.\" (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 1.121 2001/05/04 14:21:56 stevesk Exp $
+.\" $OpenBSD: sshd.8,v 1.133 2001/06/23 17:48:19 itojun Exp $
.Dd September 25, 1999
.Dt SSHD 8
.Os
.Nm
rereads its configuration file when it receives a hangup signal,
.Dv SIGHUP ,
-by executing itself with the name it was started as, ie.
+by executing itself with the name it was started as, i.e.,
.Pa /usr/sbin/sshd .
.Pp
The options are as follows:
Only user names are valid; a numerical user ID isn't recognized.
By default login is allowed regardless of the user name.
.Pp
+.It Cm AuthorizedKeysFile
+Specifies the file that contains the public RSA keys that can be used
+for RSA authentication in protocol version 1.
+.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 '%',
+%h is replaced by the home directory of the user being authenticated and
+%u is replaced by the username of that user.
+After expansion,
+.Cm AuthorizedKeysFile
+is taken to be an absolute path or one relative to the user's home
+directory.
+The default is
+.Dq .ssh/authorized_keys
.It Cm Banner
In some jurisdictions, sending a warning message before authentication
may be relevant for getting legal protection.
authentication.
The default is
.Dq yes .
-.It Cm Ciphers
-Specifies the ciphers allowed for protocol version 2.
-Multiple ciphers must be comma-separated.
-The default is
-.Dq aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour.
.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.
+The default is
+.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.
for data integrity protection.
Multiple algorithms must be comma-separated.
The default is
-.Pp
-.Bd -literal
- ``hmac-md5,hmac-sha1,hmac-ripemd160,hmac-ripemd160@openssh.com,
- hmac-sha1-96,hmac-md5-96''
-.Ed
+.Dq hmac-md5,hmac-sha1,hmac-ripemd160,hmac-sha1-96,hmac-md5-96 .
.It Cm MaxStartups
Specifies the maximum number of concurrent unauthenticated connections to the
.Nm
Specifies whether
.Xr login 1
is used for interactive login sessions.
+The default is
+.Dq no .
Note that
.Xr login 1
is never used for remote command execution.
-The default is
-.Dq no .
+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
+cookies.
.It Cm X11DisplayOffset
Specifies the first display number available for
.Nm sshd Ns 's
.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.
.It Cm XAuthLocation
Specifies the location of the
.Xr xauth 1
The default is
.Pa /usr/X11R6/bin/xauth .
.El
+.Ss Time Formats
+.Pp
+.Nm
+command-line arguments and configuration file options that specify time
+may be expressed using a sequence of the form:
+.Sm off
+.Ar time Oo Ar qualifier Oc ,
+.Sm on
+where
+.Ar time
+is a positive integer value and
+.Ar qualifier
+is one of the following:
+.Pp
+.Bl -tag -width Ds -compact -offset indent
+.It Cm <none>
+seconds
+.It Cm s | Cm S
+seconds
+.It Cm m | Cm M
+minutes
+.It Cm h | Cm H
+hours
+.It Cm d | Cm D
+days
+.It Cm w | Cm W
+weeks
+.El
+.Pp
+Each member of the sequence is added together to calculate
+the total time value.
+.Pp
+Time format examples:
+.Pp
+.Bl -tag -width Ds -compact -offset indent
+.It 600
+600 seconds (10 minutes)
+.It 10m
+10 minutes
+.It 1h30m
+1 hour 30 minutes (90 minutes)
+.El
.Sh LOGIN PROCESS
When a user successfully logs in,
.Nm
Runs user's shell or command.
.El
.Sh AUTHORIZED_KEYS FILE FORMAT
-The
.Pa $HOME/.ssh/authorized_keys
-file lists the RSA keys that are
-permitted for RSA authentication in protocol version 1.
