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+SSHD_CONFIG(5)            OpenBSD Programmer's Manual           SSHD_CONFIG(5)
+
+NAME
+     sshd_config - OpenSSH SSH daemon configuration file
+
+SYNOPSIS
+     /etc/ssh/sshd_config
+
+DESCRIPTION
+     sshd(8) reads configuration data from /etc/ssh/sshd_config (or the file
+     specified with -f on the command line).  The file contains keyword-
+     argument pairs, one per line.  Lines starting with `#' and empty lines
+     are interpreted as comments.  Arguments may optionally be enclosed in
+     double quotes (") in order to represent arguments containing spaces.
+
+     The possible keywords and their meanings are as follows (note that
+     keywords are case-insensitive and arguments are case-sensitive):
+
+     AcceptEnv
+             Specifies what environment variables sent by the client will be
+             copied into the session's environ(7).  See SendEnv in
+             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
+             `*' and `?'.  Multiple environment variables may be separated by
+             whitespace or spread across multiple 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.
+
+     AddressFamily
+             Specifies which address family should be used by sshd(8).  Valid
+             arguments are ``any'', ``inet'' (use IPv4 only), or ``inet6''
+             (use IPv6 only).  The default is ``any''.
+
+     AllowAgentForwarding
+             Specifies whether ssh-agent(1) forwarding is permitted.  The
+             default is ``yes''.  Note that disabling agent forwarding does
+             not improve security unless users are also denied shell access,
+             as they can always install their own forwarders.
+
+     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: DenyUsers, AllowUsers, DenyGroups, and finally
+             AllowGroups.
+
+             See PATTERNS in ssh_config(5) for more information on patterns.
+
+     AllowTcpForwarding
+             Specifies whether TCP forwarding is permitted.  The available
+             options are ``yes'' or ``all'' to allow TCP forwarding, ``no'' to
+             prevent all TCP forwarding, ``local'' to allow local (from the
+             perspective of ssh(1)) forwarding only or ``remote'' to allow
+             remote forwarding only.  The default is ``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.
+
+     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: DenyUsers,
+             AllowUsers, DenyGroups, and finally AllowGroups.
+
+             See PATTERNS in ssh_config(5) for more information on patterns.
+
+     AuthenticationMethods
+             Specifies the authentication methods that must be successfully
+             completed for a user to be granted access.  This option must be
+             followed by one or more comma-separated lists of authentication
+             method names.  Successful authentication requires completion of
+             every method in at least one of these lists.
+
+             For example, an argument of ``publickey,password
+             publickey,keyboard-interactive'' would require the user to
+             complete public key authentication, followed by either password
+             or keyboard interactive authentication.  Only methods that are
+             next in one or more lists are offered at each stage, so for this
+             example, it would not be possible to attempt password or
+             keyboard-interactive authentication before public key.
+
+             This option is only available for SSH protocol 2 and will yield a
+             fatal error if enabled if protocol 1 is also enabled.  Note that
+             each authentication method listed should also be explicitly
+             enabled in the configuration.  The default is not to require
+             multiple authentication; successful completion of a single
+             authentication method is sufficient.
+
+     AuthorizedKeysCommand
+             Specifies a program to be used to look up the user's public keys.
+             The program will be invoked with a single argument of the
+             username being authenticated, and should produce on standard
+             output zero or more lines of authorized_keys output (see
+             AUTHORIZED_KEYS in sshd(8)).  If a key supplied by
+             AuthorizedKeysCommand does not successfully authenticate and
+             authorize the user then public key authentication continues using
+             the usual AuthorizedKeysFile files.  By default, no
+             AuthorizedKeysCommand is run.
+
+     AuthorizedKeysCommandUser
+             Specifies the user under whose account the AuthorizedKeysCommand
+             is run.  It is recommended to use a dedicated user that has no
+             other role on the host than running authorized keys commands.
+
+     AuthorizedKeysFile
+             Specifies the file that contains the public keys that can be used
+             for user authentication.  The format is described in the
+             AUTHORIZED_KEYS FILE FORMAT section of sshd(8).
