'\" te .\" Copyright (c) 1983 Eric P. Allman .\" Copyright (c) 1988, 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. 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All Rights Reserved. .TH SMRSH 8 "June 20, 2021" .SH NAME smrsh \- restricted shell for sendmail .SH SYNOPSIS .nf \fBsmrsh\fR \fB-c\fR \fIcommand\fR .fi .SH DESCRIPTION The \fBsmrsh\fR program is intended as a replacement for the \fBsh\fR command in the \fBprog\fR mailer in \fBsendmail\fR(8) configuration files. The \fBsmrsh\fR program sharply limits commands that can be run using the \fB|program\fR syntax of \fBsendmail\fR. This improves overall system security. \fBsmrsh\fR limits the set of programs that a programmer can execute, even if \fBsendmail\fR runs a program without going through an \fBalias\fR or \fBforward\fR file. .sp .LP Briefly, \fBsmrsh\fR limits programs to be in the directory \fB/var/adm/sm.bin\fR, allowing system administrators to choose the set of acceptable commands. It also rejects any commands with the characters: \fB,\fR, \fB<\fR, \fB>\fR, \fB|\fR, \fB;\fR, \fB&\fR, \fB$\fR, \fB\er\fR (RETURN), or \fB\en\fR (NEWLINE) on the command line to prevent end run attacks. .sp .LP Initial pathnames on programs are stripped, so forwarding to \fB/usr/ucb/vacation\fR, \fB/usr/bin/vacation\fR, \fB/home/server/mydir/bin/vacation\fR, and \fBvacation\fR all actually forward to \fB/var/adm/sm.bin/vacation\fR. .sp .LP System administrators should be conservative about populating \fB/var/adm/sm.bin\fR. Reasonable additions are utilities such as \fBvacation\fR(1) and \fBprocmail\fR. Never include any shell or shell-like program (for example, \fBperl\fR) in the \fBsm.bin\fR directory. This does not restrict the use of \fBshell\fR or \fBperl\fR scrips in the \fBsm.bin\fR directory (using the \fB#!\fR syntax); it simply disallows the execution of arbitrary programs. .SH OPTIONS The following options are supported: .sp .ne 2 .na \fB\fB-c\fR \fIcommand\fR\fR .ad .RS 14n Where \fIcommand\fR is a valid command, executes \fIcommand\fR. .RE .SH FILES .ne 2 .na \fB\fB/var/adm/sm.bin\fR\fR .ad .RS 19n directory for restricted programs .RE .SH SEE ALSO .BR attributes (7), .BR sendmail (8)