Index: head/crypto/openssh/pathnames.h =================================================================== --- head/crypto/openssh/pathnames.h (revision 169965) +++ head/crypto/openssh/pathnames.h (revision 169966) @@ -1,174 +1,174 @@ /* $OpenBSD: pathnames.h,v 1.16 2006/03/25 22:22:43 djm Exp $ */ /* * Author: Tatu Ylonen * Copyright (c) 1995 Tatu Ylonen , Espoo, Finland * All rights reserved * * As far as I am concerned, the code I have written for this software * can be used freely for any purpose. Any derived versions of this * software must be clearly marked as such, and if the derived work is * incompatible with the protocol description in the RFC file, it must be * called by a name other than "ssh" or "Secure Shell". */ #define ETCDIR "/etc" #ifndef SSHDIR #define SSHDIR ETCDIR "/ssh" #endif #ifndef _PATH_SSH_PIDDIR #define _PATH_SSH_PIDDIR "/var/run" #endif /* * System-wide file containing host keys of known hosts. This file should be * world-readable. */ #define _PATH_SSH_SYSTEM_HOSTFILE SSHDIR "/ssh_known_hosts" /* backward compat for protocol 2 */ #define _PATH_SSH_SYSTEM_HOSTFILE2 SSHDIR "/ssh_known_hosts2" /* * Of these, ssh_host_key must be readable only by root, whereas ssh_config * should be world-readable. */ #define _PATH_SERVER_CONFIG_FILE SSHDIR "/sshd_config" #define _PATH_HOST_CONFIG_FILE SSHDIR "/ssh_config" #define _PATH_HOST_KEY_FILE SSHDIR "/ssh_host_key" #define _PATH_HOST_DSA_KEY_FILE SSHDIR "/ssh_host_dsa_key" #define _PATH_HOST_RSA_KEY_FILE SSHDIR "/ssh_host_rsa_key" #define _PATH_DH_MODULI SSHDIR "/moduli" /* Backwards compatibility */ #define _PATH_DH_PRIMES SSHDIR "/primes" #ifndef _PATH_SSH_PROGRAM #define _PATH_SSH_PROGRAM "/usr/bin/ssh" #endif /* * The process id of the daemon listening for connections is saved here to * make it easier to kill the correct daemon when necessary. */ #define _PATH_SSH_DAEMON_PID_FILE _PATH_SSH_PIDDIR "/sshd.pid" /* * The directory in user\'s home directory in which the files reside. The * directory should be world-readable (though not all files are). */ #define _PATH_SSH_USER_DIR ".ssh" /* * Per-user file containing host keys of known hosts. This file need not be * readable by anyone except the user him/herself, though this does not * contain anything particularly secret. */ #define _PATH_SSH_USER_HOSTFILE "~/.ssh/known_hosts" /* backward compat for protocol 2 */ #define _PATH_SSH_USER_HOSTFILE2 "~/.ssh/known_hosts2" /* * Name of the default file containing client-side authentication key. This * file should only be readable by the user him/herself. */ #define _PATH_SSH_CLIENT_IDENTITY ".ssh/identity" #define _PATH_SSH_CLIENT_ID_DSA ".ssh/id_dsa" #define _PATH_SSH_CLIENT_ID_RSA ".ssh/id_rsa" /* * Configuration file in user\'s home directory. This file need not be * readable by anyone but the user him/herself, but does not contain anything * particularly secret. If the user\'s home directory resides on an NFS * volume where root is mapped to nobody, this may need to be world-readable. */ #define _PATH_SSH_USER_CONFFILE ".ssh/config" /* * File containing a list of those rsa keys that permit logging in as this * user. This file need not be readable by anyone but the user him/herself, * but does not contain anything particularly secret. If the user\'s home * directory resides on an NFS volume where root is mapped to nobody, this * may need to be world-readable. (This file is read by the daemon which is * running as root.) */ #define _PATH_SSH_USER_PERMITTED_KEYS ".ssh/authorized_keys" /* backward compat for protocol v2 */ #define _PATH_SSH_USER_PERMITTED_KEYS2 ".ssh/authorized_keys2" /* * Per-user and system-wide ssh "rc" files. These files are executed with * /bin/sh before starting the shell or command if they exist. They will be * passed "proto cookie" as arguments if X11 forwarding with spoofing is in * use. xauth will be run if neither of these exists. */ #define _PATH_SSH_USER_RC ".ssh/rc" #define _PATH_SSH_SYSTEM_RC SSHDIR "/sshrc" /* * Ssh-only version of /etc/hosts.equiv. Additionally, the daemon may use * ~/.rhosts and /etc/hosts.equiv if rhosts authentication is enabled. */ #define _PATH_SSH_HOSTS_EQUIV SSHDIR "/shosts.equiv" #define _PATH_RHOSTS_EQUIV "/etc/hosts.equiv" /* * Default location of askpass */ #ifndef _PATH_SSH_ASKPASS_DEFAULT -#define _PATH_SSH_ASKPASS_DEFAULT "/usr/X11R6/bin/ssh-askpass" +#define _PATH_SSH_ASKPASS_DEFAULT "/usr/local/bin/ssh-askpass" #endif /* Location of ssh-keysign for hostbased authentication */ #ifndef _PATH_SSH_KEY_SIGN #define _PATH_SSH_KEY_SIGN "/usr/libexec/ssh-keysign" #endif /* xauth for X11 forwarding */ #ifndef _PATH_XAUTH -#define _PATH_XAUTH "/usr/X11R6/bin/xauth" +#define _PATH_XAUTH "/usr/local/bin/xauth" #endif /* UNIX domain socket for X11 server; displaynum will replace %u */ #ifndef _PATH_UNIX_X #define _PATH_UNIX_X "/tmp/.X11-unix/X%u" #endif /* for scp */ #ifndef _PATH_CP #define _PATH_CP "cp" #endif /* for sftp */ #ifndef _PATH_SFTP_SERVER #define _PATH_SFTP_SERVER "/usr/libexec/sftp-server" #endif /* chroot directory for unprivileged user when UsePrivilegeSeparation=yes */ #ifndef _PATH_PRIVSEP_CHROOT_DIR #define _PATH_PRIVSEP_CHROOT_DIR "/var/empty" #endif /* for passwd change */ #ifndef _PATH_PASSWD_PROG #define _PATH_PASSWD_PROG "/usr/bin/passwd" #endif #ifndef _PATH_LS #define _PATH_LS "ls" #endif /* path to login program */ #ifndef LOGIN_PROGRAM # ifdef LOGIN_PROGRAM_FALLBACK # define LOGIN_PROGRAM LOGIN_PROGRAM_FALLBACK # else # define LOGIN_PROGRAM "/usr/bin/login" # endif #endif /* LOGIN_PROGRAM */ /* Askpass program define */ #ifndef ASKPASS_PROGRAM #define ASKPASS_PROGRAM "/usr/lib/ssh/ssh-askpass" #endif /* ASKPASS_PROGRAM */ Index: head/crypto/openssh/ssh_config.5 =================================================================== --- head/crypto/openssh/ssh_config.5 (revision 169965) +++ head/crypto/openssh/ssh_config.5 (revision 169966) @@ -1,1111 +1,1111 @@ .\" -*- nroff -*- .\" .\" Author: Tatu Ylonen .\" Copyright (c) 1995 Tatu Ylonen , Espoo, Finland .\" All rights reserved .\" .\" As far as I am concerned, the code I have written for this software .\" can be used freely for any purpose. Any derived versions of this .\" software must be clearly marked as such, and if the derived work is .\" incompatible with the protocol description in the RFC file, it must be .\" called by a name other than "ssh" or "Secure Shell". .\" .\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved. .\" Copyright (c) 1999 Aaron Campbell. All rights reserved. .\" Copyright (c) 1999 Theo de Raadt. All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. .\" .\" $OpenBSD: ssh_config.5,v 1.97 2006/07/27 08:00:50 jmc Exp $ .\" $FreeBSD$ .Dd September 25, 1999 .Dt SSH_CONFIG 5 .Os .Sh NAME .Nm ssh_config .Nd OpenSSH SSH client configuration files .Sh SYNOPSIS .Bl -tag -width Ds -compact .It Pa ~/.ssh/config .It Pa /etc/ssh/ssh_config .El .Sh DESCRIPTION .Xr ssh 1 obtains configuration data from the following sources in the following order: .Pp .Bl -enum -offset indent -compact .It command-line options .It user's configuration file .Pq Pa ~/.ssh/config .It system-wide configuration file .Pq Pa /etc/ssh/ssh_config .El .Pp For each parameter, the first obtained value will be used. The configuration files contain sections separated by .Dq Host specifications, and that section is only applied for hosts that match one of the patterns given in the specification. The matched host name is the one given on the command line. .Pp Since the first obtained value for each parameter is used, more host-specific declarations should be given near the beginning of the file, and general defaults at the end. .Pp The configuration file has the following format: .Pp Empty lines and lines starting with .Ql # are comments. Otherwise a line is of the format .Dq keyword arguments . Configuration options may be separated by whitespace or optional whitespace and exactly one .Ql = ; the latter