+             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,
+             AuthorizedKeysFile is taken to be an absolute path or one
+             relative to the user's home directory.  Multiple files may be
+             listed, separated by whitespace.  The default is
+             ``.ssh/authorized_keys .ssh/authorized_keys2''.
+
+     AuthorizedPrincipalsFile
+             Specifies a file that lists principal names that are accepted for
+             certificate authentication.  When using certificates signed by a
+             key listed in TrustedUserCAKeys, this file lists names, one of
+             which must appear in the certificate for it to be accepted for
+             authentication.  Names are listed one per line preceded by key
+             options (as described in AUTHORIZED_KEYS FILE FORMAT in sshd(8)).
+             Empty lines and comments starting with `#' are ignored.
+
+             AuthorizedPrincipalsFile 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,
+             AuthorizedPrincipalsFile is taken to be an absolute path or one
+             relative to the user's home directory.
+
+             The default is ``none'', i.e. not to use a principals file - in
+             this case, the username of the user must appear in a
+             certificate's principals list for it to be accepted.  Note that
+             AuthorizedPrincipalsFile is only used when authentication
+             proceeds using a CA listed in TrustedUserCAKeys and is not
+             consulted for certification authorities trusted via
+             ~/.ssh/authorized_keys, though the principals= key option offers
+             a similar facility (see sshd(8) for details).
+
+     Banner  The contents of the specified file are sent to the remote user
+             before authentication is allowed.  If the argument is ``none''
+             then no banner is displayed.  This option is only available for
+             protocol version 2.  By default, no banner is displayed.
+
+     ChallengeResponseAuthentication
+             Specifies whether challenge-response authentication is allowed
+             (e.g. via PAM or though authentication styles supported in
+             login.conf(5)) The default is ``yes''.
+
+     ChrootDirectory
+             Specifies the pathname of a directory to chroot(2) to after
+             authentication.  All components of the pathname must be root-
+             owned directories that are not writable by any other user or
+             group.  After the chroot, sshd(8) changes the working directory
+             to the user's home directory.
+
+             The pathname may contain the following tokens that are expanded
+             at runtime once the connecting user has been authenticated: %% 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.
+
+             The ChrootDirectory must contain the necessary files and
+             directories to support the user's session.  For an interactive
+             session this requires at least a shell, typically sh(1), and
+             basic /dev nodes such as null(4), zero(4), stdin(4), stdout(4),
+             stderr(4), arandom(4) and tty(4) devices.  For file transfer
+             sessions using ``sftp'', no additional configuration of the
+             environment is necessary if the in-process sftp server is used,
+             though sessions which use logging do require /dev/log inside the
+             chroot directory (see sftp-server(8) for details).
+
+             The default is not to chroot(2).
+
+     Ciphers
+             Specifies the ciphers allowed for protocol version 2.  Multiple
+             ciphers must be comma-separated.  The supported ciphers are
+             ``3des-cbc'', ``aes128-cbc'', ``aes192-cbc'', ``aes256-cbc'',
+             ``aes128-ctr'', ``aes192-ctr'', ``aes256-ctr'',
+             ``aes128-gcm@openssh.com'', ``aes256-gcm@openssh.com'',
+             ``arcfour128'', ``arcfour256'', ``arcfour'', ``blowfish-cbc'',
+             and ``cast128-cbc''.  The default is:
+
+                aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,
+                aes128-gcm@openssh.com,aes256-gcm@openssh.com,
+                aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,
+                aes256-cbc,arcfour
+
+     ClientAliveCountMax
+             Sets the number of client alive messages (see below) which may be
+             sent without 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 TCPKeepAlive (below).  The client
+             alive messages are sent through the encrypted channel and
+             therefore will not be spoofable.  The TCP keepalive option
+             enabled by TCPKeepAlive is spoofable.  The client alive mechanism
+             is valuable when the client or server depend on knowing when a
+             connection has become inactive.
+
+             The default value is 3.  If ClientAliveInterval (see below) is
+             set to 15, and ClientAliveCountMax is left at the default,
+             unresponsive SSH clients will be disconnected after approximately
+             45 seconds.  This option applies to protocol version 2 only.
+
+     ClientAliveInterval
+             Sets a timeout interval in seconds after which if no data has
+             been received from the client, 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.
