Man page or keyword search:   man All Sections 1 - General Commands 2 - System Calls 3 - Subroutines, Functions 4 - Special Files 5 - File Formats 6 - Games and Screensavers 7 - Macros and Conventions 8 - Maintenence Commands 9 - Kernel Interface New Commands Server 4.4BSD AIX Alpinelinux Archlinux Aros BSDOS BSDi Bifrost CentOS Cygwin Darwin Debian DigitalUNIX DragonFly ElementaryOS Fedora FreeBSD Gentoo GhostBSD HP-UX Haiku Hurd IRIX Inferno JazzOS Kali Knoppix LinuxMint MacOSX Mageia Mandriva Manjaro Minix MirBSD NeXTSTEP NetBSD OPENSTEP OSF1 OpenBSD OpenDarwin OpenIndiana OpenMandriva OpenServer OpenSuSE OpenVMS Oracle PC-BSD Peanut Pidora Plan9 QNX Raspbian RedHat Scientific Slackware SmartOS Solaris SuSE SunOS Syllable Tru64 UNIXv7 Ubuntu Ultrix UnixWare Xenix YellowDog aLinux   12896 pages apropos Keyword Search (all sections) Output format html ascii pdf view pdf save postscript

SMRSH(8)							     SMRSH(8)

NAME
  smrsh - restricted shell for sendmail

SYNOPSIS
  smrsh -c command

DESCRIPTION
  The smrsh program is intended as a replacement for sh for use in the
  ``prog'' mailer in sendmail(8) configuration files.  It sharply limits the
  commands that can be run using the ``|program'' syntax of 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, smrsh limits the set of programs that he or she can execute.

  Briefly, smrsh limits programs to be in a single directory, by default
  /usr/adm/sm.bin, allowing the system administrator to choose the set of
  acceptable commands, and to the shell builtin commands ``exec'', ``exit'',
  and ``echo''.	 It also rejects any commands with the characters ``', `<',
  `>', `;', `$', `(', `)', `\r' (carriage return), or `\n' (newline) on the
  command line to prevent ``end run'' attacks.	It allows ``||'' and ``&&''
  to enable commands like: ``"|exec /usr/local/bin/filter || exit 75"''

  Initial pathnames on programs are stripped, so forwarding to
  ``/usr/ucb/vacation'', ``/usr/bin/vacation'',
  ``/home/server/mydir/bin/vacation'', and ``vacation'' all actually forward
  to ``/usr/adm/sm.bin/vacation''.

  System administrators should be conservative about populating the sm.bin
  directory.  For example, a reasonable additions is vacation(1), and the
  like.	 No matter how brow-beaten you may be, never include any shell or
  shell-like program (such as 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 arbi-
  trary programs.  Also, including mail filtering programs such as proc-
  mail(1) is a very bad idea.  procmail(1) allows users to run arbitrary pro-
  grams in their procmailrc(5).

COMPILATION
  Compilation should be trivial on most systems.  You may need to use
  -DSMRSH_PATH=\"path\" to adjust the default search path (defaults to
  ``/bin:/usr/bin:/usr/ucb'') and/or -DSMRSH_CMDDIR=\"dir\" to change the
  default program directory (defaults to ``/usr/adm/sm.bin'').

FILES
  /usr/adm/sm.bin - default directory for restricted programs on most OSs

  /var/adm/sm.bin - directory for restricted programs on HP UX and Solaris

  /usr/libexec/sm.bin - directory for restricted programs on FreeBSD (>= 3.3)
  and DragonFly BSD

SEE ALSO
  sendmail(8)

                             _         _         _ 
                            | |       | |       | |     
                            | |       | |       | |     
                         __ | | __ __ | | __ __ | | __  
                         \ \| |/ / \ \| |/ / \ \| |/ /  
                          \ \ / /   \ \ / /   \ \ / /   
                           \   /     \   /     \   /    
                            \_/       \_/       \_/ 

Vote for polarhome