk controller. In RAID0, data is split into blocks that are written across all the drives in the array. As seen in the following illustration, instead of having to wait on the system to write 256k to one disk, RAID0 can simultaneously write 64k to each of the four disks in the array, offering superior I/O performance. This performance can be enhanced further by using multiple disk controllers. image::striping.png[Disk Striping Illustration] Each disk in a RAID0 stripe must be of the same size, since I/O requests are interleaved to read or write to multiple disks in parallel. [NOTE] ==== RAID0 does _not_ provide any redundancy. This means that if one disk in the array fails, all of the data on the disks is lost. If the data is important, implement a backup strategy that regularly saves backups to a remote system or device. ==== The process for creating a software, GEOM-based RAID0 on a FreeBSD system using commodity disks is as follows. Once the stripe is created, refer to man:gstripe[8] for more information on how to control an existing stripe. [.procedure] **** *Procedure: Creating a Stripe of Unformatted ATA Disks* . Load the [.filename]#geom_stripe.ko# module: + [source,shell] .... # kldload geom_stripe .... . Ensure that a suitable mount point exists. If this volume will become a root partition, then temporarily use another mount point such as [.filename]#/mnt#. . Determine the device names for the disks which will be striped, and create the new stripe device. For example, to stripe two unused and unpartitioned ATA disks with device names of [.filename]#/dev/ad2# and [.filename]#/dev/ad3#: + [source,shell] .... # gstripe label -v st0 /dev/ad2 /dev/ad3 Metadata value stored on /dev/ad2. Metadata value stored on /dev/ad3. Done. .... . Write a standard label, also known as a partition table, on the new volume and install the default bootstrap code: + [source,shell] .... # bsdlabel -wB /dev/stripe/st0 .... . This process should create two other devices in [.filename]#/dev/stripe# in addition to [.filename]#st0#. Those include [.filename]#st0a# and [.filename]#st0c#. At this point, a UFS file system can be created on [.filename]#st0a# using `newfs`: + [source,shell] .... # newfs -U /dev/stripe/st0a .... + Many numbers will glide across the screen, and after a few seconds, the process will be complete. The volume has been created and is ready to be mounted. . To manually mount the created disk stripe: + [source,shell] .... # mount /dev/stripe/st0a /mnt .... . To mount this striped file system automatically during the boot process, place the volume information in [.filename]#/etc/fstab#. In this example, a permanent mount point, named [.filename]#stripe#, is created: + [source,shell] .... # mkdir /stripe # echo "/dev/stripe/st0a /stripe ufs rw 2 2" \ >> /etc/fstab .... . The [.filename]#geom_stripe.ko# module must also be automatically loaded during system initialization, by adding a line to [.filename]#/boot/loader.conf#: + [source,shell] .... # echo 'geom_stripe_load="YES"' >> /boot/loader.conf .... **** [[geom-mirror]] == RAID1 - Mirroring RAID1, or _mirroring_, is the technique of writing the same data to more than one disk drive. Mirrors are usually used to guard against data loss due to drive failure. Each drive in a mirror contains an identical copy of the data. When an individual drive fails, the mirror continues to work, providing data from the drives that are still functioning. The computer keeps running, and the administrator has time to replace the failed drive without user interruption. Two common situations are illustrated in these examples. The first creates a mirror out of two new drives and uses it as a replacement for an existing single drive. The second example creates a mirror on a single new drive, copies the old drive's data to it, then inserts the old drive into the mirror. While this procedure is slightly more complicated, it only requires one new drive. Traditionally, the two drives in a mirror are identical in model and capacity, but man:gmirror[8] does not require that. Mirrors created with dissimilar drives will have a capacity equal to that of the smallest drive in the mirror. Extra space on larger drives will be unused. Drives inserted into the mirror later must have at least as much capacity as the smallest drive already in the mirror. [WARNING] ==== The mirroring procedures shown here are non-destructive, but as with any major disk operation, make a full backup first. ==== [WARNING] ==== While man:dump[8] is used in these procedures to copy file systems, it does not work on file systems with soft updates journaling. See man:tunefs[8] for information on detecting and disabling soft updates journaling. ==== [[geom-mirror-metadata]] === Metadata Issues Many disk systems store metadata at the end of each disk. Old metadata should be erased before reusing the disk for a mirror. Most problems are caused by two particular types of leftover metadata: GPT partition tables and old metadata from a previous mirror. GPT metadata can be erased with man:gpart[8]. This example erases both primary and backup GPT partition tables from disk [.filename]#ada8#: [source,shell] .... # gpart destroy -F ada8 .... A disk can be removed from an active mirror and the metadata erased in one step using man:gmirror[8]. Here, the example disk [.filename]#ada8# is removed from the active mirror [.filename]#gm4#: [source,shell] .... # gmirror remove gm4 ada8 .... If the mirror is not running, but old mirror metadata is still on the disk, use `gmirror clear` to remove it: [source,shell] .... # gmirror clear ada8 .... man:gmirror[8] stores one block of metadata at the end of the disk. As GPT partition schemes also store metadata at the end of the disk, mirroring entire GPT disks with man:gmirror[8] is not recommended. MBR partitioning is used here because it only stores a partition table at the start of the disk and does not conflict with the mirror metadata. [[geom-mirror-two-new-disks]] === Creating a Mirror with Two New Disks In this example, FreeBSD has already been installed on a single disk, [.filename]#ada0#. Two new disks, [.filename]#ada1# and [.filename]#ada2#, have been connected to the system. A new mirror will be created on these two disks and used to replace the old single disk. The [.filename]#geom_mirror.ko# kernel module must either be built into the kernel or loaded at boot- or run-time. Manually load the kernel module now: [source,shell] .... # gmirror load .... Create the mirror with the two new drives: [source,shell] .... # gmirror label -v gm0 /dev/ada1 /dev/ada2 .... [.filename]#gm0# is a user-chosen device name assigned to the new mirror. After the mirror has been started, this device name appears in [.filename]#/dev/mirror/#. MBR and bsdlabel partition tables can now be created on the mirror with man:gpart[8]. This example uses a traditional file system layout, with partitions for [.filename]#/#, swap, [.filename]#/var#, [.filename]#/tmp#, and [.filename]#/usr#. A single [.filename]#/# and a swap partition will also work. Partitions on the mirror do not have to be the same size as those on the existing disk, but they must be large enough to hold all the data already present on [.filename]#ada0#. [source,shell] .... # gpart create -s MBR mirror/gm0 # gpart add -t freebsd -a 4k mirror/gm0 # gpart show mirror/gm0 => 63 156301423 mirror/gm0 MBR (74G) 63 63 - free - (31k) 126 156301299 1 freebsd (74G) 156301425 61 - free - (30k) .... [source,shell] .... # gpart create -s BSD mirror/gm0s1 # gpart add -t freebsd-ufs -a 4k -s 2g mirror/gm0s1 # gpart add -t freebsd-swap -a 4k -s 4g mirror/gm0s1 # gpart add -t freebsd-ufs -a 4k -s 2g mirror/gm0s1 # gpart add -t freebsd-ufs -a 4k -s 1g mirror/gm0s1 # gpart add -t freebsd-ufs -a 4k mirror/gm0s1 # gpart show mirror/gm0s1 => 0 156301299 mirror/gm0s1 BSD (74G) 0 2 - free - (1.0k) 2 4194304 1 freebsd-ufs (2.0G) 4194306 8388608 2 freebsd-swap (4.0G) 12582914 4194304 4 freebsd-ufs (2.0G) 16777218 2097152 5 freebsd-ufs (1.0G) 18874370 137426928 6 freebsd-ufs (65G) 156301298 1 - free - (512B) .... Make the mirror bootable by installing bootcode in the MBR and bsdlabel and setting the active slice: [source,shell] .... # gpart bootcode -b /boot/mbr mirror/gm0 # gpart set -a active -i 1 mirror/gm0 # gpart bootcode -b /boot/boot mirror/gm0s1 .... Format the file systems on the new mirror, enabling soft-updates. [source,shell] .... # newfs -U /dev/mirror/gm0s1a # newfs -U /dev/mirror/gm0s1d # newfs -U /dev/mirror/gm0s1e # newfs -U /dev/mirror/gm0s1f .... File systems from the original [.filename]#ada0# disk can now be copied onto the mirror with man:dump[8] and man:restore[8]. [source,shell] .... # mount /dev/mirror/gm0s1a /mnt # dump -C16 -b64 -0aL -f - / | (cd /mnt && restore -rf -) # mount /dev/mirror/gm0s1d /mnt/var # mount /dev/mirror/gm0s1e /mnt/tmp # mount /dev/mirror/gm0s1f /mnt/usr # dump -C16 -b64 -0aL -f - /var | (cd /mnt/var && restore -rf -) # dump -C16 -b64 -0aL -f - /tmp | (cd /mnt/tmp && restore -rf -) # dump -C16 -b64 -0aL -f - /usr | (cd /mnt/usr && restore -rf -) .... Edit [.filename]#/mnt/etc/fstab# to point to the new mirror file systems: [.programlisting] .... # Device Mountpoint FStype Options Dump Pass# /dev/mirror/gm0s1a / ufs rw 1 1 /dev/mirror/gm0s1b none swap sw 0 0 /dev/mirror/gm0s1d /var ufs rw 2 2 /dev/mirror/gm0s1e /tmp ufs rw 2 2 /dev/mirror/gm0s1f /usr ufs rw 2 2 .... If the [.filename]#geom_mirror.ko# kernel module has not been built into the kernel, [.filename]#/mnt/boot/loader.conf# is edited to load the module at boot: [.programlisting] .... geom_mirror_load="YES" .... Reboot the system to test the new mirror and verify that all data has been copied. The BIOS will see the mirror as two individual drives rather than a mirror. Since the drives are identical, it does not matter which is selected to boot. See <> if there are problems booting. Powering down and disconnecting the original [.filename]#ada0# disk will allow it to be kept as an offline backup. In use, the mirror will behave just like the original single drive. [[geom-mirror-existing-drive]] === Creating a Mirror with an Existing Drive In this example, FreeBSD has already been installed on a single disk, [.filename]#ada0#. A new disk, [.filename]#ada1#, has been connected to the system. A one-disk mirror will be created on the new disk, the existing system copied onto it, and then the old disk will be inserted into the mirror. This slightly complex procedure is required because `gmirror` needs to put a 512-byte block of metadata at the end of each disk, and the existing [.filename]#ada0# has usually had all of its space already allocated. Load the [.filename]#geom_mirror.ko# kernel module: [source,shell] .... # gmirror load .... Check the media size of the original disk with `diskinfo`: [source,shell] .... # diskinfo -v ada0 | head -n3 /dev/ada0 512 # sectorsize 1000204821504 # mediasize in bytes (931G) .... Create a mirror on the new disk. To make certain that the mirror capacity is not any larger than the original [.filename]#ada0# drive, man:gnop[8] is used to create a fake drive of the exact same size. This drive does not store any data, but is used only to limit the size of the mirror. When man:gmirror[8] creates the mirror, it will restrict the capacity to the size of [.filename]#gzero.nop#, even if the new [.filename]#ada1# drive has more space. Note that the _1000204821504_ in the second line is equal to [.filename]#ada0#'s media size as shown by `diskinfo` above. [source,shell] .... # geom zero load # gnop create -s 1000204821504 gzero # gmirror label -v gm0 gzero.nop ada1 # gmirror forget gm0 .... Since [.filename]#gzero.nop# does not store any data, the mirror does not see it as connected. The mirror is told to "forget" unconnected components, removing references to [.filename]#gzero.nop#. The result is a mirror device containing only a single disk, [.filename]#ada1#. After creating [.filename]#gm0#, view the partition table on [.filename]#ada0#. This output is from a 1 TB drive. If there is some unallocated space at the end of the drive, the contents may be copied directly from [.filename]#ada0# to the new mirror. However, if the output shows that all of the space on the disk is allocated, as in the following listing, there is no space available for the 512-byte mirror metadata at the end of the disk. [source,shell] .... # gpart show ada0 => 63 1953525105 ada0 MBR (931G) 63 1953525105 1 freebsd [active] (931G) .... In this case, the partition table must be edited to reduce the capacity by one sector on [.filename]#mirror/gm0#. The procedure will be explained later. In either case, partition tables on the primary disk should be first copied using `gpart backup` and `gpart restore`. [source,shell] .... # gpart backup ada0 > table.ada0 # gpart backup ada0s1 > table.ada0s1 .... These commands create two files, [.filename]#table.ada0# and [.filename]#table.ada0s1#. This example is from a 1 TB drive: [source,shell] .... # cat table.ada0 MBR 4 1 freebsd 63 1953525105 [active] .... [source,shell] .... # cat table.ada0s1 BSD 8 1 freebsd-ufs 0 4194304 2 freebsd-swap 4194304 33554432 4 freebsd-ufs 37748736 50331648 5 freebsd-ufs 88080384 41943040 6 freebsd-ufs 130023424 838860800 7 freebsd-ufs 968884224 984640881 .... If no free space is shown at the end of the disk, the size of both the slice and the last partition must be reduced by one sector. Edit the two files, reducing the size of both the slice and last partition by one. These are the last numbers in each listing. [source,shell] .... # cat table.ada0 MBR 4 1 freebsd 63 1953525104 [active] .... [source,shell] .... # cat table.ada0s1 BSD 8 1 freebsd-ufs 0 4194304 2 freebsd-swap 4194304 33554432 4 freebsd-ufs 37748736 50331648 5 freebsd-ufs 88080384 41943040 6 freebsd-ufs 130023424 838860800 7 freebsd-ufs 968884224 984640880 .... If at least one sector was unallocated at the end of the disk, these two files can be used without modification. Now restore the partition table into [.filename]#mirror/gm0#: [source,shell] .... # gpart restore mirror/gm0 < table.ada0 # gpart restore mirror/gm0s1 < table.ada0s1 .... Check the partition table with `gpart show`. This example has [.filename]#gm0s1a# for [.filename]#/#, [.filename]#gm0s1d# for [.filename]#/var#, [.filename]#gm0s1e# for [.filename]#/usr#, [.filename]#gm0s1f# for [.filename]#/data1#, and [.filename]#gm0s1g# for [.filename]#/data2#. [source,shell] .... # gpart show mirror/gm0 => 63 1953525104 mirror/gm0 MBR (931G) 63 1953525042 1 freebsd [active] (931G) 1953525105 62 - free - (31k) # gpart show mirror/gm0s1 => 0 1953525042 mirror/gm0s1 BSD (931G) 0 2097152 1 freebsd-ufs (1.0G) 2097152 16777216 2 freebsd-swap (8.0G) 18874368 41943040 4 freebsd-ufs (20G) 60817408 20971520 5 freebsd-ufs (10G) 81788928 629145600 6 freebsd-ufs (300G) 710934528 1242590514 7 freebsd-ufs (592G) 1953525042 63 - free - (31k) .... Both the slice and the last partition must have at least one free block at the end of the disk. Create file systems on these new partitions. The number of partitions will vary to match the original disk, [.filename]#ada0#. [source,shell] .... # newfs -U /dev/mirror/gm0s1a # newfs -U /dev/mirror/gm0s1d # newfs -U /dev/mirror/gm0s1e # newfs -U /dev/mirror/gm0s1f # newfs -U /dev/mirror/gm0s1g .... Make the mirror bootable by installing bootcode in the MBR and bsdlabel and setting the active slice: [source,shell] .... # gpart bootcode -b /boot/mbr mirror/gm0 # gpart set -a active -i 1 mirror/gm0 # gpart bootcode -b /boot/boot mirror/gm0s1 .... Adjust [.filename]#/etc/fstab# to use the new partitions on the mirror. Back up this file first by copying it to [.filename]#/etc/fstab.orig#. [source,shell] .... # cp /etc/fstab /etc/fstab.orig .... Edit [.filename]#/etc/fstab#, replacing [.filename]#/dev/ada0# with [.filename]#mirror/gm0#. [.programlisting] .... # Device Mountpoint FStype Options Dump Pass# /dev/mirror/gm0s1a / ufs rw 1 1 /dev/mirror/gm0s1b none swap sw 0 0 /dev/mirror/gm0s1d /var ufs rw 2 2 /dev/mirror/gm0s1e /usr ufs rw 2 2 /dev/mirror/gm0s1f /data1 ufs rw 2 2 /dev/mirror/gm0s1g /data2 ufs rw 2 2 .... If the [.filename]#geom_mirror.ko# kernel module has not been built into the kernel, edit [.filename]#/boot/loader.conf# to load it at boot: [.programlisting] .... geom_mirror_load="YES" .... File systems from the original disk can now be copied onto the mirror with man:dump[8] and man:restore[8]. Each file system dumped with `dump -L` will create a snapshot first, which can take some time. [source,shell] .... # mount /dev/mirror/gm0s1a /mnt # dump -C16 -b64 -0aL -f - / | (cd /mnt && restore -rf -) # mount /dev/mirror/gm0s1d /mnt/var # mount /dev/mirror/gm0s1e /mnt/usr # mount /dev/mirror/gm0s1f /mnt/data1 # mount /dev/mirror/gm0s1g /mnt/data2 # dump -C16 -b64 -0aL -f - /usr | (cd /mnt/usr && restore -rf -) # dump -C16 -b64 -0aL -f - /var | (cd /mnt/var && restore -rf -) # dump -C16 -b64 -0aL -f - /data1 | (cd /mnt/data1 && restore -rf -) # dump -C16 -b64 -0aL -f - /data2 | (cd /mnt/data2 && restore -rf -) .... Restart the system, booting from [.filename]#ada1#. If everything is working, the system will boot from [.filename]#mirror/gm0#, which now contains the same data as [.filename]#ada0# had previously. See <> if there are problems booting. At this point, the mirror still consists of only the single [.filename]#ada1# disk. After booting from [.filename]#mirror/gm0# successfully, the final step is inserting [.filename]#ada0# into the mirror. [IMPORTANT] ==== When [.filename]#ada0# is inserted into the mirror, its former contents will be overwritten by data from the mirror. Make certain that [.filename]#mirror/gm0# has the same contents as [.filename]#ada0# before adding [.filename]#ada0# to the mirror. If the contents previously copied by man:dump[8] and man:restore[8] are not identical to what was on [.filename]#ada0#, revert [.filename]#/etc/fstab# to mount the file systems on [.filename]#ada0#, reboot, and start the whole procedure again. ==== [source,shell] .... # gmirror insert gm0 ada0 GEOM_MIRROR: Device gm0: rebuilding provider ada0 .... Synchronization between the two disks will start immediately. Use `gmirror status` to view the progress. [source,shell] .... # gmirror status Name Status Components mirror/gm0 DEGRADED ada1 (ACTIVE) ada0 (SYNCHRONIZING, 64%) .... After a while, synchronization will finish. [source,shell] .... GEOM_MIRROR: Device gm0: rebuilding provider ada0 finished. # gmirror status Name Status Components mirror/gm0 COMPLETE ada1 (ACTIVE) ada0 (ACTIVE) .... [.filename]#mirror/gm0# now consists of the two disks [.filename]#ada0# and [.filename]#ada1#, and the contents are automatically synchronized with each other. In use, [.filename]#mirror/gm0# will behave just like the original single drive. [[gmirror-troubleshooting]] === Troubleshooting If the system no longer boots, BIOS settings may have to be changed to boot from one of the new mirrored drives. Either mirror drive can be used for booting, as they contain identical data. If the boot stops with this message, something is wrong with the mirror device: [source,shell] .... Mounting from ufs:/dev/mirror/gm0s1a failed with error 19. Loader variables: vfs.root.mountfrom=ufs:/dev/mirror/gm0s1a vfs.root.mountfrom.options=rw Manual root filesystem specification: : [options] Mount using filesystem and with the specified (optional) option list. - eg. ufs:/dev/da0s1a + e.g. ufs:/dev/da0s1a zfs:tank cd9660:/dev/acd0 ro (which is equivalent to: mount -t cd9660 -o ro /dev/acd0 /) ? List valid disk boot devices . Yield 1 second (for background tasks) Abort manual input mountroot> .... Forgetting to load the [.filename]#geom_mirror.ko# module in [.filename]#/boot/loader.conf# can cause this problem. To fix it, boot from a FreeBSD installation media and choose `Shell` at the first prompt. Then load the mirror module and mount the mirror device: [source,shell] .... # gmirror load # mount /dev/mirror/gm0s1a /mnt .... Edit [.filename]#/mnt/boot/loader.conf#, adding a line to load the mirror module: [.programlisting] .... geom_mirror_load="YES" .... Save the file and reboot. Other problems that cause `error 19` require more effort to fix. Although the system should boot from [.filename]#ada0#, another prompt to select a shell will appear if [.filename]#/etc/fstab# is incorrect. Enter `ufs:/dev/ada0s1a` at the boot loader prompt and press kbd:[Enter]. Undo the edits in [.filename]#/etc/fstab# then mount the file systems from the original disk ([.filename]#ada0#) instead of the mirror. Reboot the system and try the procedure again. [source,shell] .... Enter full pathname of shell or RETURN for /bin/sh: # cp /etc/fstab.orig /etc/fstab # reboot .... === Recovering from Disk Failure The benefit of disk mirroring is that an individual disk can fail without causing the mirror to lose any data. In the above example, if [.filename]#ada0# fails, the mirror will continue to work, providing data from the remaining working drive, [.filename]#ada1#. To replace the failed drive, shut down the system and physically replace the failed drive with a new drive of equal or greater capacity. Manufacturers use somewhat arbitrary values when rating drives in gigabytes, and the only way to really be sure is to compare the total count of sectors shown by `diskinfo -v`. A drive with larger capacity than the mirror will work, although the extra space on the new drive will not be used. After the computer is powered back up, the mirror will be running in a "degraded" mode with only one drive. The mirror is told to forget drives that are not currently connected: [source,shell] .... # gmirror forget gm0 .... Any old metadata should be cleared from the replacement disk using the instructions in <>. Then the replacement disk, [.filename]#ada4# for this example, is inserted into the mirror: [source,shell] .... # gmirror insert gm0 /dev/ada4 .... Resynchronization begins when the new drive is inserted into the mirror. This process of copying mirror data to a new drive can take a while. Performance of the mirror will be greatly reduced during the copy, so inserting new drives is best done when there is low demand on the computer. Progress can be monitored with `gmirror status`, which shows drives that are being synchronized and the percentage of completion. During resynchronization, the status will be `DEGRADED`, changing to `COMPLETE` when the process is finished. [[geom-raid3]] == RAID3 - Byte-level Striping with Dedicated Parity RAID3 is a method used to combine several disk drives into a single volume with a dedicated parity disk. In a RAID3 system, data is split up into a number of bytes that are written across all the drives in the array except for one disk which acts as a dedicated parity disk. This means that disk reads from a RAID3 implementation access all disks in the array. Performance can be enhanced by using multiple disk controllers. The RAID3 array provides a fault tolerance of 1 drive, while providing a capacity of 1 - 1/n times the total capacity of all drives in the array, where n is the number of hard drives in the array. Such a configuration is mostly suitable for storing data of larger sizes such as multimedia files. At least 3 physical hard drives are required to build a RAID3 array. Each disk must be of the same size, since I/O requests are interleaved to read or write to multiple disks in parallel. Also, due to the nature of RAID3, the number of drives must be equal to 3, 5, 9, 17, and so on, or 2^n + 1. This section demonstrates how to create a software RAID3 on a FreeBSD system. [NOTE] ==== While it is theoretically possible to boot from a RAID3 array on FreeBSD, that configuration is uncommon and is not advised. ==== === Creating a Dedicated RAID3 Array In FreeBSD, support for RAID3 is implemented by the man:graid3[8] GEOM class. Creating a dedicated RAID3 array on FreeBSD requires the following steps. [.procedure] . First, load the [.filename]#geom_raid3.ko# kernel module by issuing one of the following commands: + [source,shell] .... # graid3 load .... + or: + [source,shell] .... # kldload geom_raid3 .... . Ensure that a suitable mount point exists. This command creates a new directory to use as the mount point: + [source,shell] .... # mkdir /multimedia .... . Determine the device names for the disks which will be added to the array, and create the new RAID3 device. The final device listed will act as the dedicated parity disk. This example uses three unpartitioned ATA drives: [.filename]#ada1# and [.filename]#ada2# for data, and [.filename]#ada3# for parity. + [source,shell] .... # graid3 label -v gr0 /dev/ada1 /dev/ada2 /dev/ada3 Metadata value stored on /dev/ada1. Metadata value stored on /dev/ada2. Metadata value stored on /dev/ada3. Done. .... . Partition the newly created [.filename]#gr0# device and put a UFS file system on it: + [source,shell] .... # gpart create -s GPT /dev/raid3/gr0 # gpart add -t freebsd-ufs /dev/raid3/gr0 # newfs -j /dev/raid3/gr0p1 .... + Many numbers will glide across the screen, and after a bit of time, the process will be complete. The volume has been created and is ready to be mounted: + [source,shell] .... # mount /dev/raid3/gr0p1 /multimedia/ .... + The RAID3 array is now ready to use. Additional configuration is needed to retain this setup across system reboots. [.procedure] . The [.filename]#geom_raid3.ko# module must be loaded before the array can be mounted. To automatically load the kernel module during system initialization, add the following line to [.filename]#/boot/loader.conf#: + [.programlisting] .... geom_raid3_load="YES" .... . The following volume information must be added to [.filename]#/etc/fstab# in order to automatically mount the array's file system during the system boot process: + [.programlisting] .... /dev/raid3/gr0p1 /multimedia ufs rw 2 2 .... [[geom-graid]] == Software RAID Devices Some motherboards and expansion cards add some simple hardware, usually just a ROM, that allows the computer to boot from a RAID array. After booting, access to the RAID array is handled by software running on the computer's main processor. This "hardware-assisted software RAID" gives RAID arrays that are not dependent on any particular operating system, and which are functional even before an operating system is loaded. Several levels of RAID are supported, depending on the hardware in use. See man:graid[8] for a complete list. man:graid[8] requires the [.filename]#geom_raid.ko# kernel module, which is included in the [.filename]#GENERIC# kernel starting with FreeBSD 9.1. If needed, it can be loaded manually with `graid load`. [[geom-graid-creating]] === Creating an Array Software RAID devices often have a menu that can be entered by pressing special keys when the computer is booting. The menu can be used to create and delete RAID arrays. man:graid[8] can also create arrays directly from the command line. `graid label` is used to create a new array. The motherboard used for this example has an Intel software RAID chipset, so the Intel metadata format is specified. The new array is given a label of [.filename]#gm0#, it is a mirror (RAID1), and uses drives [.filename]#ada0# and [.filename]#ada1#. [CAUTION] ==== Some space on the drives will be overwritten when they are made into a new array. Back up existing data first! ==== [source,shell] .... # graid label Intel gm0 RAID1 ada0 ada1 GEOM_RAID: Intel-a29ea104: Array Intel-a29ea104 created. GEOM_RAID: Intel-a29ea104: Disk ada0 state changed from NONE to ACTIVE. GEOM_RAID: Intel-a29ea104: Subdisk gm0:0-ada0 state changed from NONE to ACTIVE. GEOM_RAID: Intel-a29ea104: Disk ada1 state changed from NONE to ACTIVE. GEOM_RAID: Intel-a29ea104: Subdisk gm0:1-ada1 state changed from NONE to ACTIVE. GEOM_RAID: Intel-a29ea104: Array started. GEOM_RAID: Intel-a29ea104: Volume gm0 state changed from STARTING to OPTIMAL. Intel-a29ea104 created GEOM_RAID: Intel-a29ea104: Provider raid/r0 for volume gm0 created. .... A status check shows the new mirror is ready for use: [source,shell] .... # graid status Name Status Components raid/r0 OPTIMAL ada0 (ACTIVE (ACTIVE)) ada1 (ACTIVE (ACTIVE)) .... The array device appears in [.filename]#/dev/raid/#. The first array is called [.filename]#r0#. Additional arrays, if present, will be [.filename]#r1#, [.filename]#r2#, and so on. The BIOS menu on some of these devices can create arrays with special characters in their names. To avoid problems with those special characters, arrays are given simple numbered names like [.filename]#r0#. To show the actual labels, like [.filename]#gm0# in the example above, use man:sysctl[8]: [source,shell] .... # sysctl kern.geom.raid.name_format=1 .... [[geom-graid-volumes]] === Multiple Volumes Some software RAID devices support more than one _volume_ on an array. Volumes work like partitions, allowing space on the physical drives to be split and used in different ways. For example, Intel software RAID devices support two volumes. This example creates a 40 G mirror for safely storing the operating system, followed by a 20 G RAID0 (stripe) volume for fast temporary storage: [source,shell] .... # graid label -S 40G Intel gm0 RAID1 ada0 ada1 # graid add -S 20G gm0 RAID0 .... Volumes appear as additional [.filename]#rX# entries in [.filename]#/dev/raid/#. An array with two volumes will show [.filename]#r0# and [.filename]#r1#. See man:graid[8] for the number of volumes supported by different software RAID devices. [[geom-graid-converting]] === Converting a Single Drive to a Mirror Under certain specific conditions, it is possible to convert an existing single drive to a man:graid[8] array without reformatting. To avoid data loss during the conversion, the existing drive must meet these minimum requirements: * The drive must be partitioned with the MBR partitioning scheme. GPT or other partitioning schemes with metadata at the end of the drive will be overwritten and corrupted by the man:graid[8] metadata. * There must be enough unpartitioned and unused space at the end of the drive to hold the man:graid[8] metadata. This metadata varies in size, but the largest occupies 64 M, so at least that much free space is recommended. If the drive meets these requirements, start by making a full backup. Then create a single-drive mirror with that drive: [source,shell] .... # graid label Intel gm0 RAID1 ada0 NONE .... man:graid[8] metadata was written to the end of the drive in the unused space. A second drive can now be inserted into the mirror: [source,shell] .... # graid insert raid/r0 ada1 .... Data from the original drive will immediately begin to be copied to the second drive. The mirror will operate in degraded status until the copy is complete. [[geom-graid-inserting]] === Inserting New Drives into the Array Drives can be inserted into an array as replacements for drives that have failed or are missing. If there are no failed or missing drives, the new drive becomes a spare. For example, inserting a new drive into a working two-drive mirror results in a two-drive mirror with one spare drive, not a three-drive mirror. In the example mirror array, data immediately begins to be copied to the newly-inserted drive. Any existing information on the new drive will be overwritten. [source,shell] .... # graid insert raid/r0 ada1 GEOM_RAID: Intel-a29ea104: Disk ada1 state changed from NONE to ACTIVE. GEOM_RAID: Intel-a29ea104: Subdisk gm0:1-ada1 state changed from NONE to NEW. GEOM_RAID: Intel-a29ea104: Subdisk gm0:1-ada1 state changed from NEW to REBUILD. GEOM_RAID: Intel-a29ea104: Subdisk gm0:1-ada1 rebuild start at 0. .... [[geom-graid-removing]] === Removing Drives from the Array Individual drives can be permanently removed from a from an array and their metadata erased: [source,shell] .... # graid remove raid/r0 ada1 GEOM_RAID: Intel-a29ea104: Disk ada1 state changed from ACTIVE to OFFLINE. GEOM_RAID: Intel-a29ea104: Subdisk gm0:1-[unknown] state changed from ACTIVE to NONE. GEOM_RAID: Intel-a29ea104: Volume gm0 state changed from OPTIMAL to DEGRADED. .... [[geom-graid-stopping]] === Stopping the Array An array can be stopped without removing metadata from the drives. The array will be restarted when the system is booted. [source,shell] .... # graid stop raid/r0 .... [[geom-graid-status]] === Checking Array Status Array status can be checked at any time. After a drive was added to the mirror in the example above, data is being copied from the original drive to the new drive: [source,shell] .... # graid status Name Status Components raid/r0 DEGRADED ada0 (ACTIVE (ACTIVE)) ada1 (ACTIVE (REBUILD 28%)) .... Some types of arrays, like `RAID0` or `CONCAT`, may not be shown in the status report if disks have failed. To see these partially-failed arrays, add `-ga`: [source,shell] .... # graid status -ga Name Status Components Intel-e2d07d9a BROKEN ada6 (ACTIVE (ACTIVE)) .... [[geom-graid-deleting]] === Deleting Arrays Arrays are destroyed by deleting all of the volumes from them. When the last volume present is deleted, the array is stopped and metadata is removed from the drives: [source,shell] .... # graid delete raid/r0 .... [[geom-graid-unexpected]] === Deleting Unexpected Arrays Drives may unexpectedly contain man:graid[8] metadata, either from previous use or manufacturer testing. man:graid[8] will detect these drives and create an array, interfering with access to the individual drive. To remove the unwanted metadata: [.procedure] . Boot the system. At the boot menu, select `2` for the loader prompt. Enter: + [source,shell] .... OK set kern.geom.raid.enable=0 OK boot .... + The system will boot with man:graid[8] disabled. . Back up all data on the affected drive. . As a workaround, man:graid[8] array detection can be disabled by adding + [.programlisting] .... kern.geom.raid.enable=0 .... + to [.filename]#/boot/loader.conf#. + To permanently remove the man:graid[8] metadata from the affected drive, boot a FreeBSD installation CD-ROM or memory stick, and select `Shell`. Use `status` to find the name of the array, typically `raid/r0`: + [source,shell] .... # graid status Name Status Components raid/r0 OPTIMAL ada0 (ACTIVE (ACTIVE)) ada1 (ACTIVE (ACTIVE)) .... + Delete the volume by name: + [source,shell] .... # graid delete raid/r0 .... + If there is more than one volume shown, repeat the process for each volume. After the last array has been deleted, the volume will be destroyed. + Reboot and verify data, restoring from backup if necessary. After the metadata has been removed, the `kern.geom.raid.enable=0` entry in [.filename]#/boot/loader.conf# can also be removed. [[geom-ggate]] == GEOM Gate Network GEOM provides a simple mechanism for providing remote access to devices such as disks, CDs, and file systems through the use of the GEOM Gate network daemon, ggated. The system with the device runs the server daemon which handles requests made by clients using ggatec. The devices should not contain any sensitive data as the connection between the client and the server is not encrypted. Similar to NFS, which is discussed in crossref:network-servers[network-nfs,"Network File System (NFS)"], ggated is configured using an exports file. This file specifies which systems are permitted to access the exported resources and what level of access they are offered. For example, to give the client `192.168.1.5` read and write access to the fourth slice on the first SCSI disk, create [.filename]#/etc/gg.exports# with this line: [.programlisting] .... 192.168.1.5 RW /dev/da0s4d .... Before exporting the device, ensure it is not currently mounted. Then, start ggated: [source,shell] .... # ggated .... Several options are available for specifying an alternate listening port or changing the default location of the exports file. Refer to man:ggated[8] for details. To access the exported device on the client machine, first use `ggatec` to specify the IP address of the server and the device name of the exported device. If successful, this command will display a `ggate` device name to mount. Mount that specified device name on a free mount point. This example connects to the [.filename]#/dev/da0s4d# partition on `192.168.1.1`, then mounts [.filename]#/dev/ggate0# on [.filename]#/mnt#: [source,shell] .... # ggatec create -o rw 192.168.1.1 /dev/da0s4d ggate0 # mount /dev/ggate0 /mnt .... The device on the server may now be accessed through [.filename]#/mnt# on the client. For more details about `ggatec` and a few usage examples, refer to man:ggatec[8]. [NOTE] ==== The mount will fail if the device is currently mounted on either the server or any other client on the network. If simultaneous access is needed to network resources, use NFS instead. ==== When the device is no longer needed, unmount it with `umount` so that the resource is available to other clients. [[geom-glabel]] == Labeling Disk Devices During system initialization, the FreeBSD kernel creates device nodes as devices are found. This method of probing for devices raises some issues. For instance, what if a new disk device is added via USB? It is likely that a flash device may be handed the device name of [.filename]#da0# and the original [.filename]#da0# shifted to [.filename]#da1#. This will cause issues mounting file systems if they are listed in [.filename]#/etc/fstab# which may also prevent the system from booting. One solution is to chain SCSI devices in order so a new device added to the SCSI card will be issued unused device numbers. But what about USB devices which may replace the primary SCSI disk? This happens because USB devices are usually probed before the SCSI card. One solution is to only insert these devices after the system has been booted. Another method is to use only a single ATA drive and never list the SCSI devices in [.filename]#/etc/fstab#. A better solution is to use `glabel` to label the disk devices and use the labels in [.filename]#/etc/fstab#. Since `glabel` stores the label in the last sector of a given provider, the label will remain persistent across reboots. By using this label as a device, the file-system may always be mounted regardless of what device node it is accessed through. [NOTE] ==== `glabel` can create both transient and permanent labels. Only permanent labels are consistent across reboots. Refer to man:glabel[8] for more information on the differences between labels. ==== === Label Types and Examples Permanent labels can be a generic or a file system label. Permanent file system labels can be created with man:tunefs[8] or man:newfs[8]. These types of labels are created in a sub-directory of [.filename]#/dev#, and will be named according to the file system type. For example, UFS2 file system labels will be created in [.filename]#/dev/ufs#. Generic permanent labels can be created with `glabel label`. These are not file system specific and will be created in [.filename]#/dev/label#. Temporary labels are destroyed at the next reboot. These labels are created in [.filename]#/dev/label# and are suited to experimentation. A temporary label can be created using `glabel create`. To create a permanent label for a UFS2 file system without destroying any data, issue the following command: [source,shell] .... # tunefs -L home /dev/da3 .... A label should now exist in [.filename]#/dev/ufs# which may be added to [.filename]#/etc/fstab#: [.programlisting] .... /dev/ufs/home /home ufs rw 2 2 .... [NOTE] ==== The file system must not be mounted while attempting to run `tunefs`. ==== Now the file system may be mounted: [source,shell] .... # mount /home .... From this point on, so long as the [.filename]#geom_label.ko# kernel module is loaded at boot with [.filename]#/boot/loader.conf# or the `GEOM_LABEL` kernel option is present, the device node may change without any ill effect on the system. File systems may also be created with a default label by using the `-L` flag with `newfs`. Refer to man:newfs[8] for more information. The following command can be used to destroy the label: [source,shell] .... # glabel destroy home .... The following example shows how to label the partitions of a boot disk. .Labeling Partitions on the Boot Disk [example] ==== By permanently labeling the partitions on the boot disk, the system should be able to continue to boot normally, even if the disk is moved to another controller or transferred to a different system. For this example, it is assumed that a single ATA disk is used, which is currently recognized by the system as [.filename]#ad0#. It is also assumed that the standard FreeBSD partition scheme is used, with [.filename]#/#, [.filename]#/var#, [.filename]#/usr# and [.filename]#/tmp#, as well as a swap partition. Reboot the system, and at the man:loader[8] prompt, press kbd:[4] to boot into single user mode. Then enter the following commands: [source,shell] .... # glabel label rootfs /dev/ad0s1a GEOM_LABEL: Label for provider /dev/ad0s1a is label/rootfs # glabel label var /dev/ad0s1d GEOM_LABEL: Label for provider /dev/ad0s1d is label/var # glabel label usr /dev/ad0s1f GEOM_LABEL: Label for provider /dev/ad0s1f is label/usr # glabel label tmp /dev/ad0s1e GEOM_LABEL: Label for provider /dev/ad0s1e is label/tmp # glabel label swap /dev/ad0s1b GEOM_LABEL: Label for provider /dev/ad0s1b is label/swap # exit .... The system will continue with multi-user boot. After the boot completes, edit [.filename]#/etc/fstab# and replace the conventional device names, with their respective labels. The final [.filename]#/etc/fstab# will look like this: [.programlisting] .... # Device Mountpoint FStype Options Dump Pass# /dev/label/swap none swap sw 0 0 /dev/label/rootfs / ufs rw 1 1 /dev/label/tmp /tmp ufs rw 2 2 /dev/label/usr /usr ufs rw 2 2 /dev/label/var /var ufs rw 2 2 .... The system can now be rebooted. If everything went well, it will come up normally and `mount` will show: [source,shell] .... # mount /dev/label/rootfs on / (ufs, local) devfs on /dev (devfs, local) /dev/label/tmp on /tmp (ufs, local, soft-updates) /dev/label/usr on /usr (ufs, local, soft-updates) /dev/label/var on /var (ufs, local, soft-updates) .... ==== The man:glabel[8] class supports a label type for UFS file systems, based on the unique file system id, `ufsid`. These labels may be found in [.filename]#/dev/ufsid# and are created automatically during system startup. It is possible to use `ufsid` labels to mount partitions using [.filename]#/etc/fstab#. Use `glabel status` to receive a list of file systems and their corresponding `ufsid` labels: [source,shell] .... % glabel status Name Status Components ufsid/486b6fc38d330916 N/A ad4s1d ufsid/486b6fc16926168e N/A ad4s1f .... In the above example, [.filename]#ad4s1d# represents [.filename]#/var#, while [.filename]#ad4s1f# represents [.filename]#/usr#. Using the `ufsid` values shown, these partitions may now be mounted with the following entries in [.filename]#/etc/fstab#: [.programlisting] .... /dev/ufsid/486b6fc38d330916 /var ufs rw 2 2 /dev/ufsid/486b6fc16926168e /usr ufs rw 2 2 .... Any partitions with `ufsid` labels can be mounted in this way, eliminating the need to manually create permanent labels, while still enjoying the benefits of device name independent mounting. [[geom-gjournal]] == UFS Journaling Through GEOM Support for journals on UFS file systems is available on FreeBSD. The implementation is provided through the GEOM subsystem and is configured using `gjournal`. Unlike other file system journaling implementations, the `gjournal` method is block based and not implemented as part of the file system. It is a GEOM extension. Journaling stores a log of file system transactions, such as changes that make up a complete disk write operation, before meta-data and file writes are committed to the disk. This transaction log can later be replayed to redo file