.\" (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 1.42 2005/02/28 00:54:10 djm Exp $
+.\" $OpenBSD: ssh_config.5,v 1.61 2005/07/08 12:53:10 jmc Exp $
.Dd September 25, 1999
.Dt SSH_CONFIG 5
.Os
.Nd OpenSSH SSH client configuration files
.Sh SYNOPSIS
.Bl -tag -width Ds -compact
-.It Pa $HOME/.ssh/config
+.It Pa ~/.ssh/config
.It Pa /etc/ssh/ssh_config
.El
.Sh DESCRIPTION
command-line options
.It
user's configuration file
-.Pq Pa $HOME/.ssh/config
+.Pq Pa ~/.ssh/config
.It
system-wide configuration file
.Pq Pa /etc/ssh/ssh_config
The default is
.Dq no .
.It Cm BindAddress
-Specify the interface to transmit from on machines with multiple
-interfaces or aliased addresses.
+Use the specified address on the local machine as the source address of
+the connection.
+Only useful on systems with more than one address.
Note that this option does not work if
.Cm UsePrivilegedPort
is set to
.Dq aes128-ctr ,
.Dq aes192-ctr ,
.Dq aes256-ctr ,
+.Dq arcfour128 ,
+.Dq arcfour256 ,
.Dq arcfour ,
.Dq blowfish-cbc ,
and
.Dq cast128-cbc .
The default is
.Bd -literal
- ``aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour,
- aes192-cbc,aes256-cbc''
+ ``aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour128,
+ arcfour256,arcfour,aes192-cbc,aes256-cbc,aes128-ctr,
+ aes192-ctr,aes256-ctr''
.Ed
.It Cm ClearAllForwardings
Specifies that all local, remote and dynamic port forwardings
program before they are accepted (see
.Xr ssh-add 1
for details).
+If the
+.Cm ControlPath
+can not be opened,
+.Nm ssh
+will continue without connecting to a master instance.
+.Pp
+X11 and
+.Xr ssh-agent 1
+forwarding is supported over these multiplexed connections, however the
+display and agent fowarded will be the one belonging to the master
+connection i.e. it is not possible to forward multiple displays or agents.
+.Pp
+Two additional options allow for opportunistic multiplexing: try to use a
+master connection but fall back to creating a new one if one does not already
+exist.
+These options are:
+.Dq auto
+and
+.Dq autoask .
+The latter requires confirmation like the
+.Dq ask
+option.
.It Cm ControlPath
-Specify the path to the control socket used for connection sharing.
-See
+Specify the path to the control socket used for connection sharing as described
+in the
.Cm ControlMaster
-above.
+section above or the string
+.Dq none
+to disable connection sharing.
+In the path,
+.Ql %h
+will be substituted by the target host name,
+.Ql %p
+the port and
+.Ql %r
+by the remote login username.
+It is recommended that any
+.Cm ControlPath
+used for opportunistic connection sharing include
+all three of these escape sequences.
+This ensures that shared connections are uniquely identified.
.It Cm DynamicForward
Specifies that a TCP/IP port on the local machine be forwarded
over the secure channel, and the application
The default is
.Dq no .
Note that this option applies to protocol version 2 only.
+.It Cm HashKnownHosts
+Indicates that
+.Nm ssh
+should hash host names and addresses when they are added to
+.Pa ~/.ssh/known_hosts .
+These hashed names may be used normally by
+.Nm ssh
+and
+.Nm sshd ,
+but they do not reveal identifying information should the file's contents
+be disclosed.
+The default is
+.Dq no .
+Note that hashing of names and addresses will not be retrospectively applied
+to existing known hosts files, but these may be manually hashed using
+.Xr ssh-keygen 1 .
.It Cm HostbasedAuthentication
Specifies whether to try rhosts based authentication with public key
authentication.
Specifies a file from which the user's RSA or DSA authentication identity
is read.
The default is
-.Pa $HOME/.ssh/identity
+.Pa ~/.ssh/identity
for protocol version 1, and
-.Pa $HOME/.ssh/id_rsa
+.Pa ~/.ssh/id_rsa
and
-.Pa $HOME/.ssh/id_dsa
+.Pa ~/.ssh/id_dsa
for protocol version 2.
Additionally, any identities represented by the authentication agent
will be used for authentication.
.It Cm LocalForward
Specifies that a TCP/IP port on the local machine be forwarded over
the secure channel to the specified host and port from the remote machine.