+
+     Compression
+             Specifies whether compression is allowed, or delayed until the
+             user has authenticated successfully.  The argument must be
+             ``yes'', ``delayed'', or ``no''.  The default is ``delayed''.
+
+     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:
+             DenyUsers, AllowUsers, DenyGroups, and finally AllowGroups.
+
+             See PATTERNS in ssh_config(5) for more information on patterns.
+
+     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: DenyUsers,
+             AllowUsers, DenyGroups, and finally AllowGroups.
+
+             See PATTERNS in ssh_config(5) for more information on patterns.
+
+     ForceCommand
+             Forces the execution of the command specified by ForceCommand,
+             ignoring any command supplied by the client and ~/.ssh/rc if
+             present.  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 Match block.  The command
+             originally supplied by the client is available in the
+             SSH_ORIGINAL_COMMAND environment variable.  Specifying a command
+             of ``internal-sftp'' will force the use of an in-process sftp
+             server that requires no support files when used with
+             ChrootDirectory.
+
+     GatewayPorts
+             Specifies whether remote hosts are allowed to connect to ports
+             forwarded for the client.  By default, sshd(8) binds remote port
+             forwardings to the loopback address.  This prevents other remote
+             hosts from connecting to forwarded ports.  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 ``no'' to force remote port
+             forwardings to be available to the local host only, ``yes'' to
+             force remote port forwardings to bind to the wildcard address, or
+             ``clientspecified'' to allow the client to select the address to
+             which the forwarding is bound.  The default is ``no''.
+
+     GSSAPIAuthentication
+             Specifies whether user authentication based on GSSAPI is allowed.
+             The default is ``no''.  Note that this option applies to protocol
+             version 2 only.
+
+     GSSAPICleanupCredentials
+             Specifies whether to automatically destroy the user's credentials
+             cache on logout.  The default is ``yes''.  Note that this option
+             applies to protocol version 2 only.
+
+     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
+             RhostsRSAAuthentication and applies to protocol version 2 only.
+             The default is ``no''.
+
+     HostbasedUsesNameFromPacketOnly
+             Specifies whether or not the server will attempt to perform a
+             reverse name lookup when matching the name in the ~/.shosts,
+             ~/.rhosts, and /etc/hosts.equiv files during
+             HostbasedAuthentication.  A setting of ``yes'' means that sshd(8)
+             uses the name supplied by the client rather than attempting to
+             resolve the name from the TCP connection itself.  The default is
+             ``no''.
+
+     HostCertificate
+             Specifies a file containing a public host certificate.  The
+             certificate's public key must match a private host key already
+             specified by HostKey.  The default behaviour of sshd(8) is not to
+             load any certificates.
+
+     HostKey
+             Specifies a file containing a private host key used by SSH.  The
+             default is /etc/ssh/ssh_host_key for protocol version 1, and
+             /etc/ssh/ssh_host_dsa_key, /etc/ssh/ssh_host_ecdsa_key and
+             /etc/ssh/ssh_host_rsa_key for protocol version 2.  Note that
+             sshd(8) will refuse to use a file if it is group/world-
+             accessible.  It is possible to have multiple host key files.
+             ``rsa1'' keys are used for version 1 and ``dsa'', ``ecdsa'' or
+             ``rsa'' are used for version 2 of the SSH protocol.
+
+     IgnoreRhosts
+             Specifies that .rhosts and .shosts files will not be used in
+             RhostsRSAAuthentication or HostbasedAuthentication.
+
+             /etc/hosts.equiv and /etc/shosts.equiv are still used.  The
+             default is ``yes''.
+
+     IgnoreUserKnownHosts
+             Specifies whether sshd(8) should ignore the user's
+             ~/.ssh/known_hosts during RhostsRSAAuthentication or
+             HostbasedAuthentication.  The default is ``no''.