system transactions, preventing file system inconsistencies. This method provides another mechanism to protect against data loss and inconsistencies of the file system. Unlike Soft Updates, which tracks and enforces meta-data updates, and snapshots, which create an image of the file system, a log is stored in disk space specifically for this task. For better performance, the journal may be stored on another disk. In this configuration, the journal provider or storage device should be listed after the device to enable journaling on. The [.filename]#GENERIC# kernel provides support for `gjournal`. To automatically load the [.filename]#geom_journal.ko# kernel module at boot time, add the following line to [.filename]#/boot/loader.conf#: [.programlisting] .... geom_journal_load="YES" .... If a custom kernel is used, ensure the following line is in the kernel configuration file: [.programlisting] .... options GEOM_JOURNAL .... Once the module is loaded, a journal can be created on a new file system using the following steps. In this example, [.filename]#da4# is a new SCSI disk: [source,shell] .... # gjournal load # gjournal label /dev/da4 .... This will load the module and create a [.filename]#/dev/da4.journal# device node on [.filename]#/dev/da4#. A UFS file system may now be created on the journaled device, then mounted on an existing mount point: [source,shell] .... # newfs -O 2 -J /dev/da4.journal # mount /dev/da4.journal /mnt .... [NOTE] ==== In the case of several slices, a journal will be created for each individual slice. For instance, if [.filename]#ad4s1# and [.filename]#ad4s2# are both slices, then `gjournal` will create [.filename]#ad4s1.journal# and [.filename]#ad4s2.journal#. ==== Journaling may also be enabled on current file systems by using `tunefs`. However, _always_ make a backup before attempting to alter an existing file system. In most cases, `gjournal` will fail if it is unable to create the journal, but this does not protect against data loss incurred as a result of misusing `tunefs`. Refer to man:gjournal[8] and man:tunefs[8] for more information about these commands. It is possible to journal the boot disk of a FreeBSD system. Refer to the article extref:{gjournal-desktop}[Implementing UFS Journaling on a Desktop PC] for detailed instructions. diff --git a/documentation/content/en/books/handbook/mail/_index.adoc b/documentation/content/en/books/handbook/mail/_index.adoc index 565e546b12..e433388bc6 100644 --- a/documentation/content/en/books/handbook/mail/_index.adoc +++ b/documentation/content/en/books/handbook/mail/_index.adoc @@ -1,1119 +1,1119 @@ --- title: Chapter 29. Electronic Mail part: IV. Network Communication prev: books/handbook/ppp-and-slip next: books/handbook/network-servers description: This chapter provides a basic introduction to running a mail server on FreeBSD, as well as an introduction to sending and receiving email using FreeBSD tags: ["mail", "sendmail", "MTA", "SMTP", "user agents", "fetchmail", "procmail", "alpine", "mut"] showBookMenu: true weight: 34 path: "/books/handbook/" --- [[mail]] = Electronic Mail :doctype: book :toc: macro :toclevels: 1 :icons: font :sectnums: :sectnumlevels: 6 :sectnumoffset: 29 :partnums: :source-highlighter: rouge :experimental: :images-path: books/handbook/mail/ ifdef::env-beastie[] ifdef::backend-html5[] :imagesdir: ../../../../images/{images-path} endif::[] ifndef::book[] include::shared/authors.adoc[] include::shared/mirrors.adoc[] include::shared/releases.adoc[] include::shared/attributes/attributes-{{% lang %}}.adoc[] include::shared/{{% lang %}}/teams.adoc[] include::shared/{{% lang %}}/mailing-lists.adoc[] include::shared/{{% lang %}}/urls.adoc[] toc::[] endif::[] ifdef::backend-pdf,backend-epub3[] include::../../../../../shared/asciidoctor.adoc[] endif::[] endif::[] ifndef::env-beastie[] toc::[] include::../../../../../shared/asciidoctor.adoc[] endif::[] [[mail-synopsis]] == Synopsis "Electronic Mail", better known as email, is one of the most widely used forms of communication today. This chapter provides a basic introduction to running a mail server on FreeBSD, as well as an introduction to sending and receiving email using FreeBSD For more complete coverage of this subject, refer to the books listed in crossref:bibliography[bibliography,Bibliography]. After reading this chapter, you will know: * Which software components are involved in sending and receiving electronic mail. * Where basic Sendmail configuration files are located in FreeBSD. * The difference between remote and local mailboxes. * How to block spammers from illegally using a mail server as a relay. * How to install and configure an alternate Mail Transfer Agent, replacing Sendmail. * How to troubleshoot common mail server problems. * How to set up the system to send mail only. * How to use mail with a dialup connection. * How to configure SMTP authentication for added security. * How to install and use a Mail User Agent, such as mutt, to send and receive email. * How to download mail from a remote POP or IMAP server. * How to automatically apply filters and rules to incoming email. Before reading this chapter, you should: * Properly set up a network connection (crossref:advanced-networking[advanced-networking,Advanced Networking]). * Properly set up the DNS information for a mail host (crossref:network-servers[network-servers,Network Servers]). * Know how to install additional third-party software (crossref:ports[ports,Installing Applications: Packages and Ports]). [[mail-using]] == Mail Components There are five major parts involved in an email exchange: the Mail User Agent (MUA), the Mail Transfer Agent (MTA), a mail host, a remote or local mailbox, and DNS. This section provides an overview of these components. Mail User Agent (MUA):: The Mail User Agent (MUA) is an application which is used to compose, send, and receive emails. This application can be a command line program, such as the built-in `mail` utility or a third-party application from the Ports Collection, such as mutt, alpine, or elm. Dozens of graphical programs are also available in the Ports Collection, including Claws Mail, Evolution, and Thunderbird. Some organizations provide a web mail program which can be accessed through a web browser. More information about installing and using a MUA on FreeBSD can be found in <>. Mail Transfer Agent (MTA):: The Mail Transfer Agent (MTA) is responsible for receiving incoming mail and delivering outgoing mail. FreeBSD ships with Sendmail as the default MTA, but it also supports numerous other mail server daemons, including Exim, Postfix, and qmail. Sendmail configuration is described in <>. If another MTA is installed using the Ports Collection, refer to its post-installation message for FreeBSD-specific configuration details and the application's website for more general configuration instructions. Mail Host and Mailboxes:: The mail host is a server that is responsible for delivering and receiving mail for a host or a network. The mail host collects all mail sent to the domain and stores it either in the default [.filename]#mbox# or the alternative Maildir format, depending on the configuration. Once mail has been stored, it may either be read locally using a MUA or remotely accessed and collected using protocols such as POP or IMAP. If mail is read locally, a POP or IMAP server does not need to be installed. + To access mailboxes remotely, a POP or IMAP server is required as these protocols allow users to connect to their mailboxes from remote locations. IMAP offers several advantages over POP. These include the ability to store a copy of messages on a remote server after they are downloaded and concurrent updates. IMAP can be useful over low-speed links as it allows users to fetch the structure of messages without downloading them. It can also perform tasks such as searching on the server in order to minimize data transfer between clients and servers. + Several POP and IMAP servers are available in the Ports Collection. These include package:mail/qpopper[], package:mail/imap-uw[], package:mail/courier-imap[], and package:mail/dovecot2[]. + [WARNING] ==== It should be noted that both POP and IMAP transmit information, including username and password credentials, in clear-text. To secure the transmission of information across these protocols, consider tunneling sessions over man:ssh[1] (crossref:security[security-ssh-tunneling,"SSH Tunneling"]) or using SSL (crossref:security[openssl,"OpenSSL"]). ==== Domain Name System (DNS):: The Domain Name System (DNS) and its daemon `named` play a large role in the delivery of email. In order to deliver mail from one site to another, the MTA will look up the remote site in DNS to determine which host will receive mail for the destination. This process also occurs when mail is sent from a remote host to the MTA. + In addition to mapping hostnames to IP addresses, DNS is responsible for storing information specific to mail delivery, known as Mail eXchanger MX records. The MX record specifies which hosts will receive mail for a particular domain. + To view the MX records for a domain, specify the type of record. Refer to man:host[1], for more details about this command: + [source,shell] .... % host -t mx FreeBSD.org FreeBSD.org mail is handled by 10 mx1.FreeBSD.org .... + Refer to crossref:network-servers[network-dns,"Domain Name System (DNS)"] for more information about DNS and its configuration. [[sendmail]] == Sendmail Configuration Files Sendmail is the default MTA installed with FreeBSD. It accepts mail from MUAs and delivers it to the appropriate mail host, as defined by its configuration. Sendmail can also accept network connections and deliver mail to local mailboxes or to another program. The configuration files for Sendmail are located in [.filename]#/etc/mail#. This section describes these files in more detail. [.filename]#/etc/mail/access#:: This access database file defines which hosts or IP addresses have access to the local mail server and what kind of access they have. Hosts listed as `OK`, which is the default option, are allowed to send mail to this host as long as the mail's final destination is the local machine. Hosts listed as `REJECT` are rejected for all mail connections. Hosts listed as `RELAY` are allowed to send mail for any destination using this mail server. Hosts listed as `ERROR` will have their mail returned with the specified mail error. If a host is listed as `SKIP`, Sendmail will abort the current search for this entry without accepting or rejecting the mail. Hosts listed as `QUARANTINE` will have their messages held and will receive the specified text as the reason for the hold. + Examples of using these options for both IPv4 and IPv6 addresses can be found in the FreeBSD sample configuration, [.filename]#/etc/mail/access.sample#: + [.programlisting] .... # $FreeBSD$ # # Mail relay access control list. Default is to reject mail unless the # destination is local, or listed in /etc/mail/local-host-names # ## Examples (commented out for safety) #From:cyberspammer.com ERROR:"550 We don't accept mail from spammers" #From:okay.cyberspammer.com OK #Connect:sendmail.org RELAY #To:sendmail.org RELAY #Connect:128.32 RELAY #Connect:128.32.2 SKIP #Connect:IPv6:1:2:3:4:5:6:7 RELAY #Connect:suspicious.example.com QUARANTINE:Mail from suspicious host #Connect:[127.0.0.3] OK #Connect:[IPv6:1:2:3:4:5:6:7:8] OK .... + To configure the access database, use the format shown in the sample to make entries in [.filename]#/etc/mail/access#, but do not put a comment symbol (`#`) in front of the entries. Create an entry for each host or network whose access should be configured. Mail senders that match the left side of the table are affected by the action on the right side of the table. + Whenever this file is updated, update its database and restart Sendmail: + [source,shell] .... # makemap hash /etc/mail/access < /etc/mail/access # service sendmail restart .... [.filename]#/etc/mail/aliases#:: This database file contains a list of virtual mailboxes that are expanded to users, files, programs, or other aliases. Here are a few entries to illustrate the file format: + [.programlisting] .... root: localuser ftp-bugs: joe,eric,paul bit.bucket: /dev/null procmail: "|/usr/local/bin/procmail" .... + The mailbox name on the left side of the colon is expanded to the target(s) on the right. The first entry expands the `root` mailbox to the `localuser` mailbox, which is then looked up in the [.filename]#/etc/mail/aliases# database. If no match is found, the message is delivered to `localuser`. The second entry shows a mail list. Mail to `ftp-bugs` is expanded to the three local mailboxes `joe`, `eric`, and `paul`. A remote mailbox could be specified as _user@example.com_. The third entry shows how to write mail to a file, in this case [.filename]#/dev/null#. The last entry demonstrates how to send mail to a program, [.filename]#/usr/local/bin/procmail#, through a UNIX(R) pipe. Refer to man:aliases[5] for more information about the format of this file. + Whenever this file is updated, run `newaliases` to update and initialize the aliases database. [.filename]#/etc/mail/sendmail.cf#:: This is the master configuration file for Sendmail. It controls the overall behavior of Sendmail, including everything from rewriting email addresses to printing rejection messages to remote mail servers. Accordingly, this configuration file is quite complex. Fortunately, this file rarely needs to be changed for standard mail servers. + The master Sendmail configuration file can be built from man:m4[1] macros that define the features and behavior of Sendmail. Refer to [.filename]#/usr/src/contrib/sendmail/cf/README# for some of the details. + Whenever changes to this file are made, Sendmail needs to be restarted for the changes to take effect. [.filename]#/etc/mail/virtusertable#:: This database file maps mail addresses for virtual domains and users to real mailboxes. These mailboxes can be local, remote, aliases defined in [.filename]#/etc/mail/aliases#, or files. This allows multiple virtual domains to be hosted on one machine. + FreeBSD provides a sample configuration file in [.filename]#/etc/mail/virtusertable.sample# to further demonstrate its format. The following example demonstrates how to create custom entries using that format: + [.programlisting] .... root@example.com root postmaster@example.com postmaster@noc.example.net @example.com joe .... + This file is processed in a first match order. When an email address matches the address on the left, it is mapped to the local mailbox listed on the right. The format of the first entry in this example maps a specific email address to a local mailbox, whereas the format of the second entry maps a specific email address to a remote mailbox. Finally, any email address from `example.com` which has not matched any of the previous entries will match the last mapping and be sent to the local mailbox `joe`. When creating custom entries, use this format and add them to [.filename]#/etc/mail/virtusertable#. Whenever this file is edited, update its database and restart Sendmail: + [source,shell] .... # makemap hash /etc/mail/virtusertable < /etc/mail/virtusertable # service sendmail restart .... [.filename]#/etc/mail/relay-domains#:: In a default FreeBSD installation, Sendmail is configured to only send mail from the host it is running on. For example, if a POP server is available, users will be able to check mail from remote locations but they will not be able to send outgoing emails from outside locations. Typically, a few moments after the attempt, an email will be sent from `MAILER-DAEMON` with a `5.7 Relaying Denied` message. + The most straightforward solution is to add the ISP's FQDN to [.filename]#/etc/mail/relay-domains#. If multiple addresses are needed, add them one per line: + [.programlisting] .... your.isp.example.com other.isp.example.net users-isp.example.org www.example.org .... + After creating or editing this file, restart Sendmail with `service sendmail restart`. + Now any mail sent through the system by any host in this list, provided the user has an account on the system, will succeed. This allows users to send mail from the system remotely without opening the system up to relaying SPAM from the Internet. [[mail-changingmta]] == Changing the Mail Transfer Agent FreeBSD comes with Sendmail already installed as the MTA which is in charge of outgoing and incoming mail. However, the system administrator can change the system's MTA. A wide choice of alternative MTAs is available from the `mail` category of the FreeBSD Ports Collection. Once a new MTA is installed, configure and test the new software before replacing Sendmail. Refer to the documentation of the new MTA for information on how to configure the software. Once the new MTA is working, use the instructions in this section to disable Sendmail and configure FreeBSD to use the replacement MTA. [[mail-disable-sendmail]] === Disable Sendmail [WARNING] ==== If Sendmail's outgoing mail service is disabled, it is important that it is replaced with an alternative mail delivery system. Otherwise, system functions such as man:periodic[8] will be unable to deliver their results by email. Many parts of the system expect a functional MTA. If applications continue to use Sendmail's binaries to try to send email after they are disabled, mail could go into an inactive Sendmail queue and never be delivered. ==== In order to completely disable Sendmail, add or edit the following lines in [.filename]#/etc/rc.conf#: [.programlisting] .... sendmail_enable="NO" sendmail_submit_enable="NO" sendmail_outbound_enable="NO" sendmail_msp_queue_enable="NO" .... To only disable Sendmail's incoming mail service, use only this entry in [.filename]#/etc/rc.conf#: [.programlisting] .... sendmail_enable="NO" .... More information on Sendmail's startup options is available in man:rc.sendmail[8]. === Replace the Default MTA When a new MTA is installed using the Ports Collection, its startup script is also installed and startup instructions are mentioned in its package message. Before starting the new MTA, stop the running Sendmail processes. This example stops all of these services, then starts the Postfix service: [source,shell] .... # service sendmail stop # service postfix start .... To start the replacement MTA at system boot, add its configuration line to [.filename]#/etc/rc.conf#. This entry enables the Postfix MTA: [.programlisting] .... postfix_enable="YES" .... Some extra configuration is needed as Sendmail is so ubiquitous that some software assumes it is already installed and configured. Check [.filename]#/etc/periodic.conf# and make sure that these values are set to `NO`. If this file does not exist, create it with these entries: [.programlisting] .... daily_clean_hoststat_enable="NO" daily_status_mail_rejects_enable="NO" daily_status_include_submit_mailq="NO" daily_submit_queuerun="NO" .... Some alternative MTAs provide their own compatible implementations of the Sendmail command-line interface in order to facilitate using them as drop-in replacements for Sendmail. However, some MUAs may try to execute standard Sendmail binaries instead of the new MTA's binaries. FreeBSD uses [.filename]#/etc/mail/mailer.conf# to map the expected Sendmail binaries to the location of the new binaries. More information about this mapping can be found in man:mailwrapper[8]. The default [.filename]#/etc/mail/mailer.conf# looks like this: [.programlisting] .... # $FreeBSD$ # # Execute the "real" sendmail program, named /usr/libexec/sendmail/sendmail # sendmail /usr/libexec/sendmail/sendmail send-mail /usr/libexec/sendmail/sendmail mailq /usr/libexec/sendmail/sendmail newaliases /usr/libexec/sendmail/sendmail hoststat /usr/libexec/sendmail/sendmail purgestat /usr/libexec/sendmail/sendmail .... When any of the commands listed on the left are run, the system actually executes the associated command shown on the right. This system makes it easy to change what binaries are executed when these default binaries are invoked. Some MTAs, when installed using the Ports Collection, will prompt to update this file for the new binaries. For example, Postfix will update the file like this: [.programlisting] .... # # Execute the Postfix sendmail program, named /usr/local/sbin/sendmail # sendmail /usr/local/sbin/sendmail send-mail /usr/local/sbin/sendmail mailq /usr/local/sbin/sendmail newaliases /usr/local/sbin/sendmail .... If the installation of the MTA does not automatically update [.filename]#/etc/mail/mailer.conf#, edit this file in a text editor so that it points to the new binaries. This example points to the binaries installed by package:mail/ssmtp[]: [.programlisting] .... sendmail /usr/local/sbin/ssmtp send-mail /usr/local/sbin/ssmtp mailq /usr/local/sbin/ssmtp newaliases /usr/local/sbin/ssmtp hoststat /usr/bin/true purgestat /usr/bin/true .... Once everything is configured, it is recommended to reboot the system. Rebooting provides the opportunity to ensure that the system is correctly configured to start the new MTA automatically on boot. [[mail-trouble]] == Troubleshooting === Why do I have to use the FQDN for hosts on my site? The host may actually be in a different domain. For example, in order for a host in `foo.bar.edu` to reach a host called `mumble` in the `bar.edu` domain, refer to it by the Fully-Qualified Domain Name FQDN, `mumble.bar.edu`, instead of just `mumble`. This is because the version of BIND which ships with FreeBSD no longer provides default abbreviations for non-FQDNs other than the local domain. An unqualified host such as `mumble` must either be found as `mumble.foo.bar.edu`, or it will be searched for in the root domain. In older versions of BIND, the search continued across `mumble.bar.edu`, and `mumble.edu`. RFC 1535 details why this is considered bad practice or even a security hole. As a good workaround, place the line: [.programlisting] .... search foo.bar.edu bar.edu .... instead of the previous: [.programlisting] .... domain foo.bar.edu .... into [.filename]#/etc/resolv.conf#. However, make sure that the search order does not go beyond the "boundary between local and public administration", as RFC 1535 calls it. === How can I run a mail server on a dial-up PPP host? Connect to a FreeBSD mail gateway on the LAN. The PPP connection is non-dedicated. One way to do this is to get a full-time Internet server to provide secondary MX services for the domain. In this example, the domain is `example.com` and the ISP has configured `example.net` to provide secondary MX services to the domain: [.programlisting] .... example.com. MX 10 example.com. MX 20 example.net. .... Only one host should be specified as the final recipient. For Sendmail, add `Cw example.com` in [.filename]#/etc/mail/sendmail.cf# on `example.com`. When the sending MTA attempts to deliver mail, it will try to connect to the system, `example.com`, over the PPP link. This will time out if the destination is offline. The MTA will automatically deliver it to the secondary MX site at the Internet Service Provider (ISP), `example.net`. The secondary MX site will periodically try to connect to the primary MX host, `example.com`. Use something like this as a login script: [.programlisting] .... #!/bin/sh # Put me in /usr/local/bin/pppmyisp ( sleep 60 ; /usr/sbin/sendmail -q ) & /usr/sbin/ppp -direct pppmyisp .... When creating a separate login script for users, instead use `sendmail -qRexample.com` in the script above. This will force all mail in the queue for `example.com` to be processed immediately. A further refinement of the situation can be seen from this example from the {freebsd-isp}: [.programlisting] .... > we provide the secondary MX for a customer. The customer connects to > our services several times a day automatically to get the mails to > his primary MX (We do not call his site when a mail for his domains > arrived). Our sendmail sends the mailqueue every 30 minutes. At the > moment he has to stay 30 minutes online to be sure that all mail is > gone to the primary MX. > > Is there a command that would initiate sendmail to send all the mails > now? The user has not root-privileges on our machine of course. In the privacy flags section of sendmail.cf, there is a definition Opgoaway,restrictqrun Remove restrictqrun to allow non-root users to start the queue processing. You might also like to rearrange the MXs. We are the 1st MX for our customers like this, and we have defined: # If we are the best MX for a host, try directly instead of generating # local config error. OwTrue That way a remote site will deliver straight to you, without trying the customer connection. You then send to your customer. Only works for hosts, so you need to get your customer to name their mail machine customer.com as well as hostname.customer.com in the DNS. Just put an A record in the DNS for customer.com. .... [[mail-advanced]] == Advanced Topics This section covers more involved topics such as mail configuration and setting up mail for an entire domain. [[mail-config]] === Basic Configuration Out of the box, one can send email to external hosts as long as [.filename]#/etc/resolv.conf# is configured or the network has access to a configured DNS server. To have email delivered to the MTA on the FreeBSD host, do one of the following: * Run a DNS server for the domain. * Get mail delivered directly to the FQDN for the machine. In order to have mail delivered directly to a host, it must have a permanent static IP address, not a dynamic IP address. If the system is behind a firewall, it must be configured to allow SMTP traffic. To receive mail directly at a host, one of these two must be configured: * Make sure that the lowest-numbered MX record in DNS points to the host's static IP address. * Make sure there is no MX entry in the DNS for the host. Either of the above will allow mail to be received directly at the host. Try this: [source,shell] .... # hostname example.FreeBSD.org # host example.FreeBSD.org example.FreeBSD.org has address 204.216.27.XX .... In this example, mail sent directly to mailto:yourlogin@example.FreeBSD.org[yourlogin@example.FreeBSD.org] should work without problems, assuming Sendmail is running correctly on `example.FreeBSD.org`. For this example: [source,shell] .... # host example.FreeBSD.org example.FreeBSD.org has address 204.216.27.XX example.FreeBSD.org mail is handled (pri=10) by nevdull.FreeBSD.org .... All mail sent to `example.FreeBSD.org` will be collected on `hub` under the same username instead of being sent directly to your host. The above information is handled by the DNS server. The DNS record that carries mail routing information is the MX entry. If no MX record exists, mail will be delivered directly to the host by way of its IP address. The MX entry for `freefall.FreeBSD.org` at one time looked like this: [.programlisting] .... freefall MX 30 mail.crl.net freefall MX 40 agora.rdrop.com freefall MX 10 freefall.FreeBSD.org freefall MX 20 who.cdrom.com .... `freefall` had many MX entries. The lowest MX number is the host that receives mail directly, if available. If it is not accessible for some reason, the next lower-numbered host will accept messages temporarily, and pass it along when a lower-numbered host becomes available. Alternate MX sites should have separate Internet connections in order to be most useful. Your ISP can provide this service. [[mail-domain]] === Mail for a Domain -When configuring a MTA for a network, any mail sent to hosts in its domain should be diverted to the MTA so that users can receive their mail on the master mail server. +When configuring an MTA for a network, any mail sent to hosts in its domain should be diverted to the MTA so that users can receive their mail on the master mail server. To make life easiest, a user account with the same _username_ should exist on both the MTA and the system with the MUA. Use man:adduser[8] to create the user accounts. The MTA must be the designated mail exchanger for each workstation on the network. This is done in the DNS configuration with an MX record: [.programlisting] .... example.FreeBSD.org A 204.216.27.XX ; Workstation MX 10 nevdull.FreeBSD.org ; Mailhost .... This will redirect mail for the workstation to the MTA no matter where the A record points. The mail is sent to the MX host. This must be configured on a DNS server. If the network does not run its own DNS server, talk to the ISP or DNS provider. The following is an example of virtual email hosting. Consider a customer with the domain `customer1.org`, where all the mail for `customer1.org` should be sent to `mail.myhost.com`. The DNS entry should look like this: [.programlisting] .... customer1.org MX 10 mail.myhost.com .... An `A` record is _not_ needed for `customer1.org` in order to only handle email for that domain. However, running `ping` against `customer1.org` will not work unless an `A` record exists for it. Tell the MTA which domains and/or hostnames it should accept mail for. Either of the following will work for Sendmail: * Add the hosts to [.filename]#/etc/mail/local-host-names# when using the `FEATURE(use_cw_file)`. * Add a `Cwyour.host.com` line to [.filename]#/etc/sendmail.cf#. [[outgoing-only]] == Setting Up to Send Only There are many instances where one may only want to send mail through a relay. Some examples are: * The computer is a desktop machine that needs to use programs such as man:mail[1], using the ISP's mail relay. * The computer is a server that does not handle mail locally, but needs to pass off all mail to a relay for processing. While any MTA is capable of filling this particular niche, it can be difficult to properly configure a full-featured MTA just to handle offloading mail. Programs such as Sendmail and Postfix are overkill for this use. Additionally, a typical Internet access service agreement may forbid one from running a "mail server". The easiest way to fulfill those needs is to install the package:mail/ssmtp[] port: [source,shell] .... # cd /usr/ports/mail/ssmtp # make install replace clean .... Once installed, package:mail/ssmtp[] can be configured with [.filename]#/usr/local/etc/ssmtp/ssmtp.conf#: [.programlisting] .... root=yourrealemail@example.com mailhub=mail.example.com rewriteDomain=example.com hostname=_HOSTNAME_ .... Use the real email address for `root`. Enter the ISP's outgoing mail relay in place of `mail.example.com`. Some ISPs call this the "outgoing mail server" or "SMTP server". Make sure to disable Sendmail, including the outgoing mail service. See <> for details. package:mail/ssmtp[] has some other options available. Refer to the examples in [.filename]#/usr/local/etc/ssmtp# or the manual page of ssmtp for more information. Setting up ssmtp in this manner allows any software on the computer that needs to send mail to function properly, while not violating the ISP's usage policy or allowing the computer to be hijacked for spamming. [[SMTP-dialup]] == Using Mail with a Dialup Connection When using a static IP address, one should not need to adjust the default configuration. Set the hostname to the assigned Internet name and Sendmail will do the rest. When using a dynamically assigned IP address and a dialup PPP connection to the Internet, one usually has a mailbox on the ISP's mail server. In this example, the ISP's domain is `example.net`, the user name is `user`, the hostname is `bsd.home`, and the ISP has allowed `relay.example.net` as a mail relay. In order to retrieve mail from the ISP's mailbox, install a retrieval agent from the Ports Collection. package:mail/fetchmail[] is a good choice as it supports many different protocols. Usually, the ISP will provide POP. When using user PPP, email can be automatically fetched when an Internet connection is established with the following entry in [.filename]#/etc/ppp/ppp.linkup#: [.programlisting] .... MYADDR: !bg su user -c fetchmail .... When using Sendmail to deliver mail to non-local accounts, configure Sendmail to process the mail queue as soon as the Internet connection is established. To do this, add this line after the above `fetchmail` entry in [.filename]#/etc/ppp/ppp.linkup#: [.programlisting] .... !bg su user -c "sendmail -q" .... In this example, there is an account for `user` on `bsd.home`. In the home directory of `user` on `bsd.home`, create a [.filename]#.fetchmailrc# which contains this line: [.programlisting] .... poll example.net protocol pop3 fetchall pass MySecret .... This file should not be readable by anyone except `user` as it contains the password `MySecret`. In order to send mail with the correct `from:` header, configure Sendmail to use mailto:user@example.net[user@example.net] rather than mailto:user@bsd.home[user@bsd.home] and to send all mail via `relay.example.net`, allowing quicker mail transmission. The following [.filename]#.mc# should suffice: [.programlisting] .... VERSIONID(`bsd.home.mc version 1.0') OSTYPE(bsd4.4)dnl FEATURE(nouucp)dnl MAILER(local)dnl MAILER(smtp)dnl Cwlocalhost Cwbsd.home MASQUERADE_AS(`example.net')dnl FEATURE(allmasquerade)dnl FEATURE(masquerade_envelope)dnl FEATURE(nocanonify)dnl FEATURE(nodns)dnl define(`SMART_HOST', `relay.example.net') Dmbsd.home define(`confDOMAIN_NAME',`bsd.home')dnl define(`confDELIVERY_MODE',`deferred')dnl .... Refer to the previous section for details of how to convert this file into the [.filename]#sendmail.cf# format. Do not forget to restart Sendmail after updating [.filename]#sendmail.cf#. [[SMTP-Auth]] == SMTP Authentication Configuring SMTP authentication on the MTA provides a number of benefits. SMTP authentication adds a layer of security to Sendmail, and provides mobile users who switch hosts the ability to use the same MTA without the need to reconfigure their mail client's settings each time. [.procedure] . Install package:security/cyrus-sasl2[] from the Ports Collection. This port supports a number of compile-time options. For the SMTP authentication method demonstrated in this example, make sure that `LOGIN` is not disabled. . After installing package:security/cyrus-sasl2[], edit [.filename]#/usr/local/lib/sasl2/Sendmail.conf#, or create it if it does not exist, and add the following line: + [.programlisting] .... pwcheck_method: saslauthd .... . Next, install package:security/cyrus-sasl2-saslauthd[] and add the following line to [.filename]#/etc/rc.conf#: + [.programlisting] .... saslauthd_enable="YES" .... + Finally, start the saslauthd daemon: + [source,shell] .... # service saslauthd start .... + This daemon serves as a broker for Sendmail to authenticate against the FreeBSD man:passwd[5] database. This saves the trouble of creating a new set of usernames and passwords for each user that needs to use SMTP authentication, and keeps the login and mail password the same. . Next, edit [.filename]#/etc/make.conf# and add the following lines: + [.programlisting] .... SENDMAIL_CFLAGS=-I/usr/local/include/sasl -DSASL SENDMAIL_LDADD=/usr/local/lib/libsasl2.so .... + These lines provide Sendmail the proper configuration options for linking to package:cyrus-sasl2[] at compile time. Make sure that package:cyrus-sasl2[] has been installed before recompiling Sendmail. . Recompile Sendmail by executing the following commands: + [source,shell] .... # cd /usr/src/lib/libsmutil # make cleandir && make obj && make # cd /usr/src/lib/libsm # make cleandir && make obj && make # cd /usr/src/usr.sbin/sendmail # make cleandir && make obj && make && make install .... + This compile should not have any problems if [.filename]#/usr/src# has not changed extensively and the shared libraries it needs are available. . After Sendmail has been compiled and reinstalled, edit [.filename]#/etc/mail/freebsd.mc# or the local [.filename]#.mc#. Many administrators choose to use the output from man:hostname[1] as the name of [.filename]#.mc# for uniqueness. Add these lines: + [.programlisting] .... dnl set SASL options TRUST_AUTH_MECH(`GSSAPI DIGEST-MD5 CRAM-MD5 LOGIN')dnl define(`confAUTH_MECHANISMS', `GSSAPI DIGEST-MD5 CRAM-MD5 LOGIN')dnl .... + These options configure the different methods available to Sendmail for authenticating users. To use a method other than pwcheck, refer to the Sendmail documentation. . Finally, run man:make[1] while in [.filename]#/etc/mail#. That will run the new [.filename]#.mc# and create a [.filename]#.cf# named either [.filename]#freebsd.cf# or the name used for the local [.filename]#.mc#. Then, run `make install restart`, which will copy the file to [.filename]#sendmail.cf#, and properly restart Sendmail. For more information about this process, refer to [.filename]#/etc/mail/Makefile#. To test the configuration, use a MUA to send a test message. For further investigation, set the `LogLevel` of Sendmail to `13` and watch [.filename]#/var/log/maillog# for any errors. For more information, refer to http://www.sendmail.org/~ca/email/auth.html[SMTP authentication]. [[mail-agents]] == Mail User Agents A MUA is an application that is used to send and receive email. As email "evolves" and becomes more complex, MUAs are becoming increasingly powerful and provide users increased functionality and flexibility. The `mail` category of the FreeBSD Ports Collection contains numerous MUAs. These include graphical email clients such as Evolution or Balsa and console based clients such as mutt or alpine. [[mail-command]] === `mail` man:mail[1] is the default MUA installed with FreeBSD. It is a console based MUA that offers the basic functionality required to send and receive text-based email. It provides limited attachment support and can only access local mailboxes. Although `mail` does not natively support interaction with POP or IMAP servers, these mailboxes may be downloaded to a local [.filename]#mbox# using an application such as fetchmail. In order to send and receive email, run `mail`: [source,shell] .... % mail .... The contents of the user's mailbox in [.filename]#/var/mail# are automatically read by `mail`. Should the mailbox be empty, the utility exits with a message indicating that no mail could be found. If mail exists, the application interface starts, and a list of messages will be displayed. Messages are automatically numbered, as can be seen in the following example: [source,shell] .... Mail version 8.1 6/6/93. Type ? for help. "/var/mail/marcs": 3 messages 3 new >N 1 root@localhost Mon Mar 8 14:05 14/510 "test" N 2 root@localhost Mon Mar 8 14:05 14/509 "user account" N 3 root@localhost Mon Mar 8 14:05 14/509 "sample" .... Messages can now be read by typing kbd:[t] followed by the message number. This example reads the first email: [source,shell] .... & t 1 Message 1: From root@localhost Mon Mar 8 14:05:52 2004 X-Original-To: marcs@localhost Delivered-To: marcs@localhost To: marcs@localhost Subject: test Date: Mon, 8 Mar 2004 14:05:52 +0200 (SAST) From: root@localhost (Charlie Root) This is a test message, please reply if you receive it. .... As seen in this example, the message will be displayed with full headers. To display the list of messages again, press kbd:[h]. If the email requires a reply, press either kbd:[R] or kbd:[r] `mail` keys. kbd:[R] instructs `mail` to reply only to the sender of the email, while kbd:[r] replies to all other recipients of the message. These commands can be suffixed with the mail number of the message to reply to. After typing the response, the end of the message should be marked by a single kbd:[.] on its own line. An example can be seen below: [source,shell] .... & R 1 To: root@localhost Subject: Re: test Thank you, I did get your email. . EOT .... In order to send a new email, press kbd:[m], followed by the recipient email address. Multiple recipients may be specified by separating each address with the kbd:[,] delimiter. The subject of the message may then be entered, followed by the message contents. The end of the message should be specified by putting a single kbd:[.] on its own line. [source,shell] .... & mail root@localhost Subject: I mastered mail Now I can send and receive email using mail ... :) . EOT .... While using `mail`, press kbd:[?] to display help at any time. Refer to man:mail[1] for more help on how to use `mail`. [NOTE] ==== man:mail[1] was not designed to handle attachments and thus deals with them poorly. Newer MUAs handle attachments in a more intelligent way. Users who prefer to use `mail` may find the package:converters/mpack[] port to be of considerable use. ==== [[mutt-command]] === mutt mutt is a powerful MUA, with many features, including: * The ability to thread messages. * PGP support for digital signing and encryption of email. * MIME support. * Maildir support. * Highly customizable. Refer to http://www.mutt.org[http://www.mutt.org] for more information on mutt. mutt may be installed using the package:mail/mutt[] port. After the port has been installed, mutt can be started by issuing the following command: [source,shell] .... % mutt .... mutt will automatically read and display the contents of the user mailbox in [.filename]#/var/mail#. If no mails are found, mutt will wait for commands from the user. The example below shows mutt displaying a list of messages: image::mutt1.png[] To read an email, select it using the cursor keys and press kbd:[Enter]. An example of mutt displaying email can be seen below: image::mutt2.png[] Similar to man:mail[1], mutt can be used to reply only to the sender of the message as well as to all recipients. To reply only to the sender of the email, press kbd:[r]. To send a group reply to the original sender as well as all the message recipients, press kbd:[g]. [NOTE] ==== By default, mutt uses the man:vi[1] editor for creating and replying to emails. Each user can customize this by creating or editing the [.filename]#.muttrc# in their home directory and setting the `editor` variable or by setting the `EDITOR` environment variable. Refer to http://www.mutt.org/[http://www.mutt.org/] for more information about configuring mutt. ==== To compose a new mail message, press kbd:[m]. After a valid subject has been given, mutt will start man:vi[1] so the email can be written. Once the contents of the email are complete, save and quit from `vi`. mutt will resume, displaying a summary screen of the mail that is to be delivered. In order to send the mail, press kbd:[y]. An example of the summary screen can be seen below: image::mutt3.png[] mutt contains extensive help which can be accessed from most of the menus by pressing kbd:[?]