The smrsh Program
The sendmail program normally runs any program it finds in the user’s ~/.forward file. A cracker can attack any user, including root, by having permission to modify the user’s ~/.forward file. Consider the following modifications, for example:
\user |"/usr/ucb/vacation user" ← OK |"/tmp/x.sh" ← an attack! |"cp /bin/sh /home/george/.x; chmod u+s /home/george/.x" ← an attack!
As an aid in preventing such attacks, V8.1
sendmail first offered the
smrsh (sendmail restricted shell) program. V8.7
sendmail offered the FEATURE(smrsh) (Configure to Use smrsh on page 380) as
an easy way to install smrsh with your
mc configuration file.
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