format is useful to avoid the need to quote whitespace when specifying configuration options using the .Nm ssh , .Nm scp , and .Nm sftp .Fl o option. Arguments may optionally be enclosed in double quotes .Pq \&" in order to represent arguments containing spaces. .Pp The possible keywords and their meanings are as follows (note that keywords are case-insensitive and arguments are case-sensitive): .Bl -tag -width Ds .It Cm Host Restricts the following declarations (up to the next .Cm Host keyword) to be only for those hosts that match one of the patterns given after the keyword. A single .Ql * as a pattern can be used to provide global defaults for all hosts. The host is the .Ar hostname argument given on the command line (i.e. the name is not converted to a canonicalized host name before matching). .Pp See .Sx PATTERNS for more information on patterns. .It Cm AddressFamily Specifies which address family to use when connecting. Valid arguments are .Dq any , .Dq inet (use IPv4 only), or .Dq inet6 (use IPv6 only). .It Cm BatchMode If set to .Dq yes , passphrase/password querying will be disabled. This option is useful in scripts and other batch jobs where no user is present to supply the password. The argument must be .Dq yes or .Dq no . The default is .Dq no . .It Cm BindAddress Use the specified address on the local machine as the source address of the connection. Only useful on systems with more than one address. Note that this option does not work if .Cm UsePrivilegedPort is set to .Dq yes . .It Cm ChallengeResponseAuthentication Specifies whether to use challenge-response authentication. The argument to this keyword must be .Dq yes or .Dq no . The default is .Dq yes . .It Cm CheckHostIP If this flag is set to .Dq yes , .Xr ssh 1 will additionally check the host IP address in the .Pa known_hosts file. This allows ssh to detect if a host key changed due to DNS spoofing. If the option is set to .Dq no , the check will not be executed. The default is .Dq no . .It Cm Cipher Specifies the cipher to use for encrypting the session in protocol version 1. Currently, .Dq blowfish , .Dq 3des , and .Dq des are supported. .Ar des is only supported in the .Xr ssh 1 client for interoperability with legacy protocol 1 implementations that do not support the .Ar 3des cipher. Its use is strongly discouraged due to cryptographic weaknesses. The default is .Dq 3des . .It Cm Ciphers Specifies the ciphers allowed for protocol version 2 in order of preference. Multiple ciphers must be comma-separated. The supported ciphers are .Dq 3des-cbc , .Dq aes128-cbc , .Dq aes192-cbc , .Dq aes256-cbc , .Dq aes128-ctr , .Dq aes192-ctr , .Dq aes256-ctr , .Dq arcfour128 , .Dq arcfour256 , .Dq arcfour , .Dq blowfish-cbc , and .Dq cast128-cbc . The default is: .Bd -literal -offset 3n aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour128, arcfour256,arcfour,aes192-cbc,aes256-cbc,aes128-ctr, aes192-ctr,aes256-ctr .Ed .It Cm ClearAllForwardings Specifies that all local, remote, and dynamic port forwardings specified in the configuration files or on the command line be cleared. This option is primarily useful when used from the .Xr ssh 1 command line to clear port forwardings set in configuration files, and is automatically set by .Xr scp 1 and .Xr sftp 1 . The argument must be .Dq yes or .Dq no . The default is .Dq no . .It Cm Compression Specifies whether to use compression. The argument must be .Dq yes or .Dq no . The default is .Dq no . .It Cm CompressionLevel Specifies the compression level to use if compression is enabled. The argument must be an integer from 1 (fast) to 9 (slow, best). The default level is 6, which is good for most applications. The meaning of the values is the same as in .Xr gzip 1 . Note that this option applies to protocol version 1 only. .It Cm ConnectionAttempts Specifies the number of tries (one per second) to make before exiting. The argument must be an integer. This may be useful in scripts if the connection sometimes fails. The default is 1. .It Cm ConnectTimeout Specifies the timeout (in seconds) used when connecting to the SSH server, instead of using the default system TCP timeout. This value is used only when the target is down or really unreachable, not when it refuses the connection. .It Cm ControlMaster Enables the sharing of multiple sessions over a single network connection. When set to .Dq yes , .Xr ssh 1 will listen for connections on a control socket specified using the .Cm ControlPath argument. Additional sessions can connect to this socket using the same .Cm ControlPath with .Cm ControlMaster set to .Dq no (the default). These sessions will try to reuse the master instance's network connection rather than initiating new ones, but will fall back to connecting normally if the control socket does not exist, or is not listening. .Pp Setting this to .Dq ask will cause ssh to listen for control connections, but require confirmation using the .Ev SSH_ASKPASS program before they are accepted (see .Xr ssh-add 1 for details). If the .Cm ControlPath cannot be opened, ssh will continue without connecting to a master instance. .Pp X11 and .Xr ssh-agent 1 forwarding is supported over these multiplexed connections, however the display and agent forwarded will be the one belonging to the master connection i.e. it is not possible to forward multiple displays or agents. .Pp Two additional options allow for opportunistic multiplexing: try to use a master connection but fall back to creating a new one if one does not already exist. These options are: .Dq auto and .Dq autoask . The latter requires confirmation like the .Dq ask option. .It Cm ControlPath Specify the path to the control socket used for connection sharing as described in the .Cm ControlMaster section above or the string .Dq none to disable connection sharing. In the path, .Ql %l will be substituted by the local host name, .Ql %h will be substituted by the target host name, .Ql %p the port, and .Ql %r by the remote login username. It is recommended that any .Cm ControlPath used for opportunistic connection sharing include at least %h, %p, and %r. This ensures that shared connections are uniquely identified. .It Cm DynamicForward Specifies that a TCP port on the local machine be forwarded over the secure channel, and the application protocol is then used to determine where to connect to from the remote machine. .Pp The argument must be .Sm off .Oo Ar bind_address : Oc Ar port . .Sm on IPv6 addresses can be specified by enclosing addresses in square brackets or by using an alternative syntax: .Oo Ar bind_address Ns / Oc Ns Ar port . By default, the local port is bound in accordance with the .Cm GatewayPorts setting. However, an explicit .Ar bind_address may be used to bind the connection to a specific address. The .Ar bind_address of .Dq localhost indicates that the listening port be bound for local use only, while an empty address or .Sq * indicates that the port should be available from all interfaces. .Pp Currently the SOCKS4 and SOCKS5 protocols are supported, and .Xr ssh 1 will act as a SOCKS server. Multiple forwardings may be specified, and additional forwardings can be given on the command line. Only the superuser can forward privileged ports. .It Cm EnableSSHKeysign Setting this option to .Dq yes in the global client configuration file .Pa /etc/ssh/ssh_config enables the use of the helper program .Xr ssh-keysign 8 during .Cm HostbasedAuthentication . The argument must be .Dq yes or .Dq no . The default is .Dq no . This option should be placed in the non-hostspecific section. See .Xr ssh-keysign 8 for more information. .It Cm EscapeChar Sets the escape character (default: .Ql ~ ) . The escape character can also be set on the command line. The argument should be a single character, .Ql ^ followed by a letter, or .Dq none to disable the escape character entirely (making the connection transparent for binary data). .It Cm