+
+     IPQoS   Specifies the IPv4 type-of-service or DSCP class for the
+             connection.  Accepted values are ``af11'', ``af12'', ``af13'',
+             ``af21'', ``af22'', ``af23'', ``af31'', ``af32'', ``af33'',
+             ``af41'', ``af42'', ``af43'', ``cs0'', ``cs1'', ``cs2'', ``cs3'',
+             ``cs4'', ``cs5'', ``cs6'', ``cs7'', ``ef'', ``lowdelay'',
+             ``throughput'', ``reliability'', or a numeric value.  This option
+             may take one or two arguments, separated by whitespace.  If one
+             argument is specified, it is used as the packet class
+             unconditionally.  If two values are specified, the first is
+             automatically selected for interactive sessions and the second
+             for non-interactive sessions.  The default is ``lowdelay'' for
+             interactive sessions and ``throughput'' for non-interactive
+             sessions.
+
+     KerberosAuthentication
+             Specifies whether the password provided by the user for
+             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 ``no''.
+
+     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 ``no''.
+
+     KerberosOrLocalPasswd
+             If password authentication through Kerberos fails then the
+             password will be validated via any additional local mechanism
+             such as /etc/passwd.  The default is ``yes''.
+
+     KerberosTicketCleanup
+             Specifies whether to automatically destroy the user's ticket
+             cache file on logout.  The default is ``yes''.
+
+     KexAlgorithms
+             Specifies the available KEX (Key Exchange) algorithms.  Multiple
+             algorithms must be comma-separated.  The default is
+             ``ecdh-sha2-nistp256'', ``ecdh-sha2-nistp384'',
+             ``ecdh-sha2-nistp521'', ``diffie-hellman-group-exchange-sha256'',
+             ``diffie-hellman-group-exchange-sha1'',
+             ``diffie-hellman-group14-sha1'', ``diffie-hellman-group1-sha1''.
+
+     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).
+
+     ListenAddress
+             Specifies the local addresses sshd(8) should listen on.  The
+             following forms may be used:
+
+                   ListenAddress host|IPv4_addr|IPv6_addr
+                   ListenAddress host|IPv4_addr:port
+                   ListenAddress [host|IPv6_addr]:port
+
+             If port is not specified, sshd will listen on the address and all
+             prior Port options specified.  The default is to listen on all
+             local addresses.  Multiple ListenAddress options are permitted.
+             Additionally, any Port options must precede this option for non-
+             port qualified addresses.
+
+     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.
+
+     LogLevel
+             Gives the verbosity level that is used when logging messages from
+             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.
+
+     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 algorithms that contain ``-etm'' calculate the
+             MAC after encryption (encrypt-then-mac).  These are considered
+             safer and their use recommended.  The default is:
+
+                   hmac-md5-etm@openssh.com,hmac-sha1-etm@openssh.com,
+                   umac-64-etm@openssh.com,umac-128-etm@openssh.com,
+                   hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,
+                   hmac-ripemd160-etm@openssh.com,hmac-sha1-96-etm@openssh.com,
+                   hmac-md5-96-etm@openssh.com,
+                   hmac-md5,hmac-sha1,umac-64@openssh.com,umac-128@openssh.com,
+                   hmac-sha2-256,hmac-sha2-512,hmac-ripemd160,
+                   hmac-sha1-96,hmac-md5-96
+
+     Match   Introduces a conditional block.  If all of the criteria on the
+             Match line are satisfied, the keywords on the following lines
+             override those set in the global section of the config file,
+             until either another Match line or the end of the file.
+
+             The arguments to Match are one or more criteria-pattern pairs.
+             The available criteria are User, Group, Host, LocalAddress,
+             LocalPort, and Address.  The match patterns may consist of single
+             entries or comma-separated lists and may use the wildcard and
+             negation operators described in the PATTERNS section of
+             ssh_config(5).
+
+             The patterns in an Address criteria may additionally contain
+             addresses to match in CIDR address/masklen format, e.g.
+             ``192.0.2.0/24'' or ``3ffe:ffff::/32''.  Note that the mask
+             length provided must be consistent with the address - it is an
+             error to specify a mask length that is too long for the address
+             or one with bits set in this host portion of the address.  For
+             example, ``192.0.2.0/33'' and ``192.0.2.0/8'' respectively.
