.\" (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 1.23 2003/10/12 13:12:13 jmc Exp $
+.\" $OpenBSD: ssh_config.5,v 1.34 2004/05/06 11:24:23 jmc Exp $
.Dd September 25, 1999
.Dt SSH_CONFIG 5
.Os
.Cm ForwardX11Trusted
option is also enabled.
.It Cm ForwardX11Trusted
-If the this option is set to
+If this option is set to
.Dq yes
then remote X11 clients will have full access to the original X11 display.
If this option is set to
host key database instead of
.Pa /etc/ssh/ssh_known_hosts .
.It Cm GSSAPIAuthentication
-Specifies whether authentication based on GSSAPI may be used, either using
-the result of a successful key exchange, or using GSSAPI user
-authentication.
+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 is possible to have
multiple identity files specified in configuration files; all these
identities will be tried in sequence.
-.It Cm KeepAlive
-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
+.It Cm IdentitiesOnly
+Specifies that
+.Nm ssh
+should only use the authentication identity files configured in the
+.Nm
+files,
+even if the
+.Nm ssh-agent
+offers more identities.
+The argument to this keyword must be
.Dq yes
-(to send keepalives), 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 keepalives, the value should be set to
+or
+.Dq no .
+This option is intented for situations where
+.Nm ssh-agent
+offers many different identities.
+The default is
.Dq no .
.It Cm LocalForward
Specifies that a TCP/IP port on the local machine be forwarded over
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 the wildcard characters
+.Ql \&*
+and
+.Ql \&? .
+Multiple environment variables may be separated by whitespace or spread
+across multiple
+.Cm SendEnv
+directives.
+The default is not to send any environment variables.
+.It Cm ServerAliveInterval
+Sets a timeout interval in seconds after which if no data has been received
+from the server,
+.Nm ssh
+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 ServerAliveCountMax
+Sets the number of server alive messages (see above) which may be
+sent without
+.Nm ssh
+receiving any messages back from the server.
+If this threshold is reached while server alive messages are being sent,
+.Nm 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
+(above) is set to 15, and
+.Cm ServerAliveCountMax
+is left at the default, if the server becomes unresponsive ssh
+will disconnect after approximately 45 seconds.
.It Cm SmartcardDevice
Specifies which smartcard device to use.
The argument to this keyword is the device
.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 UsePrivilegedPort
Specifies whether to use a privileged port for outgoing connections.
The argument must be
.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.
This file is used by the
.Nm ssh
client.
-This file does not usually contain any sensitive information,
-but the recommended permissions are read/write for the user, and not
-accessible by others.
+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
andersk / openssh.git / blobdiff