. The top line also displays the keyboard shortcuts where appropriate. [[alpine-command]] === alpine alpine is aimed at a beginner user, but also includes some advanced features. [WARNING] ==== alpine has had several remote vulnerabilities discovered in the past, which allowed remote attackers to execute arbitrary code as users on the local system, by the action of sending a specially-prepared email. While _known_ problems have been fixed, alpine code is written in an insecure style and the FreeBSD Security Officer believes there are likely to be other undiscovered vulnerabilities. Users install alpine at their own risk. ==== The current version of alpine may be installed using the package:mail/alpine[] port. Once the port has installed, alpine can be started by issuing the following command: [source,shell] .... % alpine .... The first time alpine runs, it displays a greeting page with a brief introduction, as well as a request from the alpine development team to send an anonymous email message allowing them to judge how many users are using their client. To send this anonymous message, press kbd:[Enter]. Alternatively, press kbd:[E] to exit the greeting without sending an anonymous message. An example of the greeting page is shown below: image::pine1.png[] The main menu is then presented, which can be navigated using the cursor keys. This main menu provides shortcuts for the composing new mails, browsing mail directories, and administering address book entries. Below the main menu, relevant keyboard shortcuts to perform functions specific to the task at hand are shown. The default directory opened by alpine is [.filename]#inbox#. To view the message index, press kbd:[I], or select the [.guimenuitem]#MESSAGE INDEX# option shown below: image::pine2.png[] The message index shows messages in the current directory and can be navigated by using the cursor keys. Highlighted messages can be read by pressing kbd:[Enter]. image::pine3.png[] In the screenshot below, a sample message is displayed by alpine. Contextual keyboard shortcuts are displayed at the bottom of the screen. An example of one of a shortcut is kbd:[r], which tells the MUA to reply to the current message being displayed. image::pine4.png[] Replying to an email in alpine is done using the pico editor, which is installed by default with alpine. pico makes it easy to navigate the message and is easier for novice users to use than man:vi[1] or man:mail[1]. Once the reply is complete, the message can be sent by pressing kbd:[Ctrl+X]. alpine will ask for confirmation before sending the message. image::pine5.png[] alpine can be customized using the [.guimenuitem]#SETUP# option from the main menu. Consult http://www.washington.edu/alpine/[http://www.washington.edu/alpine/] for more information. [[mail-fetchmail]] == Using fetchmail fetchmail is a full-featured IMAP and POP client. It allows users to automatically download mail from remote IMAP and POP servers and save it into local mailboxes where it can be accessed more easily. fetchmail can be installed using the package:mail/fetchmail[] port, and offers various features, including: * Support for the POP3, APOP, KPOP, IMAP, ETRN and ODMR protocols. * Ability to forward mail using SMTP, which allows filtering, forwarding, and aliasing to function normally. * May be run in daemon mode to check periodically for new messages. * Can retrieve multiple mailboxes and forward them, based on configuration, to different local users. This section explains some of the basic features of fetchmail. This utility requires a [.filename]#.fetchmailrc# configuration in the user's home directory in order to run correctly. This file includes server information as well as login credentials. Due to the sensitive nature of the contents of this file, it is advisable to make it readable only by the user, with the following command: [source,shell] .... % chmod 600 .fetchmailrc .... The following [.filename]#.fetchmailrc# serves as an example for downloading a single user mailbox using POP. It tells fetchmail to connect to `example.com` using a username of `joesoap` and a password of `XXX`. This example assumes that the user `joesoap` exists on the local system. [.programlisting] .... poll example.com protocol pop3 username "joesoap" password "XXX" .... The next example connects to multiple POP and IMAP servers and redirects to different local usernames where applicable: [.programlisting] .... poll example.com proto pop3: user "joesoap", with password "XXX", is "jsoap" here; user "andrea", with password "XXXX"; poll example2.net proto imap: user "john", with password "XXXXX", is "myth" here; .... fetchmail can be run in daemon mode by running it with `-d`, followed by the interval (in seconds) that fetchmail should poll servers listed in [.filename]#.fetchmailrc#. The following example configures fetchmail to poll every 600 seconds: [source,shell] .... % fetchmail -d 600 .... More information on fetchmail can be found at http://www.fetchmail.info/[http://www.fetchmail.info/]. [[mail-procmail]] == Using procmail procmail is a powerful application used to filter incoming mail. It allows users to define "rules" which can be matched to incoming mails to perform specific functions or to reroute mail to alternative mailboxes or email addresses. procmail can be installed using the package:mail/procmail[] port. Once installed, it can be directly integrated into most MTAs. Consult the MTA documentation for more information. Alternatively, procmail can be integrated by adding the following line to a [.filename]#.forward# in the home directory of the user: [.programlisting] .... "|exec /usr/local/bin/procmail || exit 75" .... The following section displays some basic procmail rules, as well as brief descriptions of what they do. Rules must be inserted into a [.filename]#.procmailrc#, which must reside in the user's home directory. The majority of these rules can be found in man:procmailex[5]. To forward all mail from mailto:user@example.com[user@example.com] to an external address of mailto:goodmail@example2.com[goodmail@example2.com]: [.programlisting] .... :0 * ^From.*user@example.com ! goodmail@example2.com .... To forward all mails shorter than 1000 bytes to an external address of mailto:goodmail@example2.com[goodmail@example2.com]: [.programlisting] .... :0 * < 1000 ! goodmail@example2.com .... To send all mail sent to mailto:alternate@example.com[alternate@example.com] to a mailbox called [.filename]#alternate#: [.programlisting] .... :0 * ^TOalternate@example.com alternate .... To send all mail with a subject of "Spam" to [.filename]#/dev/null#: [.programlisting] .... :0 ^Subject:.*Spam /dev/null .... A useful recipe that parses incoming `FreeBSD.org` mailing lists and places each list in its own mailbox: [.programlisting] .... :0 * ^Sender:.owner-freebsd-\/[^@]+@FreeBSD.ORG { LISTNAME=${MATCH} :0 * LISTNAME??^\/[^@]+ FreeBSD-${MATCH} } .... diff --git a/documentation/content/en/books/handbook/network-servers/_index.adoc b/documentation/content/en/books/handbook/network-servers/_index.adoc index 3bc99dd05b..1b8d48eb95 100644 --- a/documentation/content/en/books/handbook/network-servers/_index.adoc +++ b/documentation/content/en/books/handbook/network-servers/_index.adoc @@ -1,3016 +1,3017 @@ --- title: Chapter 30. Network Servers part: IV. Network Communication prev: books/handbook/mail next: books/handbook/firewalls description: This chapter covers some of the more frequently used network services on UNIX systems tags: ["network", "servers", "inetd", "NFS", "NIS", "LDAP", "DHCP", "DNS", "Apache HTTP", "FTP", "Samba", "NTP", "iSCSI"] showBookMenu: true weight: 35 path: "/books/handbook/" --- [[network-servers]] = Network Servers :doctype: book :toc: macro :toclevels: 1 :icons: font :sectnums: :sectnumlevels: 6 :sectnumoffset: 30 :partnums: :source-highlighter: rouge :experimental: :images-path: books/handbook/network-servers/ ifdef::env-beastie[] ifdef::backend-html5[] :imagesdir: ../../../../images/{images-path} endif::[] ifndef::book[] include::shared/authors.adoc[] include::shared/mirrors.adoc[] include::shared/releases.adoc[] include::shared/attributes/attributes-{{% lang %}}.adoc[] include::shared/{{% lang %}}/teams.adoc[] include::shared/{{% lang %}}/mailing-lists.adoc[] include::shared/{{% lang %}}/urls.adoc[] toc::[] endif::[] ifdef::backend-pdf,backend-epub3[] include::../../../../../shared/asciidoctor.adoc[] endif::[] endif::[] ifndef::env-beastie[] toc::[] include::../../../../../shared/asciidoctor.adoc[] endif::[] [[network-servers-synopsis]] == Synopsis This chapter covers some of the more frequently used network services on UNIX(R) systems. This includes installing, configuring, testing, and maintaining many different types of network services. Example configuration files are included throughout this chapter for reference. By the end of this chapter, readers will know: * How to manage the inetd daemon. * How to set up the Network File System (NFS). * How to set up the Network Information Server (NIS) for centralizing and sharing user accounts. * How to set FreeBSD up to act as an LDAP server or client * How to set up automatic network settings using DHCP. * How to set up a Domain Name Server (DNS). * How to set up the Apache HTTP Server. * How to set up a File Transfer Protocol (FTP) server. * How to set up a file and print server for Windows(R) clients using Samba. * How to synchronize the time and date, and set up a time server using the Network Time Protocol (NTP). * How to set up iSCSI. This chapter assumes a basic knowledge of: * [.filename]#/etc/rc# scripts. * Network terminology. * Installation of additional third-party software (crossref:ports[ports,Installing Applications: Packages and Ports]). [[network-inetd]] == The inetd Super-Server The man:inetd[8] daemon is sometimes referred to as a Super-Server because it manages connections for many services. Instead of starting multiple applications, only the inetd service needs to be started. When a connection is received for a service that is managed by inetd, it determines which program the connection is destined for, spawns a process for that program, and delegates the program a socket. Using inetd for services that are not heavily used can reduce system load, when compared to running each daemon individually in stand-alone mode. Primarily, inetd is used to spawn other daemons, but several trivial protocols are handled internally, such as chargen, auth, time, echo, discard, and daytime. This section covers the basics of configuring inetd. [[network-inetd-conf]] === Configuration File Configuration of inetd is done by editing [.filename]#/etc/inetd.conf#. Each line of this configuration file represents an application which can be started by inetd. By default, every line starts with a comment (`#`), meaning that inetd is not listening for any applications. To configure inetd to listen for an application's connections, remove the `#` at the beginning of the line for that application. After saving your edits, configure inetd to start at system boot by editing [.filename]#/etc/rc.conf#: [.programlisting] .... inetd_enable="YES" .... To start inetd now, so that it listens for the service you configured, type: [source,shell] .... # service inetd start .... Once inetd is started, it needs to be notified whenever a modification is made to [.filename]#/etc/inetd.conf#: [[network-inetd-reread]] .Reloading the inetd Configuration File [example] ==== [source,shell] .... # service inetd reload .... ==== Typically, the default entry for an application does not need to be edited beyond removing the `#`. In some situations, it may be appropriate to edit the default entry. As an example, this is the default entry for man:ftpd[8] over IPv4: [.programlisting] .... ftp stream tcp nowait root /usr/libexec/ftpd ftpd -l .... The seven columns in an entry are as follows: [.programlisting] .... service-name socket-type protocol {wait|nowait}[/max-child[/max-connections-per-ip-per-minute[/max-child-per-ip]]] user[:group][/login-class] server-program server-program-arguments .... where: service-name:: The service name of the daemon to start. It must correspond to a service listed in [.filename]#/etc/services#. This determines which port inetd listens on for incoming connections to that service. When using a custom service, it must first be added to [.filename]#/etc/services#. socket-type:: Either `stream`, `dgram`, `raw`, or `seqpacket`. Use `stream` for TCP connections and `dgram` for UDP services. protocol:: Use one of the following protocol names: + [.informaltable] [cols="1,1", frame="none", options="header"] |=== | Protocol Name | Explanation |tcp or tcp4 |TCP IPv4 |udp or udp4 |UDP IPv4 |tcp6 |TCP IPv6 |udp6 |UDP IPv6 |tcp46 |Both TCP IPv4 and IPv6 |udp46 |Both UDP IPv4 and IPv6 |=== {wait|nowait}[/max-child[/max-connections-per-ip-per-minute[/max-child-per-ip]]]:: In this field, `wait` or `nowait` must be specified. `max-child`, `max-connections-per-ip-per-minute` and `max-child-per-ip` are optional. + `wait|nowait` indicates whether or not the service is able to handle its own socket. `dgram` socket types must use `wait` while `stream` daemons, which are usually multi-threaded, should use `nowait`. `wait` usually hands off multiple sockets to a single daemon, while `nowait` spawns a child daemon for each new socket. + The maximum number of child daemons inetd may spawn is set by `max-child`. For example, to limit ten instances of the daemon, place a `/10` after `nowait`. Specifying `/0` allows an unlimited number of children. + `max-connections-per-ip-per-minute` limits the number of connections from any particular IP address per minute. Once the limit is reached, further connections from this IP address will be dropped until the end of the minute. For example, a value of `/10` would limit any particular IP address to ten connection attempts per minute. `max-child-per-ip` limits the number of child processes that can be started on behalf on any single IP address at any moment. These options can limit excessive resource consumption and help to prevent Denial of Service attacks. + An example can be seen in the default settings for man:fingerd[8]: + [.programlisting] .... finger stream tcp nowait/3/10 nobody /usr/libexec/fingerd fingerd -k -s .... user:: The username the daemon will run as. Daemons typically run as `root`, `daemon`, or `nobody`. server-program:: The full path to the daemon. If the daemon is a service provided by inetd internally, use `internal`. server-program-arguments:: Used to specify any command arguments to be passed to the daemon on invocation. If the daemon is an internal service, use `internal`. [[network-inetd-cmdline]] === Command-Line Options Like most server daemons, inetd has a number of options that can be used to modify its behavior. By default, inetd is started with `-wW -C 60`. These options enable TCP wrappers for all services, including internal services, and prevent any IP address from requesting any service more than 60 times per minute. To change the default options which are passed to inetd, add an entry for `inetd_flags` in [.filename]#/etc/rc.conf#. If inetd is already running, restart it with `service inetd restart`. The available rate limiting options are: -c maximum:: Specify the default maximum number of simultaneous invocations of each service, where the default is unlimited. May be overridden on a per-service basis by using `max-child` in [.filename]#/etc/inetd.conf#. -C rate:: Specify the default maximum number of times a service can be invoked from a single IP address per minute. May be overridden on a per-service basis by using `max-connections-per-ip-per-minute` in [.filename]#/etc/inetd.conf#. -R rate:: Specify the maximum number of times a service can be invoked in one minute, where the default is `256`. A rate of `0` allows an unlimited number. -s maximum:: Specify the maximum number of times a service can be invoked from a single IP address at any one time, where the default is unlimited. May be overridden on a per-service basis by using `max-child-per-ip` in [.filename]#/etc/inetd.conf#. Additional options are available. Refer to man:inetd[8] for the full list of options. [[network-inetd-security]] === Security Considerations Many of the daemons which can be managed by inetd are not security-conscious. Some daemons, such as fingerd, can provide information that may be useful to an attacker. Only enable the services which are needed and monitor the system for excessive connection attempts. `max-connections-per-ip-per-minute`, `max-child` and `max-child-per-ip` can be used to limit such attacks. -By default, TCP wrappers is enabled. +By default, TCP wrappers are enabled. Consult man:hosts_access[5] for more information on placing TCP restrictions on various inetd invoked daemons. [[network-nfs]] == Network File System (NFS) FreeBSD supports the Network File System (NFS), which allows a server to share directories and files with clients over a network. With NFS, users and programs can access files on remote systems as if they were stored locally. NFS has many practical uses. Some of the more common uses include: * Data that would otherwise be duplicated on each client can be kept in a single location and accessed by clients on the network. * Several clients may need access to the [.filename]#/usr/ports/distfiles# directory. Sharing that directory allows for quick access to the source files without having to download them to each client. * On large networks, it is often more convenient to configure a central NFS server on which all user home directories are stored. Users can log into a client anywhere on the network and have access to their home directories. * Administration of NFS exports is simplified. For example, there is only one file system where security or backup policies must be set. * Removable media storage devices can be used by other machines on the network. This reduces the number of devices throughout the network and provides a centralized location to manage their security. It is often more convenient to install software on multiple machines from a centralized installation media. NFS consists of a server and one or more clients. The client remotely accesses the data that is stored on the server machine. In order for this to function properly, a few processes have to be configured and running. These daemons must be running on the server: [.informaltable] [cols="1,1", frame="none", options="header"] |=== | Daemon | Description |nfsd |The NFS daemon which services requests from NFS clients. |mountd |The NFS mount daemon which carries out requests received from nfsd. |rpcbind | This daemon allows NFS clients to discover which port the NFS server is using. |=== Running man:nfsiod[8] on the client can improve performance, but is not required. [[network-configuring-nfs]] === Configuring the Server The file systems which the NFS server will share are specified in [.filename]#/etc/exports#. Each line in this file specifies a file system to be exported, which clients have access to that file system, and any access options. When adding entries to this file, each exported file system, its properties, and allowed hosts must occur on a single line. If no clients are listed in the entry, then any client on the network can mount that file system. The following [.filename]#/etc/exports# entries demonstrate how to export file systems. The examples can be modified to match the file systems and client names on the reader's network. There are many options that can be used in this file, but only a few will be mentioned here. See man:exports[5] for the full list of options. This example shows how to export [.filename]#/cdrom# to three hosts named _alpha_, _bravo_, and _charlie_: [.programlisting] .... /cdrom -ro alpha bravo charlie .... The `-ro` flag makes the file system read-only, preventing clients from making any changes to the exported file system. This example assumes that the host names are either in DNS or in [.filename]#/etc/hosts#. Refer to man:hosts[5] if the network does not have a DNS server. The next example exports [.filename]#/home# to three clients by IP address. This can be useful for networks without DNS or [.filename]#/etc/hosts# entries. The `-alldirs` flag allows subdirectories to be mount points. In other words, it will not automatically mount the subdirectories, but will permit the client to mount the directories that are required as needed. [.programlisting] .... /usr/home -alldirs 10.0.0.2 10.0.0.3 10.0.0.4 .... This next example exports [.filename]#/a# so that two clients from different domains may access that file system. The `-maproot=root` allows `root` on the remote system to write data on the exported file system as `root`. If `-maproot=root` is not specified, the client's `root` user will be mapped to the server's `nobody` account and will be subject to the access limitations defined for `nobody`. [.programlisting] .... /a -maproot=root host.example.com box.example.org .... A client can only be specified once per file system. For example, if [.filename]#/usr# is a single file system, these entries would be invalid as both entries specify the same host: [.programlisting] .... # Invalid when /usr is one file system /usr/src client /usr/ports client .... The correct format for this situation is to use one entry: [.programlisting] .... /usr/src /usr/ports client .... The following is an example of a valid export list, where [.filename]#/usr# and [.filename]#/exports# are local file systems: [.programlisting] .... # Export src and ports to client01 and client02, but only # client01 has root privileges on it /usr/src /usr/ports -maproot=root client01 /usr/src /usr/ports client02 # The client machines have root and can mount anywhere # on /exports. Anyone in the world can mount /exports/obj read-only /exports -alldirs -maproot=root client01 client02 /exports/obj -ro .... To enable the processes required by the NFS server at boot time, add these options to [.filename]#/etc/rc.conf#: [.programlisting] .... rpcbind_enable="YES" nfs_server_enable="YES" mountd_enable="YES" .... The server can be started now by running this command: [source,shell] .... # service nfsd start .... Whenever the NFS server is started, mountd also starts automatically. However, mountd only reads [.filename]#/etc/exports# when it is started. To make subsequent [.filename]#/etc/exports# edits take effect immediately, force mountd to reread it: [source,shell] .... # service mountd reload .... === Configuring the Client To enable NFS clients, set this option in each client's [.filename]#/etc/rc.conf#: [.programlisting] .... nfs_client_enable="YES" .... Then, run this command on each NFS client: [source,shell] .... # service nfsclient start .... The client now has everything it needs to mount a remote file system. In these examples, the server's name is `server` and the client's name is `client`. To mount [.filename]#/home# on `server` to the [.filename]#/mnt# mount point on `client`: [source,shell] .... # mount server:/home /mnt .... The files and directories in [.filename]#/home# will now be available on `client`, in the [.filename]#/mnt# directory. To mount a remote file system each time the client boots, add it to [.filename]#/etc/fstab#: [.programlisting] .... server:/home /mnt nfs rw 0 0 .... Refer to man:fstab[5] for a description of all available options. === Locking Some applications require file locking to operate correctly. To enable locking, add these lines to [.filename]#/etc/rc.conf# on both the client and server: [.programlisting] .... rpc_lockd_enable="YES" rpc_statd_enable="YES" .... Then start the applications: [source,shell] .... # service lockd start # service statd start .... If locking is not required on the server, the NFS client can be configured to lock locally by including `-L` when running mount. Refer to man:mount_nfs[8] for further details. [[network-autofs]] === Automating Mounts with man:autofs[5] [NOTE] ==== The man:autofs[5] automount facility is supported starting with FreeBSD 10.1-RELEASE. To use the automounter functionality in older versions of FreeBSD, use man:amd[8] instead. This chapter only describes the man:autofs[5] automounter. ==== The man:autofs[5] facility is a common name for several components that, together, allow for automatic mounting of remote and local filesystems whenever a file or directory within that file system is accessed. It consists of the kernel component, man:autofs[5], and several userspace applications: man:automount[8], man:automountd[8] and man:autounmountd[8]. It serves as an alternative for man:amd[8] from previous FreeBSD releases. -Amd is still provided for backward compatibility purposes, as the two use different map format; the one used by autofs is the same as with other SVR4 automounters, such as the ones in Solaris, MacOS X, and Linux. +amd is still provided for backward compatibility purposes, as the two use different map formats; the one used by autofs is the same as with other SVR4 automounters, such as the ones in Solaris, MacOS X, and Linux. The man:autofs[5] virtual filesystem is mounted on specified mountpoints by man:automount[8], usually invoked during boot. -Whenever a process attempts to access file within the man:autofs[5] mountpoint, the kernel will notify man:automountd[8] daemon and pause the triggering process. The man:automountd[8] daemon will handle kernel requests by finding the proper map and mounting the filesystem according to it, then signal the kernel to release blocked process. The man:autounmountd[8] daemon automatically unmounts automounted filesystems after some time, unless they are still being used. +Whenever a process attempts to access a file within the man:autofs[5] mountpoint, the kernel will notify man:automountd[8] daemon and pause the triggering process. +The man:automountd[8] daemon will handle kernel requests by finding the proper map and mounting the filesystem according to it, then signal the kernel to release blocked process. +The man:autounmountd[8] daemon automatically unmounts automounted filesystems after some time, unless they are still being used. The primary autofs configuration file is [.filename]#/etc/auto_master#. It assigns individual maps to top-level mounts. For an explanation of [.filename]#auto_master# and the map syntax, refer to man:auto_master[5]. There is a special automounter map mounted on [.filename]#/net#. When a file is accessed within this directory, man:autofs[5] looks up the corresponding remote mount and automatically mounts it. For instance, an attempt to access a file within [.filename]#/net/foobar/usr# would tell man:automountd[8] to mount the [.filename]#/usr# export from the host `foobar`. .Mounting an Export with man:autofs[5] [example] ==== In this example, `showmount -e` shows the exported file systems that can be mounted from the NFS server, `foobar`: [source,shell] .... % showmount -e foobar Exports list on foobar: /usr 10.10.10.0 /a 10.10.10.0 % cd /net/foobar/usr .... ==== The output from `showmount` shows [.filename]#/usr# as an export. When changing directories to [.filename]#/host/foobar/usr#, man:automountd[8] intercepts the request and attempts to resolve the hostname `foobar`. If successful, man:automountd[8] automatically mounts the source export. To enable man:autofs[5] at boot time, add this line to [.filename]#/etc/rc.conf#: [.programlisting] .... autofs_enable="YES" .... Then man:autofs[5] can be started by running: [source,shell] .... # service automount start # service automountd start # service autounmountd start .... The man:autofs[5] map format is the same as in other operating systems. Information about this format from other sources can be useful, like the http://web.archive.org/web/20160813071113/http://images.apple.com/business/docs/Autofs.pdf[Mac OS X document]. Consult the man:automount[8], man:automountd[8], man:autounmountd[8], and man:auto_master[5] manual pages for more information. [[network-nis]] == Network Information System (NIS) Network Information System (NIS) is designed to centralize administration of UNIX(R)-like systems such as Solaris(TM), HP-UX, AIX(R), Linux, NetBSD, OpenBSD, and FreeBSD. NIS was originally known as Yellow Pages but the name was changed due to trademark issues. This is the reason why NIS commands begin with `yp`. NIS is a Remote Procedure Call (RPC)-based client/server system that allows a group of machines within an NIS domain to share a common set of configuration files. This permits a system administrator to set up NIS client systems with only minimal configuration data and to add, remove, or modify configuration data from a single location. FreeBSD uses version 2 of the NIS protocol. === NIS Terms and Processes Table 28.1 summarizes the terms and important processes used by NIS: .NIS Terminology [cols="1,1", frame="none", options="header"] |=== | Term | Description |NIS domain name |NIS servers and clients share an NIS domain name. Typically, this name does not have anything to do with DNS. |man:rpcbind[8] |This service enables RPC and must be running in order to run an NIS server or act as an NIS client. |man:ypbind[8] |This service binds an NIS client to its NIS server. It will take the NIS domain name and use RPC to connect to the server. It is the core of client/server communication in an NIS environment. If this service is not running on a client machine, it will not be able to access the NIS server. |man:ypserv[8] |This is the process for the NIS server. If this service stops running, the server will no longer be able to respond to NIS requests so hopefully, there is a slave server to take over. Some non-FreeBSD clients will not try to reconnect using a slave server and the ypbind process may need to be restarted on these clients. |man:rpc.yppasswdd[8] |This process only runs on NIS master servers. This daemon allows NIS clients to change their NIS passwords. If this daemon is not running, users will have to login to the NIS master server and change their passwords there. |=== === Machine Types There are three types of hosts in an NIS environment: * NIS master server + This server acts as a central repository for host configuration information and maintains the authoritative copy of the files used by all of the NIS clients. The [.filename]#passwd#, [.filename]#group#, and other various files used by NIS clients are stored on the master server. While it is possible for one machine to be an NIS master server for more than one NIS domain, this type of configuration will not be covered in this chapter as it assumes a relatively small-scale NIS environment. * NIS slave servers + NIS slave servers maintain copies of the NIS master's data files in order to provide redundancy. Slave servers also help to balance the load of the master server as NIS clients always attach to the NIS server which responds first. * NIS clients + NIS clients authenticate against the NIS server during log on. Information in many files can be shared using NIS. The [.filename]#master.passwd#, [.filename]#group#, and [.filename]#hosts# files are commonly shared via NIS. Whenever a process on a client needs information that would normally be found in these files locally, it makes a query to the NIS server that it is bound to instead. === Planning Considerations This section describes a sample NIS environment which consists of 15 FreeBSD machines with no centralized point of administration. Each machine has its own [.filename]#/etc/passwd# and [.filename]#/etc/master.passwd#. These files are kept in sync with each other only through manual intervention. Currently, when a user is added to the lab, the process must be repeated on all 15 machines. The configuration of the lab will be as follows: [.informaltable] [cols="1,1,1", frame="none", options="header"] |=== | Machine name | IP address | Machine role |`ellington` |`10.0.0.2` |NIS master |`coltrane` |`10.0.0.3` |NIS slave |`basie` |`10.0.0.4` |Faculty workstation |`bird` |`10.0.0.5` |Client machine |`cli[1-11]` |`10.0.0.[6-17]` |Other client machines |=== If this is the first time an NIS scheme is being developed, it should be thoroughly planned ahead of time. Regardless of network size, several decisions need to be made as part of the planning process. ==== Choosing a NIS Domain Name When a client broadcasts its requests for info, it includes the name of the NIS domain that it is part of. This is how multiple servers on one network can tell which server should answer which request. Think of the NIS domain name as the name for a group of hosts. Some organizations choose to use their Internet domain name for their NIS domain name. This is not recommended as it can cause confusion when trying to debug network problems. The NIS domain name should be unique within the network and it is helpful if it describes the group of machines it represents. For example, the Art department at Acme Inc. might be in the "acme-art"NIS domain. This example will use the domain name `test-domain`. However, some non-FreeBSD operating systems require the NIS domain name to be the same as the Internet domain name. If one or more machines on the network have this restriction, the Internet domain name _must_ be used as the NIS domain name. ==== Physical Server Requirements There are several things to keep in mind when choosing a machine to use as a NIS server. Since NIS clients depend upon the availability of the server, choose a machine that is not rebooted frequently. The NIS server should ideally be a stand alone machine whose sole purpose is to be an NIS server. If the network is not heavily used, it is acceptable to put the NIS server on a machine running other services. However, if the NIS server becomes unavailable, it will adversely affect all NIS clients. === Configuring the NIS Master Server The canonical copies of all NIS files are stored on the master server. The databases used to store the information are called NIS maps. In FreeBSD, these maps are stored in [.filename]#/var/yp/[domainname]# where [.filename]#[domainname]# is the name of the NIS domain. Since multiple domains are supported, it is possible to have several directories, one for each domain. Each domain will have its own independent set of maps. NIS master and slave servers handle all NIS requests through man:ypserv[8]. This daemon is responsible for receiving incoming requests from NIS clients, translating the requested domain and map name to a path to the corresponding database file, and transmitting data from the database back to the client. Setting up a master NIS server can be relatively straight forward, depending on environmental needs. Since FreeBSD provides built-in NIS support, it only needs to be enabled by adding the following lines to [.filename]#/etc/rc.conf#: [.programlisting] .... nisdomainname="test-domain" <.> nis_server_enable="YES" <.> nis_yppasswdd_enable="YES" <.> .... <.> This line sets the NIS domain name to `test-domain`. <.> This automates the start up of the NIS server processes when the system boots. <.> This enables the man:rpc.yppasswdd[8] daemon so that users can change their NIS password from a client machine. Care must be taken in a multi-server domain where the server machines are also NIS clients. It is generally a good idea to force the servers to bind to themselves rather than allowing them to broadcast bind requests and possibly become bound to each other. Strange failure modes can result if one server goes down and others are dependent upon it. Eventually, all the clients will time out and attempt to bind to other servers, but the delay involved can be considerable and the failure mode is still present since the servers might bind to each other all over again. A server that is also a client can be forced to bind to a particular server by adding these additional lines to [.filename]#/etc/rc.conf#: [.programlisting] .... nis_client_enable="YES" <.> nis_client_flags="-S test-domain,server" <.> .... <.> This enables running client stuff as well. <.> This line sets the NIS domain name to `test-domain` and bind to itself. After saving the edits, type `/etc/netstart` to restart the network and apply the values defined in [.filename]#/etc/rc.conf#. Before initializing the NIS maps, start man:ypserv[8]: [source,shell] .... # service ypserv start .... ==== Initializing the NIS Maps NIS maps are generated from the configuration files in [.filename]#/etc# on the NIS master, with one exception: [.filename]#/etc/master.passwd#. This is to prevent the propagation of passwords to all the servers in the NIS domain. Therefore, before the NIS maps are initialized, configure the primary password files: [source,shell] .... # cp /etc/master.passwd /var/yp/master.passwd # cd /var/yp # vi master.passwd .... It is advisable to remove all entries for system accounts as well as any user accounts that do not need to be propagated to the NIS clients, such as the `root` and any other administrative accounts. [NOTE] ==== Ensure that the [.filename]#/var/yp/master.passwd# is neither group or world readable by setting its permissions to `600`. ==== After completing this task, initialize the NIS maps. FreeBSD includes the man:ypinit[8] script to do this. When generating maps for the master server, include `-m` and specify the NIS domain name: [source,shell] .... ellington# ypinit -m test-domain Server Type: MASTER Domain: test-domain Creating an YP server will require that you answer a few questions. Questions will all be asked at the beginning of the procedure. Do you want this procedure to quit on non-fatal errors? [y/n: n] n Ok, please remember to go back and redo manually whatever fails. If not, something might not work. At this point, we have to construct a list of this domains YP servers. rod.darktech.org is already known as master server. Please continue to add any slave servers, one per line. When you are done with the list, type a . master server : ellington next host to add: coltrane next host to add: ^D The current list of NIS servers looks like this: ellington coltrane Is this correct? [y/n: y] y [..output from map generation..] NIS Map update completed. ellington has been setup as an YP master server without any errors. .... This will create [.filename]#/var/yp/Makefile# from [.filename]#/var/yp/Makefile.dist#. By default, this file assumes that the environment has a single NIS server with only FreeBSD clients. Since `test-domain` has a slave server, edit this line in [.filename]#/var/yp/Makefile# so that it begins with a comment (`#`): [.programlisting] .... NOPUSH = "True" .... ==== Adding New Users Every time a new user is created, the user account must be added to the master NIS server and the NIS maps rebuilt. Until this occurs, the new user will not be able to login anywhere except on the NIS master. For example, to add the new user `jsmith` to the `test-domain` domain, run these commands on the master server: [source,shell] .... # pw useradd jsmith # cd /var/yp # make test-domain .... The user could also be added using `adduser jsmith` instead of `pw useradd smith`. === Setting up a NIS Slave Server To set up an NIS slave server, log on to the slave server and edit [.filename]#/etc/rc.conf# as for the master server. Do not generate any NIS maps, as these already exist on the master server. When running `ypinit` on the slave server, use `-s` (for slave) instead of `-m` (for master). This option requires the name of the NIS master in addition to the domain name, as seen in this example: [source,shell] .... coltrane# ypinit -s ellington test-domain Server Type: SLAVE Domain: test-domain Master: ellington Creating an YP server will require that you answer a few questions. Questions will all be asked at the beginning of the procedure. Do you want this procedure to quit on non-fatal errors? [y/n: n] n Ok, please remember to go back and redo manually whatever fails. If not, something might not work. There will be no further questions. The remainder of the procedure should take a few minutes, to copy the databases from ellington. Transferring netgroup... ypxfr: Exiting: Map successfully transferred Transferring netgroup.byuser... ypxfr: Exiting: Map successfully transferred Transferring netgroup.byhost... ypxfr: Exiting: Map successfully transferred Transferring master.passwd.byuid... ypxfr: Exiting: Map successfully transferred Transferring passwd.byuid... ypxfr: Exiting: Map successfully transferred Transferring passwd.byname... ypxfr: Exiting: Map successfully transferred Transferring group.bygid... ypxfr: Exiting: Map successfully transferred Transferring group.byname... ypxfr: Exiting: Map successfully transferred Transferring services.byname... ypxfr: Exiting: Map successfully transferred Transferring rpc.bynumber... ypxfr: Exiting: Map successfully transferred Transferring rpc.byname... ypxfr: Exiting: Map successfully transferred Transferring protocols.byname... ypxfr: Exiting: Map successfully transferred Transferring master.passwd.byname... ypxfr: Exiting: Map successfully transferred Transferring networks.byname... ypxfr: Exiting: Map successfully transferred Transferring networks.byaddr... ypxfr: Exiting: Map successfully transferred Transferring netid.byname... ypxfr: Exiting: Map successfully transferred Transferring hosts.byaddr... ypxfr: Exiting: Map successfully transferred Transferring protocols.bynumber... ypxfr: Exiting: Map successfully transferred Transferring ypservers... ypxfr: Exiting: Map successfully transferred Transferring hosts.byname... ypxfr: Exiting: Map successfully transferred coltrane has been setup as an YP slave server without any errors. Remember to update map ypservers on ellington. .... This will generate a directory on the slave server called [.filename]#/var/yp/test-domain# which contains copies of the NIS master server's maps. Adding these [.filename]#/etc/crontab# entries on each slave server will force the slaves to sync their maps with the maps on the master server: [.programlisting] .... 