.\" (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.8,v 1.132 2001/06/23 03:03:59 markus Exp $
+.\" $OpenBSD: sshd.8,v 1.140 2001/08/16 19:18:34 jakob Exp $
.Dd September 25, 1999
.Dt SSHD 8
.Os
.Ss SSH protocol version 2
.Pp
Version 2 works similarly:
-Each host has a host-specific DSA key used to identify the host.
+Each host has a host-specific key (RSA or DSA) used to identify the host.
However, when the daemon starts, it does not generate a server key.
Forward security is provided through a Diffie-Hellman key agreement.
This key agreement results in a shared session key.
.It Fl b Ar bits
Specifies the number of bits in the ephemeral protocol version 1
server key (default 768).
-.Pp
.It Fl d
Debug mode.
The server sends verbose debug output to the system
Nothing is sent to the system log.
Normally the beginning,
authentication, and termination of each connection is logged.
+.It Fl t
+Test mode.
+Only check the validity of the configuration file and sanity of the keys.
+This is useful for updating
+.Nm
+reliably as configuration options may change.
.It Fl u Ar len
This option is used to specify the size of the field
in the
wildcards in the patterns.
Only user names are valid; a numerical user ID isn't recognized.
By default login is allowed regardless of the user name.
+If the pattern takes the form USER@HOST then USER and HOST
+are separately checked, allowing you to restrict logins to particular
+users from particular hosts.
.Pp
.It Cm AuthorizedKeysFile
-Specifies the file that contains the public RSA keys that can be used
-for RSA authentication in protocol version 1.
+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
set-up. The following tokens are defined; %% is replaces by a literal '%',
This option is only available for protocol version 2.
.Pp
.It Cm ChallengeResponseAuthentication
-Specifies whether
-challenge response
-authentication is allowed.
-Currently there is only support for
-.Xr skey 1
-authentication.
+Specifies whether challenge response authentication is allowed.
+All authentication styles from
+.Xr login.conf 5
+are supported.
The default is
.Dq yes .
-.It Cm CheckMail
-Specifies whether
-.Nm
-should check for new mail for interactive logins.
-The default is
-.Dq no .
.It Cm Ciphers
Specifies the ciphers allowed for protocol version 2.
Multiple ciphers must be comma-separated.
.Dq aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour.
.It Cm ClientAliveInterval
Sets a timeout interval in seconds after which if no data has been received
-from the client,
+from the client,
.Nm
will send a message through the encrypted
channel to request a response from the client.
sent without
.Nm
receiving any messages back from the client. If this threshold is
-reached while client alive messages are being sent,
+reached while client alive messages are being sent,
.Nm
will disconnect the client, terminating the session. It is important
-to note that the use of client alive messages is very different from
+to note that the use of client alive messages is very different from
.Cm Keepalive
(below). The client alive messages are sent through the
encrypted channel and therefore will not be spoofable. The TCP keepalive
The default value is 3. If you set
.Cm ClientAliveInterval
(above) to 15, and leave this value at the default, unresponsive ssh clients
-will be disconnected after approximately 45 seconds.
+will be disconnected after approximately 45 seconds.
.It Cm DenyGroups
This keyword can be followed by a number of group names, separated
by spaces.
Note that
.Xr login 1
is never used for remote command execution.
-Note also, that if this is enabled,
-.Cm X11Forwarding
+Note also, that if this is enabled,
+.Cm X11Forwarding
will be disabled because
.Xr login 1
does not know how to handle
-.Xr xauth 1
+.Xr xauth 1
cookies.
.It Cm X11DisplayOffset
Specifies the first display number available for
.Dq no .
Note that disabling X11 forwarding does not improve security in any
way, as users can always install their own forwarders.
-X11 forwarding is automatically disabled if
-.Cm UseLogin
-is enabled.
+X11 forwarding is automatically disabled if
+.Cm UseLogin
+is enabled.
.It Cm XAuthLocation
Specifies the location of the
.Xr xauth 1
.It Cm no-pty
Prevents tty allocation (a request to allocate a pty will fail).
.It Cm permitopen="host:port"
-Limit local
+Limit local
.Li ``ssh -L''
port forwarding such that it may only connect to the specified host and
-port. Multiple
+port. Multiple
.Cm permitopen
-options may be applied separated by commas. No pattern matching is
-performed on the specified hostnames, they must be literal domains or
+options may be applied separated by commas. No pattern matching is
+performed on the specified hostnames, they must be literal domains or
addresses.
.El
.Ss Examples
Markus Friedl contributed the support for SSH
protocol versions 1.5 and 2.0.
.Sh SEE ALSO
-.Xr moduli 5 ,
-.Xr rlogin 1 ,
-.Xr rsh 1 ,
.Xr scp 1 ,
.Xr sftp 1 ,
.Xr ssh 1 ,
.Xr ssh-add 1 ,
.Xr ssh-agent 1 ,
.Xr ssh-keygen 1 ,
+.Xr login.conf 5 ,
+.Xr moduli 5 ,
.Xr sftp-server 8
.Rs
.%A T. Ylonen
.%A T. Rinne
.%A S. Lehtinen
.%T "SSH Protocol Architecture"
-.%N draft-ietf-secsh-architecture-07.txt
-.%D January 2001
+.%N draft-ietf-secsh-architecture-09.txt
+.%D July 2001
.%O work in progress material
.Re
.Rs
andersk / openssh.git / blobdiff