smrsh(1M) System Administration Commands smrsh(1M)
NAME
smrsh - restricted shell for sendmail
SYNOPSIS
smrsh -c command
DESCRIPTION
The smrsh program is intended as a replacement for the sh command in the prog mailer in sendmail(1M) configuration files. The smrsh program
sharply limits commands that can be run using the |program syntax of sendmail. This improves overall system security. smrsh limits the set
of programs that a programmer can execute, even if sendmail runs a program without going through an alias or forward file.
Briefly, smrsh limits programs to be in the directory /var/adm/sm.bin, allowing system administrators to choose the set of acceptable com-
mands. It also rejects any commands with the characters: ,, <, >, |, ;, &, $,
(<RETURN>), or
(<NEWLINE>) on the command line to pre-
vent end run attacks.
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/var/adm/sm.bin/vacation.
System administrators should be conservative about populating /var/adm/sm.bin. Reasonable additions are utilities such as vacation(1) and
procmail. Never include any shell or shell-like program (for example, perl) in the sm.bin directory. This does not restrict the use of
shell or perl scrips in the sm.bin directory (using the #! syntax); it simply disallows the execution of arbitrary programs.
OPTIONS
The following options are supported:
-c command
Where command is a valid command, executes command.
FILES
/var/adm/sm.bin directory for restricted programs
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
+-----------------------------+-----------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+-----------------------------+-----------------------------+
|Availability |SUNWcsr, SUNWcsu |
+-----------------------------+-----------------------------+
SEE ALSO
sendmail(1M), , attributes(5)
SunOS 5.10 6 Nov 1998 smrsh(1M)