+
+             Only a subset of keywords may be used on the lines following a
+             Match keyword.  Available keywords are AcceptEnv,
+             AllowAgentForwarding, AllowGroups, AllowTcpForwarding,
+             AllowUsers, AuthenticationMethods, AuthorizedKeysCommand,
+             AuthorizedKeysCommandUser, AuthorizedKeysFile,
+             AuthorizedPrincipalsFile, Banner, ChrootDirectory, DenyGroups,
+             DenyUsers, ForceCommand, GatewayPorts, GSSAPIAuthentication,
+             HostbasedAuthentication, HostbasedUsesNameFromPacketOnly,
+             KbdInteractiveAuthentication, KerberosAuthentication,
+             MaxAuthTries, MaxSessions, PasswordAuthentication,
+             PermitEmptyPasswords, PermitOpen, PermitRootLogin, PermitTunnel,
+             PubkeyAuthentication, RhostsRSAAuthentication, RSAAuthentication,
+             X11DisplayOffset, X11Forwarding and X11UseLocalHost.
+
+     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.
+
+     MaxSessions
+             Specifies the maximum number of open sessions permitted per
+             network connection.  The default is 10.
+
+     MaxStartups
+             Specifies the maximum number of concurrent unauthenticated
+             connections to the SSH daemon.  Additional connections will be
+             dropped until authentication succeeds or the LoginGraceTime
+             expires for a connection.  The default is 10:30:100.
+
+             Alternatively, random early drop can be enabled by specifying the
+             three colon separated values ``start:rate:full'' (e.g.
+             "10:30:60").  sshd(8) will refuse connection attempts with a
+             probability of ``rate/100'' (30%) if there are currently
+             ``start'' (10) unauthenticated connections.  The probability
+             increases linearly 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''.
+
+     PermitOpen
+             Specifies the destinations to which TCP port forwarding is
+             permitted.  The forwarding specification must be one of the
+             following forms:
+
+                   PermitOpen host:port
+                   PermitOpen IPv4_addr:port
+                   PermitOpen [IPv6_addr]:port
+
+             Multiple forwards may be specified by separating them with
+             whitespace.  An argument of ``any'' can be used to remove all
+             restrictions and permit any forwarding requests.  An argument of
+             ``none'' can be used to prohibit all forwarding requests.  By
+             default all port forwarding requests are permitted.
+
+     PermitRootLogin
+             Specifies whether root can log in 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
+             authentication 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 log in.
+
+     PermitTunnel
+             Specifies whether tun(4) device forwarding is allowed.  The
+             argument must be ``yes'', ``point-to-point'' (layer 3),
+             ``ethernet'' (layer 2), or ``no''.  Specifying ``yes'' permits
+             both ``point-to-point'' and ``ethernet''.  The default is ``no''.
+
+     PermitUserEnvironment
+             Specifies whether ~/.ssh/environment and environment= options in
+             ~/.ssh/authorized_keys are processed by sshd(8).  The default is
+             ``no''.  Enabling environment processing may enable users to
+             bypass access restrictions in some configurations using
+             mechanisms such as LD_PRELOAD.
+
+     PidFile
+             Specifies the file that contains the process ID of the SSH
+             daemon.  The default is /var/run/sshd.pid.
+
+     Port    Specifies the port number that sshd(8) listens on.  The default
+             is 22.  Multiple options of this type are permitted.  See also
+             ListenAddress.
+
+     PrintLastLog
+             Specifies whether sshd(8) should print the date and time of the
+             last user login when a user logs in interactively.  The default
+             is ``yes''.
+
+     PrintMotd
+             Specifies whether sshd(8) 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(8) supports.  The possible
+             values are `1' and `2'.  Multiple versions must be comma-
+             separated.  The default is `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 ``2,1'' is identical to ``1,2''.
+
+     PubkeyAuthentication
+             Specifies whether public key authentication is allowed.  The
+             default is ``yes''.  Note that this option applies to protocol
+             version 2 only.
+
+     RevokedKeys
+             Specifies revoked public keys.  Keys listed in this file will be
+             refused for public key authentication.  Note that if this file is
+             not readable, then public key authentication will be refused for
+             all users.  Keys may be specified as a text file, listing one
+             public key per line, or as an OpenSSH Key Revocation List (KRL)
+             as generated by ssh-keygen(1).  For more information on KRLs, see
+             the KEY REVOCATION LISTS section in ssh-keygen(1).
