.\" (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 1.232 2006/07/10 16:04:21 jmc Exp $
-.Dd September 25, 1999
+.\" $OpenBSD: sshd.8,v 1.238 2008/02/09 12:15:43 mcbride Exp $
+.Dd $Mdocdate$
.Dt SSHD 8
.Os
.Sh NAME
.Nm
(OpenSSH Daemon) is the daemon program for
.Xr ssh 1 .
-Together these programs replace rlogin and rsh, and
-provide secure encrypted communications between two untrusted hosts
+Together these programs replace
+.Xr rlogin 1
+and
+.Xr rsh 1 ,
+and provide secure encrypted communications between two untrusted hosts
over an insecure network.
.Pp
.Nm
When this option is specified,
.Nm
will send the output to the standard error instead of the system log.
-.It Fl f Ar configuration_file
+.It Fl f Ar config_file
Specifies the name of the configuration file.
The default is
.Pa /etc/ssh/sshd_config .
to use from those offered by the server.
Additionally, session integrity is provided
through a cryptographic message authentication code
-(hmac-sha1 or hmac-md5).
+(hmac-md5, hmac-sha1, umac-64 or hmac-ripemd160).
.Pp
Finally, the server and the client enter an authentication dialog.
The client tries to authenticate itself using
a leading
.Ql \&*LOCKED\&*
on FreeBSD and a leading
-.Ql \&!!
-on Linux). If there is a requirement to disable password authentication
+.Ql \&!
+on most Linuxes).
+If there is a requirement to disable password authentication
for the account while allowing still public-key, then the passwd field
should be set to something other than these values (eg
.Ql NP
An example might be a key that permits remote backups but nothing else.
Note that the client may specify TCP and/or X11
forwarding unless they are explicitly prohibited.
+The command originally supplied by the client is available in the
+.Ev SSH_ORIGINAL_COMMAND
+environment variable.
Note that this option applies to shell, command or subsystem execution.
.It Cm environment="NAME=value"
Specifies that the string is to be added to the environment when
but allows host-based authentication without permitting login with
rlogin/rsh.
.Pp
+.It ~/.ssh/
+This directory is the default location for all user-specific configuration
+and authentication information.
+There is no general requirement to keep the entire contents of this directory
+secret, but the recommended permissions are read/write/execute for the user,
+and not accessible by others.
+.Pp
.It ~/.ssh/authorized_keys
Lists the public keys (RSA/DSA) that can be used for logging in as this user.
The format of this file is described above.
-This file is not highly sensitive, but the recommended
+The content of the file is not highly sensitive, but the recommended
permissions are read/write for the user, and not accessible by others.
.Pp
+If this file, the
+.Pa ~/.ssh
+directory, or the user's home directory are writable
+by other users, then the file could be modified or replaced by unauthorized
+users.
+In this case,
+.Nm
+will not allow it to be used unless the
+.Cm StrictModes
+option has been set to
+.Dq no .
+The recommended permissions can be set by executing
+.Dq chmod go-w ~/ ~/.ssh ~/.ssh/authorized_keys .
+.Pp
.It ~/.ssh/environment
This file is read into the environment at login (if it exists).
It can only contain empty lines, comment lines (that start with
but allows host-based authentication without permitting login with
rlogin/rsh.
.Pp
-.It /etc/ssh/ssh_known_hosts
-Systemwide list of known host keys.
-This file should be prepared by the
-system administrator to contain the public host keys of all machines in the
-organization.
-The format of this file is described above.
-This file should be writable only by root/the owner and
-should be world-readable.
-.Pp
.It /etc/ssh/ssh_host_key
.It /etc/ssh/ssh_host_dsa_key
.It /etc/ssh/ssh_host_rsa_key
These files are created using
.Xr ssh-keygen 1 .
.Pp
+.It /etc/ssh/ssh_known_hosts
+Systemwide list of known host keys.
+This file should be prepared by the
+system administrator to contain the public host keys of all machines in the
+organization.
+The format of this file is described above.
+This file should be writable only by root/the owner and
+should be world-readable.
+.Pp
.It /etc/ssh/sshd_config
Contains configuration data for
.Nm sshd .
.Xr ssh-add 1 ,
.Xr ssh-agent 1 ,
.Xr ssh-keygen 1 ,
+.Xr ssh-keyscan 1 ,
.Xr chroot 2 ,
.Xr hosts_access 5 ,
.Xr login.conf 5 ,