.\" (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 1.84 2008/03/25 11:58:02 djm Exp $
-.Dd $Mdocdate: March 27 2008 $
+.\" $OpenBSD: sshd_config.5,v 1.106 2009/04/21 15:13:17 stevesk Exp $
+.Dd $Mdocdate: April 21 2009 $
.Dt SSHD_CONFIG 5
.Os
.Sh NAME
(use IPv6 only).
The default is
.Dq any .
+.It Cm AllowAgentForwarding
+Specifies whether
+.Xr ssh-agent 1
+forwarding is permitted.
+The default is
+.Dq 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.
.It Cm AllowGroups
This keyword can be followed by a list of group name patterns, separated
by spaces.
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.
-All authentication styles from
-.Xr login.conf 5
-are supported.
+Specifies whether challenge-response authentication is allowed (e.g. via
+PAM or though authentication styles supported in
+.Xr login.conf 5 )
The default is
.Dq yes .
.It Cm ChrootDirectory
to after authentication.
This path, and all its components, must be root-owned directories that are
not writable by any other user or group.
+After the chroot,
+.Xr sshd 8
+changes the working directory to the user's home directory.
.Pp
The path may contain the following tokens that are expanded at runtime once
the connecting user has been authenticated: %% is replaced by a literal '%',
The
.Cm ChrootDirectory
must contain the necessary files and directories to support the
-users' session.
+user's session.
For an interactive session this requires at least a shell, typically
.Xr sh 1 ,
and basic
For file transfer sessions using
.Dq sftp ,
no additional configuration of the environment is necessary if the
-in-process sftp server is used (see
-.Cm Subsystem
+in-process sftp server is used,
+though sessions which use logging do require
+.Pa /dev/log
+inside the chroot directory (see
+.Xr sftp-server 8
for details).
.Pp
The default is not to
.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
+aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,
+aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,
+aes256-cbc,arcfour
.Ed
.It Cm ClientAliveCountMax
Sets the number of client alive messages (see below) which may be
.It Cm GSSAPIAuthentication
Specifies whether user authentication based on GSSAPI is allowed.
The default is
-.Dq no .
+.Dq yes .
+Note that this option applies to protocol version 2 only.
+.It Cm GSSAPIDelegateCredentials
+Specifies whether delegated credentials are stored in the user's environment.
+The default is
+.Dq yes .
+.It Cm GSSAPIKeyExchange
+Specifies whether key exchange based on GSSAPI is allowed. GSSAPI key exchange
+doesn't rely on ssh keys to verify host identity.
+The default is
+.Dq yes .
Note that this option applies to protocol version 2 only.
.It Cm GSSAPICleanupCredentials
Specifies whether to automatically destroy the user's credentials cache
The default is
.Dq yes .
Note that this option applies to protocol version 2 only.
+.It Cm GSSAPICredentialsPath
+If specified, the delegated GSSAPI credential is stored in the
+given path, overwriting any existing credentials.
+Paths can be specified with syntax similar to the AuthorizedKeysFile
+option (i.e., accepting %h and %u tokens).
+When using this option,
+setting 'GssapiCleanupCredentials no' is recommended,
+so logging out of one session
+doesn't remove the credentials in use by another session of
+the same user.
+Currently only implemented for the GSI mechanism.
+.It Cm GSIAllowLimitedProxy
+Specifies whether to accept limited proxy credentials for
+authentication.
+The default is
+.Dq no .
+.It Cm GSSAPIStrictAcceptorCheck
+Determines whether to be strict about the identity of the GSSAPI acceptor
+a client authenticates against. If
+.Dq yes
+then the client must authenticate against the
+.Pa host
+service on the current hostname. If
+.Dq no
+then the client may authenticate against any service key stored in the
+machine's default store. This facility is provided to assist with operation
+on multi homed machines.
+The default is
+.Dq yes .
+Note that this option applies only to protocol version 2 GSSAPI connections,
+and setting it to
+.Dq no
+may only work with recent Kerberos GSSAPI libraries.
+.It Cm GSSAPIStoreCredentialsOnRekey
+Controls whether the user's GSSAPI credentials should be updated following a
+successful connection rekeying. This option can be used to accepted renewed
+or updated credentials from a compatible client. The default is
+.Dq no .
.It Cm HostbasedAuthentication
Specifies whether rhosts or /etc/hosts.equiv authentication together
with successful public key client host authentication is allowed
set in the global section of the config file, until either another
.Cm Match
line or the end of the file.
+.Pp
The arguments to
.Cm Match
are one or more criteria-pattern pairs.
.Cm Host ,
and
.Cm Address .
+The match patterns may consist of single entries or comma-separated
+lists and may use the wildcard and negation operators described in the
+.Sx PATTERNS
+section of
+.Xr ssh_config 5 .
+.Pp
+The patterns in an
+.Cm Address
+criteria may additionally contain addresses to match in CIDR
+address/masklen format, e.g.\&
+.Dq 192.0.2.0/24
+or
+.Dq 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,
+.Dq 192.0.2.0/33
+and
+.Dq 192.0.2.0/8
+respectively.
+.Pp
Only a subset of keywords may be used on the lines following a
.Cm Match
keyword.
Available keywords are
+.Cm AllowAgentForwarding ,
.Cm AllowTcpForwarding ,
.Cm Banner ,
+.Cm ChrootDirectory ,
.Cm ForceCommand ,
.Cm GatewayPorts ,
-.Cm GSSApiAuthentication ,
+.Cm GSSAPIAuthentication ,
+.Cm HostbasedAuthentication ,
.Cm KbdInteractiveAuthentication ,
.Cm KerberosAuthentication ,
+.Cm MaxAuthTries ,
+.Cm MaxSessions ,
.Cm PasswordAuthentication ,
+.Cm PermitEmptyPasswords ,
.Cm PermitOpen ,
.Cm PermitRootLogin ,
.Cm RhostsRSAAuthentication ,
.Cm RSAAuthentication ,
.Cm X11DisplayOffset ,
-.Cm X11Forwarding ,
+.Cm X11Forwarding
and
.Cm X11UseLocalHost .
.It Cm MaxAuthTries
Once the number of failures reaches half this value,
additional failures are logged.
The default is 6.
+.It Cm MaxSessions
+Specifies the maximum number of open sessions permitted per network connection.
+The default is 10.
.It Cm MaxStartups
Specifies the maximum number of concurrent unauthenticated connections to the
SSH daemon.
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.
+The minimum value is 512, and the default is 1024.
.It Cm StrictModes
Specifies whether
.Xr sshd 8
as a non-root user.
The default is
.Dq no .
+.It Cm PermitPAMUserChange
+If set to
+.Dq yes
+this will enable PAM authentication to change the name of the user being
+authenticated. The default is
+.Dq no .
.It Cm UsePrivilegeSeparation
Specifies whether
.Xr sshd 8
andersk / gssapi-openssh.git / blobdiff