sshd_config.0

OpenSSL Source code for SFTP, SSH, and many others

     LoginGraceTime
             The server disconnects after this time if the user has not sucM--
             cessfully logged in.  If the value is 0, there is no time limit.
             The default is 600 (seconds).

     LogLevel
             Gives the verbosity level that is used when logging messages from
             sshd.  The possible values are: QUIET, FATAL, ERROR, INFO, VERM--
             BOSE, 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.

     MACs    Specifies the available MAC (message authentication code) algoM--
             rithms.  The MAC algorithm is used in protocol version 2 for data
             integrity protection.  Multiple algorithms must be comma-sepaM--
             rated.  The default is
             ``hmac-md5,hmac-sha1,hmac-ripemd160,hmac-sha1-96,hmac-md5-96''.

     MaxStartups
             Specifies the maximum number of concurrent unauthenticated conM--
             nections to the sshd daemon.  Additional connections will be
             dropped until authentication succeeds or the LoginGraceTime
             expires for a connection.  The default is 10.

             Alternatively, random early drop can be enabled by specifying the
             three colon separated values ``start:rate:full'' (e.g.,
             "10:30:60").  sshd will refuse connection attempts with a probaM--
             bility of ``rate/100'' (30%) if there are currently ``start''
             (10) unauthenticated connections.  The probability increases linM--
             early and all connection attempts are refused if the number of
             unauthenticated connections reaches ``full'' (60).

     PasswordAuthentication
             Specifies whether password authentication is allowed.  The
             default is ``yes''.

     PermitEmptyPasswords
             When password authentication is allowed, it specifies whether the
             server allows login to accounts with empty password strings.  The
             default is ``no''.

     PermitRootLogin
             Specifies whether root can login using ssh(1).  The argument must
             be ``yes'', ``without-password'', ``forced-commands-only'' or
             ``no''.  The default is ``yes''.

             If this option is set to ``without-password'' password authentiM--
             cation is disabled for root.

             If this option is set to ``forced-commands-only'' root login with
             public key authentication will be allowed, but only if the
             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.

             If this option is set to ``no'' root is not allowed to login.

     PidFile
             Specifies the file that contains the process identifier of the
             sshd daemon.  The default is /var/run/sshd.pid.

     Port    Specifies the port number that sshd listens on.  The default is
             22.  Multiple options of this type are permitted.  See also
             ListenAddress.

     PrintLastLog
             Specifies whether sshd should print the date and time when the
             user last logged in.  The default is ``yes''.

     PrintMotd
             Specifies whether sshd should print /etc/motd when a user logs in
             interactively.  (On some systems it is also printed by the shell,
             /etc/profile, or equivalent.)  The default is ``yes''.

     Protocol
             Specifies the protocol versions sshd should support.  The possiM--
             ble values are ``1'' and ``2''.  Multiple versions must be comma-
             separated.  The default is ``2,1''.

     PubkeyAuthentication
             Specifies whether public key authentication is allowed.  The
             default is ``yes''.  Note that this option applies to protocol
             version 2 only.

     RhostsAuthentication
             Specifies whether authentication using rhosts or /etc/hosts.equiv
             files is sufficient.  Normally, this method should not be permitM--
             ted because it is insecure.  RhostsRSAAuthentication should be
             used instead, because it performs RSA-based host authentication
             in addition to normal rhosts or /etc/hosts.equiv authentication.
             The default is ``no''.  This option applies to protocol version 1
             only.

     RhostsRSAAuthentication
             Specifies whether rhosts or /etc/hosts.equiv authentication
             together with successful RSA host authentication is allowed.  The
             default is ``no''.  This option applies to protocol version 1
             only.

     RSAAuthentication
             Specifies whether pure RSA authentication is allowed.  The
             default is ``yes''.  This option applies to protocol version 1
             only.

     ServerKeyBits
             Defines the number of bits in the ephemeral protocol version 1
             server key.  The minimum value is 512, and the default is 768.

     StrictModes
             Specifies whether sshd 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
             ``yes''.

     Subsystem
             Configures an external subsystem (e.g., file transfer daemon).
             Arguments should be a subsystem name and a command to execute
             upon subsystem request.  The command sftp-server(8) implements
             the ``sftp'' file transfer subsystem.  By default no subsystems
             are defined.  Note that this option applies to protocol version 2
             only.

     SyslogFacility
             Gives the facility code that is used when logging messages from
             sshd.  The possible values are: DAEMON, USER, AUTH, LOCAL0,
             LOCAL1, LOCAL2, LOCAL3, LOCAL4, LOCAL5, LOCAL6, LOCAL7.  The
             default is AUTH.

     UseLogin
             Specifies whether login(1) is used for interactive login sesM--
             sions.  The default is ``no''.  Note that login(1) is never used
             for remote command execution.  Note also, that if this is
             enabled, X11Forwarding will be disabled because login(1) does not
             know how to handle xauth(1) cookies.  If UsePrivilegeSeparation
             is specified, it will be disabled after authentication.

     UsePrivilegeSeparation
             Specifies whether sshd 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 conM--
             taining any corruption within the unprivileged processes.  The
             default is ``yes''.

     VerifyReverseMapping
             Specifies whether sshd should try to verify 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 ``no''.

     X11DisplayOffset
             Specifies the first display number available for sshd's X11 forM--
             warding.  This prevents sshd from interfering with real X11
             servers.  The default is 10.

     X11Forwarding
             Specifies whether X11 forwarding is permitted.  The default is
             ``no''.  Note that disabling X11 forwarding does not improve
             security in any way, as users can always install their own forM--
             warders.  X11 forwarding is automatically disabled if UseLogin is
             enabled.

     X11UseLocalhost
             Specifies whether sshd 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 DISPLAY environment variable to
             ``localhost''.  This prevents remote hosts from connecting to the
             fake display.  However, some older X11 clients may not function
             with this configuration.  X11UseLocalhost may be set to ``no'' to
             specify that the forwarding server should be bound to the wildM--
             card address.  The argument must be ``yes'' or ``no''.  The
             default is ``yes''.

     XAuthLocation
             Specifies the location of the xauth(1) program.  The default is
             /usr/X11R6/bin/xauth.

   Time Formats

     sshd command-line arguments and configuration file options that specify
     time may be expressed using a sequence of the form: time[qualifier],
     where time is a positive integer value and qualifier is one of the folM--
     lowing:

           <none>  seconds
           s | S   seconds
           m | M   minutes
           h | H   hours
           d | D   days
           w | W   weeks

     Each member of the sequence is added together to calculate the total time
     value.

     Time format examples:

           600     600 seconds (10 minutes)
           10m     10 minutes
           1h30m   1 hour 30 minutes (90 minutes)

FILES
     /etc/ssh/sshd_config
             Contains configuration data for sshd.  This file should be
             writable by root only, but it is recommended (though not necesM--
             sary) that it be world-readable.

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 creM--
     ated 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.

SEE ALSO
     sshd(8)

BSD                           September 25, 1999                           BSD