197 lines
6.3 KiB
Groff
197 lines
6.3 KiB
Groff
.\" Copyright (c) 1983, 1989, 1991 The Regents of the University of California.
|
|
.\" All rights reserved.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\" 3. All advertising materials mentioning features or use of this software
|
|
.\" must display the following acknowledgement:
|
|
.\" This product includes software developed by the University of
|
|
.\" California, Berkeley and its contributors.
|
|
.\" 4. Neither the name of the University nor the names of its contributors
|
|
.\" may be used to endorse or promote products derived from this software
|
|
.\" without specific prior written permission.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
|
|
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
|
|
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
.\" SUCH DAMAGE.
|
|
.\"
|
|
.\" @(#)rshd.8 6.11 (Berkeley) 4/20/91
|
|
.\"
|
|
.Dd April 20, 1991
|
|
.Dt RSHD 8
|
|
.Os BSD 4.2
|
|
.Sh NAME
|
|
.Nm rshd
|
|
.Nd remote shell server
|
|
.Sh SYNOPSIS
|
|
.Nm rshd
|
|
.Op Fl aln
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Nm rshd
|
|
server
|
|
is the server for the
|
|
.Xr rcmd 3
|
|
routine and, consequently, for the
|
|
.Xr rsh 1
|
|
program. The server provides remote execution facilities
|
|
with authentication based on privileged port numbers from trusted hosts.
|
|
.Pp
|
|
The
|
|
.Nm rshd
|
|
server
|
|
listens for service requests at the port indicated in
|
|
the ``cmd'' service specification; see
|
|
.Xr services 5 .
|
|
When a service request is received the following protocol
|
|
is initiated:
|
|
.Bl -enum
|
|
.It
|
|
The server checks the client's source port.
|
|
If the port is not in the range 512-1023, the server
|
|
aborts the connection.
|
|
.It
|
|
The server reads characters from the socket up
|
|
to a null (`\e0') byte. The resultant string is
|
|
interpreted as an
|
|
.Tn ASCII
|
|
number, base 10.
|
|
.It
|
|
If the number received in step 2 is non-zero,
|
|
it is interpreted as the port number of a secondary
|
|
stream to be used for the
|
|
.Em stderr .
|
|
A second connection is then created to the specified
|
|
port on the client's machine. The source port of this
|
|
second connection is also in the range 512-1023.
|
|
.It
|
|
The server checks the client's source address
|
|
and requests the corresponding host name (see
|
|
.Xr gethostbyaddr 3 ,
|
|
.Xr hosts 5
|
|
and
|
|
.Xr named 8 ) .
|
|
If the hostname cannot be determined,
|
|
the dot-notation representation of the host address is used.
|
|
If the hostname is in the same domain as the server (according to
|
|
the last two components of the domain name),
|
|
or if the
|
|
.Fl a
|
|
option is given,
|
|
the addresses for the hostname are requested,
|
|
verifying that the name and address correspond.
|
|
If address verification fails, the connection is aborted
|
|
with the message, ``Host address mismatch.''
|
|
.It
|
|
A null terminated user name of at most 16 characters
|
|
is retrieved on the initial socket. This user name
|
|
is interpreted as the user identity on the
|
|
.Em client Ns 's
|
|
machine.
|
|
.It
|
|
A null terminated user name of at most 16 characters
|
|
is retrieved on the initial socket. This user name
|
|
is interpreted as a user identity to use on the
|
|
.Sy server Ns 's
|
|
machine.
|
|
.It
|
|
A null terminated command to be passed to a
|
|
shell is retrieved on the initial socket. The length of
|
|
the command is limited by the upper bound on the size of
|
|
the system's argument list.
|
|
.It
|
|
.Nm Rshd
|
|
then validates the user using
|
|
.Xr ruserok 3 ,
|
|
which uses the file
|
|
.Pa /etc/hosts.equiv
|
|
and the
|
|
.Pa .rhosts
|
|
file found in the user's home directory. The
|
|
.Fl l
|
|
option prevents
|
|
.Xr ruserok 3
|
|
from doing any validation based on the user's ``.rhosts'' file,
|
|
unless the user is the superuser.
|
|
.It
|
|
A null byte is returned on the initial socket
|
|
and the command line is passed to the normal login
|
|
shell of the user. The
|
|
shell inherits the network connections established
|
|
by
|
|
.Nm rshd .
|
|
.Pp
|
|
Transport-level keepalive messages are enabled unless the
|
|
.Fl n
|
|
option is present.
|
|
The use of keepalive messages allows sessions to be timed out
|
|
if the client crashes or becomes unreachable.
|
|
.El
|
|
.Sh DIAGNOSTICS
|
|
Except for the last one listed below,
|
|
all diagnostic messages
|
|
are returned on the initial socket,
|
|
after which any network connections are closed.
|
|
An error is indicated by a leading byte with a value of
|
|
1 (0 is returned in step 9 above upon successful completion
|
|
of all the steps prior to the execution of the login shell).
|
|
.Bl -tag -width indent
|
|
.It Sy Locuser too long.
|
|
The name of the user on the client's machine is
|
|
longer than 16 characters.
|
|
.It Sy Ruser too long.
|
|
The name of the user on the remote machine is
|
|
longer than 16 characters.
|
|
.It Sy Command too long .
|
|
The command line passed exceeds the size of the argument
|
|
list (as configured into the system).
|
|
.It Sy Login incorrect.
|
|
No password file entry for the user name existed.
|
|
.It Sy Remote directory.
|
|
The
|
|
.Xr chdir
|
|
command to the home directory failed.
|
|
.It Sy Permission denied.
|
|
The authentication procedure described above failed.
|
|
.It Sy Can't make pipe.
|
|
The pipe needed for the
|
|
.Em stderr ,
|
|
wasn't created.
|
|
.It Sy Can't fork; try again.
|
|
A
|
|
.Xr fork
|
|
by the server failed.
|
|
.It Sy <shellname>: ...
|
|
The user's login shell could not be started. This message is returned
|
|
on the connection associated with the
|
|
.Em stderr ,
|
|
and is not preceded by a flag byte.
|
|
.El
|
|
.Sh SEE ALSO
|
|
.Xr rsh 1 ,
|
|
.Xr rcmd 3 ,
|
|
.Xr ruserok 3
|
|
.Sh BUGS
|
|
The authentication procedure used here assumes the integrity
|
|
of each client machine and the connecting medium. This is
|
|
insecure, but is useful in an ``open'' environment.
|
|
.Pp
|
|
A facility to allow all data exchanges to be encrypted should be
|
|
present.
|
|
.Pp
|
|
A more extensible protocol (such as Telnet) should be used.
|