ExitOnForwardFailure Specifies whether .Xr ssh 1 should terminate the connection if it cannot set up all requested dynamic, local, and remote port forwardings. The argument must be .Dq yes or .Dq no . The default is .Dq no . .It Cm ForwardAgent Specifies whether the connection to the authentication agent (if any) will be forwarded to the remote machine. The argument must be .Dq yes or .Dq no . The default is .Dq no . .Pp Agent forwarding should be enabled with caution. Users with the ability to bypass file permissions on the remote host (for the agent's Unix-domain socket) can access the local agent through the forwarded connection. An attacker cannot obtain key material from the agent, however they can perform operations on the keys that enable them to authenticate using the identities loaded into the agent. .It Cm ForwardX11 Specifies whether X11 connections will be automatically redirected over the secure channel and .Ev DISPLAY set. The argument must be .Dq yes or .Dq no . The default is .Dq no . .Pp X11 forwarding should be enabled with caution. Users with the ability to bypass file permissions on the remote host (for the user's X11 authorization database) can access the local X11 display through the forwarded connection. An attacker may then be able to perform activities such as keystroke monitoring if the .Cm ForwardX11Trusted option is also enabled. .It Cm ForwardX11Trusted If this option is set to .Dq yes , remote X11 clients will have full access to the original X11 display. .Pp If this option is set to .Dq no , remote X11 clients will be considered untrusted and prevented from stealing or tampering with data belonging to trusted X11 clients. Furthermore, the .Xr xauth 1 token used for the session will be set to expire after 20 minutes. Remote clients will be refused access after this time. .Pp The default is .Dq no . .Pp See the X11 SECURITY extension specification for full details on the restrictions imposed on untrusted clients. .It Cm GatewayPorts Specifies whether remote hosts are allowed to connect to local forwarded ports. By default, .Xr ssh 1 binds local port forwardings to the loopback address. This prevents other remote hosts from connecting to forwarded ports. .Cm GatewayPorts can be used to specify that ssh should bind local port forwardings to the wildcard address, thus allowing remote hosts to connect to forwarded ports. The argument must be .Dq yes or .Dq no . The default is .Dq no . .It Cm GlobalKnownHostsFile Specifies a file to use for the global host key database instead of .Pa /etc/ssh/ssh_known_hosts . .It Cm GSSAPIAuthentication Specifies whether user authentication based on GSSAPI is allowed. The default is .Dq no . Note that this option applies to protocol version 2 only. .It Cm GSSAPIDelegateCredentials Forward (delegate) credentials to the server. The default is .Dq no . Note that this option applies to protocol version 2 only. .It Cm HashKnownHosts Indicates that .Xr ssh 1 should hash host names and addresses when they are added to .Pa ~/.ssh/known_hosts . These hashed names may be used normally by .Xr ssh 1 and .Xr sshd 8 , but they do not reveal identifying information should the file's contents be disclosed. The default is .Dq no . Note that existing names and addresses in known hosts files will not be converted automatically, but may be manually hashed using .Xr ssh-keygen 1 . .It Cm HostbasedAuthentication Specifies whether to try rhosts based authentication with public key authentication. The argument must be .Dq yes or .Dq no . The default is .Dq no . This option applies to protocol version 2 only and is similar to .Cm RhostsRSAAuthentication . .It Cm HostKeyAlgorithms Specifies the protocol version 2 host key algorithms that the client wants to use in order of preference. The default for this option is: .Dq ssh-rsa,ssh-dss . .It Cm HostKeyAlias Specifies an alias that should be used instead of the real host name when looking up or saving the host key in the host key database files. This option is useful for tunneling SSH connections or for multiple servers running on a single host. .It Cm HostName Specifies the real host name to log into. This can be used to specify nicknames or abbreviations for hosts. The default is the name given on the command line. Numeric IP addresses are also permitted (both on the command line and in .Cm HostName specifications). .It Cm IdentitiesOnly Specifies that .Xr ssh 1 should only use the authentication identity files configured in the .Nm files, even if .Xr ssh-agent 1 offers more identities. The argument to this keyword must be .Dq yes or .Dq no . This option is intended for situations where ssh-agent offers many different identities. The default is .Dq no . .It Cm IdentityFile Specifies a file from which the user's RSA or DSA authentication identity is read. The default is .Pa ~/.ssh/identity for protocol version 1, and .Pa ~/.ssh/id_rsa and .Pa ~/.ssh/id_dsa for protocol version 2. Additionally, any identities represented by the authentication agent will be used for authentication. .Pp The file name may use the tilde syntax to refer to a user's home directory or one of the following escape characters: .Ql %d (local user's home directory), .Ql %u (local user name), .Ql %l (local host name), .Ql %h (remote host name) or .Ql %r (remote user name). .Pp It is possible to have multiple identity files specified in configuration files; all these identities will be tried in sequence. .It Cm KbdInteractiveDevices Specifies the list of methods to use in keyboard-interactive authentication. Multiple method names must be comma-separated. The default is to use the server specified list. The methods available vary depending on what the server supports. For an OpenSSH server, it may be zero or more of: .Dq bsdauth , .Dq pam , and .Dq skey . .It Cm LocalCommand Specifies a command to execute on the local machine after successfully connecting to the server. The command string extends to the end of the line, and is executed with .Pa /bin/sh . This directive is ignored unless .Cm PermitLocalCommand has been enabled. .It Cm LocalForward Specifies that a TCP port on the local machine be forwarded over the secure channel to the specified host and port from the remote machine. The first argument must be .Sm off .Oo Ar bind_address : Oc Ar port .Sm on and the second argument must be .Ar host : Ns Ar hostport . IPv6 addresses can be specified by enclosing addresses in square brackets or by using an alternative syntax: .Oo Ar bind_address Ns / Oc Ns Ar port and .Ar host Ns / Ns Ar hostport . Multiple forwardings may be specified, and additional forwardings can be given on the command line. Only the superuser can forward privileged ports. By default, the local port is bound in accordance with the .Cm GatewayPorts setting. However, an explicit .Ar bind_address may be used to bind the connection to a specific address. The .Ar bind_address of .Dq localhost indicates that the listening port be bound for local use only, while an empty address or .Sq * indicates that the port should be available from all interfaces. .It Cm LogLevel Gives the verbosity level that is used when logging messages from .Xr ssh 1 . The possible values are: QUIET, FATAL, ERROR, INFO, VERBOSE, DEBUG, DEBUG1, DEBUG2, and DEBUG3. The default is INFO. DEBUG and DEBUG1 are equivalent. DEBUG2 and DEBUG3 each specify higher levels of verbose output. .It Cm MACs Specifies the MAC (message authentication code) algorithms in order of preference. The MAC algorithm is used in protocol version 2 for data integrity protection. Multiple algorithms must be comma-separated. The default is: .Dq hmac-md5,hmac-sha1,hmac-ripemd160,hmac-sha1-96,hmac-md5-96 . .It Cm NoHostAuthenticationForLocalhost This option can be used if the home directory is shared across machines. In this case localhost will refer to a different machine on each of the machines and the user will get many warnings about changed host keys. However, this option disables host authentication for localhost. The argument to this keyword must be .Dq yes or .Dq no . The default is to check the host key for localhost. .It Cm NumberOfPasswordPrompts Specifies the number of password prompts before giving up. The argument to this keyword must be an integer. The default is 3. .It Cm PasswordAuthentication Specifies whether to use password authentication. The argument to this keyword must be .Dq yes or .Dq no . The default is .Dq yes . .It Cm PermitLocalCommand Allow local command execution via the .Ic LocalCommand option or using the .Ic !