.\" (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.1,v 1.280 2008/11/09 12:34:47 tobias Exp $
+.\" $OpenBSD: ssh.1,v 1.288 2009/12/29 16:38:41 stevesk Exp $
.Dd $Mdocdate$
.Dt SSH 1
.Os
.Pp
Agent forwarding should be enabled with caution.
Users with the ability to bypass file permissions on the remote host
-(for the agent's Unix-domain socket)
-can access the local agent through the forwarded connection.
+(for the agent's
+.Ux Ns -domain
+socket) can access the local agent through the forwarded connection.
An attacker cannot obtain key material from the agent,
however they can perform operations on the keys that enable them to
authenticate using the identities loaded into the agent.
.Ar cipher_spec
is a comma-separated list of ciphers
listed in order of preference.
-The supported ciphers are:
-3des-cbc,
-aes128-cbc,
-aes192-cbc,
-aes256-cbc,
-aes128-ctr,
-aes192-ctr,
-aes256-ctr,
-arcfour128,
-arcfour256,
-arcfour,
-blowfish-cbc,
-and
-cast128-cbc.
-The default is:
-.Bd -literal -offset indent
-aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour128,
-arcfour256,arcfour,aes192-cbc,aes256-cbc,aes128-ctr,
-aes192-ctr,aes256-ctr
-.Ed
+See the
+.Cm Ciphers
+keyword for more information.
.It Fl D Xo
.Sm off
.Oo Ar bind_address : Oc
.It RekeyLimit
.It RemoteForward
.It RhostsRSAAuthentication
+.It RoutingDomain
.It RSAAuthentication
.It SendEnv
.It ServerAliveInterval
.Cm GatewayPorts
option is enabled (see
.Xr sshd_config 5 ) .
+.Pp
+If the
+.Ar port
+argument is
+.Ql 0 ,
+the listen port will be dynamically allocated on the server and reported
+to the client at run time.
.It Fl S Ar ctl_path
Specifies the location of a control socket for connection sharing.
Refer to the description of
if an error occurred.
.Sh AUTHENTICATION
The OpenSSH SSH client supports SSH protocols 1 and 2.
-Protocol 2 is the default, with
-.Nm
-falling back to protocol 1 if it detects protocol 2 is unsupported.
-These settings may be altered using the
+The default is to use protocol 2 only,
+though this can be changed via the
.Cm Protocol
option in
-.Xr ssh_config 5 ,
-or enforced using the
+.Xr ssh_config 5
+or the
.Fl 1
and
.Fl 2
options (see above).
Both protocols support similar authentication methods,
-but protocol 2 is preferred since
+but protocol 2 is the default since
it provides additional mechanisms for confidentiality
(the traffic is encrypted using AES, 3DES, Blowfish, CAST128, or Arcfour)
and integrity (hmac-md5, hmac-sha1, umac-64, hmac-ripemd160).