20 * * * * root /usr/libexec/ypxfr passwd.byname 21 * * * * root /usr/libexec/ypxfr passwd.byuid .... These entries are not mandatory because the master server automatically attempts to push any map changes to its slaves. However, since clients may depend upon the slave server to provide correct password information, it is recommended to force frequent password map updates. This is especially important on busy networks where map updates might not always complete. To finish the configuration, run `/etc/netstart` on the slave server in order to start the NIS services. === Setting Up an NIS Client An NIS client binds to an NIS server using man:ypbind[8]. This daemon broadcasts RPC requests on the local network. These requests specify the domain name configured on the client. If an NIS server in the same domain receives one of the broadcasts, it will respond to ypbind, which will record the server's address. If there are several servers available, the client will use the address of the first server to respond and will direct all of its NIS requests to that server. The client will automatically ping the server on a regular basis to make sure it is still available. If it fails to receive a reply within a reasonable amount of time, ypbind will mark the domain as unbound and begin broadcasting again in the hopes of locating another server. To configure a FreeBSD machine to be an NIS client: [.procedure] ==== . Edit [.filename]#/etc/rc.conf# and add the following lines in order to set the NIS domain name and start man:ypbind[8] during network startup: + [.programlisting] .... nisdomainname="test-domain" nis_client_enable="YES" .... . To import all possible password entries from the NIS server, use `vipw` to remove all user accounts except one from [.filename]#/etc/master.passwd#. When removing the accounts, keep in mind that at least one local account should remain and this account should be a member of `wheel`. If there is a problem with NIS, this local account can be used to log in remotely, become the superuser, and fix the problem. Before saving the edits, add the following line to the end of the file: + [.programlisting] .... +::::::::: .... + This line configures the client to provide anyone with a valid account in the NIS server's password maps an account on the client. There are many ways to configure the NIS client by modifying this line. One method is described in <>. For more detailed reading, refer to the book `Managing NFS and NIS`, published by O'Reilly Media. . To import all possible group entries from the NIS server, add this line to [.filename]#/etc/group#: + [.programlisting] .... +:*:: .... ==== To start the NIS client immediately, execute the following commands as the superuser: [source,shell] .... # /etc/netstart # service ypbind start .... After completing these steps, running `ypcat passwd` on the client should show the server's [.filename]#passwd# map. === NIS Security Since RPC is a broadcast-based service, any system running ypbind within the same domain can retrieve the contents of the NIS maps. To prevent unauthorized transactions, man:ypserv[8] supports a feature called "securenets" which can be used to restrict access to a given set of hosts. By default, this information is stored in [.filename]#/var/yp/securenets#, unless man:ypserv[8] is started with `-p` and an alternate path. This file contains entries that consist of a network specification and a network mask separated by white space. Lines starting with `#` are considered to be comments. A sample [.filename]#securenets# might look like this: [.programlisting] .... # allow connections from local host -- mandatory 127.0.0.1 255.255.255.255 # allow connections from any host # on the 192.168.128.0 network 192.168.128.0 255.255.255.0 # allow connections from any host # between 10.0.0.0 to 10.0.15.255 # this includes the machines in the testlab 10.0.0.0 255.255.240.0 .... If man:ypserv[8] receives a request from an address that matches one of these rules, it will process the request normally. If the address fails to match a rule, the request will be ignored and a warning message will be logged. If the [.filename]#securenets# does not exist, `ypserv` will allow connections from any host. crossref:security[tcpwrappers,"TCP Wrapper"] is an alternate mechanism for providing access control instead of [.filename]#securenets#. While either access control mechanism adds some security, they are both vulnerable to "IP spoofing" attacks. All NIS-related traffic should be blocked at the firewall. Servers using [.filename]#securenets# may fail to serve legitimate NIS clients with archaic TCP/IP implementations. Some of these implementations set all host bits to zero when doing broadcasts or fail to observe the subnet mask when calculating the broadcast address. While some of these problems can be fixed by changing the client configuration, other problems may force the retirement of these client systems or the abandonment of [.filename]#securenets#. The use of TCP Wrapper increases the latency of the NIS server. The additional delay may be long enough to cause timeouts in client programs, especially in busy networks with slow NIS servers. If one or more clients suffer from latency, convert those clients into NIS slave servers and force them to bind to themselves. ==== Barring Some Users In this example, the `basie` system is a faculty workstation within the NIS domain. The [.filename]#passwd# map on the master NIS server contains accounts for both faculty and students. This section demonstrates how to allow faculty logins on this system while refusing student logins. To prevent specified users from logging on to a system, even if they are present in the NIS database, use `vipw` to add `-_username_` with the correct number of colons towards the end of [.filename]#/etc/master.passwd# on the client, where _username_ is the username of a user to bar from logging in. The line with the blocked user must be before the `+` line that allows NIS users. In this example, `bill` is barred from logging on to `basie`: [source,shell] .... basie# cat /etc/master.passwd root:[password]:0:0::0:0:The super-user:/root:/bin/csh toor:[password]:0:0::0:0:The other super-user:/root:/bin/sh daemon:*:1:1::0:0:Owner of many system processes:/root:/usr/sbin/nologin operator:*:2:5::0:0:System &:/:/usr/sbin/nologin bin:*:3:7::0:0:Binaries Commands and Source,,,:/:/usr/sbin/nologin tty:*:4:65533::0:0:Tty Sandbox:/:/usr/sbin/nologin kmem:*:5:65533::0:0:KMem Sandbox:/:/usr/sbin/nologin games:*:7:13::0:0:Games pseudo-user:/usr/games:/usr/sbin/nologin news:*:8:8::0:0:News Subsystem:/:/usr/sbin/nologin man:*:9:9::0:0:Mister Man Pages:/usr/share/man:/usr/sbin/nologin bind:*:53:53::0:0:Bind Sandbox:/:/usr/sbin/nologin uucp:*:66:66::0:0:UUCP pseudo-user:/var/spool/uucppublic:/usr/libexec/uucp/uucico xten:*:67:67::0:0:X-10 daemon:/usr/local/xten:/usr/sbin/nologin pop:*:68:6::0:0:Post Office Owner:/nonexistent:/usr/sbin/nologin nobody:*:65534:65534::0:0:Unprivileged user:/nonexistent:/usr/sbin/nologin -bill::::::::: +::::::::: basie# .... [[network-netgroups]] === Using Netgroups Barring specified users from logging on to individual systems becomes unscaleable on larger networks and quickly loses the main benefit of NIS: _centralized_ administration. Netgroups were developed to handle large, complex networks with hundreds of users and machines. Their use is comparable to UNIX(R) groups, where the main difference is the lack of a numeric ID and the ability to define a netgroup by including both user accounts and other netgroups. To expand on the example used in this chapter, the NIS domain will be extended to add the users and systems shown in Tables 28.2 and 28.3: .Additional Users [cols="1,1", frame="none", options="header"] |=== | User Name(s) | Description |`alpha`, `beta` |IT department employees |`charlie`, `delta` |IT department apprentices |`echo`, `foxtrott`, `golf`, ... |employees |`able`, `baker`, ... |interns |=== .Additional Systems [cols="1,1", frame="none", options="header"] |=== | Machine Name(s) | Description |`war`, `death`, `famine`, `pollution` |Only IT employees are allowed to log onto these servers. |`pride`, `greed`, `envy`, `wrath`, `lust`, `sloth` |All members of the IT department are allowed to login onto these servers. |`one`, `two`, `three`, `four`, ... |Ordinary workstations used by employees. |`trashcan` |A very old machine without any critical data. Even interns are allowed to use this system. |=== When using netgroups to configure this scenario, each user is assigned to one or more netgroups and logins are then allowed or forbidden for all members of the netgroup. When adding a new machine, login restrictions must be defined for all netgroups. When a new user is added, the account must be added to one or more netgroups. If the NIS setup is planned carefully, only one central configuration file needs modification to grant or deny access to machines. The first step is the initialization of the NIS`netgroup` map. In FreeBSD, this map is not created by default. On the NIS master server, use an editor to create a map named [.filename]#/var/yp/netgroup#. This example creates four netgroups to represent IT employees, IT apprentices, employees, and interns: [.programlisting] .... IT_EMP (,alpha,test-domain) (,beta,test-domain) IT_APP (,charlie,test-domain) (,delta,test-domain) USERS (,echo,test-domain) (,foxtrott,test-domain) \ (,golf,test-domain) INTERNS (,able,test-domain) (,baker,test-domain) .... Each entry configures a netgroup. The first column in an entry is the name of the netgroup. Each set of brackets represents either a group of one or more users or the name of another netgroup. When specifying a user, the three comma-delimited fields inside each group represent: . The name of the host(s) where the other fields representing the user are valid. If a hostname is not specified, the entry is valid on all hosts. . The name of the account that belongs to this netgroup. . The NIS domain for the account. Accounts may be imported from other NIS domains into a netgroup. If a group contains multiple users, separate each user with whitespace. Additionally, each field may contain wildcards. See man:netgroup[5] for details. Netgroup names longer than 8 characters should not be used. The names are case sensitive and using capital letters for netgroup names is an easy way to distinguish between user, machine and netgroup names. Some non-FreeBSD NIS clients cannot handle netgroups containing more than 15 entries. This limit may be circumvented by creating several sub-netgroups with 15 users or fewer and a real netgroup consisting of the sub-netgroups, as seen in this example: [.programlisting] .... BIGGRP1 (,joe1,domain) (,joe2,domain) (,joe3,domain) [...] BIGGRP2 (,joe16,domain) (,joe17,domain) [...] BIGGRP3 (,joe31,domain) (,joe32,domain) BIGGROUP BIGGRP1 BIGGRP2 BIGGRP3 .... Repeat this process if more than 225 (15 times 15) users exist within a single netgroup. To activate and distribute the new NIS map: [source,shell] .... ellington# cd /var/yp ellington# make .... This will generate the three NIS maps [.filename]#netgroup#, [.filename]#netgroup.byhost# and [.filename]#netgroup.byuser#. Use the map key option of man:ypcat[1] to check if the new NIS maps are available: [source,shell] .... ellington% ypcat -k netgroup ellington% ypcat -k netgroup.byhost ellington% ypcat -k netgroup.byuser .... The output of the first command should resemble the contents of [.filename]#/var/yp/netgroup#. The second command only produces output if host-specific netgroups were created. The third command is used to get the list of netgroups for a user. To configure a client, use man:vipw[8] to specify the name of the netgroup. For example, on the server named `war`, replace this line: [.programlisting] .... +::::::::: .... with [.programlisting] .... +@IT_EMP::::::::: .... This specifies that only the users defined in the netgroup `IT_EMP` will be imported into this system's password database and only those users are allowed to login to this system. This configuration also applies to the `~` function of the shell and all routines which convert between user names and numerical user IDs. In other words, `cd ~_user_` will not work, `ls -l` will show the numerical ID instead of the username, and `find . -user joe -print` will fail with the message `No such user`. To fix this, import all user entries without allowing them to login into the servers. This can be achieved by adding an extra line: [.programlisting] .... +:::::::::/usr/sbin/nologin .... This line configures the client to import all entries but to replace the shell in those entries with [.filename]#/usr/sbin/nologin#. Make sure that extra line is placed _after_ `+@IT_EMP:::::::::`. Otherwise, all user accounts imported from NIS will have [.filename]#/usr/sbin/nologin# as their login shell and no one will be able to login to the system. To configure the less important servers, replace the old `+:::::::::` on the servers with these lines: [.programlisting] .... +@IT_EMP::::::::: +@IT_APP::::::::: +:::::::::/usr/sbin/nologin .... The corresponding lines for the workstations would be: [.programlisting] .... +@IT_EMP::::::::: +@USERS::::::::: +:::::::::/usr/sbin/nologin .... NIS supports the creation of netgroups from other netgroups which can be useful if the policy regarding user access changes. One possibility is the creation of role-based netgroups. For example, one might create a netgroup called `BIGSRV` to define the login restrictions for the important servers, another netgroup called `SMALLSRV` for the less important servers, and a third netgroup called `USERBOX` for the workstations. Each of these netgroups contains the netgroups that are allowed to login onto these machines. The new entries for the NIS`netgroup` map would look like this: [.programlisting] .... BIGSRV IT_EMP IT_APP SMALLSRV IT_EMP IT_APP ITINTERN USERBOX IT_EMP ITINTERN USERS .... This method of defining login restrictions works reasonably well when it is possible to define groups of machines with identical restrictions. Unfortunately, this is the exception and not the rule. Most of the time, the ability to define login restrictions on a per-machine basis is required. Machine-specific netgroup definitions are another possibility to deal with the policy changes. In this scenario, the [.filename]#/etc/master.passwd# of each system contains two lines starting with "+". The first line adds a netgroup with the accounts allowed to login onto this machine and the second line adds all other accounts with [.filename]#/usr/sbin/nologin# as shell. It is recommended to use the "ALL-CAPS" version of the hostname as the name of the netgroup: [.programlisting] .... +@BOXNAME::::::::: +:::::::::/usr/sbin/nologin .... Once this task is completed on all the machines, there is no longer a need to modify the local versions of [.filename]#/etc/master.passwd# ever again. All further changes can be handled by modifying the NIS map. Here is an example of a possible `netgroup` map for this scenario: [.programlisting] .... # Define groups of users first IT_EMP (,alpha,test-domain) (,beta,test-domain) IT_APP (,charlie,test-domain) (,delta,test-domain) DEPT1 (,echo,test-domain) (,foxtrott,test-domain) DEPT2 (,golf,test-domain) (,hotel,test-domain) DEPT3 (,india,test-domain) (,juliet,test-domain) ITINTERN (,kilo,test-domain) (,lima,test-domain) D_INTERNS (,able,test-domain) (,baker,test-domain) # # Now, define some groups based on roles USERS DEPT1 DEPT2 DEPT3 BIGSRV IT_EMP IT_APP SMALLSRV IT_EMP IT_APP ITINTERN USERBOX IT_EMP ITINTERN USERS # # And a groups for a special tasks # Allow echo and golf to access our anti-virus-machine SECURITY IT_EMP (,echo,test-domain) (,golf,test-domain) # # machine-based netgroups # Our main servers WAR BIGSRV FAMINE BIGSRV # User india needs access to this server POLLUTION BIGSRV (,india,test-domain) # # This one is really important and needs more access restrictions DEATH IT_EMP # # The anti-virus-machine mentioned above ONE SECURITY # # Restrict a machine to a single user TWO (,hotel,test-domain) # [...more groups to follow] .... It may not always be advisable to use machine-based netgroups. When deploying a couple of dozen or hundreds of systems, role-based netgroups instead of machine-based netgroups may be used to keep the size of the NIS map within reasonable limits. === Password Formats NIS requires that all hosts within an NIS domain use the same format for encrypting passwords. If users have trouble authenticating on an NIS client, it may be due to a differing password format. In a heterogeneous network, the format must be supported by all operating systems, where DES is the lowest common standard. To check which format a server or client is using, look at this section of [.filename]#/etc/login.conf#: [.programlisting] .... default:\ :passwd_format=des:\ :copyright=/etc/COPYRIGHT:\ [Further entries elided] .... In this example, the system is using the DES format for password hashing. Other possible values include `blf` for Blowfish, `md5` for MD5, `sha256` and `sha512` for SHA-256 and SHA-512 respectively. For more information and the up to date list of what is available on your system, consult the man:crypt[3] manpage. If the format on a host needs to be edited to match the one being used in the NIS domain, the login capability database must be rebuilt after saving the change: [source,shell] .... # cap_mkdb /etc/login.conf .... [NOTE] ==== The format of passwords for existing user accounts will not be updated until each user changes their password _after_ the login capability database is rebuilt. ==== [[network-ldap]] == Lightweight Directory Access Protocol (LDAP) The Lightweight Directory Access Protocol (LDAP) is an application layer protocol used to access, modify, and authenticate objects using a distributed directory information service. Think of it as a phone or record book which stores several levels of hierarchical, homogeneous information. It is used in Active Directory and OpenLDAP networks and allows users to access to several levels of internal information utilizing a single account. For example, email authentication, pulling employee contact information, and internal website authentication might all make use of a single user account in the LDAP server's record base. This section provides a quick start guide for configuring an LDAP server on a FreeBSD system. It assumes that the administrator already has a design plan which includes the type of information to store, what that information will be used for, which users should have access to that information, and how to secure this information from unauthorized access. === LDAP Terminology and Structure LDAP uses several terms which should be understood before starting the configuration. All directory entries consist of a group of _attributes_. Each of these attribute sets contains a unique identifier known as a _Distinguished Name_ (DN) which is normally built from several other attributes such as the common or _Relative Distinguished Name_ (RDN). Similar to how directories have absolute and relative paths, consider a DN as an absolute path and the RDN as the relative path. An example LDAP entry looks like the following. This example searches for the entry for the specified user account (`uid`), organizational unit (`ou`), and organization (`o`): [source,shell] .... % ldapsearch -xb "uid=trhodes,ou=users,o=example.com" # extended LDIF # # LDAPv3 # base with scope subtree # filter: (objectclass=*) # requesting: ALL # # trhodes, users, example.com dn: uid=trhodes,ou=users,o=example.com mail: trhodes@example.com cn: Tom Rhodes uid: trhodes telephoneNumber: (123) 456-7890 # search result search: 2 result: 0 Success # numResponses: 2 # numEntries: 1 .... This example entry shows the values for the `dn`, `mail`, `cn`, `uid`, and `telephoneNumber` attributes. The cn attribute is the RDN. More information about LDAP and its terminology can be found at http://www.openldap.org/doc/admin24/intro.html[http://www.openldap.org/doc/admin24/intro.html]. [[ldap-config]] === Configuring an LDAP Server FreeBSD does not provide a built-in LDAP server. Begin the configuration by installing package:net/openldap-server[] package or port: [source,shell] .... # pkg install openldap-server .... There is a large set of default options enabled in the extref:{linux-users}[package, software]. Review them by running `pkg info openldap-server`. If they are not sufficient (for example if SQL support is needed), please consider recompiling the port using the appropriate crossref:ports[ports-using,framework]. The installation creates the directory [.filename]#/var/db/openldap-data# to hold the data. The directory to store the certificates must be created: [source,shell] .... # mkdir /usr/local/etc/openldap/private .... The next phase is to configure the Certificate Authority. The following commands must be executed from [.filename]#/usr/local/etc/openldap/private#. This is important as the file permissions need to be restrictive and users should not have access to these files. More detailed information about certificates and their parameters can be found in crossref:security[openssl,"OpenSSL"]. To create the Certificate Authority, start with this command and follow the prompts: [source,shell] .... # openssl req -days 365 -nodes -new -x509 -keyout ca.key -out ../ca.crt .... The entries for the prompts may be generic _except_ for the `Common Name`. This entry must be _different_ than the system hostname. If this will be a self signed certificate, prefix the hostname with `CA` for Certificate Authority. The next task is to create a certificate signing request and a private key. Input this command and follow the prompts: [source,shell] .... # openssl req -days 365 -nodes -new -keyout server.key -out server.csr .... During the certificate generation process, be sure to correctly set the `Common Name` attribute. The Certificate Signing Request must be signed with the Certificate Authority in order to be used as a valid certificate: [source,shell] .... # openssl x509 -req -days 365 -in server.csr -out ../server.crt -CA ../ca.crt -CAkey ca.key -CAcreateserial .... The final part of the certificate generation process is to generate and sign the client certificates: [source,shell] .... # openssl req -days 365 -nodes -new -keyout client.key -out client.csr # openssl x509 -req -days 3650 -in client.csr -out ../client.crt -CA ../ca.crt -CAkey ca.key .... Remember to use the same `Common Name` attribute when prompted. When finished, ensure that a total of eight (8) new files have been generated through the proceeding commands. The daemon running the OpenLDAP server is [.filename]#slapd#. Its configuration is performed through [.filename]#slapd.ldif#: the old [.filename]#slapd.conf# has been deprecated by OpenLDAP. http://www.openldap.org/doc/admin24/slapdconf2.html[Configuration examples] for [.filename]#slapd.ldif# are available and can also be found in [.filename]#/usr/local/etc/openldap/slapd.ldif.sample#. Options are documented in slapd-config(5). Each section of [.filename]#slapd.ldif#, like all the other LDAP attribute sets, is uniquely identified through a DN. Be sure that no blank lines are left between the `dn:` statement and the desired end of the section. In the following example, TLS will be used to implement a secure channel. The first section represents the global configuration: [.programlisting] .... # # See slapd-config(5) for details on configuration options. # This file should NOT be world readable. # dn: cn=config objectClass: olcGlobal cn: config # # # Define global ACLs to disable default read access. # olcArgsFile: /var/run/openldap/slapd.args olcPidFile: /var/run/openldap/slapd.pid olcTLSCertificateFile: /usr/local/etc/openldap/server.crt olcTLSCertificateKeyFile: /usr/local/etc/openldap/private/server.key olcTLSCACertificateFile: /usr/local/etc/openldap/ca.crt #olcTLSCipherSuite: HIGH olcTLSProtocolMin: 3.1 olcTLSVerifyClient: never .... The Certificate Authority, server certificate and server private key files must be specified here. It is recommended to let the clients choose the security cipher and omit option `olcTLSCipherSuite` (incompatible with TLS clients other than [.filename]#openssl#). Option `olcTLSProtocolMin` lets the server require a minimum security level: it is recommended. While verification is mandatory for the server, it is not for the client: `olcTLSVerifyClient: never`. The second section is about the backend modules and can be configured as follows: [.programlisting] .... # # Load dynamic backend modules: # dn: cn=module,cn=config objectClass: olcModuleList cn: module olcModulepath: /usr/local/libexec/openldap olcModuleload: back_mdb.la #olcModuleload: back_bdb.la #olcModuleload: back_hdb.la #olcModuleload: back_ldap.la #olcModuleload: back_passwd.la #olcModuleload: back_shell.la .... The third section is devoted to load the needed `ldif` schemas to be used by the databases: they are essential. [.programlisting] .... dn: cn=schema,cn=config objectClass: olcSchemaConfig cn: schema include: file:///usr/local/etc/openldap/schema/core.ldif include: file:///usr/local/etc/openldap/schema/cosine.ldif include: file:///usr/local/etc/openldap/schema/inetorgperson.ldif include: file:///usr/local/etc/openldap/schema/nis.ldif .... Next, the frontend configuration section: [.programlisting] .... # Frontend settings # dn: olcDatabase={-1}frontend,cn=config objectClass: olcDatabaseConfig objectClass: olcFrontendConfig olcDatabase: {-1}frontend olcAccess: to * by * read # # Sample global access control policy: # Root DSE: allow anyone to read it # Subschema (sub)entry DSE: allow anyone to read it # Other DSEs: # Allow self write access # Allow authenticated users read access # Allow anonymous users to authenticate # #olcAccess: to dn.base="" by * read #olcAccess: to dn.base="cn=Subschema" by * read #olcAccess: to * # by self write # by users read # by anonymous auth # # if no access controls are present, the default policy # allows anyone and everyone to read anything but restricts # updates to rootdn. (e.g., "access to * by * read") # # rootdn can always read and write EVERYTHING! # olcPasswordHash: {SSHA} # {SSHA} is already the default for olcPasswordHash .... Another section is devoted to the _configuration backend_, the only way to later access the OpenLDAP server configuration is as a global super-user. [.programlisting] .... dn: olcDatabase={0}config,cn=config objectClass: olcDatabaseConfig olcDatabase: {0}config olcAccess: to * by * none olcRootPW: {SSHA}iae+lrQZILpiUdf16Z9KmDmSwT77Dj4U .... The default administrator username is `cn=config`. Type [.filename]#slappasswd# in a shell, choose a password and use its hash in `olcRootPW`. If this option is not specified now, before [.filename]#slapd.ldif# is imported, no one will be later able to modify the _global configuration_ section. The last section is about the database backend: [.programlisting] .... ####################################################################### # LMDB database definitions ####################################################################### # dn: olcDatabase=mdb,cn=config objectClass: olcDatabaseConfig objectClass: olcMdbConfig olcDatabase: mdb olcDbMaxSize: 1073741824 olcSuffix: dc=domain,dc=example olcRootDN: cn=mdbadmin,dc=domain,dc=example # Cleartext passwords, especially for the rootdn, should # be avoided. See slappasswd(8) and slapd-config(5) for details. # Use of strong authentication encouraged. olcRootPW: {SSHA}X2wHvIWDk6G76CQyCMS1vDCvtICWgn0+ # The database directory MUST exist prior to running slapd AND # should only be accessible by the slapd and slap tools. # Mode 700 recommended. olcDbDirectory: /var/db/openldap-data # Indices to maintain olcDbIndex: objectClass eq .... This database hosts the _actual contents_ of the LDAP directory. Types other than `mdb` are available. Its super-user, not to be confused with the global one, is configured here: a (possibly custom) username in `olcRootDN` and the password hash in `olcRootPW`; [.filename]#slappasswd# can be used as before. This http://www.openldap.org/devel/gitweb.cgi?p=openldap.git;a=tree;f=tests/data/regressions/its8444;h=8a5e808e63b0de3d2bdaf2cf34fecca8577ca7fd;hb=HEAD[repository] contains four examples of [.filename]#slapd.ldif#. To convert an existing [.filename]#slapd.conf# into [.filename]#slapd.ldif#, refer to http://www.openldap.org/doc/admin24/slapdconf2.html[this page] (please note that this may introduce some unuseful options). When the configuration is completed, [.filename]#slapd.ldif# must be placed in an empty directory. It is recommended to create it as: [source,shell] .... # mkdir /usr/local/etc/openldap/slapd.d/ .... Import the configuration database: [source,shell] .... # /usr/local/sbin/slapadd -n0 -F /usr/local/etc/openldap/slapd.d/ -l /usr/local/etc/openldap/slapd.ldif .... Start the [.filename]#slapd# daemon: [source,shell] .... # /usr/local/libexec/slapd -F /usr/local/etc/openldap/slapd.d/ .... Option `-d` can be used for debugging, as specified in slapd(8). To verify that the server is running and working: [source,shell] .... # ldapsearch -x -b '' -s base '(objectclass=*)' namingContexts # extended LDIF # # LDAPv3 # base <> with scope baseObject # filter: (objectclass=*) # requesting: namingContexts # # dn: namingContexts: dc=domain,dc=example # search result search: 2 result: 0 Success # numResponses: 2 # numEntries: 1 .... The server must still be trusted. If that has never been done before, follow these instructions. Install the OpenSSL package or port: [source,shell] .... # pkg install openssl .... From the directory where [.filename]#ca.crt# is stored (in this example, [.filename]#/usr/local/etc/openldap#), run: [source,shell] .... # c_rehash . .... Both the CA and the server certificate are now correctly recognized in their respective roles. To verify this, run this command from the [.filename]#server.crt# directory: [source,shell] .... # openssl verify -verbose -CApath . server.crt .... If [.filename]#slapd# was running, restart it. As stated in [.filename]#/usr/local/etc/rc.d/slapd#, to properly run [.filename]#slapd# at boot the following lines must be added to [.filename]#/etc/rc.conf#: [.programlisting] .... slapd_enable="YES" slapd_flags='-h "ldapi://%2fvar%2frun%2fopenldap%2fldapi/ ldap://0.0.0.0/"' slapd_sockets="/var/run/openldap/ldapi" slapd_cn_config="YES" .... [.filename]#slapd# does not provide debugging at boot. Check [.filename]#/var/log/debug.log#, [.filename]#dmesg -a# and [.filename]#/var/log/messages# for this purpose. The following example adds the group `team` and the user `john` to the `domain.example` LDAP database, which is still empty. First, create the file [.filename]#domain.ldif#: [source,shell] .... # cat domain.ldif dn: dc=domain,dc=example objectClass: dcObject objectClass: organization o: domain.example dc: domain dn: ou=groups,dc=domain,dc=example objectClass: top objectClass: organizationalunit ou: groups dn: ou=users,dc=domain,dc=example objectClass: top objectClass: organizationalunit ou: users dn: cn=team,ou=groups,dc=domain,dc=example objectClass: top objectClass: posixGroup cn: team gidNumber: 10001 dn: uid=john,ou=users,dc=domain,dc=example objectClass: top objectClass: account objectClass: posixAccount objectClass: shadowAccount cn: John McUser uid: john uidNumber: 10001 gidNumber: 10001 homeDirectory: /home/john/ loginShell: /usr/bin/bash userPassword: secret .... See the OpenLDAP documentation for more details. Use [.filename]#slappasswd# to replace the plain text password `secret` with a hash in `userPassword`. The path specified as `loginShell` must exist in all the systems where `john` is allowed to login. Finally, use the `mdb` administrator to modify the database: [source,shell] .... # ldapadd -W -D "cn=mdbadmin,dc=domain,dc=example" -f domain.ldif .... Modifications to the _global configuration_ section can only be performed by the global super-user. For example, assume that the option `olcTLSCipherSuite: HIGH:MEDIUM:SSLv3` was initially specified and must now be deleted. First, create a file that contains the following: [source,shell] .... # cat global_mod dn: cn=config changetype: modify delete: olcTLSCipherSuite .... Then, apply the modifications: [source,shell] .... # ldapmodify -f global_mod -x -D "cn=config" -W .... When asked, provide the password chosen in the _configuration backend_ section. The username is not required: here, `cn=config` represents the DN of the database section to be modified. Alternatively, use `ldapmodify` to delete a single line of the database, `ldapdelete` to delete a whole entry. If something goes wrong, or if the global super-user cannot access the configuration backend, it is possible to delete and re-write the whole configuration: [source,shell] .... # rm -rf /usr/local/etc/openldap/slapd.d/ .... [.filename]#slapd.ldif# can then be edited and imported again. Please, follow this procedure only when no other solution is available. This is the configuration of the server only. The same machine can also host an LDAP client, with its own separate configuration. [[network-dhcp]] == Dynamic Host Configuration Protocol (DHCP) The Dynamic Host Configuration Protocol (DHCP) allows a system to connect to a network in order to be assigned the necessary addressing information for communication on that network. FreeBSD includes the OpenBSD version of `dhclient` which is used by the client to obtain the addressing information. FreeBSD does not install a DHCP server, but several servers are available in the FreeBSD Ports Collection. The DHCP protocol is fully described in http://www.freesoft.org/CIE/RFC/2131/[RFC 2131]. Informational resources are also available at http://www.isc.org/downloads/dhcp/[isc.org/downloads/dhcp/]. This section describes how to use the built-in DHCP client. It then describes how to install and configure a DHCP server. [NOTE] ==== In FreeBSD, the man:bpf[4] device is needed by both the DHCP server and DHCP client. This device is included in the [.filename]#GENERIC# kernel that is installed with FreeBSD. Users who prefer to create a custom kernel need to keep this device if DHCP is used. It should be noted that [.filename]#bpf# also allows privileged users to run network packet sniffers on that system. ==== === Configuring a DHCP Client DHCP client support is included in the FreeBSD installer, making it easy to configure a newly installed system to automatically receive its networking addressing information from an existing DHCP server. Refer to crossref:bsdinstall[bsdinstall-post,"Accounts, Time Zone, Services and Hardening"] for examples of network configuration. When `dhclient` is executed on the client machine, it begins broadcasting requests for configuration information. By default, these requests use UDP port 68. The server replies on UDP port 67, giving the client an IP address and other relevant network information such as a subnet mask, default gateway, and DNS server addresses. This information is in the form of a DHCP "lease" and is valid for a configurable time. This allows stale IP addresses for clients no longer connected to the network to automatically be reused. DHCP clients can obtain a great deal of information from the server. An exhaustive list may be found in man:dhcp-options[5]. By default, when a FreeBSD system boots, its DHCP client runs in the background, or _asynchronously_. Other startup scripts continue to run while the DHCP process completes, which speeds up system startup. Background DHCP works well when the DHCP server responds quickly to the client's requests. However, DHCP may take a long time to complete on some systems. If network services attempt to run before DHCP has assigned the network addressing information, they will fail. Using DHCP in _synchronous_ mode prevents this problem as it pauses startup until the DHCP configuration has completed. This line in [.filename]#/etc/rc.conf# is used to configure background or asynchronous mode: [.programlisting] .... ifconfig_fxp0="DHCP" .... This line may already exist if the system was configured to use DHCP during installation. Replace the _fxp0_ shown in these examples with the name of the interface to be dynamically configured, as described in crossref:config[config-network-setup,“Setting Up Network Interface Cards”]. To instead configure the system to use synchronous mode, and to pause during startup while DHCP completes, use "`SYNCDHCP`": [.programlisting] .... ifconfig_fxp0="SYNCDHCP" .... Additional client options are available. Search for `dhclient` in man:rc.conf[5] for details. The DHCP client uses the following files: * [.filename]#/etc/dhclient.conf# + The configuration file used by `dhclient`. Typically, this file contains only comments as the defaults are suitable for most clients. This configuration file is described in man:dhclient.conf[5]. * [.filename]#/sbin/dhclient# + More information about the command itself can be found in man:dhclient[8]. * [.filename]#/sbin/dhclient-script# + The FreeBSD-specific DHCP client configuration script. It is described in man:dhclient-script[8], but should not need any user modification to function properly. * [.filename]#/var/db/dhclient.leases.interface# + The DHCP client keeps a database of valid leases in this file, which is written as a log and is described in man:dhclient.leases[5]. [[network-dhcp-server]] === Installing and Configuring a DHCP Server This section demonstrates how to configure a FreeBSD system to act as a DHCP server using the Internet Systems Consortium (ISC) implementation of the DHCP server. This implementation and its documentation can be installed using the package:net/isc-dhcp44-server[] package or port. The installation of package:net/isc-dhcp44-server[] installs a sample configuration file. Copy [.filename]#/usr/local/etc/dhcpd.conf.example# to [.filename]#/usr/local/etc/dhcpd.conf# and make any edits to this new file. The configuration file is comprised of declarations for subnets and hosts which define the information that is provided to DHCP clients. For example, these lines configure the following: [.programlisting] .... option domain-name "example.org";<.> option domain-name-servers ns1.example.org;<.> option subnet-mask 255.255.255.0;<.> default-lease-time 600;<.> max-lease-time 72400;<.> ddns-update-style none;<.> subnet 10.254.239.0 netmask 255.255.255.224 { range 10.254.239.10 10.254.239.20;<.> option routers rtr-239-0-1.example.org, rtr-239-0-2.example.org;<.> } host fantasia { hardware ethernet 08:00:07:26:c0:a5;<.> fixed-address fantasia.fugue.com;<.> } .... <.> This option specifies the default search domain that will be provided to clients. Refer to man:resolv.conf[5] for more information. <.> This option specifies a comma separated list of DNS servers that the client should use. They can be listed by their Fully Qualified Domain Names (FQDN), as seen in the example, or by their IP addresses. <.> The subnet mask that will be provided to clients. <.> The default lease expiry time in seconds. A client can be configured to override this value. <.> The maximum allowed length of time, in seconds, for a lease. Should a client request a longer lease, a lease will still be issued, but it will only be valid for `max-lease-time`. <.> The default of `none` disables dynamic DNS updates. Changing this to `interim` configures the DHCP server to update a DNS server whenever it hands out a lease so that the DNS server knows which IP addresses are associated with which computers in the network. Do not change the default setting unless the DNS server has been configured to support dynamic DNS. <.> This line creates a pool of available IP addresses which are reserved for allocation to DHCP clients. The range of addresses must be valid for the network or subnet specified in the previous line. <.> Declares the default gateway that is valid for the network or subnet specified before the opening `{` bracket. <.> Specifies the hardware MAC address of a client so that the DHCP server can recognize the client when it makes a request. <.> Specifies that this host should always be given the same IP address. Using the hostname is correct, since the DHCP server will resolve the hostname before returning the lease information. This configuration file supports many more options. Refer to dhcpd.conf(5), installed with the server, for details and examples. Once the configuration of [.filename]#dhcpd.conf# is complete, enable the DHCP server in [.filename]#/etc/rc.conf#: [.programlisting] .... dhcpd_enable="YES" dhcpd_ifaces="dc0" .... Replace the `dc0` with the interface (or interfaces, separated by whitespace) that the DHCP server should listen on for DHCP client requests. Start the server by issuing the following command: [source,shell] .... # service isc-dhcpd start .... Any future changes to the configuration of the server will require the dhcpd service to be stopped and then started using man:service[8]. The DHCP server uses the following files. Note that the manual pages are installed with the server software. * [.filename]#/usr/local/sbin/dhcpd# + More information about the dhcpd server can be found in dhcpd(8). * [.filename]#/usr/local/etc/dhcpd.conf# + The server configuration file needs to contain all the information that should be provided to clients, along with information regarding the operation of the server. This configuration file is described in dhcpd.conf(5). * [.filename]#/var/db/dhcpd.leases# + The DHCP server keeps a database of leases it has issued in this file, which is written as a log. Refer to dhcpd.leases(5), which gives a slightly longer description. * [.filename]#/usr/local/sbin/dhcrelay# + This daemon is used in advanced environments where one DHCP server forwards a request from a client to another DHCP server on a separate network. If this functionality is required, install the package:net/isc-dhcp44-relay[] package or port. The installation includes dhcrelay(8) which provides more detail. [[network-dns]] == Domain Name System (DNS) Domain Name System (DNS) is the protocol through which domain names are mapped to IP addresses, and vice versa. DNS is coordinated across the Internet through a somewhat complex system of authoritative root, Top Level Domain (TLD), and other smaller-scale name servers, which host and cache individual domain information. It is not necessary to run a name server to perform DNS lookups on a system. The following table describes some of the terms associated with DNS: .DNS Terminology [cols="1,1", frame="none", options="header"] |=== | Term | Definition |Forward DNS |Mapping of hostnames to IP addresses. |Origin |Refers to the domain covered in a particular zone file. |Resolver |A system process through which a machine queries a name server for zone information. |Reverse DNS |Mapping of IP addresses to hostnames. |Root zone |The beginning of the Internet zone hierarchy. All zones fall under the root zone, similar to how all files in a file system fall under the root directory. |Zone |An individual domain, subdomain, or portion of the DNS administered by the same authority. |=== Examples of zones: * `.` is how the root zone is usually referred to in documentation. * `org.` is a Top Level Domain (TLD) under the root zone. * `example.org.` is a zone under the `org.`TLD. * `1.168.192.in-addr.arpa` is a zone referencing all IP addresses which fall under the `192.168.1.*`IP address space. As one can see, the more specific part of a hostname appears to its left. For example, `example.org.` is more specific than `org.`, as `org.