105 lines
3.8 KiB
Groff
105 lines
3.8 KiB
Groff
.\" Copyright (c) 1993 Eric P. Allman
|
|
.\" Copyright (c) 1993
|
|
.\" 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.
|
|
.\"
|
|
.\" @(#)smrsh.8 8.2 (Berkeley) 1/9/96
|
|
.\"
|
|
.TH SMRSH 8 11/02/93
|
|
.SH NAME
|
|
smrsh \- restricted shell for sendmail
|
|
.SH SYNOPSIS
|
|
.B smrsh
|
|
.B \-c
|
|
command
|
|
.SH DESCRIPTION
|
|
The
|
|
.I smrsh
|
|
program is intended as a replacement for
|
|
.I sh
|
|
for use in the ``prog'' mailer in
|
|
.IR sendmail (8)
|
|
configuration files.
|
|
It sharply limits the commands that can be run using the
|
|
``|program'' syntax of
|
|
.I sendmail
|
|
in order to improve the over all security of your system.
|
|
Briefly, even if a ``bad guy'' can get sendmail to run a program
|
|
without going through an alias or forward file,
|
|
.I smrsh
|
|
limits the set of programs that he or she can execute.
|
|
.PP
|
|
Briefly,
|
|
.I smrsh
|
|
limits programs to be in the directory
|
|
/usr/libexec/sm.bin,
|
|
allowing the system administrator to choose the set of acceptable commands.
|
|
It also rejects any commands with the characters
|
|
`\`', `<', `>', `|', `;', `&', `$', `(', `)', `\er' (carriage return),
|
|
or `\en' (newline)
|
|
on the command line to prevent ``end run'' attacks.
|
|
.PP
|
|
Initial pathnames on programs are stripped,
|
|
so forwarding to ``/usr/bin/vacation'',
|
|
``/home/server/mydir/bin/vacation'',
|
|
and
|
|
``vacation''
|
|
all actually forward to
|
|
``/usr/libexec/sm.bin/vacation''.
|
|
.PP
|
|
System administrators should be conservative about populating
|
|
/usr/libexec/sm.bin.
|
|
Reasonable additions are
|
|
.IR vacation (1),
|
|
.IR procmail (1),
|
|
and the like.
|
|
No matter how brow-beaten you may be,
|
|
never include any shell or shell-like program
|
|
(such as
|
|
.IR perl (1))
|
|
in the
|
|
sm.bin
|
|
directory.
|
|
Note that this does not restrict the use of shell or perl scripts
|
|
in the sm.bin directory (using the ``#!'' syntax);
|
|
it simply disallows execution of arbitrary programs.
|
|
.SH COMPILATION
|
|
Compilation should be trivial on most systems.
|
|
You may need to use \-DPATH=\e"\fIpath\fP\e"
|
|
to adjust the default search path
|
|
(defaults to ``/bin:/usr/bin'')
|
|
and/or \-DCMDBIN=\e"\fIdir\fP\e"
|
|
to change the default program directory
|
|
(defaults to ``/usr/libexec/sm.bin'').
|
|
.SH FILES
|
|
/usr/libexec/sm.bin \- directory for restricted programs
|
|
.SH SEE ALSO
|
|
sendmail(8)
|