- markus@cvs.openbsd.org 2003/08/13 08:46:31

[openssh.git] / sshd_config.5

diff --git a/sshd_config.5 b/sshd_config.5
index 31ef3996d89bbf3744b6f308b027e5875824714b..3d920cc80d74b467ba2d1dcddbd77f97b6796008 100644 (file)
--- a/sshd_config.5
+++ b/sshd_config.5
@@ -34,7 +34,7 @@
 .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 .\"
 .\" (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 1.16 2003/04/30 01:16:20 mouring Exp $
+.\" $OpenBSD: sshd_config.5,v 1.22 2003/08/13 08:46:31 markus Exp $

 .Dd September 25, 1999
 .Dt SSHD_CONFIG 5
 .Os
 .Dd September 25, 1999
 .Dt SSHD_CONFIG 5
 .Os


@@ -61,10 +61,6 @@ The possible
 keywords and their meanings are as follows (note that
 keywords are case-insensitive and arguments are case-sensitive):
 .Bl -tag -width Ds
 keywords and their meanings are as follows (note that
 keywords are case-insensitive and arguments are case-sensitive):
 .Bl -tag -width Ds

-.It Cm AFSTokenPassing
-Specifies whether an AFS token may be forwarded to the server.
-Default is
-.Dq no .

 .It Cm AllowGroups
 This keyword can be followed by a list of group name patterns, separated
 by spaces.
 .It Cm AllowGroups
 This keyword can be followed by a list of group name patterns, separated
 by spaces.


@@ -107,7 +103,8 @@ 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
 for user authentication.
 .Cm AuthorizedKeysFile
 may contain tokens of the form %T which are substituted during connection

-set-up. The following tokens are defined: %% is replaced by a literal '%',
+set-up.
+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,
 %h is replaced by the home directory of the user being authenticated and
 %u is replaced by the username of that user.
 After expansion,


@@ -138,7 +135,7 @@ The default is
 .Pp
 .Bd -literal
   ``aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour,
 .Pp
 .Bd -literal
   ``aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour,

-    aes192-cbc,aes256-cbc''
+    aes192-cbc,aes256-cbc,aes128-ctr,aes192-ctr,aes256-ctr''

 .Ed
 .It Cm ClientAliveInterval
 Sets a timeout interval in seconds after which if no data has been received
 .Ed
 .It Cm ClientAliveInterval
 Sets a timeout interval in seconds after which if no data has been received


@@ -153,20 +150,24 @@ This option applies to protocol version 2 only.
 Sets the number of client alive messages (see above) which may be
 sent without
 .Nm sshd
 Sets the number of client alive messages (see above) which may be
 sent without
 .Nm sshd

-receiving any messages back from the client. If this threshold is
-reached while client alive messages are being sent,
+receiving any messages back from the client.
+If this threshold is reached while client alive messages are being sent,

 .Nm sshd
 .Nm sshd

-will disconnect the client, terminating the session. It is important
-to note that the use of client alive messages is very different from
+will disconnect the client, terminating the session.
+It is important to note that the use of client alive messages is very
+different from

 .Cm KeepAlive
 .Cm KeepAlive

-(below). The client alive messages are sent through the
-encrypted channel and therefore will not be spoofable. The TCP keepalive
-option enabled by
+(below).
+The client alive messages are sent through the encrypted channel
+and therefore will not be spoofable.
+The TCP keepalive option enabled by

 .Cm KeepAlive
 .Cm KeepAlive

-is spoofable. The client alive mechanism is valuable when the client or
+is spoofable.
+The client alive mechanism is valuable when the client or

 server depend on knowing when a connection has become inactive.
 .Pp
 server depend on knowing when a connection has become inactive.
 .Pp

-The default value is 3. If
+The default value is 3.
+If

 .Cm ClientAliveInterval
 (above) is set to 15, and
 .Cm ClientAliveCountMax
 .Cm ClientAliveInterval
 (above) is set to 15, and
 .Cm ClientAliveCountMax


@@ -259,7 +260,6 @@ Specifies that
 and
 .Pa .shosts
 files will not be used in
 and
 .Pa .shosts
 files will not be used in

-.Cm RhostsAuthentication ,

 .Cm RhostsRSAAuthentication
 or
 .Cm HostbasedAuthentication .
 .Cm RhostsRSAAuthentication
 or
 .Cm HostbasedAuthentication .


@@ -322,8 +322,7 @@ Default is
 .It Cm KerberosTgtPassing
 Specifies whether a Kerberos TGT may be forwarded to the server.
 Default is
 .It Cm KerberosTgtPassing
 Specifies whether a Kerberos TGT may be forwarded to the server.
 Default is

-.Dq no ,
-as this only works when the Kerberos KDC is actually an AFS kaserver.
+.Dq no .

 .It Cm KerberosTicketCleanup
 Specifies whether to automatically destroy the user's ticket cache
 file on logout.
 .It Cm KerberosTicketCleanup
 Specifies whether to automatically destroy the user's ticket cache
 file on logout.


@@ -369,11 +368,12 @@ is not specified,
 .Nm sshd
 will listen on the address and all prior
 .Cm Port
 .Nm sshd
 will listen on the address and all prior
 .Cm Port

-options specified. The default is to listen on all local
-addresses.
+options specified.
+The default is to listen on all local addresses.

