smrsh(8) [suse man page]

SMRSH(8)						      System Manager's Manual							  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/lib/sendmail.d/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 ``', `<', `>', `;', `$', `(', `)', `
' (carriage return), or `
' (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/bin/vacation'', ``/usr/bin/vacation'', ``/home/server/mydir/bin/vaca-
       tion'', and ``vacation'' all actually forward to `/usr/lib/sendmail.d/bin/vacation''.

       System administrators should be conservative about populating the /usr/lib/sendmail.d/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
       /usr/lib/sendmail.d/bin/ directory.  Note that this does not restrict the use of shell or  perl	scripts  in  the  /usr/lib/sendmail.d/bin/
       directory  (using the ``#!'' syntax); it simply disallows execution of arbitrary programs.  Also, including mail filtering programs such as
       procmail(1) is a very bad idea.	procmail(1) allows users to run arbitrary programs 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'') and/or -DSMRSH_CMDDIR="dir" to change the default program directory (defaults to ``/usr/lib/sendmail.d/bin/'').

FILES

       /usr/lib/sendmail.d/bin/ - default directory for restricted programs on SuSE Linux

SEE ALSO

       sendmail(8)

							   $Date: 2004/08/06 03:55:35 $ 						  SMRSH(8)

EXTSMAIL.EXTERNALS(1)					    BSD General Commands Manual 				     EXTSMAIL.EXTERNALS(1)

NAME

     extsmail.externals -- configure which external commands to robustly send e-mail via

DESCRIPTION

     extsmail.externals is used to configure extsmaild(1).  It consists of one or more group declarations. Each group consists of zero or more
     match / reject clauses followed by one or more external declarations. An external consists of one or more assignments of key = value pairs.

     When sending messages extsmaild(1) first searches through the externals file, in order, for a group whose match / reject clauses match the
     message in question. If a group does not contain any such clauses it automatically matches all messages. Match / reject clauses currently
     match only against headers, and use standard POSiX extended regular expressions (see re_format(7) for more details).  extsmaild(1) then tries
     each external in the group, in order, to send the message successfully.

     The grammar for this file is as follows:

	   group    ::= { matches* external+ }

	   matches  ::= match
		      | reject
	   match    ::= MATCH HEADER string
	   reject   ::= REJECT HEADER string

	   external ::= EXTERNAL ID { defn+ }

	   defn     ::= ID = STRING
		      | ID = TIME

	   TIME     ::= [0-9]+[dhms]

     Valid assignments within an external are:

     sendmail
	     Defines the external shell command used to send e-mail.

     timeout
	     If extsmaild(1) is executed in daemon mode, this value defines the length of time that extsmaild(1) will retry this external before
	     giving up and trying the next external in the group. Times are specified as a number followed by d (days), h (hours) m (minutes), or
	     s (seconds). If extsmaild(1) is executed in batch mode, the timeout value is ignored.

FILES

     The extsmail configuration file is searched for, in order, in the following locations:

     ~/.extsmail/externals
	     Per-user configuration.

     /etc/extsmail/externals
	     System-wide configuration.

EXAMPLES

     The simplest externals file sending e-mail via ssh(1) looks as follows:

	   group {
	       external mymachine {
		   sendmail = "/usr/bin/ssh -q -C -l user mymachine.net /usr/sbin/sendmail"
	       }
	   }
     where mymachine is a human-friendly name given to an external (it does not effect processing), and user is the username on the remote machine
     mymachine.net.

     A more complex example using multiple groups, message matching, and multiple external commands looks as follows:

	   group {
	       match header "^To:.*@foo.com"

	       external foo {
		   sendmail = "/usr/bin/ssh -q -C -l user shell.foo.com /usr/sbin/sendmail"
	       }
	   }

	   group {
	       external mymachine {
		   sendmail = "/usr/bin/ssh -q -C -l user mymachine.net /usr/sbin/sendmail"
	       }

	       external bk {
		   sendmail = "/usr/bin/ssh -q -C -l user bk.mymachine.net /usr/sbin/sendmail"
	       }
	   }

SEE ALSO

     extsmail(1), extsmail.conf(5), extsmaild(1)

AUTHORS

     Laurence Tratt <http://tratt.net/laurie/>

BSD
								 November 2, 2008							       BSD