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.\" 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/local/ticra/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/local/ticra/bin/vacation''.
.PP
System administrators should be conservative about populating
/usr/local/ticra/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 \-DBINDIR=\e"\fIdir\fP\e"
to change the default program directory
(defaults to ``/usr/local/ticra/bin'').
.SH FILES
/usr/local/ticra/bin \- directory for restricted programs
.SH SEE ALSO
sendmail(8)
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