106 lines
3.8 KiB
Groff
106 lines
3.8 KiB
Groff
.\" Copyright (c) 1993 Eric P. Allman
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.\" Copyright (c) 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)smrsh.8 8.1 (Berkeley) 11/13/94
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.\"
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.TH SMRSH 8 11/02/93
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.SH NAME
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smrsh \- restricted shell for sendmail
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.SH SYNOPSIS
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.B smrsh
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.B \-c
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command
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.SH DESCRIPTION
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The
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.I smrsh
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program is intended as a replacement for
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.I sh
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for use in the ``prog'' mailer in
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.IR sendmail (8)
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configuration files.
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It sharply limits the commands that can be run using the
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``|program'' syntax of
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.I sendmail
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in order to improve the over all security of your system.
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Briefly, even if a ``bad guy'' can get sendmail to run a program
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without going through an alias or forward file,
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.I smrsh
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limits the set of programs that he or she can execute.
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.PP
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Briefly,
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.I smrsh
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limits programs to be in the directory
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/usr/adm/sm.bin,
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allowing the system administrator to choose the set of acceptable commands.
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It also rejects any commands with the characters
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`\`', `<', `>', `|', `;', `&', `$', `(', `)', `\r' (carriage return),
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or `\n' (newline)
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on the command line to prevent ``end run'' attacks.
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.PP
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Initial pathnames on programs are stripped,
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so forwarding to ``/usr/ucb/vacation'',
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``/usr/bin/vacation'',
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``/home/server/mydir/bin/vacation'',
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and
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``vacation''
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all actually forward to
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``/usr/adm/sm.bin/vacation''.
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.PP
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System administrators should be conservative about populating
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/usr/adm/sm.bin.
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Reasonable additions are
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.IR vacation (1),
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.IR procmail (1),
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and the like.
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No matter how brow-beaten you may be,
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never include any shell or shell-like program
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(such as
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.IR perl (1))
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in the
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sm.bin
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directory.
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Note that this does not restrict the use of shell or perl scripts
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in the sm.bin directory (using the ``#!'' syntax);
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it simply disallows execution of arbitrary programs.
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.SH COMPILATION
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Compilation should be trivial on most systems.
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You may need to use \-DPATH=\e"\fIpath\fP\e"
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to adjust the default search path
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(defaults to ``/bin:/usr/bin:/usr/ucb'')
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and/or \-DCMDBIN=\e"\fIdir\fP\e"
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to change the default program directory
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(defaults to ``/usr/adm/sm.bin'').
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.SH FILES
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/usr/adm/sm.bin \- directory for restricted programs
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.SH SEE ALSO
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sendmail(8)
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