\& Ns Ar command escape sequence in .Xr ssh 1 . The argument must be .Dq yes or .Dq no . The default is .Dq no . .It Cm Port Specifies the port number to connect on the remote host. The default is 22. .It Cm PreferredAuthentications Specifies the order in which the client should try protocol 2 authentication methods. This allows a client to prefer one method (e.g.\& .Cm keyboard-interactive ) over another method (e.g.\& .Cm password ) The default for this option is: .Do gssapi-with-mic , hostbased, publickey, keyboard-interactive, password .Dc . .It Cm Protocol Specifies the protocol versions .Xr ssh 1 should support in order of preference. The possible values are .Sq 1 and .Sq 2 . Multiple versions must be comma-separated. The default is .Dq 2,1 . This means that ssh tries version 2 and falls back to version 1 if version 2 is not available. .It Cm ProxyCommand Specifies the command to use to connect to the server. The command string extends to the end of the line, and is executed with .Pa /bin/sh . In the command string, .Ql %h will be substituted by the host name to connect and .Ql %p by the port. The command can be basically anything, and should read from its standard input and write to its standard output. It should eventually connect an .Xr sshd 8 server running on some machine, or execute .Ic sshd -i somewhere. Host key management will be done using the HostName of the host being connected (defaulting to the name typed by the user). Setting the command to .Dq none disables this option entirely. Note that .Cm CheckHostIP is not available for connects with a proxy command. .Pp This directive is useful in conjunction with .Xr nc 1 and its proxy support. For example, the following directive would connect via an HTTP proxy at 192.0.2.0: .Bd -literal -offset 3n ProxyCommand /usr/bin/nc -X connect -x 192.0.2.0:8080 %h %p .Ed .It Cm PubkeyAuthentication Specifies whether to try public key authentication. The argument to this keyword must be .Dq yes or .Dq no . The default is .Dq yes . This option applies to protocol version 2 only. .It Cm RekeyLimit Specifies the maximum amount of data that may be transmitted before the session key is renegotiated. The argument is the number of bytes, with an optional suffix of .Sq K , .Sq M , or .Sq G to indicate Kilobytes, Megabytes, or Gigabytes, respectively. The default is between .Sq 1G and .Sq 4G , depending on the cipher. This option applies to protocol version 2 only. .It Cm RemoteForward Specifies that a TCP port on the remote machine be forwarded over the secure channel to the specified host and port from the local machine. The first argument must be .Sm off .Oo Ar bind_address : Oc Ar port .Sm on and the second argument must be .Ar host : Ns Ar hostport . IPv6 addresses can be specified by enclosing addresses in square brackets or by using an alternative syntax: .Oo Ar bind_address Ns / Oc Ns Ar port and .Ar host Ns / Ns Ar hostport . Multiple forwardings may be specified, and additional forwardings can be given on the command line. Only the superuser can forward privileged ports. .Pp If the .Ar bind_address is not specified, the default is to only bind to loopback addresses. If the .Ar bind_address is .Ql * or an empty string, then the forwarding is requested to listen on all interfaces. Specifying a remote .Ar bind_address will only succeed if the server's .Cm GatewayPorts option is enabled (see .Xr sshd_config 5 ) . .It Cm RhostsRSAAuthentication Specifies whether to try rhosts based authentication with RSA host authentication. The argument must be .Dq yes or .Dq no . The default is .Dq no . This option applies to protocol version 1 only and requires .Xr ssh 1 to be setuid root. .It Cm RSAAuthentication Specifies whether to try RSA authentication. The argument to this keyword must be .Dq yes or .Dq no . RSA authentication will only be attempted if the identity file exists, or an authentication agent is running. The default is .Dq yes . Note that this option applies to protocol version 1 only. .It Cm SendEnv Specifies what variables from the local .Xr environ 7 should be sent to the server. Note that environment passing is only supported for protocol 2. The server must also support it, and the server must be configured to accept these environment variables. Refer to .Cm AcceptEnv in .Xr sshd_config 5 for how to configure the server. Variables are specified by name, which may contain wildcard characters. Multiple environment variables may be separated by whitespace or spread across multiple .Cm SendEnv directives. The default is not to send any environment variables. .Pp See .Sx PATTERNS for more information on patterns. .It Cm ServerAliveCountMax Sets the number of server alive messages (see below) which may be sent without .Xr ssh 1 receiving any messages back from the server. If this threshold is reached while server alive messages are being sent, ssh will disconnect from the server, terminating the session. It is important to note that the use of server alive messages is very different from .Cm TCPKeepAlive (below). The server alive messages are sent through the encrypted channel and therefore will not be spoofable. The TCP keepalive option enabled by .Cm TCPKeepAlive is spoofable. The server alive mechanism is valuable when the client or server depend on knowing when a connection has become inactive. .Pp The default value is 3. If, for example, .Cm ServerAliveInterval (see below) is set to 15 and .Cm ServerAliveCountMax is left at the default, if the server becomes unresponsive, ssh will disconnect after approximately 45 seconds. This option applies to protocol version 2 only. .It Cm ServerAliveInterval Sets a timeout interval in seconds after which if no data has been received from the server, .Xr ssh 1 will send a message through the encrypted channel to request a response from the server. The default is 0, indicating that these messages will not be sent to the server. This option applies to protocol version 2 only. .It Cm SmartcardDevice Specifies which smartcard device to use. The argument to this keyword is the device .Xr ssh 1 should use to communicate with a smartcard used for storing the user's private RSA key. By default, no device is specified and smartcard support is not activated. .It Cm StrictHostKeyChecking If this flag is set to .Dq yes , .Xr ssh 1 will never automatically add host keys to the .Pa ~/.ssh/known_hosts file, and refuses to connect to hosts whose host key has changed. This provides maximum protection against trojan horse attacks, though it can be annoying when the .Pa /etc/ssh/ssh_known_hosts file is poorly maintained or when connections to new hosts are frequently made. This option forces the user to manually add all new hosts. If this flag is set to .Dq no , ssh will automatically add new host keys to the user known hosts files. If this flag is set to .Dq ask , new host keys will be added to the user known host files only after the user has confirmed that is what they really want to do, and ssh will refuse to connect to hosts whose host key has changed. The host keys of known hosts will be verified automatically in all cases. The argument must be .Dq yes , .Dq no , or .Dq ask . The default is .Dq ask . .It Cm TCPKeepAlive Specifies whether the system should send TCP keepalive messages to the other side. If