-The first argument must be a port number, and the second must be
-.Ar host:port .
-IPv6 addresses can be specified with an alternative syntax:
-.Ar host/port .
-Multiple forwardings may be specified, and additional
-forwardings can be given on the command line.
+The first argument must be
+.Sm off
+.Oo Ar bind_address : Oc Ar port
+.Sm on
+and the second argument must be
+.Ar host : Ns Ar hostport .
+IPv6 addresses can be specified by enclosing addresses in square brackets or
+by using an alternative syntax:
+.Oo Ar bind_address Ns / Oc Ns Ar port
+and
+.Ar host Ns / Ns Ar hostport .
+Multiple forwardings may be specified, and additional forwardings can be
+given on the command line.
Only the superuser can forward privileged ports.
+By default, the local port is bound in accordance with the
+.Cm GatewayPorts
+setting.
+However, an explicit
+.Ar bind_address
+may be used to bind the connection to a specific address.
+The
+.Ar bind_address
+of
+.Dq localhost
+indicates that the listening port be bound for local use only, while an
+empty address or
+.Sq *
+indicates that the port should be available from all interfaces.
.It Cm LogLevel
Gives the verbosity level that is used when logging messages from
.Nm ssh .
.It Cm PreferredAuthentications
Specifies the order in which the client should try protocol 2
authentication methods.
-This allows a client to prefer one method (e.g.
+This allows a client to prefer one method (e.g.\&
.Cm keyboard-interactive )
-over another method (e.g.
+over another method (e.g.\&
.Cm password )
The default for this option is:
.Dq hostbased,publickey,keyboard-interactive,password .
.Cm CheckHostIP
is not available for connects with a proxy command.
.Pp
+This directive is useful in conjunction with
+.Xr nc 1
+and its proxy support.
+For example, the following directive would connect via an HTTP proxy at
+192.0.2.0:
+.Bd -literal -offset 3n
+ProxyCommand /usr/bin/nc -X connect -x 192.0.2.0:8080 %h %p
+.Ed
.It Cm PubkeyAuthentication
Specifies whether to try public key authentication.
The argument to this keyword must be
.It Cm RemoteForward
Specifies that a TCP/IP port on the remote machine be forwarded over
the secure channel to the specified host and port from the local machine.
-The first argument must be a port number, and the second must be
-.Ar host:port .
-IPv6 addresses can be specified with an alternative syntax:
-.Ar host/port .
+The first argument must be
+.Sm off
+.Oo Ar bind_address : Oc Ar port
+.Sm on
+and the second argument must be
+.Ar host : Ns Ar hostport .
+IPv6 addresses can be specified by enclosing addresses in square brackets
+or by using an alternative syntax:
+.Oo Ar bind_address Ns / Oc Ns Ar port
+and
+.Ar host Ns / Ns Ar hostport .
Multiple forwardings may be specified, and additional
forwardings can be given on the command line.
Only the superuser can forward privileged ports.
+.Pp
+If the
+.Ar bind_address
+is not specified, the default is to only bind to loopback addresses.
+If the
+.Ar bind_address
+is
+.Ql *
+or an empty string, then the forwarding is requested to listen on all
+interfaces.
+Specifying a remote
+.Ar bind_address
+will only succeed if the server's
+.Cm GatewayPorts
+option is enabled (see
+.Xr sshd_config 5 ) .
.It Cm RhostsRSAAuthentication
Specifies whether to try rhosts based authentication with RSA host
authentication.
.Dq yes ,
.Nm ssh
will never automatically add host keys to the
-.Pa $HOME/.ssh/known_hosts
+.Pa ~/.ssh/known_hosts
file, and refuses to connect to hosts whose host key has changed.
This provides maximum protection against trojan horse attacks,
however, can be annoying when the
.It Cm UserKnownHostsFile
Specifies a file to use for the user
host key database instead of
-.Pa $HOME/.ssh/known_hosts .
+.Pa ~/.ssh/known_hosts .
.It Cm VerifyHostKeyDNS
Specifies whether to verify the remote key using DNS and SSHFP resource
records.
.El
.Sh FILES
.Bl -tag -width Ds
-.It Pa $HOME/.ssh/config
+.It Pa ~/.ssh/config
This is the per-user configuration file.
The format of this file is described above.
This file is used by the
andersk / openssh.git / blobdiff