IRIX rmail system() and LOGNAME hole

Description:rmail is setgid mail and apparently does a system() involving the contents of untrusted user environmental variable LOGNAME. Duh.
Author:Yuri Volobuev <volobuev@T1.CHEM.UMN.EDU>
Compromise:Group mail, the uses of this are obvious
Vulnerable Systems:IRIX, 5.3, 6.2, possibly 6.3
Date:7 May 1997
Notes:Too bad Yuri Volobuev is retiring. There wouldn't be a IRIX section without him. Good job Yuri!

te: Wed, 7 May 1997 05:48:00 -0500
From: Yuri Volobuev <volobuev@T1.CHEM.UMN.EDU>
Subject: Irix: misc


7. Rmail

This one is ridiculous.  /usr/bin/rmail is sgid mail.  Man page clearly 
rmail is only required by UUCP, still, it's installed everywhere.  It's 
been known to have bugs for years, which SGI has addressed by a series of
patches.  Quite unfortunately, all of them fail to fix the problem
completely, including the most recent one, 1639 (for 6.2, it has brothers
for other releases).  It's a small and simple program, it just passes
slightly modified message from stdin to sendmail, as usually via virtue of
system().  Why it takes several shots to fix it, I just don't understand.
To exploit, set LOGNAME env to something like blah;mycommand.  
it syslogs all invocations of itself, so at least you'll know when someone
is doing something bad.  Remove sgid bit from it.

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