they are sent, death of the connection or crash of one of the machines will be properly noticed. However, this means that connections will die if the route is down temporarily, and some people find it annoying. .Pp The default is .Dq yes (to send TCP keepalive messages), and the client will notice if the network goes down or the remote host dies. This is important in scripts, and many users want it too. .Pp To disable TCP keepalive messages, the value should be set to .Dq no . .It Cm Tunnel Request .Xr tun 4 device forwarding between the client and the server. The argument must be .Dq yes , .Dq point-to-point (layer 3), .Dq ethernet (layer 2), or .Dq no . Specifying .Dq yes requests the default tunnel mode, which is .Dq point-to-point . The default is .Dq no . .It Cm TunnelDevice Specifies the .Xr tun 4 devices to open on the client .Pq Ar local_tun and the server .Pq Ar remote_tun . .Pp The argument must be .Sm off .Ar local_tun Op : Ar remote_tun . .Sm on The devices may be specified by numerical ID or the keyword .Dq any , which uses the next available tunnel device. If .Ar remote_tun is not specified, it defaults to .Dq any . The default is .Dq any:any . .It Cm UsePrivilegedPort Specifies whether to use a privileged port for outgoing connections. The argument must be .Dq yes or .Dq no . The default is .Dq no . If set to .Dq yes , .Xr ssh 1 must be setuid root. Note that this option must be set to .Dq yes for .Cm RhostsRSAAuthentication with older servers. .It Cm User Specifies the user to log in as. This can be useful when a different user name is used on different machines. This saves the trouble of having to remember to give the user name on the command line. .It Cm UserKnownHostsFile Specifies a file to use for the user host key database instead of .Pa ~/.ssh/known_hosts . .It Cm VerifyHostKeyDNS Specifies whether to verify the remote key using DNS and SSHFP resource records. If this option is set to .Dq yes , the client will implicitly trust keys that match a secure fingerprint from DNS. Insecure fingerprints will be handled as if this option was set to .Dq ask . If this option is set to .Dq ask , information on fingerprint match will be displayed, but the user will still need to confirm new host keys according to the .Cm StrictHostKeyChecking option. The argument must be .Dq yes , .Dq no , or .Dq ask . The default is .Dq no . Note that this option applies to protocol version 2 only. .Pp See also .Sx VERIFYING HOST KEYS in .Xr ssh 1 . .It Cm VersionAddendum Specifies a string to append to the regular version string to identify OS- or site-specific modifications. The default is .Dq FreeBSD-20061110 . .It Cm XAuthLocation Specifies the full pathname of the .Xr xauth 1 program. The default is -.Pa /usr/X11R6/bin/xauth . +.Pa /usr/local/bin/xauth . .El .Sh PATTERNS A .Em pattern consists of zero or more non-whitespace characters, .Sq * (a wildcard that matches zero or more characters), or .Sq ?\& (a wildcard that matches exactly one character). For example, to specify a set of declarations for any host in the .Dq .co.uk set of domains, the following pattern could be used: .Pp .Dl Host *.co.uk .Pp The following pattern would match any host in the 192.168.0.[0-9] network range: .Pp .Dl Host 192.168.0.? .Pp A .Em pattern-list is a comma-separated list of patterns. Patterns within pattern-lists may be negated by preceding them with an exclamation mark .Pq Sq !\& . For example, to allow a key to be used from anywhere within an organisation except from the .Dq dialup pool, the following entry (in authorized_keys) could be used: .Pp .Dl from=\&"!*.dialup.example.com,*.example.com\&" .Sh FILES .Bl -tag -width Ds .It Pa ~/.ssh/config This is the per-user configuration file. The format of this file is described above. This file is used by the SSH client. Because of the potential for abuse, this file must have strict permissions: read/write for the user, and not accessible by others. .It Pa /etc/ssh/ssh_config Systemwide configuration file. This file provides defaults for those values that are not specified in the user's configuration file, and for those users who do not have a configuration file. This file must be world-readable. .El .Sh SEE ALSO .Xr ssh 1 .Sh AUTHORS OpenSSH is a derivative of the original and free ssh 1.2.12 release by Tatu Ylonen. Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo de Raadt and Dug Song removed many bugs, re-added newer features and created OpenSSH. Markus Friedl contributed the support for SSH protocol versions 1.5 and 2.0. Index: head/crypto/openssh/sshd_config.5 =================================================================== --- head/crypto/openssh/sshd_config.5 (revision 169965) +++ head/crypto/openssh/sshd_config.5 (revision 169966) @@ -1,997 +1,997 @@ .\" -*- nroff -*- .\" .\" Author: Tatu Ylonen .\" Copyright (c) 1995 Tatu Ylonen , Espoo, Finland .\" All rights reserved .\" .\" As far as I am concerned, the code I have written for this software .\" can be used freely for any purpose. Any derived versions of this .\" software must be clearly marked as such, and if the derived work is .\" incompatible with the protocol description in the RFC file, it must be .\" called by a name other than "ssh" or "Secure Shell". .\" .\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved. .\" Copyright (c) 1999 Aaron Campbell. All rights reserved. .\" Copyright (c) 1999 Theo de Raadt. All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. .\" .\" $OpenBSD: sshd_config.5,v 1.70 2006/08/21 08:14:01 dtucker Exp $ .\" $FreeBSD$ .Dd September 25, 1999 .Dt SSHD_CONFIG 5 .Os .Sh NAME .Nm sshd_config .Nd OpenSSH SSH daemon configuration file .Sh SYNOPSIS .Bl -tag -width Ds -compact .It Pa /etc/ssh/sshd_config .El .Sh DESCRIPTION .Xr sshd 8 reads configuration data from .Pa /etc/ssh/sshd_config (or the file specified with .Fl f on the command line). The file contains keyword-argument pairs, one per line. Lines starting with .Ql # and empty lines are interpreted as comments. Arguments may optionally be enclosed in double quotes .Pq \&" in order to represent arguments containing spaces. .Pp The possible keywords and their meanings are as follows (note that keywords are case-insensitive and arguments are case-sensitive): .Bl -tag -width Ds .It Cm AcceptEnv Specifies what environment variables sent by the client will be copied into the session's .Xr environ 7 . See .Cm SendEnv in .Xr ssh_config 5 for how to configure the client. Note that environment passing is only supported for protocol 2. Variables are specified by name, which may contain the wildcard characters .Ql * and .Ql \&? . Multiple environment variables may be separated by whitespace or spread across multiple .Cm AcceptEnv directives. Be warned that some environment variables could be used to bypass restricted user environments. For this reason, care should be taken in the use of this directive. The default is not to accept any environment variables. .It Cm AddressFamily Specifies which address family should be used by .Xr sshd 8 . Valid arguments are .Dq any , .Dq inet (use IPv4 only), or .Dq inet6 (use IPv6 only). The default is .Dq any . .It Cm AllowGroups This keyword can be followed by a list of group name patterns, separated by spaces. If specified, login is allowed only for users whose primary group or supplementary group list matches one of the patterns. Only group names are valid; a numerical group ID is not recognized. By default, login is allowed for all groups. The allow/deny directives are processed in the following order: .Cm DenyUsers , .Cm AllowUsers , .Cm DenyGroups , and finally .Cm AllowGroups . .Pp See .Sx PATTERNS in .Xr ssh_config 5 for more information on patterns. .It Cm AllowTcpForwarding Specifies whether TCP forwarding is permitted. The default is .Dq yes . Note that disabling TCP forwarding does not improve security unless users are also denied shell access, as they can