` is more specific than the root zone. The layout of each part of a hostname is much like a file system: the [.filename]#/dev# directory falls within the root, and so on. === Reasons to Run a Name Server Name servers generally come in two forms: authoritative name servers, and caching (also known as resolving) name servers. An authoritative name server is needed when: * One wants to serve DNS information to the world, replying authoritatively to queries. * A domain, such as `example.org`, is registered and IP addresses need to be assigned to hostnames under it. * An IP address block requires reverse DNS entries (IP to hostname). * A backup or second name server, called a slave, will reply to queries. A caching name server is needed when: * A local DNS server may cache and respond more quickly than querying an outside name server. When one queries for `www.FreeBSD.org`, the resolver usually queries the uplink ISP's name server, and retrieves the reply. With a local, caching DNS server, the query only has to be made once to the outside world by the caching DNS server. Additional queries will not have to go outside the local network, since the information is cached locally. === DNS Server Configuration Unbound is provided in the FreeBSD base system. By default, it will provide DNS resolution to the local machine only. While the base system package can be configured to provide resolution services beyond the local machine, it is recommended that such requirements be addressed by installing Unbound from the FreeBSD Ports Collection. To enable Unbound, add the following to [.filename]#/etc/rc.conf#: [.programlisting] .... local_unbound_enable="YES" .... Any existing nameservers in [.filename]#/etc/resolv.conf# will be configured as forwarders in the new Unbound configuration. [NOTE] ==== If any of the listed nameservers do not support DNSSEC, local DNS resolution will fail. Be sure to test each nameserver and remove any that fail the test. The following command will show the trust tree or a failure for a nameserver running on `192.168.1.1`: -==== - [source,shell] .... % drill -S FreeBSD.org @192.168.1.1 .... +==== Once each nameserver is confirmed to support DNSSEC, start Unbound: [source,shell] .... # service local_unbound onestart .... This will take care of updating [.filename]#/etc/resolv.conf# so that queries for DNSSEC secured domains will now work. For example, run the following to validate the FreeBSD.org DNSSEC trust tree: [source,shell] .... % drill -S FreeBSD.org ;; Number of trusted keys: 1 ;; Chasing: freebsd.org. A DNSSEC Trust tree: freebsd.org. (A) |---freebsd.org. (DNSKEY keytag: 36786 alg: 8 flags: 256) |---freebsd.org. (DNSKEY keytag: 32659 alg: 8 flags: 257) |---freebsd.org. (DS keytag: 32659 digest type: 2) |---org. (DNSKEY keytag: 49587 alg: 7 flags: 256) |---org. (DNSKEY keytag: 9795 alg: 7 flags: 257) |---org. (DNSKEY keytag: 21366 alg: 7 flags: 257) |---org. (DS keytag: 21366 digest type: 1) | |---. (DNSKEY keytag: 40926 alg: 8 flags: 256) | |---. (DNSKEY keytag: 19036 alg: 8 flags: 257) |---org. (DS keytag: 21366 digest type: 2) |---. (DNSKEY keytag: 40926 alg: 8 flags: 256) |---. (DNSKEY keytag: 19036 alg: 8 flags: 257) ;; Chase successful .... [[network-apache]] == Apache HTTP Server The open source Apache HTTP Server is the most widely used web server. FreeBSD does not install this web server by default, but it can be installed from the package:www/apache24[] package or port. This section summarizes how to configure and start version 2._x_ of the Apache HTTP Server on FreeBSD. For more detailed information about Apache 2.X and its configuration directives, refer to http://httpd.apache.org/[httpd.apache.org]. === Configuring and Starting Apache In FreeBSD, the main Apache HTTP Server configuration file is installed as [.filename]#/usr/local/etc/apache2x/httpd.conf#, where _x_ represents the version number. This ASCII text file begins comment lines with a `#`. The most frequently modified directives are: `ServerRoot "/usr/local"`:: Specifies the default directory hierarchy for the Apache installation. Binaries are stored in the [.filename]#bin# and [.filename]#sbin# subdirectories of the server root and configuration files are stored in the [.filename]#etc/apache2x# subdirectory. `ServerAdmin you@example.com`:: Change this to the email address to receive problems with the server. This address also appears on some server-generated pages, such as error documents. `ServerName www.example.com:80`:: Allows an administrator to set a hostname which is sent back to clients for the server. For example, `www` can be used instead of the actual hostname. If the system does not have a registered DNS name, enter its IP address instead. If the server will listen on an alternate report, change `80` to the alternate port number. `DocumentRoot "/usr/local/www/apache2_x_/data"`:: The directory where documents will be served from. By default, all requests are taken from this directory, but symbolic links and aliases may be used to point to other locations. It is always a good idea to make a backup copy of the default Apache configuration file before making changes. When the configuration of Apache is complete, save the file and verify the configuration using `apachectl`. Running `apachectl configtest` should return `Syntax OK`. To launch Apache at system startup, add the following line to [.filename]#/etc/rc.conf#: [.programlisting] .... apache24_enable="YES" .... If Apache should be started with non-default options, the following line may be added to [.filename]#/etc/rc.conf# to specify the needed flags: [.programlisting] .... apache24_flags="" .... If apachectl does not report configuration errors, start `httpd` now: [source,shell] .... # service apache24 start .... The `httpd` service can be tested by entering `http://_localhost_` in a web browser, replacing _localhost_ with the fully-qualified domain name of the machine running `httpd`. The default web page that is displayed is [.filename]#/usr/local/www/apache24/data/index.html#. The Apache configuration can be tested for errors after making subsequent configuration changes while `httpd` is running using the following command: [source,shell] .... # service apache24 configtest .... [NOTE] ==== It is important to note that `configtest` is not an man:rc[8] standard, and should not be expected to work for all startup scripts. ==== === Virtual Hosting Virtual hosting allows multiple websites to run on one Apache server. The virtual hosts can be _IP-based_ or _name-based_. IP-based virtual hosting uses a different IP address for each website. Name-based virtual hosting uses the clients HTTP/1.1 headers to figure out the hostname, which allows the websites to share the same IP address. To setup Apache to use name-based virtual hosting, add a `VirtualHost` block for each website. For example, for the webserver named `www.domain.tld` with a virtual domain of `www.someotherdomain.tld`, add the following entries to [.filename]#httpd.conf#: [.programlisting] .... ServerName www.domain.tld DocumentRoot /www/domain.tld ServerName www.someotherdomain.tld DocumentRoot /www/someotherdomain.tld .... For each virtual host, replace the values for `ServerName` and `DocumentRoot` with the values to be used. For more information about setting up virtual hosts, consult the official Apache documentation at: http://httpd.apache.org/docs/vhosts/[http://httpd.apache.org/docs/vhosts/]. === Apache Modules Apache uses modules to augment the functionality provided by the basic server. Refer to http://httpd.apache.org/docs/current/mod/[http://httpd.apache.org/docs/current/mod/] for a complete listing of and the configuration details for the available modules. In FreeBSD, some modules can be compiled with the package:www/apache24[] port. Type `make config` within [.filename]#/usr/ports/www/apache24# to see which modules are available and which are enabled by default. If the module is not compiled with the port, the FreeBSD Ports Collection provides an easy way to install many modules. This section describes three of the most commonly used modules. ==== SSL support At one in point in time, support for SSL inside of Apache required a secondary module called [.filename]#mod_ssl#. This is no longer the case and the default install of Apache comes with SSL built into the web server. An example of how to enable support for SSL websites is available in the installed file, [.filename]#httpd-ssl.conf# inside of the [.filename]#/usr/local/etc/apache24/extra# directory Inside this directory is also a sample file called named [.filename]#ssl.conf-sample#. It is recommended that both files be evaluated to properly set up secure websites in the Apache web server. After the configuration of SSL is complete, the following line must be uncommented in the main [.filename]#http.conf# to activate the changes on the next restart or reload of Apache: [.programlisting] .... #Include etc/apache24/extra/httpd-ssl.conf .... [WARNING] ==== SSL version two and version three have known vulnerability issues. It is highly recommended TLS version 1.2 and 1.3 be enabled in place of the older SSL options. This can be accomplished by setting the following options in the [.filename]#ssl.conf#: ==== [.programlisting] .... SSLProtocol all -SSLv3 -SSLv2 +TLSv1.2 +TLSv1.3 SSLProxyProtocol all -SSLv2 -SSLv3 -TLSv1 -TLSv1.1 .... To complete the configuration of SSL in the web server, uncomment the following line to ensure that the configuration will be pulled into Apache during restart or reload: [.programlisting] .... # Secure (SSL/TLS) connections Include etc/apache24/extra/httpd-ssl.conf .... The following lines must also be uncommented in the [.filename]#httpd.conf# to fully support SSL in Apache: [.programlisting] .... LoadModule authn_socache_module libexec/apache24/mod_authn_socache.so LoadModule socache_shmcb_module libexec/apache24/mod_socache_shmcb.so LoadModule ssl_module libexec/apache24/mod_ssl.so .... The next step is to work with a certificate authority to have the appropriate certificates installed on the system. This will set up a chain of trust for the site and prevent any warnings of self-signed certificates. ==== [.filename]#mod_perl# The [.filename]#mod_perl# module makes it possible to write Apache modules in Perl. In addition, the persistent interpreter embedded in the server avoids the overhead of starting an external interpreter and the penalty of Perl start-up time. The [.filename]#mod_perl# can be installed using the package:www/mod_perl2[] package or port. Documentation for using this module can be found at http://perl.apache.org/docs/2.0/index.html[http://perl.apache.org/docs/2.0/index.html]. ==== [.filename]#mod_php# _PHP: Hypertext Preprocessor_ (PHP) is a general-purpose scripting language that is especially suited for web development. Capable of being embedded into HTML, its syntax draws upon C, Java(TM), and Perl with the intention of allowing web developers to write dynamically generated webpages quickly. Support for PHP for Apache and any other feature written in the language, can be added by installing the appropriate port. For all supported versions, search the package database using `pkg`: [source,shell] .... # pkg search php .... A list will be displayed including the versions and additional features they provide. The components are completely modular, meaning features are enabled by installing the appropriate port. To install PHP version 7.4 for Apache, issue the following command: [source,shell] .... # pkg install mod_php74 .... If any dependency packages need to be installed, they will be installed as well. By default, PHP will not be enabled. The following lines will need to be added to the Apache configuration file located in [.filename]#/usr/local/etc/apache24# to make it active: [.programlisting] .... SetHandler application/x-httpd-php SetHandler application/x-httpd-php-source .... In addition, the `DirectoryIndex` in the configuration file will also need to be updated and Apache will either need to be restarted or reloaded for the changes to take effect. Support for many of the PHP features may also be installed by using `pkg`. For example, to install support for XML or SSL, install their respective ports: [source,shell] .... # pkg install php74-xml php74-openssl .... As before, the Apache configuration will need to be reloaded for the changes to take effect, even in cases where it was just a module install. To perform a graceful restart to reload the configuration, issue the following command: [source,shell] .... # apachectl graceful .... Once the install is complete, there are two methods of obtaining the installed PHP support modules and the environmental information of the build. The first is to install the full PHP binary and running the command to gain the information: [source,shell] .... # pkg install php74 .... [source,shell] .... # php -i |less .... It is necessary to pass the output to a pager, such as the `more` or `less` to easier digest the amount of output. Finally, to make any changes to the global configuration of PHP there is a well documented file installed into [.filename]#/usr/local/etc/php.ini#. At the time of install, this file will not exist because there are two versions to choose from, one is [.filename]#php.ini-development# and the other is [.filename]#php.ini-production#. These are starting points to assist administrators in their deployment. ==== HTTP2 Support Apache support for the HTTP2 protocol is included by default when installing the port with `pkg`. The new version of HTTP includes many improvements over the previous version, including utilizing a single connection to a website, reducing overall roundtrips of TCP connections. Also, packet header data is compressed and HTTP2 requires encryption by default. When Apache is configured to only use HTTP2, web browsers will require secure, encrypted HTTPS connections. When Apache is configured to use both versions, HTTP1.1 will be considered a fall back option if any issues arise during the connection. While this change does require administrators to make changes, they are positive and equate to a more secure Internet for everyone. The changes are only required for sites not currently implementing SSL and TLS. [NOTE] ==== This configuration depends on the previous sections, including TLS support. It is recommended those instructions be followed before continuing with this configuration. ==== Start the process by enabling the http2 module by uncommenting the line in [.filename]#/usr/local/etc/apache24/httpd.conf# and replace the mpm_prefork module with mpm_event as the former does not support HTTP2. [.programlisting] .... LoadModule http2_module libexec/apache24/mod_http2.so LoadModule mpm_event_module libexec/apache24/mod_mpm_event.so .... [NOTE] ==== There is a separate [.filename]#mod_http2# port that is available. It exists to deliver security and bug fixes quicker than the module installed with the bundled [.filename]#apache24# port. It is not required for HTTP2 support but is available. When installed, the [.filename]#mod_h2.so# should be used in place of [.filename]#mod_http2.so# in the Apache configuration. ==== There are two methods to implement HTTP2 in Apache; one way is globally for all sites and each VirtualHost running on the system. To enable HTTP2 globally, add the following line under the ServerName directive: [.programlisting] .... Protocols h2 http/1.1 .... [NOTE] ==== To enable HTTP2 over plaintext, use h2h2chttp/1.1 in the [.filename]#httpd.conf#. ==== Having the h2c here will allow plaintext HTTP2 data to pass on the system but is not recommended. In addition, using the http/1.1 here will allow fallback to the HTTP1.1 version of the protocol should it be needed by the system. To enable HTTP2 for individual VirtualHosts, add the same line within the VirtualHost directive in either [.filename]#httpd.conf# or [.filename]#httpd-ssl.conf#. Reload the configuration using the `apachectl`[parameter]#reload# command and test the configuration either by using either of the following methods after visiting one of the hosted pages: [source,shell] .... # grep "HTTP/2.0" /var/log/httpd-access.log .... This should return something similar to the following: [.programlisting] .... 192.168.1.205 - - [18/Oct/2020:18:34:36 -0400] "GET / HTTP/2.0" 304 - 192.0.2.205 - - [18/Oct/2020:19:19:57 -0400] "GET / HTTP/2.0" 304 - 192.0.0.205 - - [18/Oct/2020:19:20:52 -0400] "GET / HTTP/2.0" 304 - 192.0.2.205 - - [18/Oct/2020:19:23:10 -0400] "GET / HTTP/2.0" 304 - .... The other method is using the web browser's built in site debugger or `tcpdump`; however, using either method is beyond the scope of this document. Support for HTTP2 reverse proxy connections by using the [.filename]#mod_proxy_http2.so# module. When configuring the ProxyPass or RewriteRules [P] statements, they should use h2:// for the connection. === Dynamic Websites In addition to mod_perl and mod_php, other languages are available for creating dynamic web content. These include Django and Ruby on Rails. ==== Django Django is a BSD-licensed framework designed to allow developers to write high performance, elegant web applications quickly. It provides an object-relational mapper so that data types are developed as Python objects. A rich dynamic database-access API is provided for those objects without the developer ever having to write SQL. It also provides an extensible template system so that the logic of the application is separated from the HTML presentation. Django depends on [.filename]#mod_python#, and an SQL database engine. In FreeBSD, the package:www/py-django[] port automatically installs [.filename]#mod_python# and supports the PostgreSQL, MySQL, or SQLite databases, with the default being SQLite. To change the database engine, type `make config` within [.filename]#/usr/ports/www/py-django#, then install the port. Once Django is installed, the application will need a project directory along with the Apache configuration in order to use the embedded Python interpreter. This interpreter is used to call the application for specific URLs on the site. To configure Apache to pass requests for certain URLs to the web application, add the following to [.filename]#httpd.conf#, specifying the full path to the project directory: [.programlisting] .... SetHandler python-program PythonPath "['/dir/to/the/django/packages/'] + sys.path" PythonHandler django.core.handlers.modpython SetEnv DJANGO_SETTINGS_MODULE mysite.settings PythonAutoReload On PythonDebug On .... Refer to https://docs.djangoproject.com[https://docs.djangoproject.com] for more information on how to use Django. ==== Ruby on Rails Ruby on Rails is another open source web framework that provides a full development stack. It is optimized to make web developers more productive and capable of writing powerful applications quickly. On FreeBSD, it can be installed using the package:www/rubygem-rails[] package or port. Refer to http://guides.rubyonrails.org[http://guides.rubyonrails.org] for more information on how to use Ruby on Rails. [[network-ftp]] == File Transfer Protocol (FTP) The File Transfer Protocol (FTP) provides users with a simple way to transfer files to and from an FTP server. FreeBSD includes FTP server software, ftpd, in the base system. FreeBSD provides several configuration files for controlling access to the FTP server. This section summarizes these files. Refer to man:ftpd[8] for more details about the built-in FTP server. === Configuration The most important configuration step is deciding which accounts will be allowed access to the FTP server. A FreeBSD system has a number of system accounts which should not be allowed FTP access. The list of users disallowed any FTP access can be found in [.filename]#/etc/ftpusers#. By default, it includes system accounts. Additional users that should not be allowed access to FTP can be added. In some cases it may be desirable to restrict the access of some users without preventing them completely from using FTP. This can be accomplished be creating [.filename]#/etc/ftpchroot# as described in man:ftpchroot[5]. This file lists users and groups subject to FTP access restrictions. To enable anonymous FTP access to the server, create a user named `ftp` on the FreeBSD system. Users will then be able to log on to the FTP server with a username of `ftp` or `anonymous`. When prompted for the password, any input will be accepted, but by convention, an email address should be used as the password. The FTP server will call man:chroot[2] when an anonymous user logs in, to restrict access to only the home directory of the `ftp` user. There are two text files that can be created to specify welcome messages to be displayed to FTP clients. The contents of [.filename]#/etc/ftpwelcome# will be displayed to users before they reach the login prompt. After a successful login, the contents of [.filename]#/etc/ftpmotd# will be displayed. Note that the path to this file is relative to the login environment, so the contents of [.filename]#~ftp/etc/ftpmotd# would be displayed for anonymous users. Once the FTP server has been configured, set the appropriate variable in [.filename]#/etc/rc.conf# to start the service during boot: [.programlisting] .... ftpd_enable="YES" .... To start the service now: [source,shell] .... # service ftpd start .... Test the connection to the FTP server by typing: [source,shell] .... % ftp localhost .... The ftpd daemon uses man:syslog[3] to log messages. By default, the system log daemon will write messages related to FTP in [.filename]#/var/log/xferlog#. The location of the FTP log can be modified by changing the following line in [.filename]#/etc/syslog.conf#: [.programlisting] .... ftp.info /var/log/xferlog .... [NOTE] ==== Be aware of the potential problems involved with running an anonymous FTP server. In particular, think twice about allowing anonymous users to upload files. It may turn out that the FTP site becomes a forum for the trade of unlicensed commercial software or worse. If anonymous FTP uploads are required, then verify the permissions so that these files cannot be read by other anonymous users until they have been reviewed by an administrator. ==== [[network-samba]] == File and Print Services for Microsoft(R) Windows(R) Clients (Samba) Samba is a popular open source software package that provides file and print services using the SMB/CIFS protocol. This protocol is built into Microsoft(R) Windows(R) systems. It can be added to non-Microsoft(R) Windows(R) systems by installing the Samba client libraries. The protocol allows clients to access shared data and printers. These shares can be mapped as a local disk drive and shared printers can be used as if they were local printers. On FreeBSD, the Samba client libraries can be installed using the package:net/samba413[] port or package. The client provides the ability for a FreeBSD system to access SMB/CIFS shares in a Microsoft(R) Windows(R) network. A FreeBSD system can also be configured to act as a Samba server by installing the same package:net/samba413[] port or package. This allows the administrator to create SMB/CIFS shares on the FreeBSD system which can be accessed by clients running Microsoft(R) Windows(R) or the Samba client libraries. === Server Configuration Samba is configured in [.filename]#/usr/local/etc/smb4.conf#. This file must be created before Samba can be used. A simple [.filename]#smb4.conf# to share directories and printers with Windows(R) clients in a workgroup is shown here. For more complex setups involving LDAP or Active Directory, it is easier to use man:samba-tool[8] to create the initial [.filename]#smb4.conf#. [.programlisting] .... [global] workgroup = WORKGROUP server string = Samba Server Version %v netbios name = ExampleMachine wins support = Yes security = user passdb backend = tdbsam # Example: share /usr/src accessible only to 'developer' user [src] path = /usr/src valid users = developer writable = yes browsable = yes read only = no guest ok = no public = no create mask = 0666 directory mask = 0755 .... ==== Global Settings Settings that describe the network are added in [.filename]#/usr/local/etc/smb4.conf#: `workgroup`:: The name of the workgroup to be served. `netbios name`:: The NetBIOS name by which a Samba server is known. By default, it is the same as the first component of the host's DNS name. `server string`:: The string that will be displayed in the output of `net view` and some other networking tools that seek to display descriptive text about the server. `wins support`:: Whether Samba will act as a WINS server. Do not enable support for WINS on more than one server on the network. ==== Security Settings The most important settings in [.filename]#/usr/local/etc/smb4.conf# are the security model and the backend password format. These directives control the options: `security`:: The most common settings are `security = share` and `security = user`. If the clients use usernames that are the same as their usernames on the FreeBSD machine, user level security should be used. This is the default security policy and it requires clients to first log on before they can access shared resources. + In share level security, clients do not need to log onto the server with a valid username and password before attempting to connect to a shared resource. This was the default security model for older versions of Samba. `passdb backend`:: Samba has several different backend authentication models. Clients may be authenticated with LDAP, NIS+, an SQL database, or a modified password file. The recommended authentication method, `tdbsam`, is ideal for simple networks and is covered here. For larger or more complex networks, `ldapsam` is recommended. `smbpasswd` was the former default and is now obsolete. ==== Samba Users FreeBSD user accounts must be mapped to the `SambaSAMAccount` database for Windows(R) clients to access the share. Map existing FreeBSD user accounts using man:pdbedit[8]: [source,shell] .... # pdbedit -a username .... This section has only mentioned the most commonly used settings. Refer to the https://wiki.samba.org[Official Samba Wiki] for additional information about the available configuration options. === Starting Samba To enable Samba at boot time, add the following line to [.filename]#/etc/rc.conf#: [.programlisting] .... samba_server_enable="YES" .... To start Samba now: [source,shell] .... # service samba_server start Performing sanity check on Samba configuration: OK Starting nmbd. Starting smbd. .... Samba consists of three separate daemons. Both the nmbd and smbd daemons are started by `samba_enable`. If winbind name resolution is also required, set: [.programlisting] .... winbindd_enable="YES" .... Samba can be stopped at any time by typing: [source,shell] .... # service samba_server stop .... Samba is a complex software suite with functionality that allows broad integration with Microsoft(R) Windows(R) networks. For more information about functionality beyond the basic configuration described here, refer to https://www.samba.org[https://www.samba.org]. [[network-ntp]] == Clock Synchronization with NTP Over time, a computer's clock is prone to drift. This is problematic as many network services require the computers on a network to share the same accurate time. Accurate time is also needed to ensure that file timestamps stay consistent. The Network Time Protocol (NTP) is one way to provide clock accuracy in a network. FreeBSD includes man:ntpd[8] which can be configured to query other NTP servers to synchronize the clock on that machine or to provide time services to other computers in the network. This section describes how to configure ntpd on FreeBSD. Further documentation can be found in [.filename]#/usr/share/doc/ntp/# in HTML format. === NTP Configuration On FreeBSD, the built-in ntpd can be used to synchronize a system's clock. -Ntpd is configured using man:rc.conf[5] variables and [.filename]#/etc/ntp.conf#, as detailed in the following sections. +ntpd is configured using man:rc.conf[5] variables and [.filename]#/etc/ntp.conf#, as detailed in the following sections. -Ntpd communicates with its network peers using UDP packets. +ntpd communicates with its network peers using UDP packets. Any firewalls between your machine and its NTP peers must be configured to allow UDP packets in and out on port 123. ==== The [.filename]#/etc/ntp.conf# file -Ntpd reads [.filename]#/etc/ntp.conf# to determine which NTP servers to query. +ntpd reads [.filename]#/etc/ntp.conf# to determine which NTP servers to query. Choosing several NTP servers is recommended in case one of the servers becomes unreachable or its clock proves unreliable. As ntpd receives responses, it favors reliable servers over the less reliable ones. The servers which are queried can be local to the network, provided by an ISP, or selected from an http://support.ntp.org/bin/view/Servers/WebHome[ online list of publicly accessible NTP servers]. When choosing a public NTP server, select one that is geographically close and review its usage policy. The `pool` configuration keyword selects one or more servers from a pool of servers. An http://support.ntp.org/bin/view/Servers/NTPPoolServers[ online list of publicly accessible NTP pools] is available, organized by geographic area. In addition, FreeBSD provides a project-sponsored pool, `0.freebsd.pool.ntp.org`. .Sample [.filename]#/etc/ntp.conf# [example] ==== This is a simple example of an [.filename]#ntp.conf# file. It can safely be used as-is; it contains the recommended `restrict` options for operation on a publicly-accessible network connection. [.programlisting] .... # Disallow ntpq control/query access. Allow peers to be added only # based on pool and server statements in this file. restrict default limited kod nomodify notrap noquery nopeer restrict source limited kod nomodify notrap noquery # Allow unrestricted access from localhost for queries and control. restrict 127.0.0.1 restrict ::1 # Add a specific server. server ntplocal.example.com iburst # Add FreeBSD pool servers until 3-6 good servers are available. tos minclock 3 maxclock 6 pool 0.freebsd.pool.ntp.org iburst # Use a local leap-seconds file. leapfile "/var/db/ntpd.leap-seconds.list" .... ==== The format of this file is described in man:ntp.conf[5]. The descriptions below provide a quick overview of just the keywords used in the sample file above. By default, an NTP server is accessible to any network host. The `restrict` keyword controls which systems can access the server. Multiple `restrict` entries are supported, each one refining the restrictions given in previous statements. The values shown in the example grant the local system full query and control access, while allowing remote systems only the ability to query the time. For more details, refer to the `Access Control Support` subsection of man:ntp.conf[5]. The `server` keyword specifies a single server to query. The file can contain multiple server keywords, with one server listed on each line. The `pool` keyword specifies a pool of servers. -Ntpd will add one or more servers from this pool as needed to reach the number of peers specified using the `tos minclock` value. +ntpd will add one or more servers from this pool as needed to reach the number of peers specified using the `tos minclock` value. The `iburst` keyword directs ntpd to perform a burst of eight quick packet exchanges with a server when contact is first established, to help quickly synchronize system time. The `leapfile` keyword specifies the location of a file containing information about leap seconds. The file is updated automatically by man:periodic[8]. The file location specified by this keyword must match the location set in the `ntp_db_leapfile` variable in [.filename]#/etc/rc.conf#. ==== NTP entries in [.filename]#/etc/rc.conf# Set `ntpd_enable=YES` to start ntpd at boot time. Once `ntpd_enable=YES` has been added to [.filename]#/etc/rc.conf#, ntpd can be started immediately without rebooting the system by typing: [source,shell] .... # service ntpd start .... Only `ntpd_enable` must be set to use ntpd. The [.filename]#rc.conf# variables listed below may also be set as needed. Set `ntpd_sync_on_start=YES` to allow ntpd to step the clock any amount, one time at startup. Normally ntpd will log an error message and exit if the clock is off by more than 1000 seconds. This option is especially useful on systems without a battery-backed realtime clock. Set `ntpd_oomprotect=YES` to protect the ntpd daemon from being killed by the system attempting to recover from an Out Of Memory (OOM) condition. Set `ntpd_config=` to the location of an alternate [.filename]#ntp.conf# file. Set `ntpd_flags=` to contain any other ntpd flags as needed, but avoid using these flags which are managed internally by [.filename]#/etc/rc.d/ntpd#: * `-p` (pid file location) * `-c` (set `ntpd_config=` instead) -==== Ntpd and the unpriveleged `ntpd` user +==== ntpd and the unpriveleged `ntpd` user -Ntpd on FreeBSD can start and run as an unpriveleged user. +ntpd on FreeBSD can start and run as an unpriveleged user. Doing so requires the man:mac_ntpd[4] policy module. The [.filename]#/etc/rc.d/ntpd# startup script first examines the NTP configuration. If possible, it loads the `mac_ntpd` module, then starts ntpd as unpriveleged user `ntpd` (user id 123). To avoid problems with file and directory access, the startup script will not automatically start ntpd as `ntpd` when the configuration contains any file-related options. The presence of any of the following in `ntpd_flags` requires manual configuration as described below to run as the `ntpd` user: * -f or --driftfile * -i or --jaildir * -k or --keyfile * -l or --logfile * -s or --statsdir The presence of any of the following keywords in [.filename]#ntp.conf# requires manual configuration as described below to run as the `ntpd` user: * crypto * driftfile * key * logdir * statsdir To manually configure ntpd to run as user `ntpd` you must: * Ensure that the `ntpd` user has access to all the files and directories specified in the configuration. * Arrange for the `mac_ntpd` module to be loaded or compiled into the kernel. See man:mac_ntpd[4] for details. * Set `ntpd_user="ntpd"` in [.filename]#/etc/rc.conf# === Using NTP with a PPP Connection ntpd does not need a permanent connection to the Internet to function properly. However, if a PPP connection is configured to dial out on demand, NTP traffic should be prevented from triggering a dial out or keeping the connection alive. This can be configured with `filter` directives in [.filename]#/etc/ppp/ppp.conf#. For example: [.programlisting] .... set filter dial 0 deny udp src eq 123 # Prevent NTP traffic from initiating dial out set filter dial 1 permit 0 0 set filter alive 0 deny udp src eq 123 # Prevent incoming NTP traffic from keeping the connection open set filter alive 1 deny udp dst eq 123 # Prevent outgoing NTP traffic from keeping the connection open set filter alive 2 permit 0/0 0/0 .... For more details, refer to the `PACKET FILTERING` section in man:ppp[8] and the examples in [.filename]#/usr/share/examples/ppp/#. [NOTE] ==== Some Internet access providers block low-numbered ports, preventing NTP from functioning since replies never reach the machine. ==== [[network-iscsi]] == iSCSI Initiator and Target Configuration iSCSI is a way to share storage over a network. Unlike NFS, which works at the file system level, iSCSI works at the block device level. In iSCSI terminology, the system that shares the storage is known as the _target_. The storage can be a physical disk, or an area representing multiple disks or a portion of a physical disk. For example, if the disk(s) are formatted with ZFS, a zvol can be created to use as the iSCSI storage. The clients which access the iSCSI storage are called _initiators_. To initiators, the storage available through iSCSI appears as a raw, unformatted disk known as a LUN. Device nodes for the disk appear in [.filename]#/dev/# and the device must be separately formatted and mounted. FreeBSD provides a native, kernel-based iSCSI target and initiator. This section describes how to configure a FreeBSD system as a target or an initiator. [[network-iscsi-target]] === Configuring an iSCSI Target To configure an iSCSI target, create the [.filename]#/etc/ctl.conf# configuration file, add a line to [.filename]#/etc/rc.conf# to make sure the man:ctld[8] daemon is automatically started at boot, and then start the daemon. The following is an example of a simple [.filename]#/etc/ctl.conf# configuration file. Refer to man:ctl.conf[5] for a more complete description of this file's available options. [.programlisting] .... portal-group pg0 { discovery-auth-group no-authentication listen 0.0.0.0 listen [::] } target iqn.2012-06.com.example:target0 { auth-group no-authentication portal-group pg0 lun 0 { path /data/target0-0 size 4G } } .... The first entry defines the `pg0` portal group. Portal groups define which network addresses the man:ctld[8] daemon will listen on. The `discovery-auth-group no-authentication` entry indicates that any initiator is allowed to perform iSCSI target discovery without authentication. Lines three and four configure man:ctld[8] to listen on all IPv4 (`listen 0.0.0.0`) and IPv6 (`listen [::]`) addresses on the default port of 3260. It is not necessary to define a portal group as there is a built-in portal group called `default`. In this case, the difference between `default` and `pg0` is that with `default`, target discovery is always denied, while with `pg0`, it is always allowed. The second entry defines a single target. Target has two possible meanings: a machine serving iSCSI or a named group of LUNs. This example uses the latter meaning, where `iqn.2012-06.com.example:target0` is the target name. This target name is suitable for testing purposes. For actual use, change `com.example` to the real domain name, reversed. The `2012-06` represents the year and month of acquiring control of that domain name, and `target0` can be any value. Any number of targets can be defined in this configuration file. The `auth-group no-authentication` line allows all initiators to connect to the specified target and `portal-group pg0` makes the target reachable through the `pg0` portal group. The next section defines the LUN. To the initiator, each LUN will be visible as a separate disk device. Multiple LUNs can be defined for each target. Each LUN is identified by a number, where LUN 0 is mandatory. The `path /data/target0-0` line defines the full path to a file or zvol backing the LUN. That path must exist before starting man:ctld[8]. The second line is optional and specifies the size of the LUN. Next, to make sure the man:ctld[8] daemon is started at boot, add this line to [.filename]#/etc/rc.conf#: [.programlisting] .... ctld_enable="YES" .... To start man:ctld[8] now, run this command: [source,shell] .... # service ctld start .... As the man:ctld[8] daemon is started, it reads [.filename]#/etc/ctl.conf#. If this file is edited after the daemon starts, use this command so that the changes take effect immediately: [source,shell] .... # service ctld reload .... ==== Authentication The previous example is inherently insecure as it uses no authentication, granting anyone full access to all targets. To require a username and password to access targets, modify the configuration as follows: [.programlisting] .... auth-group ag0 { chap username1 secretsecret chap username2 anothersecret } portal-group pg0 { discovery-auth-group no-authentication listen 0.0.0.0 listen [::] } target iqn.2012-06.com.example:target0 { auth-group ag0 portal-group pg0 lun 0 { path /data/target0-0 size 4G } } .... The `auth-group` section defines username and password pairs. An initiator trying to connect to `iqn.2012-06.com.example:target0` must first specify a defined username and secret. However, target discovery is still permitted without authentication. To require target discovery authentication, set `discovery-auth-group` to a defined `auth-group` name instead of `no-authentication`. It is common to define a single exported target for every initiator. As a shorthand for the syntax above, the username and password can be specified directly in the target entry: [.programlisting] .... target iqn.2012-06.com.example:target0 { portal-group pg0 chap username1 secretsecret lun 0 { path /data/target0-0 size 4G } } .... [[network-iscsi-initiator]] === Configuring an iSCSI Initiator [NOTE] ==== The iSCSI initiator described in this section is supported starting with FreeBSD 10.0-RELEASE. To use the iSCSI initiator available in older versions, refer to man:iscontrol[8]. ==== The iSCSI initiator requires that the man:iscsid[8] daemon is running. This daemon does not use a configuration file. To start it automatically at boot, add this line to [.filename]#/etc/rc.conf#: [.programlisting] .... iscsid_enable="YES" .... To start man:iscsid[8] now, run this command: [source,shell] .... # service iscsid start .... Connecting to a target can be done with or without an [.filename]#/etc/iscsi.conf# configuration file. This section demonstrates both types of connections. ==== Connecting to a Target Without a Configuration File To connect an initiator to a single target, specify the IP address of the portal and the name of the target: [source,shell] .... # iscsictl -A -p 10.10.10.10 -t iqn.2012-06.com.example:target0 .... To verify if the connection succeeded, run `iscsictl` without any arguments. The output should look similar to this: [.programlisting] .... Target name Target portal State iqn.2012-06.com.example:target0 10.10.10.10 Connected: da0 .... In this example, the iSCSI session was successfully established, with [.filename]#/dev/da0# representing the attached LUN. If the `iqn.2012-06.com.example:target0` target exports more than one LUN, multiple device nodes will be shown in that section of the output: [source,shell] .... Connected: da0 da1 da2. .... Any errors will be reported in the output, as well as the system logs. For example, this message usually means that the man:iscsid[8] daemon is not running: [.programlisting] .... Target name Target portal State iqn.2012-06.com.example:target0 10.10.10.10 Waiting for iscsid(8) .... The following message suggests a networking problem, such as a wrong IP address or port: [.programlisting] .... Target name Target portal State iqn.2012-06.com.example:target0 10.10.10.11 Connection refused .... This message means that the specified target name is wrong: [.programlisting] .... Target name Target portal State iqn.2012-06.com.example:target0 10.10.10.10 Not found .... This message means that the target requires authentication: [.programlisting] .... Target name Target portal State iqn.2012-06.com.example:target0 10.10.10.10 Authentication failed .... To specify a CHAP username and secret, use this syntax: [source,shell] .... # iscsictl -A -p 10.10.10.10 -t iqn.2012-06.com.example:target0 -u user -s secretsecret .... ==== Connecting to a Target with a Configuration File To connect using a configuration file, create [.filename]#/etc/iscsi.conf# with contents like this: [.programlisting] .... t0 { TargetAddress = 10.10.10.10 TargetName = iqn.2012-06.com.example:target0 AuthMethod = CHAP chapIName = user chapSecret = secretsecret } .... The `t0` specifies a nickname for the configuration file section. It will be used by the initiator to specify which configuration to use. The other lines specify the parameters to use during connection. The `TargetAddress` and `TargetName` are mandatory, whereas the other options are optional. In this example, the CHAP username and secret are shown. To connect to the defined target, specify the nickname: [source,shell] .... # iscsictl -An t0 .... Alternately, to connect to all targets defined in the configuration file, use: [source,shell] .... # iscsictl -Aa .... To make the initiator automatically connect to all targets in [.filename]#/etc/iscsi.conf#, add the following to [.filename]#/etc/rc.conf#: [.programlisting] .... iscsictl_enable="YES" iscsictl_flags="-Aa" .... diff --git a/documentation/content/en/books/handbook/security/_index.adoc b/documentation/content/en/books/handbook/security/_index.adoc index 1e83b86411..d7affaa5df 100644 --- a/documentation/content/en/books/handbook/security/_index.adoc +++ b/documentation/content/en/books/handbook/security/_index.adoc @@ -1,2603 +1,2603 @@ --- title: Chapter 14. Security part: Part III. System Administration prev: books/handbook/boot next: books/handbook/jails description: Hundreds of standard practices have been authored about how to secure systems and networks, and as a user of FreeBSD, understanding how to protect against attacks and intruders is a must tags: ["security", "one-time passwords", "TCP Wrapper", "Kerberos", "OpenSSL", "IPsec", "OpenSSH", "ACL", "advisories", "sudo", "doas", "monitoring"] showBookMenu: true weight: 18 path: "/books/handbook/" --- [[security]] = Security :doctype: book :toc: macro :toclevels: 1 :icons: font :sectnums: :sectnumlevels: 6 :sectnumoffset: 14 :partnums: :source-highlighter: rouge :experimental: :images-path: books/handbook/security/ ifdef::env-beastie[] ifdef::backend-html5[] :imagesdir: ../../../../images/{images-path} endif::[] ifndef::book[] include::shared/authors.adoc[] include::shared/mirrors.adoc[] include::shared/releases.adoc[] include::shared/attributes/attributes-{{% lang %}}.adoc[] include::shared/{{% lang %}}/teams.adoc[] include::shared/{{% lang %}}/mailing-lists.adoc[] include::shared/{{% lang %}}/urls.adoc[] toc::[] endif::[] ifdef::backend-pdf,backend-epub3[] include::../../../../../shared/asciidoctor.adoc[] endif::[] endif::[] ifndef::env-beastie[] toc::[] include::../../../../../shared/asciidoctor.adoc[] endif::[] [[security-synopsis]] == Synopsis Security, whether physical or virtual, is a topic so broad that an entire industry has evolved around it. Hundreds of standard practices have been authored about how to secure systems and networks, and as a user of FreeBSD, understanding how to protect against attacks and intruders is a must. In this chapter, several fundamentals and techniques will be discussed. The FreeBSD system comes with multiple layers of security, and many more third party utilities may be added to enhance security. After reading this chapter, you will know: * Basic FreeBSD system security concepts. * The various crypt mechanisms available in FreeBSD. * How to set up one-time password authentication. * How to configure TCP Wrapper for use with man:inetd[8]. * How to set up Kerberos on FreeBSD. * How to configure IPsec and create a VPN. * How to configure and use OpenSSH on FreeBSD. * How to use file system ACLs. * How to use pkg to audit third party