-Similarly, the
-.Pa $HOME/.ssh/authorized_keys2
-file lists the DSA and RSA keys that are
-permitted for public key authentication (PubkeyAuthentication)
+is the default file that lists the public keys that are
+permitted for RSA authentication in protocol version 1
+and for public key authentication (PubkeyAuthentication)
in protocol version 2.
+.Cm AuthorizedKeysFile
+may be used to specify an alternative file.
.Pp
Each line of the file contains one
key (empty lines and lines starting with a
.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
.Sh SSH_KNOWN_HOSTS FILE FORMAT
The
.Pa /etc/ssh_known_hosts ,
-.Pa /etc/ssh_known_hosts2 ,
-.Pa $HOME/.ssh/known_hosts ,
and
-.Pa $HOME/.ssh/known_hosts2
+.Pa $HOME/.ssh/known_hosts
files contain host public keys for all known hosts.
The global file should
be prepared by the administrator (optional), and the per-user file is
the user so their contents can be copied to known hosts files.
These files are created using
.Xr ssh-keygen 1 .
-.It Pa /etc/primes
+.It Pa /etc/moduli
Contains Diffie-Hellman groups used for the "Diffie-Hellman Group Exchange".
.It Pa /var/run/sshd.pid
Contains the process ID of the
started last).
The content of this file is not sensitive; it can be world-readable.
.It Pa $HOME/.ssh/authorized_keys
-Lists the RSA keys that can be used to log into the user's account.
-This file must be readable by root (which may on some machines imply
-it being world-readable if the user's home directory resides on an NFS
-volume).
-It is recommended that it not be accessible by others.
-The format of this file is described above.
-Users will place the contents of their
-.Pa identity.pub
-files into this file, as described in
-.Xr ssh-keygen 1 .
-.It Pa $HOME/.ssh/authorized_keys2
Lists the public keys (RSA or DSA) that can be used to log into the user's account.
This file must be readable by root (which may on some machines imply
it being world-readable if the user's home directory resides on an NFS
It is recommended that it not be accessible by others.
The format of this file is described above.
Users will place the contents of their
+.Pa identity.pub ,
.Pa id_dsa.pub
and/or
.Pa id_rsa.pub
.Xr ssh-keygen 1 .
.It Pa "/etc/ssh_known_hosts" and "$HOME/.ssh/known_hosts"
These files are consulted when using rhosts with RSA host
-authentication to check the public key of the host.
+authentication or protocol version 2 hostbased authentication
+to check the public key of the host.
The key must be listed in one of these files to be accepted.
The client uses the same files
to verify that it is connecting to the correct remote host.
should be world-readable, and
.Pa $HOME/.ssh/known_hosts
can but need not be world-readable.
-.It Pa "/etc/ssh_known_hosts2" and "$HOME/.ssh/known_hosts2"
-These files are consulted when using protocol version 2 hostbased
-authentication to check the public key of the host.
-The key must be listed in one of these files to be accepted.
-The client uses the same files
-to verify that it is connecting to the correct remote host.
-These files should be writable only by root/the owner.
-.Pa /etc/ssh_known_hosts2
-should be world-readable, and
-.Pa $HOME/.ssh/known_hosts2
-can but need not be world-readable.
.It Pa /etc/nologin
If this file exists,
.Nm
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 sftp-server 8 ,
.Xr ssh 1 ,
.Xr ssh-add 1 ,
.Xr ssh-agent 1 ,
.Xr ssh-keygen 1 ,
-.Xr rlogin 1 ,
-.Xr rsh 1
+.Xr sftp-server 8
.Rs
.%A T. Ylonen
.%A T. Kivinen
.%A N. Provos
.%A W. A. Simpson
.%T "Diffie-Hellman Group Exchange for the SSH Transport Layer Protocol"
-.%N draft-ietf-secsh-dh-group-exchange-00.txt
-.%D January 2001
+.%N draft-ietf-secsh-dh-group-exchange-01.txt
+.%D April 2001
.%O work in progress material
.Re
andersk / openssh.git / blobdiff