always install their own forwarders. .It Cm AllowUsers This keyword can be followed by a list of user name patterns, separated by spaces. If specified, login is allowed only for user names that match one of the patterns. Only user names are valid; a numerical user ID is not recognized. By default, login is allowed for all users. If the pattern takes the form USER@HOST then USER and HOST are separately checked, restricting logins to particular users from particular hosts. The allow/deny directives are processed in the following order: .Cm DenyUsers , .Cm AllowUsers , .Cm DenyGroups , and finally .Cm AllowGroups . .Pp See .Sx PATTERNS in .Xr ssh_config 5 for more information on patterns. .It Cm AuthorizedKeysFile Specifies the file that contains the public keys that can be used for user authentication. .Cm AuthorizedKeysFile may contain tokens of the form %T which are substituted during connection setup. The following tokens are defined: %% is replaced by a literal '%', %h is replaced by the home directory of the user being authenticated, and %u is replaced by the username of that user. After expansion, .Cm AuthorizedKeysFile is taken to be an absolute path or one relative to the user's home directory. The default is .Dq .ssh/authorized_keys . .It Cm Banner In some jurisdictions, sending a warning message before authentication may be relevant for getting legal protection. The contents of the specified file are sent to the remote user before authentication is allowed. This option is only available for protocol version 2. By default, no banner is displayed. .It Cm ChallengeResponseAuthentication Specifies whether challenge-response authentication is allowed. Specifically, in .Fx , this controls the use of PAM (see .Xr pam 3 ) for authentication. Note that this affects the effectiveness of the .Cm PasswordAuthentication and .Cm PermitRootLogin variables. The default is .Dq yes . .It Cm Ciphers Specifies the ciphers allowed for protocol version 2. Multiple ciphers must be comma-separated. The supported ciphers are .Dq 3des-cbc , .Dq aes128-cbc , .Dq aes192-cbc , .Dq aes256-cbc , .Dq aes128-ctr , .Dq aes192-ctr , .Dq aes256-ctr , .Dq arcfour128 , .Dq arcfour256 , .Dq arcfour , .Dq blowfish-cbc , and .Dq cast128-cbc . The default is: .Bd -literal -offset 3n aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour128, arcfour256,arcfour,aes192-cbc,aes256-cbc,aes128-ctr, aes192-ctr,aes256-ctr .Ed .It Cm ClientAliveCountMax Sets the number of client alive messages (see below) which may be sent without .Xr sshd 8 receiving any messages back from the client. If this threshold is reached while client alive messages are being sent, sshd will disconnect the client, terminating the session. It is important to note that the use of client alive messages is very different from .Cm TCPKeepAlive (below). The client alive messages are sent through the encrypted channel and therefore will not be spoofable. The TCP keepalive option enabled by .Cm TCPKeepAlive is spoofable. The client alive mechanism is valuable when the client or server depend on knowing when a connection has become inactive. .Pp The default value is 3. If .Cm ClientAliveInterval (see below) is set to 15, and .Cm ClientAliveCountMax is left at the default, unresponsive SSH clients will be disconnected after approximately 45 seconds. This option applies to protocol version 2 only. .It Cm ClientAliveInterval Sets a timeout interval in seconds after which if no data has been received from the client, .Xr sshd 8 will send a message through the encrypted channel to request a response from the client. The default is 0, indicating that these messages will not be sent to the client. This option applies to protocol version 2 only. .It Cm Compression Specifies whether compression is allowed, or delayed until the user has authenticated successfully. The argument must be .Dq yes , .Dq delayed , or .Dq no . The default is .Dq delayed . .It Cm DenyGroups This keyword can be followed by a list of group name patterns, separated by spaces. Login is disallowed for users whose primary group or supplementary group list matches one of the patterns. Only group names are valid; a numerical group ID is not recognized. By default, login is allowed for all groups. The allow/deny directives are processed in the following order: .Cm DenyUsers , .Cm AllowUsers , .Cm DenyGroups , and finally .Cm AllowGroups . .Pp See .Sx PATTERNS in .Xr ssh_config 5 for more information on patterns. .It Cm DenyUsers This keyword can be followed by a list of user name patterns, separated by spaces. Login is disallowed for user names that match one of the patterns. Only user names are valid; a numerical user ID is not recognized. By default, login is allowed for all users. If the pattern takes the form USER@HOST then USER and HOST are separately checked, restricting logins to particular users from particular hosts. The allow/deny directives are processed in the following order: .Cm DenyUsers , .Cm AllowUsers , .Cm DenyGroups , and finally .Cm AllowGroups . .Pp See .Sx PATTERNS in .Xr ssh_config 5 for more information on patterns. .It Cm ForceCommand Forces the execution of the command specified by .Cm ForceCommand , ignoring any command supplied by the client. The command is invoked by using the user's login shell with the -c option. This applies to shell, command, or subsystem execution. It is most useful inside a .Cm Match block. The command originally supplied by the client is available in the .Ev SSH_ORIGINAL_COMMAND environment variable. .It Cm GatewayPorts Specifies whether remote hosts are allowed to connect to ports forwarded for the client. By default, .Xr sshd 8 binds remote port forwardings to the loopback address. This prevents other remote hosts from connecting to forwarded ports. .Cm GatewayPorts can be used to specify that sshd should allow remote port forwardings to bind to non-loopback addresses, thus allowing other hosts to connect. The argument may be .Dq no to force remote port forwardings to be available to the local host only, .Dq yes to force remote port forwardings to bind to the wildcard address, or .Dq clientspecified to allow the client to select the address to which the forwarding is bound. The default is .Dq no . .It Cm GSSAPIAuthentication Specifies whether user authentication based on GSSAPI is allowed. The default is .Dq no . Note that this option applies to protocol version 2 only. .It Cm GSSAPICleanupCredentials Specifies whether to automatically destroy the user's credentials cache on logout. The default is .Dq yes . Note that this option applies to protocol version 2 only. .It Cm HostbasedAuthentication Specifies whether rhosts or /etc/hosts.equiv authentication together with successful public key client host authentication is allowed (host-based authentication). This option is similar to .Cm RhostsRSAAuthentication and applies to protocol version 2 only. The default is .Dq no . .It Cm HostbasedUsesNameFromPacketOnly Specifies whether or not the server will attempt to perform a reverse name lookup when matching the name in the .Pa ~/.shosts , .Pa ~/.rhosts , and .Pa /etc/hosts.equiv files during .Cm HostbasedAuthentication . A setting of .Dq yes means that .Xr sshd 8 uses the name supplied by the client rather than attempting to resolve the name from the TCP connection itself. The default is .Dq no . .It Cm HostKey Specifies a file containing a private host key used by SSH. The default is .Pa /etc/ssh/ssh_host_key for protocol version 1, and .Pa /etc/ssh/ssh_host_dsa_key for protocol version 2. Note that .Xr sshd 8 will refuse to use a file if it is group/world-accessible. It is possible to have multiple host key files. .Dq rsa1 keys are used for version 1 and .Dq dsa or .Dq rsa are used for version 2 of the SSH protocol. .It Cm IgnoreRhosts Specifies that .Pa .rhosts and .Pa .shosts files will not be used in .Cm RhostsRSAAuthentication or .Cm HostbasedAuthentication . .Pp .Pa /etc/hosts.equiv and .Pa /etc/ssh/shosts.equiv are still used. The default is .Dq yes . .It Cm IgnoreUserKnownHosts Specifies whether .Xr sshd 8 should ignore the user's .Pa ~/.ssh/known_hosts during .Cm RhostsRSAAuthentication or .Cm HostbasedAuthentication . The default is .Dq no . .It Cm KerberosAuthentication Specifies whether the password provided by the user for .Cm PasswordAuthentication will be validated through the Kerberos KDC. To use this option, the server needs a Kerberos servtab which allows the verification of the KDC's identity. The default is .Dq no . .It Cm KerberosGetAFSToken If AFS is active and the user has a Kerberos 5 TGT, attempt to acquire an AFS token before accessing the user's home directory. The default is .Dq no . .It Cm KerberosOrLocalPasswd If password authentication through Kerberos fails then the password will be validated via any additional local mechanism such as .Pa /etc/passwd . The default is .Dq yes . .It Cm KerberosTicketCleanup Specifies whether to automatically destroy the user's ticket cache file on logout. The default is .Dq yes . .It Cm KeyRegenerationInterval In protocol version 1, the ephemeral server key is automatically regenerated after this many seconds (if it has been used). The purpose of regeneration is to prevent decrypting captured sessions by later breaking into the machine and stealing the keys. The key is never stored anywhere. If the value is 0, the key is never regenerated. The default is 3600 (seconds). .It Cm ListenAddress Specifies the local addresses .Xr sshd 8 should listen on. The following forms may be used: .Pp .Bl -item -offset indent -compact .It .Cm ListenAddress .Sm off .Ar host No | Ar IPv4_addr No | Ar IPv6_addr .Sm on .It .Cm ListenAddress .Sm off .Ar host No | Ar IPv4_addr No : Ar port .Sm on .It .Cm ListenAddress .Sm off .Oo .Ar host No | Ar IPv6_addr Oc : Ar port .Sm on .El .Pp If .Ar port is not specified, sshd will listen on the address and all prior .Cm Port options specified. The default is to listen on all local addresses. Multiple .Cm ListenAddress options are permitted. Additionally, any .Cm Port options must precede this option for non-port qualified addresses. .It Cm LoginGraceTime The server disconnects after this time if the user has not successfully logged in. If the value is 0, there is no time limit. The default is 120 seconds. .It Cm LogLevel Gives the verbosity level that is used when logging messages from .Xr sshd 8 . The possible values are: QUIET, FATAL, ERROR, INFO, VERBOSE, DEBUG, DEBUG1, DEBUG2, and DEBUG3. The default is INFO. DEBUG and DEBUG1 are equivalent. DEBUG2 and DEBUG3 each specify higher levels of debugging output. Logging with a DEBUG level violates the privacy of users and is not recommended. .It Cm MACs Specifies the available MAC (message authentication code) algorithms. The MAC algorithm is used in protocol version 2 for data integrity protection. Multiple algorithms must be comma-separated. The default is: .Dq hmac-md5,hmac-sha1,hmac-ripemd160,hmac-sha1-96,hmac-md5-96 . .It Cm Match Introduces a conditional block. If all of the criteria on the .Cm Match line are satisfied, the keywords on the following lines override those set in the global section of the config file, until either another .Cm Match line or the end of the file. The arguments to .Cm Match are one or more criteria-pattern pairs. The available criteria are .Cm User , .Cm Group , .Cm Host , and .Cm Address . Only a subset of keywords may be used on the lines following a .Cm Match keyword. Available keywords are .Cm AllowTcpForwarding , .Cm ForceCommand , .Cm GatewayPorts , .Cm PermitOpen , .Cm X11DisplayOffset , .Cm X11Forwarding , and .Cm X11UseLocalHost . .It Cm MaxAuthTries Specifies the maximum number of authentication attempts permitted per connection. Once the number of failures reaches half this value, additional failures are logged. The default is 6. .It Cm MaxStartups Specifies the maximum number of concurrent unauthenticated connections to the SSH daemon. Additional connections will be dropped until authentication succeeds or the .Cm LoginGraceTime expires for a connection. The default is 10. .Pp Alternatively, random early drop can be enabled by specifying the three colon separated values .Dq start:rate:full (e.g. "10:30:60"). .Xr sshd 8 will refuse connection attempts with a probability of .Dq rate/100 (30%) if there are currently .Dq start (10) unauthenticated connections. The probability increases linearly and all connection attempts are refused if the number of unauthenticated connections reaches .Dq full (60). .It Cm PasswordAuthentication Specifies whether password authentication is allowed. The default is .Dq no , unless .Nm sshd was built without PAM support, in which case the default is .Dq yes . Note that if .Cm ChallengeResponseAuthentication is .Dq yes , and the PAM authentication policy for .Nm sshd includes .Xr pam_unix 8 , password authentication will be allowed through the challenge-response mechanism regardless of the value of .Cm PasswordAuthentication . .It Cm PermitEmptyPasswords When password authentication is allowed, it specifies whether the server allows login to accounts with empty password strings. The default is .Dq no . .It Cm PermitOpen Specifies the destinations to which TCP port forwarding is permitted. The forwarding specification must be one of the following forms: .Pp .Bl -item -offset indent -compact .It .Cm PermitOpen .Sm off .Ar host : port .Sm on .It .Cm PermitOpen .Sm off .Ar IPv4_addr : port .Sm on .It .Cm PermitOpen .Sm off .Ar \&[ IPv6_addr \&] : port .Sm on .El .Pp Multiple forwards may be specified by separating them with whitespace. An argument of .Dq any can be used to remove all restrictions and permit any forwarding requests. By default all port forwarding requests are permitted. .It Cm PermitRootLogin Specifies whether root can log in using .Xr ssh 1 . The argument must be .Dq yes , .Dq without-password , .Dq forced-commands-only , or .Dq no . The default is .Dq no . Note that if .Cm ChallengeResponseAuthentication is .Dq yes , the root user may be allowed in with its password even if .Cm PermitRootLogin is set to .Dq without-password . .Pp If this option is set to .Dq without-password , password authentication is disabled for root. .Pp If this option is set to .Dq forced-commands-only , root login with public key authentication will be allowed, but only if the .Ar command option has been specified (which may be useful for taking remote backups even if root login is normally not allowed). All other authentication methods are disabled for root. .Pp If this option is set to .Dq no , root is not allowed to log in. .It Cm PermitTunnel Specifies whether .Xr tun 4 device forwarding is allowed. The argument must be .Dq yes , .Dq point-to-point (layer 3), .Dq ethernet (layer 2), or .Dq no . Specifying .Dq yes permits both .Dq point-to-point and .Dq ethernet . The default is .Dq no . .It Cm PermitUserEnvironment Specifies whether .Pa ~/.ssh/environment and .Cm environment= options in .Pa ~/.ssh/authorized_keys are processed by .Xr sshd 8 . The default is .Dq no . Enabling environment processing may enable users to bypass access restrictions in some configurations using mechanisms such as .Ev LD_PRELOAD . .It Cm PidFile Specifies the file that contains the process ID of the SSH daemon. The default is .Pa /var/run/sshd.pid . .It Cm Port Specifies the port number that .Xr sshd 8 listens on. The default is 22. Multiple options of this type are permitted. See also .Cm ListenAddress . .It Cm PrintLastLog Specifies whether .Xr sshd 8 should print the date and time of the last user login when a user logs in interactively. The default is .Dq yes . .It Cm PrintMotd Specifies whether .Xr sshd 8 should print .Pa /etc/motd when a user logs in interactively. (On some systems it is also printed by the shell, .Pa /etc/profile , or equivalent.) The