software packages installed from the Ports Collection. * How to utilize FreeBSD security advisories. * What Process Accounting is and how to enable it on FreeBSD. * How to control user resources using login classes or the resource limits database. Before reading this chapter, you should: * Understand basic FreeBSD and Internet concepts. Additional security topics are covered elsewhere in this Handbook. For example, Mandatory Access Control is discussed in crossref:mac[mac,Mandatory Access Control] and Internet firewalls are discussed in crossref:firewalls[firewalls,Firewalls]. [[security-intro]] == Introduction Security is everyone's responsibility. A weak entry point in any system could allow intruders to gain access to critical information and cause havoc on an entire network. One of the core principles of information security is the CIA triad, which stands for the Confidentiality, Integrity, and Availability of information systems. The CIA triad is a bedrock concept of computer security as customers and users expect their data to be protected. For example, a customer expects that their credit card information is securely stored (confidentiality), that their orders are not changed behind the scenes (integrity), and that they have access to their order information at all times (availability). To provide CIA, security professionals apply a defense in depth strategy. The idea of defense in depth is to add several layers of security to prevent one single layer failing and the entire security system collapsing. For example, a system administrator cannot simply turn on a firewall and consider the network or system secure. One must also audit accounts, check the integrity of binaries, and ensure malicious tools are not installed. To implement an effective security strategy, one must understand threats and how to defend against them. What is a threat as it pertains to computer security? Threats are not limited to remote attackers who attempt to access a system without permission from a remote location. Threats also include employees, malicious software, unauthorized network devices, natural disasters, security vulnerabilities, and even competing corporations. Systems and networks can be accessed without permission, sometimes by accident, or by remote attackers, and in some cases, via corporate espionage or former employees. As a user, it is important to prepare for and admit when a mistake has led to a security breach and report possible issues to the security team. As an administrator, it is important to know of the threats and be prepared to mitigate them. When applying security to systems, it is recommended to start by securing the basic accounts and system configuration, and then to secure the network layer so that it adheres to the system policy and the organization's security procedures. Many organizations already have a security policy that covers the configuration of technology devices. The policy should include the security configuration of workstations, desktops, mobile devices, phones, production servers, and development servers. In many cases, standard operating procedures (SOPs) already exist. When in doubt, ask the security team. The rest of this introduction describes how some of these basic security configurations are performed on a FreeBSD system. The rest of this chapter describes some specific tools which can be used when implementing a security policy on a FreeBSD system. [[security-accounts]] === Preventing Logins In securing a system, a good starting point is an audit of accounts. Ensure that `root` has a strong password and that this password is not shared. Disable any accounts that do not need login access. To deny login access to accounts, two methods exist. The first is to lock the account. This example locks the `toor` account: [source,shell] .... # pw lock toor .... The second method is to prevent login access by changing the shell to [.filename]#/usr/sbin/nologin#. Only the superuser can change the shell for other users: [source,shell] .... # chsh -s /usr/sbin/nologin toor .... The [.filename]#/usr/sbin/nologin# shell prevents the system from assigning a shell to the user when they attempt to login. [[security-accountmgmt]] === Permitted Account Escalation In some cases, system administration needs to be shared with other users. FreeBSD has two methods to handle this. The first one, which is not recommended, is a shared root password used by members of the `wheel` group. With this method, a user types `su` and enters the password for `wheel` whenever superuser access is needed. The user should then type `exit` to leave privileged access after finishing the commands that required administrative access. To add a user to this group, edit [.filename]#/etc/group# and add the user to the end of the `wheel` entry. The user must be separated by a comma character with no space. The second, and recommended, method to permit privilege escalation is to install the package:security/sudo[] package or port. This software provides additional auditing, more fine-grained user control, and can be configured to lock users into running only the specified privileged commands. After installation, use `visudo` to edit [.filename]#/usr/local/etc/sudoers#. This example creates a new `webadmin` group, adds the `trhodes` account to that group, and configures that group access to restart package:apache24[]: [source,shell] .... # pw groupadd webadmin -M trhodes -g 6000 # visudo %webadmin ALL=(ALL) /usr/sbin/service apache24 * .... [[security-passwords]] === Password Hashes Passwords are a necessary evil of technology. When they must be used, they should be complex and a powerful hash mechanism should be used to encrypt the version that is stored in the password database. FreeBSD supports the DES, MD5, SHA256, SHA512, and Blowfish hash algorithms in its `crypt()` library. The default of SHA512 should not be changed to a less secure hashing algorithm, but can be changed to the more secure Blowfish algorithm. [NOTE] ==== Blowfish is not part of AES and is not considered compliant with any Federal Information Processing Standards (FIPS). Its use may not be permitted in some environments. ==== To determine which hash algorithm is used to encrypt a user's password, the superuser can view the hash for the user in the FreeBSD password database. Each hash starts with a symbol which indicates the type of hash mechanism used to encrypt the password. If DES is used, there is no beginning symbol. For MD5, the symbol is `$`. For SHA256 and SHA512, the symbol is `$6$`. For Blowfish, the symbol is `$2a$`. In this example, the password for `dru` is hashed using the default SHA512 algorithm as the hash starts with `$6$`. Note that the encrypted hash, not the password itself, is stored in the password database: [source,shell] .... # grep dru /etc/master.passwd dru:$6$pzIjSvCAn.PBYQBA$PXpSeWPx3g5kscj3IMiM7tUEUSPmGexxta.8Lt9TGSi2lNQqYGKszsBPuGME0:1001:1001::0:0:dru:/usr/home/dru:/bin/csh .... The hash mechanism is set in the user's login class. For this example, the user is in the `default` login class and the hash algorithm is set with this line in [.filename]#/etc/login.conf#: [.programlisting] .... :passwd_format=sha512:\ .... To change the algorithm to Blowfish, modify that line to look like this: [.programlisting] .... :passwd_format=blf:\ .... Then run `cap_mkdb /etc/login.conf` as described in <>. Note that this change will not affect any existing password hashes. This means that all passwords should be re-hashed by asking users to run `passwd` in order to change their password. For remote logins, two-factor authentication should be used. An example of two-factor authentication is "something you have", such as a key, and "something you know", such as the passphrase for that key. Since OpenSSH is part of the FreeBSD base system, all network logins should be over an encrypted connection and use key-based authentication instead of passwords. For more information, refer to <>. Kerberos users may need to make additional changes to implement OpenSSH in their network. These changes are described in <>. [[security-pwpolicy]] === Password Policy Enforcement Enforcing a strong password policy for local accounts is a fundamental aspect of system security. In FreeBSD, password length, password strength, and password complexity can be implemented using built-in Pluggable Authentication Modules (PAM). This section demonstrates how to configure the minimum and maximum password length and the enforcement of mixed characters using the [.filename]#pam_passwdqc.so# module. This module is enforced when a user changes their password. To configure this module, become the superuser and uncomment the line containing `pam_passwdqc.so` in [.filename]#/etc/pam.d/passwd#. Then, edit that line to match the password policy: [.programlisting] .... password requisite pam_passwdqc.so min=disabled,disabled,disabled,12,10 similar=deny retry=3 enforce=users .... This example sets several requirements for new passwords. The `min` setting controls the minimum password length. It has five values because this module defines five different types of passwords based on their complexity. Complexity is defined by the type of characters that must exist in a password, such as letters, numbers, symbols, and case. The types of passwords are described in man:pam_passwdqc[8]. In this example, the first three types of passwords are disabled, meaning that passwords that meet those complexity requirements will not be accepted, regardless of their length. The `12` sets a minimum password policy of at least twelve characters, if the password also contains characters with three types of complexity. The `10` sets the password policy to also allow passwords of at least ten characters, if the password contains characters with four types of complexity. The `similar` setting denies passwords that are similar to the user's previous password. The `retry` setting provides a user with three opportunities to enter a new password. Once this file is saved, a user changing their password will see a message similar to the following: [source,shell] .... % passwd Changing local password for trhodes Old Password: You can now choose the new password. A valid password should be a mix of upper and lower case letters, digits and other characters. You can use a 12 character long password with characters from at least 3 of these 4 classes, or a 10 character long password containing characters from all the classes. Characters that form a common pattern are discarded by the check. Alternatively, if no one else can see your terminal now, you can pick this as your password: "trait-useful&knob". Enter new password: .... If a password that does not match the policy is entered, it will be rejected with a warning and the user will have an opportunity to try again, up to the configured number of retries. Most password policies require passwords to expire after so many days. To set a password age time in FreeBSD, set `passwordtime` for the user's login class in [.filename]#/etc/login.conf#. The `default` login class contains an example: [.programlisting] .... # :passwordtime=90d:\ .... So, to set an expiry of 90 days for this login class, remove the comment symbol (`#`), save the edit, and run `cap_mkdb /etc/login.conf`. To set the expiration on individual users, pass an expiration date or the number of days to expiry and a username to `pw`: [source,shell] .... # pw usermod -p 30-apr-2015 -n trhodes .... As seen here, an expiration date is set in the form of day, month, and year. For more information, see man:pw[8]. [[security-rkhunter]] === Detecting Rootkits A _rootkit_ is any unauthorized software that attempts to gain `root` access to a system. Once installed, this malicious software will normally open up another avenue of entry for an attacker. Realistically, once a system has been compromised by a rootkit and an investigation has been performed, the system should be reinstalled from scratch. There is tremendous risk that even the most prudent security or systems engineer will miss something an attacker left behind. A rootkit does do one thing useful for administrators: once detected, it is a sign that a compromise happened at some point. But, these types of applications tend to be very well hidden. This section demonstrates a tool that can be used to detect rootkits, package:security/rkhunter[]. After installation of this package or port, the system may be checked using the following command. It will produce a lot of information and will require some manual pressing of kbd:[ENTER]: [source,shell] .... # rkhunter -c .... After the process completes, a status message will be printed to the screen. This message will include the amount of files checked, suspect files, possible rootkits, and more. During the check, some generic security warnings may be produced about hidden files, the OpenSSH protocol selection, and known vulnerable versions of installed software. These can be handled now or after a more detailed analysis has been performed. Every administrator should know what is running on the systems they are responsible for. Third-party tools like rkhunter and package:sysutils/lsof[], and native commands such as `netstat` and `ps`, can show a great deal of information on the system. Take notes on what is normal, ask questions when something seems out of place, and be paranoid. While preventing a compromise is ideal, detecting a compromise is a must. [[security-ids]] === Binary Verification Verification of system files and binaries is important because it provides the system administration and security teams information about system changes. A software application that monitors the system for changes is called an Intrusion Detection System (IDS). FreeBSD provides native support for a basic IDS system. While the nightly security emails will notify an administrator of changes, the information is stored locally and there is a chance that a malicious user could modify this information in order to hide their changes to the system. As such, it is recommended to create a separate set of binary signatures and store them on a read-only, root-owned directory or, preferably, on a removable USB disk or remote rsync server. The built-in `mtree` utility can be used to generate a specification of the contents of a directory. A seed, or a numeric constant, is used to generate the specification and is required to check that the specification has not changed. This makes it possible to determine if a file or binary has been modified. Since the seed value is unknown by an attacker, faking or checking the checksum values of files will be difficult to impossible. The following example generates a set of SHA256 hashes, one for each system binary in [.filename]#/bin#, and saves those values to a hidden file in ``root``'s home directory, [.filename]#/root/.bin_chksum_mtree#: [source,shell] .... # mtree -s 3483151339707503 -c -K cksum,sha256digest -p /bin > /root/.bin_chksum_mtree # mtree: /bin checksum: 3427012225 .... The _3483151339707503_ represents the seed. This value should be remembered, but not shared. Viewing [.filename]#/root/.bin_cksum_mtree# should yield output similar to the following: [.programlisting] .... # user: root # machine: dreadnaught # tree: /bin # date: Mon Feb 3 10:19:53 2014 # . /set type=file uid=0 gid=0 mode=0555 nlink=1 flags=none . type=dir mode=0755 nlink=2 size=1024 \ time=1380277977.000000000 \133 nlink=2 size=11704 time=1380277977.000000000 \ cksum=484492447 \ sha256digest=6207490fbdb5ed1904441fbfa941279055c3e24d3a4049aeb45094596400662a cat size=12096 time=1380277975.000000000 cksum=3909216944 \ sha256digest=65ea347b9418760b247ab10244f47a7ca2a569c9836d77f074e7a306900c1e69 chflags size=8168 time=1380277975.000000000 cksum=3949425175 \ sha256digest=c99eb6fc1c92cac335c08be004a0a5b4c24a0c0ef3712017b12c89a978b2dac3 chio size=18520 time=1380277975.000000000 cksum=2208263309 \ sha256digest=ddf7c8cb92a58750a675328345560d8cc7fe14fb3ccd3690c34954cbe69fc964 chmod size=8640 time=1380277975.000000000 cksum=2214429708 \ sha256digest=a435972263bf814ad8df082c0752aa2a7bdd8b74ff01431ccbd52ed1e490bbe7 .... The machine's hostname, the date and time the specification was created, and the name of the user who created the specification are included in this report. There is a checksum, size, time, and SHA256 digest for each binary in the directory. To verify that the binary signatures have not changed, compare the current contents of the directory to the previously generated specification, and save the results to a file. This command requires the seed that was used to generate the original specification: [source,shell] .... # mtree -s 3483151339707503 -p /bin < /root/.bin_chksum_mtree >> /root/.bin_chksum_output # mtree: /bin checksum: 3427012225 .... This should produce the same checksum for [.filename]#/bin# that was produced when the specification was created. If no changes have occurred to the binaries in this directory, the [.filename]#/root/.bin_chksum_output# output file will be empty. To simulate a change, change the date on [.filename]#/bin/cat# using `touch` and run the verification command again: [source,shell] .... # touch /bin/cat # mtree -s 3483151339707503 -p /bin < /root/.bin_chksum_mtree >> /root/.bin_chksum_output # more /root/.bin_chksum_output cat changed modification time expected Fri Sep 27 06:32:55 2013 found Mon Feb 3 10:28:43 2014 .... It is recommended to create specifications for the directories which contain binaries and configuration files, as well as any directories containing sensitive data. Typically, specifications are created for [.filename]#/bin#, [.filename]#/sbin#, [.filename]#/usr/bin#, [.filename]#/usr/sbin#, [.filename]#/usr/local/bin#, [.filename]#/etc#, and [.filename]#/usr/local/etc#. More advanced IDS systems exist, such as package:security/aide[]. In most cases, `mtree` provides the functionality administrators need. It is important to keep the seed value and the checksum output hidden from malicious users. More information about `mtree` can be found in man:mtree[8]. [[security-tuning]] === System Tuning for Security In FreeBSD, many system features can be tuned using `sysctl`. A few of the security features which can be tuned to prevent Denial of Service (DoS) attacks will be covered in this section. More information about using `sysctl`, including how to temporarily change values and how to make the changes permanent after testing, can be found in crossref:config[configtuning-sysctl,“Tuning with sysctl(8)”]. [NOTE] ==== Any time a setting is changed with `sysctl`, the chance to cause undesired harm is increased, affecting the availability of the system. All changes should be monitored and, if possible, tried on a testing system before being used on a production system. ==== By default, the FreeBSD kernel boots with a security level of `-1`. This is called "insecure mode" because immutable file flags may be turned off and all devices may be read from or written to. The security level will remain at `-1` unless it is altered through `sysctl` or by a setting in the startup scripts. The security level may be increased during system startup by setting `kern_securelevel_enable` to `YES` in [.filename]#/etc/rc.conf#, and the value of `kern_securelevel` to the desired security level. See man:security[7] and man:init[8] for more information on these settings and the available security levels. [WARNING] ==== Increasing the `securelevel` can break Xorg and cause other issues. Be prepared to do some debugging. ==== The `net.inet.tcp.blackhole` and `net.inet.udp.blackhole` settings can be used to drop incoming SYN packets on closed ports without sending a return RST response. The default behavior is to return an RST to show a port is closed. Changing the default provides some level of protection against ports scans, which are used to determine which applications are running on a system. Set `net.inet.tcp.blackhole` to `2` and `net.inet.udp.blackhole` to `1`. Refer to man:blackhole[4] for more information about these settings. The `net.inet.icmp.drop_redirect` and `net.inet.ip.redirect` settings help prevent against _redirect attacks_. A redirect attack is a type of DoS which sends mass numbers of ICMP type 5 packets. Since these packets are not required, set `net.inet.icmp.drop_redirect` to `1` and set `net.inet.ip.redirect` to `0`. Source routing is a method for detecting and accessing non-routable addresses on the internal network. This should be disabled as non-routable addresses are normally not routable on purpose. To disable this feature, set `net.inet.ip.sourceroute` and `net.inet.ip.accept_sourceroute` to `0`. When a machine on the network needs to send messages to all hosts on a subnet, an ICMP echo request message is sent to the broadcast address. However, there is no reason for an external host to perform such an action. To reject all external broadcast requests, set `net.inet.icmp.bmcastecho` to `0`. Some additional settings are documented in man:security[7]. [[one-time-passwords]] == One-time Passwords By default, FreeBSD includes support for One-time Passwords In Everything (OPIE). OPIE is designed to prevent replay attacks, in which an attacker discovers a user's password and uses it to access a system. Since a password is only used once in OPIE, a discovered password is of little use to an attacker. OPIE uses a secure hash and a challenge/response system to manage passwords. The FreeBSD implementation uses the MD5 hash by default. OPIE uses three different types of passwords. The first is the usual UNIX(R) or Kerberos password. The second is the one-time password which is generated by `opiekey`. The third type of password is the "secret password" which is used to generate one-time passwords. The secret password has nothing to do with, and should be different from, the UNIX(R) password. There are two other pieces of data that are important to OPIE. One is the "seed" or "key", consisting of two letters and five digits. The other is the "iteration count", a number between 1 and 100. OPIE creates the one-time password by concatenating the seed and the secret password, applying the MD5 hash as many times as specified by the iteration count, and turning the result into six short English words which represent the one-time password. The authentication system keeps track of the last one-time password used, and the user is authenticated if the hash of the user-provided password is equal to the previous password. Since a one-way hash is used, it is impossible to generate future one-time passwords if a successfully used password is captured. The iteration count is decremented after each successful login to keep the user and the login program in sync. When the iteration count gets down to `1`, OPIE must be reinitialized. There are a few programs involved in this process. A one-time password, or a consecutive list of one-time passwords, is generated by passing an iteration count, a seed, and a secret password to man:opiekey[1]. In addition to initializing OPIE, man:opiepasswd[1] is used to change passwords, iteration counts, or seeds. The relevant credential files in [.filename]#/etc/opiekeys# are examined by man:opieinfo[1] which prints out the invoking user's current iteration count and seed. This section describes four different sorts of operations. The first is how to set up one-time-passwords for the first time over a secure connection. The second is how to use `opiepasswd` over an insecure connection. The third is how to log in over an insecure connection. The fourth is how to generate a number of keys which can be written down or printed out to use at insecure locations. === Initializing OPIE To initialize OPIE for the first time, run this command from a secure location: [source,shell] .... % opiepasswd -c Adding unfurl: Only use this method from the console; NEVER from remote. If you are using telnet, xterm, or a dial-in, type ^C now or exit with no password. Then run opiepasswd without the -c parameter. Using MD5 to compute responses. Enter new secret pass phrase: Again new secret pass phrase: ID unfurl OTP key is 499 to4268 MOS MALL GOAT ARM AVID COED .... The `-c` sets console mode which assumes that the command is being run from a secure location, such as a computer under the user's control or an SSH session to a computer under the user's control. When prompted, enter the secret password which will be used to generate the one-time login keys. This password should be difficult to guess and should be different than the password which is associated with the user's login account. It must be between 10 and 127 characters long. Remember this password. The `ID` line lists the login name (`unfurl`), default iteration count (`499`), and default seed (`to4268`). When logging in, the system will remember these parameters and display them, meaning that they do not have to be memorized. The last line lists the generated one-time password which corresponds to those parameters and the secret password. At the next login, use this one-time password. === Insecure Connection Initialization To initialize or change the secret password on an insecure system, a secure connection is needed to some place where `opiekey` can be run. This might be a shell prompt on a trusted machine. An iteration count is needed, where 100 is probably a good value, and the seed can either be specified or the randomly-generated one used. On the insecure connection, the machine being initialized, use man:opiepasswd[1]: [source,shell] .... % opiepasswd Updating unfurl: You need the response from an OTP generator. Old secret pass phrase: otp-md5 498 to4268 ext Response: GAME GAG WELT OUT DOWN CHAT New secret pass phrase: otp-md5 499 to4269 Response: LINE PAP MILK NELL BUOY TROY ID mark OTP key is 499 gr4269 LINE PAP MILK NELL BUOY TROY .... To accept the default seed, press kbd:[Return]. Before entering an access password, move over to the secure connection and give it the same parameters: [source,shell] .... % opiekey 498 to4268 Using the MD5 algorithm to compute response. Reminder: Do not use opiekey from telnet or dial-in sessions. Enter secret pass phrase: GAME GAG WELT OUT DOWN CHAT .... Switch back over to the insecure connection, and copy the generated one-time password over to the relevant program. === Generating a Single One-time Password After initializing OPIE and logging in, a prompt like this will be displayed: [source,shell] .... % telnet example.com Trying 10.0.0.1... Connected to example.com Escape character is '^]'. FreeBSD/i386 (example.com) (ttypa) login: otp-md5 498 gr4269 ext Password: .... The OPIE prompts provides a useful feature. If kbd:[Return] is pressed at the password prompt, the prompt will turn echo on and display what is typed. This can be useful when attempting to type in a password by hand from a printout. At this point, generate the one-time password to answer this login prompt. This must be done on a trusted system where it is safe to run man:opiekey[1]. There are versions of this command for Windows(R), Mac OS(R) and FreeBSD. This command needs the iteration count and the seed as command line options. Use cut-and-paste from the login prompt on the machine being logged in to. On the trusted system: [source,shell] .... % opiekey 498 to4268 Using the MD5 algorithm to compute response. Reminder: Do not use opiekey from telnet or dial-in sessions. Enter secret pass phrase: GAME GAG WELT OUT DOWN CHAT .... Once the one-time password is generated, continue to log in. === Generating Multiple One-time Passwords Sometimes there is no access to a trusted machine or secure connection. In this case, it is possible to use man:opiekey[1] to generate a number of one-time passwords beforehand. For example: [source,shell] .... % opiekey -n 5 30 zz99999 Using the MD5 algorithm to compute response. Reminder: Do not use opiekey from telnet or dial-in sessions. Enter secret pass phrase: 26: JOAN BORE FOSS DES NAY QUIT 27: LATE BIAS SLAY FOLK MUCH TRIG 28: SALT TIN ANTI LOON NEAL USE 29: RIO ODIN GO BYE FURY TIC 30: GREW JIVE SAN GIRD BOIL PHI .... The `-n 5` requests five keys in sequence, and `30` specifies what the last iteration number should be. Note that these are printed out in _reverse_ order of use. The really paranoid might want to write the results down by hand; otherwise, print the list. Each line shows both the iteration count and the one-time password. Scratch off the passwords as they are used. === Restricting Use of UNIX(R) Passwords OPIE can restrict the use of UNIX(R) passwords based on the IP address of a login session. The relevant file is [.filename]#/etc/opieaccess#, which is present by default. Refer to man:opieaccess[5] for more information on this file and which security considerations to be aware of when using it. Here is a sample [.filename]#opieaccess#: [.programlisting] .... permit 192.168.0.0 255.255.0.0 .... This line allows users whose IP source address (which is vulnerable to spoofing) matches the specified value and mask, to use UNIX(R) passwords at any time. If no rules in [.filename]#opieaccess# are matched, the default is to deny non-OPIE logins. [[tcpwrappers]] == TCP Wrapper TCP Wrapper is a host-based access control system which extends the abilities of crossref:network-servers[network-inetd,“The inetd Super-Server”]. It can be configured to provide logging support, return messages, and connection restrictions for the server daemons under the control of inetd. Refer to man:tcpd[8] for more information about TCP Wrapper and its features. TCP Wrapper should not be considered a replacement for a properly configured firewall. Instead, TCP Wrapper should be used in conjunction with a firewall and other security enhancements in order to provide another layer of protection in the implementation of a security policy. === Initial Configuration To enable TCP Wrapper in FreeBSD, add the following lines to [.filename]#/etc/rc.conf#: [.programlisting] .... inetd_enable="YES" inetd_flags="-Ww" .... Then, properly configure [.filename]#/etc/hosts.allow#. [NOTE] ==== Unlike other implementations of TCP Wrapper, the use of [.filename]#hosts.deny# is deprecated in FreeBSD. All configuration options should be placed in [.filename]#/etc/hosts.allow#. ==== In the simplest configuration, daemon connection policies are set to either permit or block, depending on the options in [.filename]#/etc/hosts.allow#. The default configuration in FreeBSD is to allow all connections to the daemons started with inetd. Basic configuration usually takes the form of `daemon : address : action`, where `daemon` is the daemon which inetd started, `address` is a valid hostname, IP address, or an IPv6 address enclosed in brackets ([ ]), and `action` is either `allow` or `deny`. TCP Wrapper uses a first rule match semantic, meaning that the configuration file is scanned from the beginning for a matching rule. When a match is found, the rule is applied and the search process stops. For example, to allow POP3 connections via the package:mail/qpopper[] daemon, the following lines should be appended to [.filename]#hosts.allow#: [.programlisting] .... # This line is required for POP3 connections: qpopper : ALL : allow .... Whenever this file is edited, restart inetd: [source,shell] .... # service inetd restart .... === Advanced Configuration TCP Wrapper provides advanced options to allow more control over the way connections are handled. In some cases, it may be appropriate to return a comment to certain hosts or daemon connections. In other cases, a log entry should be recorded or an email sent to the administrator. Other situations may require the use of a service for local connections only. This is all possible through the use of configuration options known as wildcards, expansion characters, and external command execution. Suppose that a situation occurs where a connection should be denied yet a reason should be sent to the host who attempted to establish that connection. That action is possible with `twist`. When a connection attempt is made, `twist` executes a shell command or script. An example exists in [.filename]#hosts.allow#: [.programlisting] .... # The rest of the daemons are protected. ALL : ALL \ : severity auth.info \ : twist /bin/echo "You are not welcome to use %d from %h." .... In this example, the message "You are not allowed to use _daemon name_ from _hostname_." will be returned for any daemon not configured in [.filename]#hosts.allow#. This is useful for sending a reply back to the connection initiator right after the established connection is dropped. Any message returned _must_ be wrapped in quote (`"`) characters. [WARNING] ==== It may be possible to launch a denial of service attack on the server if an attacker floods these daemons with connection requests. ==== Another possibility is to use `spawn`. Like `twist`, `spawn` implicitly denies the connection and may be used to run external shell commands or scripts. Unlike `twist`, `spawn` will not send a reply back to the host who established the connection. For example, consider the following configuration: [.programlisting] .... # We do not allow connections from example.com: ALL : .example.com \ : spawn (/bin/echo %a from %h attempted to access %d >> \ /var/log/connections.log) \ : deny .... This will deny all connection attempts from `*.example.com` and log the hostname, IP address, and the daemon to which access was attempted to [.filename]#/var/log/connections.log#. This example uses the substitution characters `%a` and `%h`. Refer to man:hosts_access[5] for the complete list. To match every instance of a daemon, domain, or IP address, use `ALL`. Another wildcard is `PARANOID` which may be used to match any host which provides an IP address that may be forged because the IP address differs from its resolved hostname. In this example, all connection requests to Sendmail which have an IP address that varies from its hostname will be denied: [.programlisting] .... # Block possibly spoofed requests to sendmail: sendmail : PARANOID : deny .... [CAUTION] ==== Using the `PARANOID` wildcard will result in denied connections if the client or server has a broken DNS setup. ==== To learn more about wildcards and their associated functionality, refer to man:hosts_access[5]. [NOTE] ==== When adding new configuration lines, make sure that any unneeded entries for that daemon are commented out in [.filename]#hosts.allow#. ==== [[kerberos5]] == Kerberos Kerberos is a network authentication protocol which was originally created by the Massachusetts Institute of Technology (MIT) as a way to securely provide authentication across a potentially hostile network. The Kerberos protocol uses strong cryptography so that both a client and server can prove their identity without sending any unencrypted secrets over the network. Kerberos can be described as an identity-verifying proxy system and as a trusted third-party authentication system. After a user authenticates with Kerberos, their communications can be encrypted to assure privacy and data integrity. The only function of Kerberos is to provide the secure authentication of users and servers on the network. It does not provide authorization or auditing functions. It is recommended that Kerberos be used with other security methods which provide authorization and audit services. The current version of the protocol is version 5, described in RFC 4120. Several free implementations of this protocol are available, covering a wide range of operating systems. MIT continues to develop their Kerberos package. It is commonly used in the US as a cryptography product, and has historically been subject to US export regulations. In FreeBSD, MITKerberos is available as the package:security/krb5[] package or port. The Heimdal Kerberos implementation was explicitly developed outside of the US to avoid export regulations. The Heimdal Kerberos distribution is included in the base FreeBSD installation, and another distribution with more configurable options is available as package:security/heimdal[] in the Ports Collection. In Kerberos users and services are identified as "principals" which are contained within an administrative grouping, called a "realm". A typical user principal would be of the form `_user_@_REALM_` (realms are traditionally uppercase). This section provides a guide on how to set up Kerberos using the Heimdal distribution included in FreeBSD. For purposes of demonstrating a Kerberos installation, the name spaces will be as follows: * The DNS domain (zone) will be `example.org`. * The Kerberos realm will be `EXAMPLE.ORG`. [NOTE] ==== Use real domain names when setting up Kerberos, even if it will run internally. This avoids DNS problems and assures inter-operation with other Kerberos realms. ==== === Setting up a Heimdal KDC The Key Distribution Center (KDC) is the centralized authentication service that Kerberos provides, the "trusted third party" of the system. It is the computer that issues Kerberos tickets, which are used for clients to authenticate to servers. As the KDC is considered trusted by all other computers in the Kerberos realm, it has heightened security concerns. Direct access to the KDC should be limited. While running a KDC requires few computing resources, a dedicated machine acting only as a KDC is recommended for security reasons. To begin, install the package:security/heimdal[] package as follows: [source,shell] .... # pkg install heimdal .... Next, update [.filename]#/etc/rc.conf# using `sysrc` as follows: [source,shell] .... # sysrc kdc_enable=yes # sysrc kadmind_enable=yes .... Next, edit [.filename]#/etc/krb5.conf# as follows: [.programlisting] .... [libdefaults] default_realm = EXAMPLE.ORG [realms] EXAMPLE.ORG = { kdc = kerberos.example.org admin_server = kerberos.example.org } [domain_realm] .example.org = EXAMPLE.ORG .... In this example, the KDC will use the fully-qualified hostname `kerberos.example.org`. The hostname of the KDC must be resolvable in the DNS. Kerberos can also use the DNS to locate KDCs, instead of a `[realms]` section in [.filename]#/etc/krb5.conf#. For large organizations that have their own DNS servers, the above example could be trimmed to: [.programlisting] .... [libdefaults] default_realm = EXAMPLE.ORG [domain_realm] .example.org = EXAMPLE.ORG .... With the following lines being included in the `example.org` zone file: [.programlisting] .... _kerberos._udp IN SRV 01 00 88 kerberos.example.org. _kerberos._tcp IN SRV 01 00 88 kerberos.example.org. _kpasswd._udp IN SRV 01 00 464 kerberos.example.org. _kerberos-adm._tcp IN SRV 01 00 749 kerberos.example.org. _kerberos IN TXT EXAMPLE.ORG .... [NOTE] ==== In order for clients to be able to find the Kerberos services, they _must_ have either a fully configured [.filename]#/etc/krb5.conf# or a minimally configured [.filename]#/etc/krb5.conf# _and_ a properly configured DNS server. ==== Next, create the Kerberos database which contains the keys of all principals (users and hosts) encrypted with a master password. It is not required to remember this password as it will be stored in [.filename]#/var/heimdal/m-key#; it would be reasonable to use a 45-character random password for this purpose. To create the master key, run `kstash` and enter a password: [source,shell] .... # kstash Master key: xxxxxxxxxxxxxxxxxxxxxxx Verifying password - Master key: xxxxxxxxxxxxxxxxxxxxxxx .... Once the master key has been created, the database should be initialized. The Kerberos administrative tool man:kadmin[8] can be used on the KDC in a mode that operates directly on the database, without using the man:kadmind[8] network service, as `kadmin -l`. This resolves the chicken-and-egg problem of trying to connect to the database before it is created. At the `kadmin` prompt, use `init` to create the realm's initial database: [source,shell] .... # kadmin -l kadmin> init EXAMPLE.ORG Realm max ticket life [unlimited]: .... Lastly, while still in `kadmin`, create the first principal using `add`. Stick to the default options for the principal for now, as these can be changed later with `modify`. Type `?