+
+     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 1024.
+
+     StrictModes
+             Specifies whether 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
+             ``yes''.  Note that this does not apply to ChrootDirectory, whose
+             permissions and ownership are checked unconditionally.
+
+     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 sftp-server(8) implements the ``sftp'' file transfer
+             subsystem.
+
+             Alternately the name ``internal-sftp'' implements an in-process
+             ``sftp'' server.  This may simplify configurations using
+             ChrootDirectory to force a different filesystem root on clients.
+
+             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(8).  The possible values are: DAEMON, USER, AUTH, LOCAL0,
+             LOCAL1, LOCAL2, LOCAL3, LOCAL4, LOCAL5, LOCAL6, LOCAL7.  The
+             default is AUTH.
+
+     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 ``ghost'' users and consuming
+             server resources.
+
+             The default is ``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.
+
+             To disable TCP keepalive messages, the value should be set to
+             ``no''.
+
+     TrustedUserCAKeys
+             Specifies a file containing public keys of certificate
+             authorities that are trusted to sign user certificates for
+             authentication.  Keys are listed one per line; empty lines and
+             comments starting with `#' are allowed.  If a certificate is
+             presented for authentication and has its signing CA key listed in
+             this file, then it may be used for authentication for any user
+             listed in the certificate's principals list.  Note that
+             certificates that lack a list of principals will not be permitted
+             for authentication using TrustedUserCAKeys.  For more details on
+             certificates, see the CERTIFICATES section in ssh-keygen(1).
+
+     UseDNS  Specifies whether 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 ``yes''.
+
+     UseLogin
+             Specifies whether login(1) is used for interactive login
+             sessions.  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.
+
+     UsePAM  Enables the Pluggable Authentication Module interface.  If set to
+             ``yes'' this will enable PAM authentication using
+             ChallengeResponseAuthentication and PasswordAuthentication in
+             addition to PAM account and session module processing for all
+             authentication types.
+
+             Because PAM challenge-response authentication usually serves an
+             equivalent role to password authentication, you should disable
+             either PasswordAuthentication or ChallengeResponseAuthentication.
+
+             If UsePAM is enabled, you will not be able to run sshd(8) as a
+             non-root user.  The default is ``no''.
+
+     UsePrivilegeSeparation
+             Specifies whether 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 ``yes''.  If UsePrivilegeSeparation is set to
+             ``sandbox'' then the pre-authentication unprivileged process is
+             subject to additional restrictions.
+
+     VersionAddendum
+             Optionally specifies additional text to append to the SSH
+             protocol banner sent by the server upon connection.  The default
+             is ``none''.
+
+     X11DisplayOffset
+             Specifies the first display number available for sshd(8)'s X11
+             forwarding.  This prevents sshd from interfering with real X11
+             servers.  The default is 10.
+
+     X11Forwarding
+             Specifies whether X11 forwarding is permitted.  The argument must
+             be ``yes'' or ``no''.  The default is ``no''.
+
+             When X11 forwarding is enabled, there may be additional exposure
+             to the server and to client displays if the sshd(8) proxy display
+             is configured to listen on the wildcard address (see
+             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 ForwardX11 in
+             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 ``no'' setting.
+
+             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 UseLogin
+             is enabled.
+
+     X11UseLocalhost
+             Specifies whether 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 DISPLAY environment variable to
+             ``localhost''.  This prevents remote hosts from connecting to the
+             proxy 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
+             wildcard address.  The argument must be ``yes'' or ``no''.  The
+             default is ``yes''.
+
+     XAuthLocation
+             Specifies the full pathname of the xauth(1) program.  The default
+             is /usr/X11R6/bin/xauth.
+
+TIME FORMATS
+     sshd(8) 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 following:
+
+           <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(8).  This file should be
+             writable by root only, but it is recommended (though not
+             necessary) that it be world-readable.
+
+SEE ALSO
+     sshd(8)
+
+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.
+
+OpenBSD 5.3                    February 6, 2013                    OpenBSD 5.3