default is .Dq yes . .It Cm Protocol Specifies the protocol versions .Xr sshd 8 supports. The possible values are .Sq 1 and .Sq 2 . Multiple versions must be comma-separated. The default is .Dq 2 . Note that the order of the protocol list does not indicate preference, because the client selects among multiple protocol versions offered by the server. Specifying .Dq 2,1 is identical to .Dq 1,2 . .It Cm PubkeyAuthentication Specifies whether public key authentication is allowed. The default is .Dq yes . Note that this option applies to protocol version 2 only. .It Cm RhostsRSAAuthentication Specifies whether rhosts or .Pa /etc/hosts.equiv authentication together with successful RSA host authentication is allowed. The default is .Dq no . This option applies to protocol version 1 only. .It Cm RSAAuthentication Specifies whether pure RSA authentication is allowed. The default is .Dq yes . This option applies to protocol version 1 only. .It Cm ServerKeyBits Defines the number of bits in the ephemeral protocol version 1 server key. The minimum value is 512, and the default is 768. .It Cm StrictModes Specifies whether .Xr sshd 8 should check file modes and ownership of the user's files and home directory before accepting login. This is normally desirable because novices sometimes accidentally leave their directory or files world-writable. The default is .Dq yes . .It Cm Subsystem Configures an external subsystem (e.g. file transfer daemon). Arguments should be a subsystem name and a command (with optional arguments) to execute upon subsystem request. The command .Xr sftp-server 8 implements the .Dq sftp file transfer subsystem. By default no subsystems are defined. Note that this option applies to protocol version 2 only. .It Cm SyslogFacility Gives the facility code that is used when logging messages from .Xr sshd 8 . The possible values are: DAEMON, USER, AUTH, LOCAL0, LOCAL1, LOCAL2, LOCAL3, LOCAL4, LOCAL5, LOCAL6, LOCAL7. The default is AUTH. .It Cm TCPKeepAlive Specifies whether the system should send TCP keepalive messages to the other side. If they are sent, death of the connection or crash of one of the machines will be properly noticed. However, this means that connections will die if the route is down temporarily, and some people find it annoying. On the other hand, if TCP keepalives are not sent, sessions may hang indefinitely on the server, leaving .Dq ghost users and consuming server resources. .Pp The default is .Dq yes (to send TCP keepalive messages), and the server will notice if the network goes down or the client host crashes. This avoids infinitely hanging sessions. .Pp To disable TCP keepalive messages, the value should be set to .Dq no . .It Cm UseDNS Specifies whether .Xr sshd 8 should look up the remote host name and check that the resolved host name for the remote IP address maps back to the very same IP address. The default is .Dq yes . .It Cm UseLogin Specifies whether .Xr login 1 is used for interactive login sessions. The default is .Dq no . Note that .Xr login 1 is never used for remote command execution. Note also, that if this is enabled, .Cm X11Forwarding will be disabled because .Xr login 1 does not know how to handle .Xr xauth 1 cookies. If .Cm UsePrivilegeSeparation is specified, it will be disabled after authentication. .It Cm UsePAM Enables the Pluggable Authentication Module interface. If set to .Dq yes this will enable PAM authentication using .Cm ChallengeResponseAuthentication and .Cm PasswordAuthentication in addition to PAM account and session module processing for all authentication types. .Pp Because PAM challenge-response authentication usually serves an equivalent role to password authentication, you should disable either .Cm PasswordAuthentication or .Cm ChallengeResponseAuthentication. .Pp If .Cm UsePAM is enabled, you will not be able to run .Xr sshd 8 as a non-root user. The default is .Dq yes . .It Cm UsePrivilegeSeparation Specifies whether .Xr sshd 8 separates privileges by creating an unprivileged child process to deal with incoming network traffic. After successful authentication, another process will be created that has the privilege of the authenticated user. The goal of privilege separation is to prevent privilege escalation by containing any corruption within the unprivileged processes. The default is .Dq yes . .It Cm VersionAddendum Specifies a string to append to the regular version string to identify OS- or site-specific modifications. The default is .Dq FreeBSD-20061110 . .It Cm X11DisplayOffset Specifies the first display number available for .Xr sshd 8 Ns 's X11 forwarding. This prevents sshd from interfering with real X11 servers. The default is 10. .It Cm X11Forwarding Specifies whether X11 forwarding is permitted. The argument must be .Dq yes or .Dq no . The default is .Dq yes . .Pp When X11 forwarding is enabled, there may be additional exposure to the server and to client displays if the .Xr sshd 8 proxy display is configured to listen on the wildcard address (see .Cm X11UseLocalhost below), though this is not the default. Additionally, the authentication spoofing and authentication data verification and substitution occur on the client side. The security risk of using X11 forwarding is that the client's X11 display server may be exposed to attack when the SSH client requests forwarding (see the warnings for .Cm ForwardX11 in .Xr ssh_config 5 ) . A system administrator may have a stance in which they want to protect clients that may expose themselves to attack by unwittingly requesting X11 forwarding, which can warrant a .Dq no setting. .Pp Note that disabling X11 forwarding does not prevent users from forwarding X11 traffic, as users can always install their own forwarders. X11 forwarding is automatically disabled if .Cm UseLogin is enabled. .It Cm X11UseLocalhost Specifies whether .Xr sshd 8 should bind the X11 forwarding server to the loopback address or to the wildcard address. By default, sshd binds the forwarding server to the loopback address and sets the hostname part of the .Ev DISPLAY environment variable to .Dq localhost . This prevents remote hosts from connecting to the proxy display. However, some older X11 clients may not function with this configuration. .Cm X11UseLocalhost may be set to .Dq no to specify that the forwarding server should be bound to the wildcard address. The argument must be .Dq yes or .Dq no . The default is .Dq yes . .It Cm XAuthLocation Specifies the full pathname of the .Xr xauth 1 program. The default is -.Pa /usr/X11R6/bin/xauth . +.Pa /usr/local/bin/xauth . .El .Sh TIME FORMATS .Xr sshd 8 command-line arguments and configuration file options that specify time may be expressed using a sequence of the form: .Sm off .Ar time Op Ar qualifier , .Sm on where .Ar time is a positive integer value and .Ar qualifier is one of the following: .Pp .Bl -tag -width Ds -compact -offset indent .It Aq Cm none seconds .It Cm s | Cm S seconds .It Cm m | Cm M minutes .It Cm h | Cm H hours .It Cm d | Cm D days .It Cm w | Cm W weeks .El .Pp Each member of the sequence is added together to calculate the total time value. .Pp Time format examples: .Pp .Bl -tag -width Ds -compact -offset indent .It 600 600 seconds (10 minutes) .It 10m 10 minutes .It 1h30m 1 hour 30 minutes (90 minutes) .El .Sh FILES .Bl -tag -width Ds .It Pa /etc/ssh/sshd_config Contains configuration data for .Xr sshd 8 . This file should be writable by root only, but it is recommended (though not necessary) that it be world-readable. .El .Sh SEE ALSO .Xr sshd 8 .Sh AUTHORS OpenSSH is a derivative of the original and free ssh 1.2.12 release by Tatu Ylonen. Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo de Raadt and Dug Song removed many bugs, re-added newer features and created OpenSSH. Markus Friedl contributed the support for SSH protocol versions 1.5 and 2.0. Niels Provos and Markus Friedl contributed support for privilege separation.