` at the prompt to see the available options. [source,shell] .... kadmin> add tillman Max ticket life [unlimited]: Max renewable life [unlimited]: Principal expiration time [never]: Password expiration time [never]: Attributes []: Password: xxxxxxxx Verifying password - Password: xxxxxxxx .... Next, start the KDC services by running: [source,shell] .... # service kdc start # service kadmind start .... While there will not be any kerberized daemons running at this point, it is possible to confirm that the KDC is functioning by obtaining a ticket for the principal that was just created: [source,shell] .... % kinit tillman tillman@EXAMPLE.ORG's Password: .... Confirm that a ticket was successfully obtained using `klist`: [source,shell] .... % klist Credentials cache: FILE:/tmp/krb5cc_1001 Principal: tillman@EXAMPLE.ORG Issued Expires Principal Aug 27 15:37:58 2013 Aug 28 01:37:58 2013 krbtgt/EXAMPLE.ORG@EXAMPLE.ORG .... The temporary ticket can be destroyed when the test is finished: [source,shell] .... % kdestroy .... === Configuring a Server to Use Kerberos The first step in configuring a server to use Kerberos authentication is to ensure that it has the correct configuration in [.filename]#/etc/krb5.conf#. The version from the KDC can be used as-is, or it can be regenerated on the new system. Next, create [.filename]#/etc/krb5.keytab# on the server. This is the main part of "Kerberizing" a service - it corresponds to generating a secret shared between the service and the KDC. The secret is a cryptographic key, stored in a "keytab". The keytab contains the server's host key, which allows it and the KDC to verify each others' identity. It must be transmitted to the server in a secure fashion, as the security of the server can be broken if the key is made public. Typically, the [.filename]#keytab# is generated on an administrator's trusted machine using `kadmin`, then securely transferred to the server, e.g., with man:scp[1]; it can also be created directly on the server if that is consistent with the desired security policy. It is very important that the keytab is transmitted to the server in a secure fashion: if the key is known by some other party, that party can impersonate any user to the server! Using `kadmin` on the server directly is convenient, because the entry for the host principal in the KDC database is also created using `kadmin`. Of course, `kadmin` is a kerberized service; a Kerberos ticket is needed to authenticate to the network service, but to ensure that the user running `kadmin` is actually present (and their session has not been hijacked), `kadmin` will prompt for the password to get a fresh ticket. The principal authenticating to the kadmin service must be permitted to use the `kadmin` interface, as specified in [.filename]#/var/heimdal/kadmind.acl#. See the section titled "Remote administration" in `info heimdal` for details on designing access control lists. Instead of enabling remote `kadmin` access, the administrator could securely connect to the KDC via the local console or man:ssh[1], and perform administration locally using `kadmin -l`. After installing [.filename]#/etc/krb5.conf#, use `add --random-key` in `kadmin`. This adds the server's host principal to the database, but does not extract a copy of the host principal key to a keytab. To generate the keytab, use `ext` to extract the server's host principal key to its own keytab: [source,shell] .... # kadmin kadmin> add --random-key host/myserver.example.org Max ticket life [unlimited]: Max renewable life [unlimited]: Principal expiration time [never]: Password expiration time [never]: Attributes []: kadmin> ext_keytab host/myserver.example.org kadmin> exit .... Note that `ext_keytab` stores the extracted key in [.filename]#/etc/krb5.keytab# by default. This is good when being run on the server being kerberized, but the `--keytab _path/to/file_` argument should be used when the keytab is being extracted elsewhere: [source,shell] .... # kadmin kadmin> ext_keytab --keytab=/tmp/example.keytab host/myserver.example.org kadmin> exit .... The keytab can then be securely copied to the server using man:scp[1] or a removable media. Be sure to specify a non-default keytab name to avoid inserting unneeded keys into the system's keytab. At this point, the server can read encrypted messages from the KDC using its shared key, stored in [.filename]#krb5.keytab#. It is now ready for the Kerberos-using services to be enabled. One of the most common such services is man:sshd[8], which supports Kerberos via the GSS-API. In [.filename]#/etc/ssh/sshd_config#, add the line: [.programlisting] .... GSSAPIAuthentication yes .... After making this change, man:sshd[8] must be restarted for the new configuration to take effect: `service sshd restart`. === Configuring a Client to Use Kerberos As it was for the server, the client requires configuration in [.filename]#/etc/krb5.conf#. Copy the file in place (securely) or re-enter it as needed. Test the client by using `kinit`, `klist`, and `kdestroy` from the client to obtain, show, and then delete a ticket for an existing principal. Kerberos applications should also be able to connect to Kerberos enabled servers. If that does not work but obtaining a ticket does, the problem is likely with the server and not with the client or the KDC. In the case of kerberized man:ssh[1], GSS-API is disabled by default, so test using `ssh -o GSSAPIAuthentication=yes _hostname_`. When testing a Kerberized application, try using a packet sniffer such as `tcpdump` to confirm that no sensitive information is sent in the clear. Various Kerberos client applications are available. With the advent of a bridge so that applications using SASL for authentication can use GSS-API mechanisms as well, large classes of client applications can use Kerberos for authentication, from Jabber clients to IMAP clients. Users within a realm typically have their Kerberos principal mapped to a local user account. Occasionally, one needs to grant access to a local user account to someone who does not have a matching Kerberos principal. For example, `tillman@EXAMPLE.ORG` may need access to the local user account `webdevelopers`. Other principals may also need access to that local account. The [.filename]#.k5login# and [.filename]#.k5users# files, placed in a user's home directory, can be used to solve this problem. For example, if the following [.filename]#.k5login# is placed in the home directory of `webdevelopers`, both principals listed will have access to that account without requiring a shared password: [.programlisting] .... tillman@example.org jdoe@example.org .... Refer to man:ksu[1] for more information about [.filename]#.k5users#. === MIT Differences The major difference between the MIT and Heimdal implementations is that `kadmin` has a different, but equivalent, set of commands and uses a different protocol. If the KDC is MIT, the Heimdal version of `kadmin` cannot be used to administer the KDC remotely, and vice versa. Client applications may also use slightly different command line options to accomplish the same tasks. Following the instructions at http://web.mit.edu/Kerberos/www/[http://web.mit.edu/Kerberos/www/] is recommended. Be careful of path issues: the MIT port installs into [.filename]#/usr/local/# by default, and the FreeBSD system applications run instead of the MIT versions if `PATH` lists the system directories first. When using MIT Kerberos as a KDC on FreeBSD, the following edits should also be made to [.filename]#rc.conf#: [.programlisting] .... kdc_program="/usr/local/sbin/kdc" kadmind_program="/usr/local/sbin/kadmind" kdc_flags="" kdc_enable="YES" kadmind_enable="YES" .... === Kerberos Tips, Tricks, and Troubleshooting When configuring and troubleshooting Kerberos, keep the following points in mind: * When using either Heimdal or MITKerberos from ports, ensure that the `PATH` lists the port's versions of the client applications before the system versions. * If all the computers in the realm do not have synchronized time settings, authentication may fail. crossref:network-servers[network-ntp,“Clock Synchronization with NTP”] describes how to synchronize clocks using NTP. * If the hostname is changed, the `host/` principal must be changed and the keytab updated. This also applies to special keytab entries like the `HTTP/` principal used for Apache's package:www/mod_auth_kerb[]. * All hosts in the realm must be both forward and reverse resolvable in DNS or, at a minimum, exist in [.filename]#/etc/hosts#. CNAMEs will work, but the A and PTR records must be correct and in place. The error message for unresolvable hosts is not intuitive: `Kerberos5 refuses authentication because Read req failed: Key table entry not found`. * Some operating systems that act as clients to the KDC do not set the permissions for `ksu` to be setuid `root`. This means that `ksu` does not work. This is a permissions problem, not a KDC error. * With MITKerberos, to allow a principal to have a ticket life longer than the default lifetime of ten hours, use `modify_principal` at the man:kadmin[8] prompt to change the `maxlife` of both the principal in question and the `krbtgt` principal. The principal can then use `kinit -l` to request a ticket with a longer lifetime. * When running a packet sniffer on the KDC to aid in troubleshooting while running `kinit` from a workstation, the Ticket Granting Ticket (TGT) is sent immediately, even before the password is typed. This is because the Kerberos server freely transmits a TGT to any unauthorized request. However, every TGT is encrypted in a key derived from the user's password. When a user types their password, it is not sent to the KDC, it is instead used to decrypt the TGT that `kinit` already obtained. If the decryption process results in a valid ticket with a valid time stamp, the user has valid Kerberos credentials. These credentials include a session key for establishing secure communications with the Kerberos server in the future, as well as the actual TGT, which is encrypted with the Kerberos server's own key. This second layer of encryption allows the Kerberos server to verify the authenticity of each TGT. * Host principals can have a longer ticket lifetime. If the user principal has a lifetime of a week but the host being connected to has a lifetime of nine hours, the user cache will have an expired host principal and the ticket cache will not work as expected. * When setting up [.filename]#krb5.dict# to prevent specific bad passwords from being used as described in man:kadmind[8], remember that it only applies to principals that have a password policy assigned to them. The format used in [.filename]#krb5.dict# is one string per line. Creating a symbolic link to [.filename]#/usr/share/dict/words# might be useful. === Mitigating Kerberos Limitations Since Kerberos is an all or nothing approach, every service enabled on the network must either be modified to work with Kerberos or be otherwise secured against network attacks. This is to prevent user credentials from being stolen and re-used. An example is when Kerberos is enabled on all remote shells but the non-Kerberized POP3 mail server sends passwords in plain text. The KDC is a single point of failure. By design, the KDC must be as secure as its master password database. The KDC should have absolutely no other services running on it and should be physically secure. The danger is high because Kerberos stores all passwords encrypted with the same master key which is stored as a file on the KDC. A compromised master key is not quite as bad as one might fear. The master key is only used to encrypt the Kerberos database and as a seed for the random number generator. As long as access to the KDC is secure, an attacker cannot do much with the master key. If the KDC is unavailable, network services are unusable as authentication cannot be performed. This can be alleviated with a single master KDC and one or more slaves, and with careful implementation of secondary or fall-back authentication using PAM. Kerberos allows users, hosts and services to authenticate between themselves. It does not have a mechanism to authenticate the KDC to the users, hosts, or services. This means that a trojaned `kinit` could record all user names and passwords. File system integrity checking tools like package:security/tripwire[] can alleviate this. === Resources and Further Information * http://www.faqs.org/faqs/Kerberos-faq/general/preamble.html[The Kerberos FAQ] * http://web.mit.edu/Kerberos/www/dialogue.html[Designing an Authentication System: a Dialog in Four Scenes] * https://www.ietf.org/rfc/rfc4120.txt[RFC 4120, The Kerberos Network Authentication Service (V5)] * http://web.mit.edu/Kerberos/www/[MIT Kerberos home page] * https://github.com/heimdal/heimdal/wiki[Heimdal Kerberos project wiki page] [[openssl]] == OpenSSL OpenSSL is an open source implementation of the SSL and TLS protocols. It provides an encryption transport layer on top of the normal communications layer, allowing it to be intertwined with many network applications and services. The version of OpenSSL included in FreeBSD supports Transport Layer Security 1.0/1.1/1.2/1.3 (TLSv1/TLSv1.1/TLSv1.2/TLSv1.3) network security protocols and can be used as a general cryptographic library. OpenSSL is often used to encrypt authentication of mail clients and to secure web based transactions such as credit card payments. Some ports, such as package:www/apache24[] and package:databases/postgresql11-server[], include a compile option for building with OpenSSL. If selected, the port will add support using OpenSSL from the base system. To instead have the port compile against OpenSSL from the package:security/openssl[] port, add the following to [.filename]#/etc/make.conf#: [.programlisting] .... DEFAULT_VERSIONS+= ssl=openssl .... Another common use of OpenSSL is to provide certificates for use with software applications. Certificates can be used to verify the credentials of a company or individual. If a certificate has not been signed by an external _Certificate Authority_ (CA), such as http://www.verisign.com[http://www.verisign.com], the application that uses the certificate will produce a warning. There is a cost associated with obtaining a signed certificate and using a signed certificate is not mandatory as certificates can be self-signed. However, using an external authority will prevent warnings and can put users at ease. This section demonstrates how to create and use certificates on a FreeBSD system. Refer to crossref:network-servers[ldap-config,“Configuring an LDAP Server”] for an example of how to create a CA for signing one's own certificates. For more information about SSL, read the free https://www.feistyduck.com/books/openssl-cookbook/[OpenSSL Cookbook]. === Generating Certificates To generate a certificate that will be signed by an external CA, issue the following command and input the information requested at the prompts. This input information will be written to the certificate. At the `Common Name` prompt, input the fully qualified name for the system that will use the certificate. If this name does not match the server, the application verifying the certificate will issue a warning to the user, rendering the verification provided by the certificate as useless. [source,shell] .... # openssl req -new -nodes -out req.pem -keyout cert.key -sha256 -newkey rsa:2048 Generating a 2048 bit RSA private key ..................+++ .............................................................+++ writing new private key to 'cert.key' ----- You are about to be asked to enter information that will be incorporated into your certificate request. What you are about to enter is what is called a Distinguished Name or a DN. There are quite a few fields but you can leave some blank For some fields there will be a default value, If you enter '.', the field will be left blank. ----- Country Name (2 letter code) [AU]:US State or Province Name (full name) [Some-State]:PA -Locality Name (eg, city) []:Pittsburgh -Organization Name (eg, company) [Internet Widgits Pty Ltd]:My Company -Organizational Unit Name (eg, section) []:Systems Administrator -Common Name (eg, YOUR name) []:localhost.example.org +Locality Name (e.g., city) []:Pittsburgh +Organization Name (e.g., company) [Internet Widgits Pty Ltd]:My Company +Organizational Unit Name (e.g., section) []:Systems Administrator +Common Name (e.g., YOUR name) []:localhost.example.org Email Address []:trhodes@FreeBSD.org Please enter the following 'extra' attributes to be sent with your certificate request A challenge password []: An optional company name []:Another Name .... Other options, such as the expire time and alternate encryption algorithms, are available when creating a certificate. A complete list of options is described in man:openssl[1]. This command will create two files in the current directory. The certificate request, [.filename]#req.pem#, can be sent to a CA who will validate the entered credentials, sign the request, and return the signed certificate. The second file, [.filename]#cert.key#, is the private key for the certificate and should be stored in a secure location. If this falls in the hands of others, it can be used to impersonate the user or the server. Alternately, if a signature from a CA is not required, a self-signed certificate can be created. First, generate the RSA key: [source,shell] .... # openssl genrsa -rand -genkey -out cert.key 2048 0 semi-random bytes loaded Generating RSA private key, 2048 bit long modulus .............................................+++ .................................................................................................................+++ e is 65537 (0x10001) .... Use this key to create a self-signed certificate. Follow the usual prompts for creating a certificate: [source,shell] .... # openssl req -new -x509 -days 365 -key cert.key -out cert.crt -sha256 You are about to be asked to enter information that will be incorporated into your certificate request. What you are about to enter is what is called a Distinguished Name or a DN. There are quite a few fields but you can leave some blank For some fields there will be a default value, If you enter '.', the field will be left blank. ----- Country Name (2 letter code) [AU]:US State or Province Name (full name) [Some-State]:PA -Locality Name (eg, city) []:Pittsburgh -Organization Name (eg, company) [Internet Widgits Pty Ltd]:My Company -Organizational Unit Name (eg, section) []:Systems Administrator +Locality Name (e.g., city) []:Pittsburgh +Organization Name (e.g., company) [Internet Widgits Pty Ltd]:My Company +Organizational Unit Name (e.g., section) []:Systems Administrator Common Name (e.g. server FQDN or YOUR name) []:localhost.example.org Email Address []:trhodes@FreeBSD.org .... This will create two new files in the current directory: a private key file [.filename]#cert.key#, and the certificate itself, [.filename]#cert.crt#. These should be placed in a directory, preferably under [.filename]#/etc/ssl/#, which is readable only by `root`. Permissions of `0700` are appropriate for these files and can be set using `chmod`. === Using Certificates One use for a certificate is to encrypt connections to the Sendmail mail server in order to prevent the use of clear text authentication. [NOTE] ==== Some mail clients will display an error if the user has not installed a local copy of the certificate. Refer to the documentation included with the software for more information on certificate installation. ==== In FreeBSD 10.0-RELEASE and above, it is possible to create a self-signed certificate for Sendmail automatically. To enable this, add the following lines to [.filename]#/etc/rc.conf#: [.programlisting] .... sendmail_enable="YES" sendmail_cert_create="YES" sendmail_cert_cn="localhost.example.org" .... This will automatically create a self-signed certificate, [.filename]#/etc/mail/certs/host.cert#, a signing key, [.filename]#/etc/mail/certs/host.key#, and a CA certificate, [.filename]#/etc/mail/certs/cacert.pem#. The certificate will use the `Common Name` specified in `sendmail_cert_cn`. After saving the edits, restart Sendmail: [source,shell] .... # service sendmail restart .... If all went well, there will be no error messages in [.filename]#/var/log/maillog#. For a simple test, connect to the mail server's listening port using `telnet`: [source,shell] .... # telnet example.com 25 Trying 192.0.34.166... Connected to example.com. Escape character is '^]'. 220 example.com ESMTP Sendmail 8.14.7/8.14.7; Fri, 18 Apr 2014 11:50:32 -0400 (EDT) ehlo example.com 250-example.com Hello example.com [192.0.34.166], pleased to meet you 250-ENHANCEDSTATUSCODES 250-PIPELINING 250-8BITMIME 250-SIZE 250-DSN 250-ETRN 250-AUTH LOGIN PLAIN 250-STARTTLS 250-DELIVERBY 250 HELP quit 221 2.0.0 example.com closing connection Connection closed by foreign host. .... If the `STARTTLS` line appears in the output, everything is working correctly. [[ipsec]] == VPN over IPsec Internet Protocol Security (IPsec) is a set of protocols which sit on top of the Internet Protocol (IP) layer. It allows two or more hosts to communicate in a secure manner by authenticating and encrypting each IP packet of a communication session. The FreeBSD IPsec network stack is based on the http://www.kame.net/[http://www.kame.net/] implementation and supports both IPv4 and IPv6 sessions. IPsec is comprised of the following sub-protocols: * _Encapsulated Security Payload (ESP)_: this protocol protects the IP packet data from third party interference by encrypting the contents using symmetric cryptography algorithms such as Blowfish and 3DES. * _Authentication Header (AH)_: this protocol protects the IP packet header from third party interference and spoofing by computing a cryptographic checksum and hashing the IP packet header fields with a secure hashing function. This is then followed by an additional header that contains the hash, to allow the information in the packet to be authenticated. * _IP Payload Compression Protocol (IPComp_): this protocol tries to increase communication performance by compressing the IP payload in order to reduce the amount of data sent. These protocols can either be used together or separately, depending on the environment. IPsec supports two modes of operation. The first mode, _Transport Mode_, protects communications between two hosts. The second mode, _Tunnel Mode_, is used to build virtual tunnels, commonly known as Virtual Private Networks (VPNs). Consult man:ipsec[4] for detailed information on the IPsec subsystem in FreeBSD. IPsec support is enabled by default on FreeBSD 11 and later. For previous versions of FreeBSD, add these options to a custom kernel configuration file and rebuild the kernel using the instructions in crossref:kernelconfig[kernelconfig,Configuring the FreeBSD Kernel]: [source,shell] .... options IPSEC IP security device crypto .... If IPsec debugging support is desired, the following kernel option should also be added: [source,shell] .... options IPSEC_DEBUG debug for IP security .... This rest of this chapter demonstrates the process of setting up an IPsecVPN between a home network and a corporate network. In the example scenario: * Both sites are connected to the Internet through a gateway that is running FreeBSD. * The gateway on each network has at least one external IP address. In this example, the corporate LAN's external IP address is `172.16.5.4` and the home LAN's external IP address is `192.168.1.12`. * The internal addresses of the two networks can be either public or private IP addresses. However, the address space must not overlap. In this example, the corporate LAN's internal IP address is `10.246.38.1` and the home LAN's internal IP address is `10.0.0.5`. [.programlisting] .... corporate home 10.246.38.1/24 -- 172.16.5.4 <--> 192.168.1.12 -- 10.0.0.5/24 .... === Configuring a VPN on FreeBSD To begin, package:security/ipsec-tools[] must be installed from the Ports Collection. This software provides a number of applications which support the configuration. The next requirement is to create two man:gif[4] pseudo-devices which will be used to tunnel packets and allow both networks to communicate properly. As `root`, run the following command on each gateway: [source,shell] .... corp-gw# ifconfig gif0 create corp-gw# ifconfig gif0 10.246.38.1 10.0.0.5 corp-gw# ifconfig gif0 tunnel 172.16.5.4 192.168.1.12 .... [source,shell] .... home-gw# ifconfig gif0 create home-gw# ifconfig gif0 10.0.0.5 10.246.38.1 home-gw# ifconfig gif0 tunnel 192.168.1.12 172.16.5.4 .... Verify the setup on each gateway, using `ifconfig gif0`. Here is the output from the home gateway: [.programlisting] .... gif0: flags=8051 mtu 1280 tunnel inet 172.16.5.4 --> 192.168.1.12 inet6 fe80::2e0:81ff:fe02:5881%gif0 prefixlen 64 scopeid 0x6 inet 10.246.38.1 --> 10.0.0.5 netmask 0xffffff00 .... Here is the output from the corporate gateway: [.programlisting] .... gif0: flags=8051 mtu 1280 tunnel inet 192.168.1.12 --> 172.16.5.4 inet 10.0.0.5 --> 10.246.38.1 netmask 0xffffff00 inet6 fe80::250:bfff:fe3a:c1f%gif0 prefixlen 64 scopeid 0x4 .... Once complete, both internal IP addresses should be reachable using man:ping[8]: [source,shell] .... home-gw# ping 10.0.0.5 PING 10.0.0.5 (10.0.0.5): 56 data bytes 64 bytes from 10.0.0.5: icmp_seq=0 ttl=64 time=42.786 ms 64 bytes from 10.0.0.5: icmp_seq=1 ttl=64 time=19.255 ms 64 bytes from 10.0.0.5: icmp_seq=2 ttl=64 time=20.440 ms 64 bytes from 10.0.0.5: icmp_seq=3 ttl=64 time=21.036 ms --- 10.0.0.5 ping statistics --- 4 packets transmitted, 4 packets received, 0% packet loss round-trip min/avg/max/stddev = 19.255/25.879/42.786/9.782 ms corp-gw# ping 10.246.38.1 PING 10.246.38.1 (10.246.38.1): 56 data bytes 64 bytes from 10.246.38.1: icmp_seq=0 ttl=64 time=28.106 ms 64 bytes from 10.246.38.1: icmp_seq=1 ttl=64 time=42.917 ms 64 bytes from 10.246.38.1: icmp_seq=2 ttl=64 time=127.525 ms 64 bytes from 10.246.38.1: icmp_seq=3 ttl=64 time=119.896 ms 64 bytes from 10.246.38.1: icmp_seq=4 ttl=64 time=154.524 ms --- 10.246.38.1 ping statistics --- 5 packets transmitted, 5 packets received, 0% packet loss round-trip min/avg/max/stddev = 28.106/94.594/154.524/49.814 ms .... As expected, both sides have the ability to send and receive ICMP packets from the privately configured addresses. Next, both gateways must be told how to route packets in order to correctly send traffic from the networks behind each gateway. The following commands will achieve this goal: [source,shell] .... corp-gw# route add 10.0.0.0 10.0.0.5 255.255.255.0 corp-gw# route add net 10.0.0.0: gateway 10.0.0.5 home-gw# route add 10.246.38.0 10.246.38.1 255.255.255.0 home-gw# route add host 10.246.38.0: gateway 10.246.38.1 .... Internal machines should be reachable from each gateway as well as from machines behind the gateways. Again, use man:ping[8] to confirm: [source,shell] .... corp-gw# ping -c 3 10.0.0.8 PING 10.0.0.8 (10.0.0.8): 56 data bytes 64 bytes from 10.0.0.8: icmp_seq=0 ttl=63 time=92.391 ms 64 bytes from 10.0.0.8: icmp_seq=1 ttl=63 time=21.870 ms 64 bytes from 10.0.0.8: icmp_seq=2 ttl=63 time=198.022 ms --- 10.0.0.8 ping statistics --- 3 packets transmitted, 3 packets received, 0% packet loss round-trip min/avg/max/stddev = 21.870/101.846/198.022/74.001 ms home-gw# ping -c 3 10.246.38.107 PING 10.246.38.1 (10.246.38.107): 56 data bytes 64 bytes from 10.246.38.107: icmp_seq=0 ttl=64 time=53.491 ms 64 bytes from 10.246.38.107: icmp_seq=1 ttl=64 time=23.395 ms 64 bytes from 10.246.38.107: icmp_seq=2 ttl=64 time=23.865 ms --- 10.246.38.107 ping statistics --- 3 packets transmitted, 3 packets received, 0% packet loss round-trip min/avg/max/stddev = 21.145/31.721/53.491/12.179 ms .... At this point, traffic is flowing between the networks encapsulated in a gif tunnel but without any encryption. Next, use IPSec to encrypt traffic using pre-shared keys (PSK). Other than the IP addresses, [.filename]#/usr/local/etc/racoon/racoon.conf# on both gateways will be identical and look similar to: [.programlisting] .... path pre_shared_key "/usr/local/etc/racoon/psk.txt"; #location of pre-shared key file log debug; #log verbosity setting: set to 'notify' when testing and debugging is complete padding # options are not to be changed { maximum_length 20; randomize off; strict_check off; exclusive_tail off; } timer # timing options. change as needed { counter 5; interval 20 sec; persend 1; # natt_keepalive 15 sec; phase1 30 sec; phase2 15 sec; } listen # address [port] that racoon will listen on { isakmp 172.16.5.4 [500]; isakmp_natt 172.16.5.4 [4500]; } remote 192.168.1.12 [500] { exchange_mode main,aggressive; doi ipsec_doi; situation identity_only; my_identifier address 172.16.5.4; peers_identifier address 192.168.1.12; lifetime time 8 hour; passive off; proposal_check obey; # nat_traversal off; generate_policy off; proposal { encryption_algorithm blowfish; hash_algorithm md5; authentication_method pre_shared_key; lifetime time 30 sec; dh_group 1; } } sainfo (address 10.246.38.0/24 any address 10.0.0.0/24 any) # address $network/$netmask $type address $network/$netmask $type ( $type being any or esp) { # $network must be the two internal networks you are joining. pfs_group 1; lifetime time 36000 sec; encryption_algorithm blowfish,3des; authentication_algorithm hmac_md5,hmac_sha1; compression_algorithm deflate; } .... For descriptions of each available option, refer to the manual page for [.filename]#racoon.conf#. The Security Policy Database (SPD) needs to be configured so that FreeBSD and racoon are able to encrypt and decrypt network traffic between the hosts. This can be achieved with a shell script, similar to the following, on the corporate gateway. This file will be used during system initialization and should be saved as [.filename]#/usr/local/etc/racoon/setkey.conf#. [.programlisting] .... flush; spdflush; # To the home network spdadd 10.246.38.0/24 10.0.0.0/24 any -P out ipsec esp/tunnel/172.16.5.4-192.168.1.12/use; spdadd 10.0.0.0/24 10.246.38.0/24 any -P in ipsec esp/tunnel/192.168.1.12-172.16.5.4/use; .... Once in place, racoon may be started on both gateways using the following command: [source,shell] .... # /usr/local/sbin/racoon -F -f /usr/local/etc/racoon/racoon.conf -l /var/log/racoon.log .... The output should be similar to the following: [source,shell] .... corp-gw# /usr/local/sbin/racoon -F -f /usr/local/etc/racoon/racoon.conf Foreground mode. 2006-01-30 01:35:47: INFO: begin Identity Protection mode. 2006-01-30 01:35:48: INFO: received Vendor ID: KAME/racoon 2006-01-30 01:35:55: INFO: received Vendor ID: KAME/racoon 2006-01-30 01:36:04: INFO: ISAKMP-SA established 172.16.5.4[500]-192.168.1.12[500] spi:623b9b3bd2492452:7deab82d54ff704a 2006-01-30 01:36:05: INFO: initiate new phase 2 negotiation: 172.16.5.4[0]192.168.1.12[0] 2006-01-30 01:36:09: INFO: IPsec-SA established: ESP/Tunnel 192.168.1.12[0]->172.16.5.4[0] spi=28496098(0x1b2d0e2) 2006-01-30 01:36:09: INFO: IPsec-SA established: ESP/Tunnel 172.16.5.4[0]->192.168.1.12[0] spi=47784998(0x2d92426) 2006-01-30 01:36:13: INFO: respond new phase 2 negotiation: 172.16.5.4[0]192.168.1.12[0] 2006-01-30 01:36:18: INFO: IPsec-SA established: ESP/Tunnel 192.168.1.12[0]->172.16.5.4[0] spi=124397467(0x76a279b) 2006-01-30 01:36:18: INFO: IPsec-SA established: ESP/Tunnel 172.16.5.4[0]->192.168.1.12[0] spi=175852902(0xa7b4d66) .... To ensure the tunnel is working properly, switch to another console and use man:tcpdump[1] to view network traffic using the following command. Replace `em0` with the network interface card as required: [source,shell] .... corp-gw# tcpdump -i em0 host 172.16.5.4 and dst 192.168.1.12 .... Data similar to the following should appear on the console. If not, there is an issue and debugging the returned data will be required. [.programlisting] .... 01:47:32.021683 IP corporatenetwork.com > 192.168.1.12.privatenetwork.com: ESP(spi=0x02acbf9f,seq=0xa) 01:47:33.022442 IP corporatenetwork.com > 192.168.1.12.privatenetwork.com: ESP(spi=0x02acbf9f,seq=0xb) 01:47:34.024218 IP corporatenetwork.com > 192.168.1.12.privatenetwork.com: ESP(spi=0x02acbf9f,seq=0xc) .... At this point, both networks should be available and seem to be part of the same network. Most likely both networks are protected by a firewall. To allow traffic to flow between them, rules need to be added to pass packets. For the man:ipfw[8] firewall, add the following lines to the firewall configuration file: [.programlisting] .... ipfw add 00201 allow log esp from any to any ipfw add 00202 allow log ah from any to any ipfw add 00203 allow log ipencap from any to any ipfw add 00204 allow log udp from any 500 to any .... [NOTE] ==== The rule numbers may need to be altered depending on the current host configuration. ==== For users of man:pf[4] or man:ipf[8], the following rules should do the trick: [.programlisting] .... pass in quick proto esp from any to any pass in quick proto ah from any to any pass in quick proto ipencap from any to any pass in quick proto udp from any port = 500 to any port = 500 pass in quick on gif0 from any to any pass out quick proto esp from any to any pass out quick proto ah from any to any pass out quick proto ipencap from any to any pass out quick proto udp from any port = 500 to any port = 500 pass out quick on gif0 from any to any .... Finally, to allow the machine to start support for the VPN during system initialization, add the following lines to [.filename]#/etc/rc.conf#: [.programlisting] .... ipsec_enable="YES" ipsec_program="/usr/local/sbin/setkey" ipsec_file="/usr/local/etc/racoon/setkey.conf" # allows setting up spd policies on boot racoon_enable="yes" .... [[openssh]] == OpenSSH OpenSSH is a set of network connectivity tools used to provide secure access to remote machines. Additionally, TCP/IP connections can be tunneled or forwarded securely through SSH connections. OpenSSH encrypts all traffic to effectively eliminate eavesdropping, connection hijacking, and other network-level attacks. OpenSSH is maintained by the OpenBSD project and is installed by default in FreeBSD. When data is sent over the network in an unencrypted form, network sniffers anywhere in between the client and server can steal user/password information or data transferred during the session. OpenSSH offers a variety of authentication and encryption methods to prevent this from happening. More information about OpenSSH is available from http://www.openssh.com/[http://www.openssh.com/]. This section provides an overview of the built-in client utilities to securely access other systems and securely transfer files from a FreeBSD system. It then describes how to configure a SSH server on a FreeBSD system. More information is available in the man pages mentioned in this chapter. === Using the SSH Client Utilities To log into a SSH server, use `ssh` and specify a username that exists on that server and the IP address or hostname of the server. If this is the first time a connection has been made to the specified server, the user will be prompted to first verify the server's fingerprint: [source,shell] .... # ssh user@example.com The authenticity of host 'example.com (10.0.0.1)' can't be established. ECDSA key fingerprint is 25:cc:73:b5:b3:96:75:3d:56:19:49:d2:5c:1f:91:3b. Are you sure you want to continue connecting (yes/no)? yes Permanently added 'example.com' (ECDSA) to the list of known hosts. Password for user@example.com: user_password .... SSH utilizes a key fingerprint system to verify the authenticity of the server when the client connects. When the user accepts the key's fingerprint by typing `yes` when connecting for the first time, a copy of the key is saved to [.filename]#.ssh/known_hosts# in the user's home directory. Future attempts to login are verified against the saved key and `ssh` will display an alert if the server's key does not match the saved key. If this occurs, the user should first verify why the key has changed before continuing with the connection. Recent versions of OpenSSH only accept SSHv2 connections. SSH protocol version 1 is obsolete. Use man:scp[1] to securely copy a file to or from a remote machine. This example copies [.filename]#COPYRIGHT# on the remote system to a file of the same name in the current directory of the local system: [source,shell] .... # scp user@example.com:/COPYRIGHT COPYRIGHT Password for user@example.com: ******* COPYRIGHT 100% |*****************************| 4735 00:00 # .... Since the fingerprint was already verified for this host, the server's key is automatically checked before prompting for the user's password. The arguments passed to `scp` are similar to `cp`. The file or files to copy is the first argument and the destination to copy to is the second. Since the file is fetched over the network, one or more of the file arguments takes the form `user@host:`. Be aware when copying directories recursively that `scp` uses `-r`, whereas `cp` uses `-R`. To open an interactive session for copying files, use `sftp`. Refer to man:sftp[1] for a list of available commands while in an `sftp` session. [[security-ssh-keygen]] ==== Key-based Authentication Instead of using passwords, a client can be configured to connect to the remote machine using keys. To generate RSA authentication keys, use `ssh-keygen`. To generate a public and private key pair, specify the type of key and follow the prompts. It is recommended to protect the keys with a memorable, but hard to guess passphrase. [source,shell] .... % ssh-keygen -t rsa Generating public/private rsa key pair. Enter file in which to save the key (/home/user/.ssh/id_rsa): Enter passphrase (empty for no passphrase): <.> Enter same passphrase again: <.> Your identification has been saved in /home/user/.ssh/id_rsa. Your public key has been saved in /home/user/.ssh/id_rsa.pub. The key fingerprint is: SHA256:54Xm9Uvtv6H4NOo6yjP/YCfODryvUU7yWHzMqeXwhq8 user@host.example.com The key's randomart image is: +---[RSA 2048]----+ | | | | | | | . o.. | | .S*+*o | | . O=Oo . . | | = Oo= oo..| | .oB.* +.oo.| | =OE**.o..=| +----[SHA256]-----+ .... <.> Type a passphrase here. It can contain spaces and symbols. <.> Retype the passphrase to verify it. The private key is stored in [.filename]#~/.ssh/id_rsa# and the public key is stored in [.filename]#~/.ssh/id_rsa.pub#. The _public_ key must be copied to [.filename]#~/.ssh/authorized_keys# on the remote machine for key-based authentication to work. [WARNING] ==== Many users believe that keys are secure by design and will use a key without a passphrase. This is _dangerous_ behavior. An administrator can verify that a key pair is protected by a passphrase by viewing the private key manually. If the private key file contains the word `ENCRYPTED`, the key owner is using a passphrase. In addition, to better secure end users, `from` may be placed in the public key file. For example, adding `from="192.168.10.5"` in front of the `ssh-rsa` prefix will only allow that specific user to log in from that IP address. ==== The options and files vary with different versions of OpenSSH. To avoid problems, consult man:ssh-keygen[1]. If a passphrase is used, the user is prompted for the passphrase each time a connection is made to the server. To load SSH keys into memory and remove the need to type the passphrase each time, use man:ssh-agent[1] and man:ssh-add[1]. Authentication is handled by `ssh-agent`, using the private keys that are loaded into it. `ssh-agent` can be used to launch another application like a shell or a window manager. To use `ssh-agent` in a shell, start it with a shell as an argument. Add the identity by running `ssh-add` and entering the passphrase for the private key. The user will then be able to `ssh` to any host that has the corresponding public key installed. For example: [source,shell] .... % ssh-agent csh % ssh-add Enter passphrase for key '/usr/home/user/.ssh/id_rsa': <.> Identity added: /usr/home/user/.ssh/id_rsa (/usr/home/user/.ssh/id_rsa) % .... <.> Enter the passphrase for the key. To use `ssh-agent` in Xorg, add an entry for it in [.filename]#~/.xinitrc#. This provides the `ssh-agent` services to all programs launched in Xorg. An example [.filename]#~/.xinitrc# might look like this: [.programlisting] .... exec ssh-agent startxfce4 .... This launches `ssh-agent`, which in turn launches XFCE, every time Xorg starts. Once Xorg has been restarted so that the changes can take effect, run `ssh-add` to load all of the SSH keys. [[security-ssh-tunneling]] ==== SSH Tunneling OpenSSH has the ability to create a tunnel to encapsulate another protocol in an encrypted session. The following command tells `ssh` to create a tunnel for telnet: [source,shell] .... % ssh -2 -N -f -L 5023:localhost:23 user@foo.example.com % .... This example uses the following options: `-2`:: Forces `ssh` to use version 2 to connect to the server. `-N`:: Indicates no command, or tunnel only. If omitted, `ssh` initiates a normal session. `-f`:: Forces `ssh` to run in the background. `-L`:: Indicates a local tunnel in _localport:remotehost:remoteport_ format. `user@foo.example.com`:: The login name to use on the specified remote SSH server. An SSH tunnel works by creating a listen socket on `localhost` on the specified `localport`. It then forwards any connections received on `localport` via the SSH connection to the specified `remotehost:remoteport`. In the example, port `5023` on the client is forwarded to port `23` on the remote machine. Since port 23 is used by telnet, this creates an encrypted telnet session through an SSH tunnel. This method can be used to wrap any number of insecure TCP protocols such as SMTP, POP3, and FTP, as seen in the following examples. .Create a Secure Tunnel for SMTP [example] ==== [source,shell] .... % ssh -2 -N -f -L 5025:localhost:25 user@mailserver.example.com user@mailserver.example.com's password: ***** % telnet localhost 5025 Trying 127.0.0.1... Connected to localhost. Escape character is '^]'. 