 Multiple
 .Cm ListenAddress
 Multiple
 .Cm ListenAddress

-options are permitted. Additionally, any
+options are permitted.
+Additionally, any

 .Cm Port
 options must precede this option for non port qualified addresses.
 .It Cm LoginGraceTime
 .Cm Port
 options must precede this option for non port qualified addresses.
 .It Cm LoginGraceTime


@@ -422,12 +422,6 @@ The probability increases linearly and all connection attempts
 are refused if the number of unauthenticated connections reaches
 .Dq full
 (60).
 are refused if the number of unauthenticated connections reaches
 .Dq full
 (60).

-.It Cm PAMAuthenticationViaKbdInt
-Specifies whether PAM challenge response authentication is allowed. This
-allows the use of most PAM challenge response authentication modules, but
-it will allow password authentication regardless of whether
-.Cm PasswordAuthentication
-is enabled.

 .It Cm PasswordAuthentication
 Specifies whether password authentication is allowed.
 The default is
 .It Cm PasswordAuthentication
 Specifies whether password authentication is allowed.
 The default is


@@ -460,8 +454,8 @@ but only if the
 .Ar command
 option has been specified
 (which may be useful for taking remote backups even if root login is
 .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.
+normally not allowed).
+All other authentication methods are disabled for root.

 .Pp
 If this option is set to
 .Dq no
 .Pp
 If this option is set to
 .Dq no


@@ -534,10 +528,6 @@ Specifies whether public key authentication is allowed.
 The default is
 .Dq yes .
 Note that this option applies to protocol version 2 only.
 The default is
 .Dq yes .
 Note that this option applies to protocol version 2 only.

-.It Cm RhostsAuthentication
-Specifies whether authentication using rhosts or /etc/hosts.equiv
-files is sufficient.
-Normally, this method should not be permitted because it is insecure.

 .Cm RhostsRSAAuthentication
 should be used
 instead, because it performs RSA-based host authentication in addition
 .Cm RhostsRSAAuthentication
 should be used
 instead, because it performs RSA-based host authentication in addition


@@ -585,6 +575,14 @@ Gives the facility code that is used when logging messages from
 The possible values are: DAEMON, USER, AUTH, LOCAL0, LOCAL1, LOCAL2,
 LOCAL3, LOCAL4, LOCAL5, LOCAL6, LOCAL7.
 The default is AUTH.
 The possible values are: DAEMON, USER, AUTH, LOCAL0, LOCAL1, LOCAL2,
 LOCAL3, LOCAL4, LOCAL5, LOCAL6, LOCAL7.
 The default is AUTH.

+.It Cm UseDNS
+Specifies whether
+.Nm sshd
+should lookup 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
 .It Cm UseLogin
 Specifies whether
 .Xr login 1


@@ -604,6 +602,13 @@ cookies.
 If
 .Cm UsePrivilegeSeparation
 is specified, it will be disabled after authentication.
 If
 .Cm UsePrivilegeSeparation
 is specified, it will be disabled after authentication.

+.It Cm UsePAM
+Enables PAM authentication (via challenge-response) and session set up. 
+If you enable this, you should probably disable 
+.Cm PasswordAuthentication .
+If you enable 
+.CM UsePAM
+then you will not be able to run sshd as a non-root user.

 .It Cm UsePrivilegeSeparation
 Specifies whether
 .Nm sshd
 .It Cm UsePrivilegeSeparation
 Specifies whether
 .Nm sshd


@@ -615,14 +620,6 @@ The goal of privilege separation is to prevent privilege
 escalation by containing any corruption within the unprivileged processes.
 The default is
 .Dq yes .
 escalation by containing any corruption within the unprivileged processes.
 The default is
 .Dq yes .

-.It Cm VerifyReverseMapping
-Specifies whether
-.Nm 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
-.Dq no .

 .It Cm X11DisplayOffset
 Specifies the first display number available for
 .Nm sshd Ns 's
 .It Cm X11DisplayOffset
 Specifies the first display number available for
 .Nm sshd Ns 's


@@ -653,7 +650,7 @@ display server may be exposed to attack when the ssh client requests
 forwarding (see the warnings for
 .Cm ForwardX11
 in
 forwarding (see the warnings for
 .Cm ForwardX11
 in

-.Xr ssh_config 5 ).
+.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
 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


@@ -699,7 +696,6 @@ The default is
 .Pa /usr/X11R6/bin/xauth .
 .El
 .Ss Time Formats
 .Pa /usr/X11R6/bin/xauth .
 .El
 .Ss Time Formats

-.Pp

 .Nm sshd
 command-line arguments and configuration file options that specify time
 may be expressed using a sequence of the form:
 .Nm sshd
 command-line arguments and configuration file options that specify time
 may be expressed using a sequence of the form:


@@ -748,6 +744,8 @@ Contains configuration data for
 This file should be writable by root only, but it is recommended
 (though not necessary) that it be world-readable.
 .El
 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.
 .Sh AUTHORS
 OpenSSH is a derivative of the original and free
 ssh 1.2.12 release by Tatu Ylonen.


@@ -759,5 +757,3 @@ Markus Friedl contributed the support for SSH
 protocol versions 1.5 and 2.0.
 Niels Provos and Markus Friedl contributed support
 for privilege separation.
 protocol versions 1.5 and 2.0.
 Niels Provos and Markus Friedl contributed support
 for privilege separation.

-.Sh SEE ALSO
-.Xr sshd 8