220 mailserver.example.com ESMTP .... This can be used in conjunction with `ssh-keygen` and additional user accounts to create a more seamless SSH tunneling environment. Keys can be used in place of typing a password, and the tunnels can be run as a separate user. ==== .Secure Access of a POP3 Server [example] ==== In this example, there is an SSH server that accepts connections from the outside. On the same network resides a mail server running a POP3 server. To check email in a secure manner, create an SSH connection to the SSH server and tunnel through to the mail server: [source,shell] .... % ssh -2 -N -f -L 2110:mail.example.com:110 user@ssh-server.example.com user@ssh-server.example.com's password: ****** .... Once the tunnel is up and running, point the email client to send POP3 requests to `localhost` on port 2110. This connection will be forwarded securely across the tunnel to `mail.example.com`. ==== .Bypassing a Firewall [example] ==== Some firewalls filter both incoming and outgoing connections. For example, a firewall might limit access from remote machines to ports 22 and 80 to only allow SSH and web surfing. This prevents access to any other service which uses a port other than 22 or 80. The solution is to create an SSH connection to a machine outside of the network's firewall and use it to tunnel to the desired service: [source,shell] .... % ssh -2 -N -f -L 8888:music.example.com:8000 user@unfirewalled-system.example.org user@unfirewalled-system.example.org's password: ******* .... In this example, a streaming Ogg Vorbis client can now be pointed to `localhost` port 8888, which will be forwarded over to `music.example.com` on port 8000, successfully bypassing the firewall. ==== === Enabling the SSH Server In addition to providing built-in SSH client utilities, a FreeBSD system can be configured as an SSH server, accepting connections from other SSH clients. To see if sshd is operating, use the man:service[8] command: [source,shell] .... # service sshd status .... If the service is not running, add the following line to [.filename]#/etc/rc.conf#. [.programlisting] .... sshd_enable="YES" .... This will start sshd, the daemon program for OpenSSH, the next time the system boots. To start it now: [source,shell] .... # service sshd start .... The first time sshd starts on a FreeBSD system, the system's host keys will be automatically created and the fingerprint will be displayed on the console. Provide users with the fingerprint so that they can verify it the first time they connect to the server. Refer to man:sshd[8] for the list of available options when starting sshd and a more complete discussion about authentication, the login process, and the various configuration files. At this point, the sshd should be available to all users with a username and password on the system. === SSH Server Security While sshd is the most widely used remote administration facility for FreeBSD, brute force and drive by attacks are common to any system exposed to public networks. Several additional parameters are available to prevent the success of these attacks and will be described in this section. It is a good idea to limit which users can log into the SSH server and from where using the `AllowUsers` keyword in the OpenSSH server configuration file. For example, to only allow `root` to log in from `192.168.1.32`, add this line to [.filename]#/etc/ssh/sshd_config#: [.programlisting] .... AllowUsers root@192.168.1.32 .... To allow `admin` to log in from anywhere, list that user without specifying an IP address: [.programlisting] .... AllowUsers admin .... Multiple users should be listed on the same line, like so: [.programlisting] .... AllowUsers root@192.168.1.32 admin .... After making changes to [.filename]#/etc/ssh/sshd_config#, tell sshd to reload its configuration file by running: [source,shell] .... # service sshd reload .... [NOTE] ==== When this keyword is used, it is important to list each user that needs to log into this machine. Any user that is not specified in that line will be locked out. Also, the keywords used in the OpenSSH server configuration file are case-sensitive. If the keyword is not spelled correctly, including its case, it will be ignored. Always test changes to this file to make sure that the edits are working as expected. Refer to man:sshd_config[5] to verify the spelling and use of the available keywords. ==== In addition, users may be forced to use two factor authentication via the use of a public and private key. When required, the user may generate a key pair through the use of man:ssh-keygen[1] and send the administrator the public key. This key file will be placed in the [.filename]#authorized_keys# as described above in the client section. To force the users to use keys only, the following option may be configured: [.programlisting] .... AuthenticationMethods publickey .... [TIP] ==== Do not confuse [.filename]#/etc/ssh/sshd_config# with [.filename]#/etc/ssh/ssh_config# (note the extra `d` in the first filename). The first file configures the server and the second file configures the client. Refer to man:ssh_config[5] for a listing of the available client settings. ==== [[fs-acl]] == Access Control Lists Access Control Lists (ACLs) extend the standard UNIX(R) permission model in a POSIX(R).1e compatible way. This permits an administrator to take advantage of a more fine-grained permissions model. The FreeBSD [.filename]#GENERIC# kernel provides ACL support for UFS file systems. Users who prefer to compile a custom kernel must include the following option in their custom kernel configuration file: [.programlisting] .... options UFS_ACL .... If this option is not compiled in, a warning message will be displayed when attempting to mount a file system with ACL support. ACLs rely on extended attributes which are natively supported in UFS2. This chapter describes how to enable ACL support and provides some usage examples. === Enabling ACL Support ACLs are enabled by the mount-time administrative flag, `acls`, which may be added to [.filename]#/etc/fstab#. The mount-time flag can also be automatically set in a persistent manner using man:tunefs[8] to modify a superblock ACLs flag in the file system header. In general, it is preferred to use the superblock flag for several reasons: * The superblock flag cannot be changed by a remount using `mount -u` as it requires a complete `umount` and fresh `mount`. This means that ACLs cannot be enabled on the root file system after boot. It also means that ACL support on a file system cannot be changed while the system is in use. * Setting the superblock flag causes the file system to always be mounted with ACLs enabled, even if there is not an [.filename]#fstab# entry or if the devices re-order. This prevents accidental mounting of the file system without ACL support. [NOTE] ==== It is desirable to discourage accidental mounting without ACLs enabled because nasty things can happen if ACLs are enabled, then disabled, then re-enabled without flushing the extended attributes. In general, once ACLs are enabled on a file system, they should not be disabled, as the resulting file protections may not be compatible with those intended by the users of the system, and re-enabling ACLs may re-attach the previous ACLs to files that have since had their permissions changed, resulting in unpredictable behavior. ==== File systems with ACLs enabled will show a plus (`+`) sign in their permission settings: [.programlisting] .... drwx------ 2 robert robert 512 Dec 27 11:54 private drwxrwx---+ 2 robert robert 512 Dec 23 10:57 directory1 drwxrwx---+ 2 robert robert 512 Dec 22 10:20 directory2 drwxrwx---+ 2 robert robert 512 Dec 27 11:57 directory3 drwxr-xr-x 2 robert robert 512 Nov 10 11:54 public_html .... In this example, [.filename]#directory1#, [.filename]#directory2#, and [.filename]#directory3# are all taking advantage of ACLs, whereas [.filename]#private# and [.filename]#public_html# are not. === Using ACLs File system ACLs can be viewed using `getfacl`. For instance, to view the ACL settings on [.filename]#test#: [source,shell] .... % getfacl test #file:test #owner:1001 #group:1001 user::rw- group::r-- other::r-- .... To change the ACL settings on this file, use `setfacl`. To remove all of the currently defined ACLs from a file or file system, include `-k`. However, the preferred method is to use `-b` as it leaves the basic fields required for ACLs to work. [source,shell] .... % setfacl -k test .... To modify the default ACL entries, use `-m`: [source,shell] .... % setfacl -m u:trhodes:rwx,group:web:r--,o::--- test .... In this example, there were no pre-defined entries, as they were removed by the previous command. This command restores the default options and assigns the options listed. If a user or group is added which does not exist on the system, an `Invalid argument` error will be displayed. Refer to man:getfacl[1] and man:setfacl[1] for more information about the options available for these commands. [[security-pkg]] == Monitoring Third Party Security Issues In recent years, the security world has made many improvements to how vulnerability assessment is handled. The threat of system intrusion increases as third party utilities are installed and configured for virtually any operating system available today. Vulnerability assessment is a key factor in security. While FreeBSD releases advisories for the base system, doing so for every third party utility is beyond the FreeBSD Project's capability. There is a way to mitigate third party vulnerabilities and warn administrators of known security issues. A FreeBSD add on utility known as pkg includes options explicitly for this purpose. pkg polls a database for security issues. The database is updated and maintained by the FreeBSD Security Team and ports developers. Please refer to crossref:ports[pkgng-intro,instructions] for installing pkg. Installation provides man:periodic[8] configuration files for maintaining the pkg audit database, and provides a programmatic method of keeping it updated. This functionality is enabled if `daily_status_security_pkgaudit_enable` is set to `YES` in man:periodic.conf[5]. Ensure that daily security run emails, which are sent to ``root``'s email account, are being read. After installation, and to audit third party utilities as part of the Ports Collection at any time, an administrator may choose to update the database and view known vulnerabilities of installed packages by invoking: [source,shell] .... # pkg audit -F .... pkg displays messages any published vulnerabilities in installed packages: [.programlisting] .... Affected package: cups-base-1.1.22.0_1 Type of problem: cups-base -- HPGL buffer overflow vulnerability. Reference: 1 problem(s) in your installed packages found. You are advised to update or deinstall the affected package(s) immediately. .... By pointing a web browser to the displayed URL, an administrator may obtain more information about the vulnerability. This will include the versions affected, by FreeBSD port version, along with other web sites which may contain security advisories. pkg is a powerful utility and is extremely useful when coupled with package:ports-mgmt/portmaster[]. [[security-advisories]] == FreeBSD Security Advisories Like many producers of quality operating systems, the FreeBSD Project has a security team which is responsible for determining the End-of-Life (EoL) date for each FreeBSD release and to provide security updates for supported releases which have not yet reached their EoL. More information about the FreeBSD security team and the supported releases is available on the link:https://www.FreeBSD.org/security[FreeBSD security page]. One task of the security team is to respond to reported security vulnerabilities in the FreeBSD operating system. Once a vulnerability is confirmed, the security team verifies the steps necessary to fix the vulnerability and updates the source code with the fix. It then publishes the details as a "Security Advisory". Security advisories are published on the link:https://www.FreeBSD.org/security/advisories/[FreeBSD website] and mailed to the {freebsd-security-notifications}, {freebsd-security}, and {freebsd-announce} mailing lists. This section describes the format of a FreeBSD security advisory. === Format of a Security Advisory Here is an example of a FreeBSD security advisory: [.programlisting] .... ============================================================================= -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 ============================================================================= FreeBSD-SA-14:04.bind Security Advisory The FreeBSD Project Topic: BIND remote denial of service vulnerability Category: contrib Module: bind Announced: 2014-01-14 Credits: ISC Affects: FreeBSD 8.x and FreeBSD 9.x Corrected: 2014-01-14 19:38:37 UTC (stable/9, 9.2-STABLE) 2014-01-14 19:42:28 UTC (releng/9.2, 9.2-RELEASE-p3) 2014-01-14 19:42:28 UTC (releng/9.1, 9.1-RELEASE-p10) 2014-01-14 19:38:37 UTC (stable/8, 8.4-STABLE) 2014-01-14 19:42:28 UTC (releng/8.4, 8.4-RELEASE-p7) 2014-01-14 19:42:28 UTC (releng/8.3, 8.3-RELEASE-p14) CVE Name: CVE-2014-0591 For general information regarding FreeBSD Security Advisories, including descriptions of the fields above, security branches, and the following sections, please visit . I. Background BIND 9 is an implementation of the Domain Name System (DNS) protocols. The named(8) daemon is an Internet Domain Name Server. II. Problem Description Because of a defect in handling queries for NSEC3-signed zones, BIND can crash with an "INSIST" failure in name.c when processing queries possessing certain properties. This issue only affects authoritative nameservers with at least one NSEC3-signed zone. Recursive-only servers are not at risk. III. Impact An attacker who can send a specially crafted query could cause named(8) to crash, resulting in a denial of service. IV. Workaround No workaround is available, but systems not running authoritative DNS service with at least one NSEC3-signed zone using named(8) are not vulnerable. V. Solution Perform one of the following: 1) Upgrade your vulnerable system to a supported FreeBSD stable or release / security branch (releng) dated after the correction date. 2) To update your vulnerable system via a source code patch: The following patches have been verified to apply to the applicable FreeBSD release branches. a) Download the relevant patch from the location below, and verify the detached PGP signature using your PGP utility. [FreeBSD 8.3, 8.4, 9.1, 9.2-RELEASE and 8.4-STABLE] # fetch http://security.FreeBSD.org/patches/SA-14:04/bind-release.patch # fetch http://security.FreeBSD.org/patches/SA-14:04/bind-release.patch.asc # gpg --verify bind-release.patch.asc [FreeBSD 9.2-STABLE] # fetch http://security.FreeBSD.org/patches/SA-14:04/bind-stable-9.patch # fetch http://security.FreeBSD.org/patches/SA-14:04/bind-stable-9.patch.asc # gpg --verify bind-stable-9.patch.asc b) Execute the following commands as root: # cd /usr/src # patch < /path/to/patch Recompile the operating system using buildworld and installworld as described in . Restart the applicable daemons, or reboot the system. 3) To update your vulnerable system via a binary patch: Systems running a RELEASE version of FreeBSD on the i386 or amd64 platforms can be updated via the man:freebsd-update[8] utility: # freebsd-update fetch # freebsd-update install VI. Correction details The following list contains the correction revision numbers for each affected branch. Branch/path Revision - ------------------------------------------------------------------------- stable/8/ r260646 releng/8.3/ r260647 releng/8.4/ r260647 stable/9/ r260646 releng/9.1/ r260647 releng/9.2/ r260647 - ------------------------------------------------------------------------- To see which files were modified by a particular revision, run the following command, replacing NNNNNN with the revision number, on a machine with Subversion installed: # svn diff -cNNNNNN --summarize svn://svn.freebsd.org/base Or visit the following URL, replacing NNNNNN with the revision number: VII. References The latest revision of this advisory is available at -----BEGIN PGP SIGNATURE----- iQIcBAEBCgAGBQJS1ZTYAAoJEO1n7NZdz2rnOvQP/2/68/s9Cu35PmqNtSZVVxVG ZSQP5EGWx/lramNf9566iKxOrLRMq/h3XWcC4goVd+gZFrvITJSVOWSa7ntDQ7TO XcinfRZ/iyiJbs/Rg2wLHc/t5oVSyeouyccqODYFbOwOlk35JjOTMUG1YcX+Zasg ax8RV+7Zt1QSBkMlOz/myBLXUjlTZ3Xg2FXVsfFQW5/g2CjuHpRSFx1bVNX6ysoG 9DT58EQcYxIS8WfkHRbbXKh9I1nSfZ7/Hky/kTafRdRMrjAgbqFgHkYTYsBZeav5 fYWKGQRJulYfeZQ90yMTvlpF42DjCC3uJYamJnwDIu8OhS1WRBI8fQfr9DRzmRua OK3BK9hUiScDZOJB6OqeVzUTfe7MAA4/UwrDtTYQ+PqAenv1PK8DZqwXyxA9ThHb zKO3OwuKOVHJnKvpOcr+eNwo7jbnHlis0oBksj/mrq2P9m2ueF9gzCiq5Ri5Syag Wssb1HUoMGwqU0roS8+pRpNC8YgsWpsttvUWSZ8u6Vj/FLeHpiV3mYXPVMaKRhVm 067BA2uj4Th1JKtGleox+Em0R7OFbCc/9aWC67wiqI6KRyit9pYiF3npph+7D5Eq 7zPsUdDd+qc+UTiLp3liCRp5w6484wWdhZO6wRtmUgxGjNkxFoNnX8CitzF8AaqO UWWemqWuz3lAZuORQ9KX =OQzQ -----END PGP SIGNATURE----- .... Every security advisory uses the following format: * Each security advisory is signed by the PGP key of the Security Officer. The public key for the Security Officer can be verified at crossref:pgpkeys[pgpkeys,OpenPGP Keys]. * The name of the security advisory always begins with `FreeBSD-SA-` (for FreeBSD Security Advisory), followed by the year in two digit format (`14:`), followed by the advisory number for that year (`04.`), followed by the name of the affected application or subsystem (`bind`). The advisory shown here is the fourth advisory for 2014 and it affects BIND. * The `Topic` field summarizes the vulnerability. * The `Category` refers to the affected part of the system which may be one of `core`, `contrib`, or `ports`. The `core` category means that the vulnerability affects a core component of the FreeBSD operating system. The `contrib` category means that the vulnerability affects software included with FreeBSD, such as BIND. The `ports` category indicates that the vulnerability affects software available through the Ports Collection. * The `Module` field refers to the component location. In this example, the `bind` module is affected; therefore, this vulnerability affects an application installed with the operating system. * The `Announced` field reflects the date the security advisory was published. This means that the security team has verified that the problem exists and that a patch has been committed to the FreeBSD source code repository. * The `Credits` field gives credit to the individual or organization who noticed the vulnerability and reported it. * The `Affects` field explains which releases of FreeBSD are affected by this vulnerability. * The `Corrected` field indicates the date, time, time offset, and releases that were corrected. The section in parentheses shows each branch for which the fix has been merged, and the version number of the corresponding release from that branch. The release identifier itself includes the version number and, if appropriate, the patch level. The patch level is the letter `p` followed by a number, indicating the sequence number of the patch, allowing users to track which patches have already been applied to the system. * The `CVE Name` field lists the advisory number, if one exists, in the public http://cve.mitre.org[cve.mitre.org] security vulnerabilities database. * The `Background` field provides a description of the affected module. * The `Problem Description` field explains the vulnerability. This can include information about the flawed code and how the utility could be maliciously used. * The `Impact` field describes what type of impact the problem could have on a system. * The `Workaround` field indicates if a workaround is available to system administrators who cannot immediately patch the system . * The `Solution` field provides the instructions for patching the affected system. This is a step by step tested and verified method for getting a system patched and working securely. * The `Correction Details` field displays each affected Subversion branch with the revision number that contains the corrected code. * The `References` field offers sources of additional information regarding the vulnerability. [[security-accounting]] == Process Accounting Process accounting is a security method in which an administrator may keep track of system resources used and their allocation among users, provide for system monitoring, and minimally track a user's commands. Process accounting has both positive and negative points. One of the positives is that an intrusion may be narrowed down to the point of entry. A negative is the amount of logs generated by process accounting, and the disk space they may require. This section walks an administrator through the basics of process accounting. [NOTE] ==== If more fine-grained accounting is needed, refer to crossref:audit[audit,Security Event Auditing]. ==== === Enabling and Utilizing Process Accounting Before using process accounting, it must be enabled using the following commands: [source,shell] .... # sysrc accounting_enable=yes # service accounting start .... The accounting information is stored in files located in [.filename]#/var/account#, which is automatically created, if necessary, the first time the accounting service starts. These files contain sensitive information, including all the commands issued by all users. Write access to the files is limited to `root`, and read access is limited to `root` and members of the `wheel` group. To also prevent members of `wheel` from reading the files, change the mode of the [.filename]#/var/account# directory to allow access only by `root`. Once enabled, accounting will begin to track information such as CPU statistics and executed commands. All accounting logs are in a non-human readable format which can be viewed using `sa`. If issued without any options, `sa` prints information relating to the number of per-user calls, the total elapsed time in minutes, total CPU and user time in minutes, and the average number of I/O operations. Refer to man:sa[8] for the list of available options which control the output. To display the commands issued by users, use `lastcomm`. For example, this command prints out all usage of `ls` by `trhodes` on the `ttyp1` terminal: [source,shell] .... # lastcomm ls trhodes ttyp1 .... Many other useful options exist and are explained in man:lastcomm[1], man:acct[5], and man:sa[8]. [[security-resourcelimits]] == Resource Limits FreeBSD provides several methods for an administrator to limit the amount of system resources an individual may use. Disk quotas limit the amount of disk space available to users. Quotas are discussed in crossref:disks[quotas,"Disk Quotas"]. Limits to other resources, such as CPU and memory, can be set using either a flat file or a command to configure a resource limits database. The traditional method defines login classes by editing [.filename]#/etc/login.conf#. While this method is still supported, any changes require a multi-step process of editing this file, rebuilding the resource database, making necessary changes to [.filename]#/etc/master.passwd#, and rebuilding the password database. This can become time consuming, depending upon the number of users to configure. `rctl` can be used to provide a more fine-grained method for controlling resource limits. This command supports more than user limits as it can also be used to set resource constraints on processes and jails. This section demonstrates both methods for controlling resources, beginning with the traditional method. [[users-limiting]] === Configuring Login Classes In the traditional method, login classes and the resource limits to apply to a login class are defined in [.filename]#/etc/login.conf#. Each user account can be assigned to a login class, where `default` is the default login class. Each login class has a set of login capabilities associated with it. A login capability is a `_name_=_value_` pair, where _name_ is a well-known identifier and _value_ is an arbitrary string which is processed accordingly depending on the _name_. [NOTE] ==== Whenever [.filename]#/etc/login.conf# is edited, the [.filename]#/etc/login.conf.db# must be updated by executing the following command: [source,shell] .... # cap_mkdb /etc/login.conf .... ==== Resource limits differ from the default login capabilities in two ways. First, for every limit, there is a _soft_ and _hard_ limit. A soft limit may be adjusted by the user or application, but may not be set higher than the hard limit. The hard limit may be lowered by the user, but can only be raised by the superuser. Second, most resource limits apply per process to a specific user. <> lists the most commonly used resource limits. All of the available resource limits and capabilities are described in detail in man:login.conf[5]. [[resource-limits]] .Login Class Resource Limits [cols="20%,80%", frame="none", options="header"] |=== | Resource Limit | Description |coredumpsize |The limit on the size of a core file generated by a program is subordinate to other limits on disk usage, such as `filesize` or disk quotas. This limit is often used as a less severe method of controlling disk space consumption. Since users do not generate core files and often do not delete them, this setting may save them from running out of disk space should a large program crash. |cputime |The maximum amount of CPU time a user's process may consume. Offending processes will be killed by the kernel. This is a limit on CPU _time_ consumed, not the percentage of the CPU as displayed in some of the fields generated by `top` and `ps`. |filesize |The maximum size of a file the user may own. Unlike disk quotas (crossref:disks[quotas,"Disk Quotas"]), this limit is enforced on individual files, not the set of all files a user owns. |maxproc |The maximum number of foreground and background processes a user can run. This limit may not be larger than the system limit specified by `kern.maxproc`. Setting this limit too small may hinder a user's productivity as some tasks, such as compiling a large program, start lots of processes. |memorylocked |The maximum amount of memory a process may request to be locked into main memory using man:mlock[2]. Some system-critical programs, such as man:amd[8], lock into main memory so that if the system begins to swap, they do not contribute to disk thrashing. |memoryuse |The maximum amount of memory a process may consume at any given time. It includes both core memory and swap usage. This is not a catch-all limit for restricting memory consumption, but is a good start. |openfiles |The maximum number of files a process may have open. In FreeBSD, files are used to represent sockets and IPC channels, so be careful not to set this too low. The system-wide limit for this is defined by `kern.maxfiles`. |sbsize |The limit on the amount of network memory a user may consume. This can be generally used to limit network communications. |stacksize |The maximum size of a process stack. This alone is not sufficient to limit the amount of memory a program may use, so it should be used in conjunction with other limits. |=== There are a few other things to remember when setting resource limits: * Processes started at system startup by [.filename]#/etc/rc# are assigned to the `daemon` login class. * Although the default [.filename]#/etc/login.conf# is a good source of reasonable values for most limits, they may not be appropriate for every system. Setting a limit too high may open the system up to abuse, while setting it too low may put a strain on productivity. * Xorg takes a lot of resources and encourages users to run more programs simultaneously. * Many limits apply to individual processes, not the user as a whole. For example, setting `openfiles` to `50` means that each process the user runs may open up to `50` files. The total amount of files a user may open is the value of `openfiles` multiplied by the value of `maxproc`. This also applies to memory consumption. For further information on resource limits and login classes and capabilities in general, refer to man:cap.mkdb[1], man:getrlimit[2], and man:login.conf[5]. === Enabling and Configuring Resource Limits The `kern.racct.enable` tunable must be set to a non-zero value. Custom kernels require specific configuration: [.programlisting] .... options RACCT options RCTL .... Once the system has rebooted into the new kernel, `rctl` may be used to set rules for the system. Rule syntax is controlled through the use of a subject, subject-id, resource, and action, as seen in this example rule: [.programlisting] .... user:trhodes:maxproc:deny=10/user .... In this rule, the subject is `user`, the subject-id is `trhodes`, the resource, `maxproc`, is the maximum number of processes, and the action is `deny`, which blocks any new processes from being created. This means that the user, `trhodes`, will be constrained to no greater than `10` processes. Other possible actions include logging to the console, passing a notification to man:devd[8], or sending a sigterm to the process. Some care must be taken when adding rules. Since this user is constrained to `10` processes, this example will prevent the user from performing other tasks after logging in and executing a `screen` session. Once a resource limit has been hit, an error will be printed, as in this example: [source,shell] .... % man test /usr/bin/man: Cannot fork: Resource temporarily unavailable eval: Cannot fork: Resource temporarily unavailable .... As another example, a jail can be prevented from exceeding a memory limit. This rule could be written as: [source,shell] .... # rctl -a jail:httpd:memoryuse:deny=2G/jail .... Rules will persist across reboots if they have been added to [.filename]#/etc/rctl.conf#. The format is a rule, without the preceding command. For example, the previous rule could be added as: [.programlisting] .... # Block jail from using more than 2G memory: jail:httpd:memoryuse:deny=2G/jail .... To remove a rule, use `rctl` to remove it from the list: [source,shell] .... # rctl -r user:trhodes:maxproc:deny=10/user .... A method for removing all rules is documented in man:rctl[8]. However, if removing all rules for a single user is required, this command may be issued: [source,shell] .... # rctl -r user:trhodes .... Many other resources exist which can be used to exert additional control over various `subjects`. See man:rctl[8] to learn about them. [[security-sudo]] == Shared Administration with Sudo System administrators often need the ability to grant enhanced permissions to users so they may perform privileged tasks. The idea that team members are provided access to a FreeBSD system to perform their specific tasks opens up unique challenges to every administrator. These team members only need a subset of access beyond normal end user levels; however, they almost always tell management they are unable to perform their tasks without superuser access. Thankfully, there is no reason to provide such access to end users because tools exist to manage this exact requirement. Up to this point, the security chapter has covered permitting access to authorized users and attempting to prevent unauthorized access. Another problem arises once authorized users have access to the system resources. In many cases, some users may need access to application startup scripts, or a team of administrators need to maintain the system. Traditionally, the standard users and groups, file permissions, and even the man:su[1] command would manage this access. And as applications required more access, as more users needed to use system resources, a better solution was required. The most used application is currently Sudo. Sudo allows administrators to configure more rigid access to system commands and provide for some advanced logging features. As a tool, it is available from the Ports Collection as package:security/sudo[] or by use of the man:pkg[8] utility. To use the man:pkg[8] tool: [source,shell] .... # pkg install sudo .... After the installation is complete, the installed `visudo` will open the configuration file with a text editor. Using `visudo` is highly recommended as it comes with a built in syntax checker to verify there are no errors before the file is saved. The configuration file is made up of several small sections which allow for extensive configuration. In the following example, web application maintainer, user1, needs to start, stop, and restart the web application known as _webservice_. To grant this user permission to perform these tasks, add this line to the end of [.filename]#/usr/local/etc/sudoers#: [.programlisting] .... user1 ALL=(ALL) /usr/sbin/service webservice * .... The user may now start _webservice_ using this command: [source,shell] .... % sudo /usr/sbin/service webservice start .... While this configuration allows a single user access to the webservice service; however, in most organizations, there is an entire web team in charge of managing the service. A single line can also give access to an entire group. These steps will create a web group, add a user to this group, and allow all members of the group to manage the service: [source,shell] .... # pw groupadd -g 6001 -n webteam .... Using the same man:pw[8] command, the user is added to the webteam group: [source,shell] .... # pw groupmod -m user1 -n webteam .... Finally, this line in [.filename]#/usr/local/etc/sudoers# allows any member of the webteam group to manage _webservice_: [.programlisting] .... %webteam ALL=(ALL) /usr/sbin/service webservice * .... Unlike man:su[1], Sudo only requires the end user password. This adds an advantage where users will not need shared passwords, a finding in most security audits and just bad all the way around. Users permitted to run applications with Sudo only enter their own passwords. This is more secure and gives better control than man:su[1], where the `root` password is entered and the user acquires all `root` permissions. [TIP] ==== Most organizations are moving or have moved toward a two factor authentication model. In these cases, the user may not have a password to enter. Sudo provides for these cases with the `NOPASSWD` variable. Adding it to the configuration above will allow all members of the _webteam_ group to manage the service without the password requirement: [.programlisting] .... %webteam ALL=(ALL) NOPASSWD: /usr/sbin/service webservice * .... ==== [[security-sudo-loggin]] === Logging Output An advantage to implementing Sudo is the ability to enable session logging. Using the built in log mechanisms and the included sudoreplay command, all commands initiated through Sudo are logged for later verification. To enable this feature, add a default log directory entry, this example uses a user variable. Several other log filename conventions exist, consult the manual page for sudoreplay for additional information. [.programlisting] .... Defaults iolog_dir=/var/log/sudo-io/%{user} .... [TIP] ==== This directory will be created automatically after the logging is configured. It is best to let the system create directory with default permissions just to be safe. In addition, this entry will also log administrators who use the sudoreplay command. To change this behavior, read and uncomment the logging options inside [.filename]#sudoers#. ==== Once this directive has been added to the [.filename]#sudoers# file, any user configuration can be updated with the request to log access. In the example shown, the updated _webteam_ entry would have the following additional changes: [.programlisting] .... %webteam ALL=(ALL) NOPASSWD: LOG_INPUT: LOG_OUTPUT: /usr/sbin/service webservice * .... From this point on, all _webteam_ members altering the status of the _webservice_ application will be logged. The list of previous and current sessions can be displayed with: [source,shell] .... # sudoreplay -l .... In the output, to replay a specific session, search for the `TSID=` entry, and pass that to sudoreplay with no other options to replay the session at normal speed. For example: [source,shell] .... # sudoreplay user1/00/00/02 .... [WARNING] ==== While sessions are logged, any administrator is able to remove sessions and leave only a question of why they had done so. It is worthwhile to add a daily check through an intrusion detection system (IDS) or similar software so that other administrators are alerted to manual alterations. ==== The `sudoreplay` is extremely extendable. Consult the documentation for more information. [[security-doas]] == Using doas as an alternative to sudo As an alternative to package:security/sudo[] package:security/doas[] can be used to provide the ability for users to get enhanced privileges. The doas utility is available via the ports collection in package:security/doas[] or via the man:pkg[8] utility. After the installation [.filename]#/usr/local/etc/doas.conf# must be configured to grant access for users for specific commands, or roles. The simpliest entry could be the following, which grants local_user root permissions without asking for its password when executing the doas command. [source,shell] .... permit nopass local_user as root .... For more configuration examples, please read man:doas.conf[5]. After the installation and configuration of the `doas` utility, a command can now be executed with enhanced privileges, like for example. [source,shell] .... $ doas vi /etc/rc.conf .... diff --git a/documentation/content/en/books/handbook/usb-device-mode/_index.adoc b/documentation/content/en/books/handbook/usb-device-mode/_index.adoc index 11c65d34fb..ba62cedfc5 100644 --- a/documentation/content/en/books/handbook/usb-device-mode/_index.adoc +++ b/documentation/content/en/books/handbook/usb-device-mode/_index.adoc @@ -1,316 +1,316 @@ --- title: Chapter 26. USB Device Mode / USB OTG part: Part III. System Administration prev: books/handbook/dtrace next: books/handbook/partiv description: This chapter covers the use of USB Device Mode and USB On The Go (USB OTG) in FreeBSD tags: ["OTG", "USB"] showBookMenu: true weight: 30 path: "/books/handbook/" --- [[usb-device-mode]] = USB Device Mode / USB OTG :doctype: book :toc: macro :toclevels: 1 :icons: font :sectnums: :sectnumlevels: 6 :sectnumoffset: 26 :partnums: :source-highlighter: rouge :experimental: :images-path: books/handbook/usb-device-mode/ ifdef::env-beastie[] ifdef::backend-html5[] :imagesdir: ../../../../images/{images-path} endif::[] ifndef::book[] include::shared/authors.adoc[] include::shared/mirrors.adoc[] include::shared/releases.adoc[] include::shared/attributes/attributes-{{% lang %}}.adoc[] include::shared/{{% lang %}}/teams.adoc[] include::shared/{{% lang %}}/mailing-lists.adoc[] include::shared/{{% lang %}}/urls.adoc[] toc::[] endif::[] ifdef::backend-pdf,backend-epub3[] include::../../../../../shared/asciidoctor.adoc[] endif::[] endif::[] ifndef::env-beastie[] toc::[] include::../../../../../shared/asciidoctor.adoc[] endif::[] [[usb-device-mode-synopsis]] == Synopsis This chapter covers the use of USB Device Mode and USB On The Go (USB OTG) in FreeBSD. This includes virtual serial consoles, virtual network interfaces, and virtual USB drives. When running on hardware that supports USB device mode or USB OTG, like that built into many embedded boards, the FreeBSD USB stack can run in _device mode_. Device mode makes it possible for the computer to present itself as different kinds of USB device classes, including serial ports, network adapters, and mass storage, or a combination thereof. A USB host like a laptop or desktop computer is able to access them just like physical USB devices. Device mode is sometimes called the "USB gadget mode". There are two basic ways the hardware can provide the device mode functionality: with a separate "client port", which only supports the device mode, and with a USB OTG port, which can provide both device and host mode. For USB OTG ports, the USB stack switches between host-side and device-side automatically, depending on what is connected to the port. Connecting a USB device like a memory stick to the port causes FreeBSD to switch to host mode. Connecting a USB host like a computer causes FreeBSD to switch to device mode. Single purpose "client ports" always work in device mode. What FreeBSD presents to the USB host depends on the `hw.usb.template` sysctl. Some templates provide a single device, such as a serial terminal; others provide multiple ones, which can all be used at the same time. An example is the template 10, which provides a mass storage device, a serial console, and a network interface. See man:usb_template[4] for the list of available values. Note that in some cases, depending on the hardware and the hosts operating system, for the host to notice the configuration change, it must be either physically disconnected and reconnected, or forced to rescan the USB bus in a system-specific way. When FreeBSD is running on the host, man:usbconfig[8] `reset` can be used. This also must be done after loading [.filename]#usb_template.ko# if the USB host was already connected to the USBOTG socket. After reading this chapter, you will know: * How to set up USB Device Mode functionality on FreeBSD. * How to configure the virtual serial port on FreeBSD. * How to connect to the virtual serial port from various operating systems. * How to configure FreeBSD to provide a virtual USB network interface. * How to configure FreeBSD to provide a virtual USB storage device. [[usb-device-mode-terminals]] == USB Virtual Serial Ports === Configuring USB Device Mode Serial Ports Virtual serial port support is provided by templates number 3, 8, and 10. Note that template 3 works with Microsoft Windows 10 without the need for special drivers and INF files. Other host operating systems work with all three templates. Both man:usb_template[4] and man:umodem[4] kernel modules must be loaded. To enable USB device mode serial ports, add those lines to [.filename]#/etc/ttys#: [.programlisting] .... ttyU0 "/usr/libexec/getty 3wire" vt100 onifconsole secure ttyU1 "/usr/libexec/getty 3wire" vt100 onifconsole secure .... Then add these lines to [.filename]#/etc/devd.conf#: [.programlisting] .... notify 100 { match "system" "DEVFS"; match "subsystem" "CDEV"; match "type" "CREATE"; match "cdev" "ttyU[0-9]+"; action "/sbin/init q"; }; .... Reload the configuration if man:devd[8] is already running: [source,shell] .... # service devd restart .... Make sure the necessary modules are loaded and the correct template is set at boot by adding those lines to [.filename]#/boot/loader.conf#, creating it if it does not already exist: [source,shell] .... umodem_load="YES" hw.usb.template=3 .... To load the module and set the template without rebooting use: [source,shell] .... # kldload umodem # sysctl hw.usb.template=3 .... === Connecting to USB Device Mode Serial Ports from FreeBSD To connect to a board configured to provide USB device mode serial ports, connect the USB host, such as a laptop, to the boards USB OTG or USB client port. Use `pstat -t` on the host to list the terminal lines. -Near the end of the list you should see a USB serial port, eg "ttyU0". +Near the end of the list you should see a USB serial port, e.g. "ttyU0". To open the connection, use: [source,shell] .... # cu -l /dev/ttyU0 .... After pressing the kbd:[Enter] key a few times you will see a login prompt. === Connecting to USB Device Mode Serial Ports from macOS To connect to a board configured to provide USB device mode serial ports, connect the USB host, such as a laptop, to the boards USB OTG or USB client port. To open the connection, use: [source,shell] .... # cu -l /dev/cu.usbmodemFreeBSD1 .... === Connecting to USB Device Mode Serial Ports from Linux To connect to a board configured to provide USB device mode serial ports, connect the USB host, such as a laptop, to the boards USB OTG or USB client port. To open the connection, use: [source,shell] .... # minicom -D /dev/ttyACM0 .... === Connecting to USB Device Mode Serial Ports from Microsoft Windows 10 To connect to a board configured to provide USB device mode serial ports, connect the USB host, such as a laptop, to the boards USB OTG or USB client port. To open a connection you will need a serial terminal program, such as PuTTY. To check the COM port name used by Windows, run Device Manager, expand "Ports (COM & LPT)". You will see a name similar to "USB Serial Device (COM4)". Run serial terminal program of your choice, for example PuTTY. In the PuTTY dialog set "Connection type" to "Serial", type the COMx obtained from Device Manager in the "Serial line" dialog box and click Open. [[usb-device-mode-network]] == USB Device Mode Network Interfaces Virtual network interfaces support is provided by templates number 1, 8, and 10. Note that none of them works with Microsoft Windows. Other host operating systems work with all three templates. Both man:usb_template[4] and man:if_cdce[4] kernel modules must be loaded. Make sure the necessary modules are loaded and the correct template is set at boot by adding those lines to [.filename]#/boot/loader.conf#, creating it if it does not already exist: [.programlisting] .... if_cdce_load="YES" hw.usb.template=1 .... To load the module and set the template without rebooting use: [source,shell] .... # kldload if_cdce # sysctl hw.usb.template=1 .... [[usb-device-mode-storage]] == USB Virtual Storage Device [NOTE] ==== The man:cfumass[4] driver is a USB device mode driver first available in FreeBSD 12.0. ==== Mass Storage target is provided by templates 0 and 10. Both man:usb_template[4] and man:cfumass[4] kernel modules must be loaded. man:cfumass[4] interfaces to the CTL subsystem, the same one that is used for iSCSI or Fibre Channel targets. On the host side, USB Mass Storage initiators can only access a single LUN, LUN 0. === Configuring USB Mass Storage Target Using the cfumass Startup Script The simplest way to set up a read-only USB storage target is to use the [.filename]#cfumass# rc script. To configure it this way, copy the files to be presented to the USB host machine into the `/var/cfumass` directory, and add this line to [.filename]#/etc/rc.conf#: [.programlisting] .... cfumass_enable="YES" .... To configure the target without restarting, run this command: [source,shell] .... # service cfumass start .... Differently from serial and network functionality, the template should not be set to 0 or 10 in [.filename]#/boot/loader.conf#. This is because the LUN must be set up before setting the template. The cfumass startup script sets the correct template number automatically when started. === Configuring USB Mass Storage Using Other Means The rest of this chapter provides detailed description of setting the target without using the cfumass rc file. -This is necessary if eg one wants to provide a writeable LUN. +This is necessary if e.g. one wants to provide a writeable LUN. USB Mass Storage does not require the man:ctld[8] daemon to be running, although it can be used if desired. This is different from iSCSI. Thus, there are two ways to configure the target: man:ctladm[8], or man:ctld[8]. Both require the [.filename]#cfumass.ko# kernel module to be loaded. The module can be loaded manually: [source,shell] .... # kldload cfumass .... If [.filename]#cfumass.ko# has not been built into the kernel, [.filename]#/boot/loader.conf# can be set to load the module at boot: [.programlisting] .... cfumass_load="YES" .... A LUN can be created without the man:ctld[8] daemon: [source,shell] .... # ctladm create -b block -o file=/data/target0 .... This presents the contents of the image file [.filename]#/data/target0# as a LUN to the USB host. The file must exist before executing the command. To configure the LUN at system startup, add the command to [.filename]#/etc/rc.local#. man:ctld[8] can also be used to manage LUNs. Create [.filename]#/etc/ctl.conf#, add a line to [.filename]#/etc/rc.conf# to make sure man:ctld[8] is automatically started at boot, and then start the daemon. This is an example of a simple [.filename]#/etc/ctl.conf# configuration file. Refer to man:ctl.conf[5] for a more complete description of the options. [.programlisting] .... target naa.50015178f369f092 { lun 0 { path /data/target0 size 4G } } .... The example creates a single target with a single LUN. The `naa.50015178f369f092` is a device identifier composed of 32 random hexadecimal digits. The `path` line defines the full path to a file or zvol backing the LUN. That file must exist before starting man:ctld[8]. The second line is optional and specifies the size of the LUN. To make sure the man:ctld[8] daemon is started at boot, add this line to [.filename]#/etc/rc.conf#: [.programlisting] .... ctld_enable="YES" .... To start man:ctld[8] now, run this command: [source,shell] .... # service ctld start .... As the man:ctld[8] daemon is started, it reads [.filename]#/etc/ctl.conf#. If this file is edited after the daemon starts, reload the changes so they take effect immediately: [source,shell] .... # service ctld reload ....