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Article #3350

Another Sendmail security problem

#3350
From: Felix Lee
Date: Sat, 29 Apr 1989 03:18
27 lines
1836 bytes
In article <28952@ucbvax.BERKELEY.EDU>,
   Jim Haynes <haynes@ucscc.ucsc.EDU> describes
a problem similar to something I've found recently.

Our Sendmail under SunOS 4.0 will apparently run "|program" recipients
with arbitrary uids.  I've been unable to duplicate this with Sendmail
5.59 running on a Vax, but this may be a vagary of configuration.

My .forward file currently includes "|cookie", where "cookie" is a
script that just records the id that it's run by.  So far I have about
a dozen different cookies, mostly from local users who have sent me
mail, several from daemon, and a few from local users who have not
sent me mail.

Watching the mail queue, mail to me gets expanded to my mailbox and
"|cookie"; the message gets dropped in my mailbox, and "|cookie" gets
queued.  The control file for the "|cookie" delivery doesn't keep the
recipient id; something arbitrary (like the sender, or the recipient
of the previous message) is used when the queue gets run.  I leave it
to sendmail experts to delve the internal state that controls this.

(The original "|cookie" was intended to be a harmless prank on someone
whose .forward file was writable by other.  It was something like
	grep -s "Cookie" || (fortune | mail -s "Cookie" `whoami`)
but then, random people started getting cookies..)
--
Felix Lee	flee@shire.cs.psu.edu	*!psuvax1!shire!flee
Technical Details
Message-ID: <FLEE.89Apr28231830@shire.cs.psu.edu>
Path: arc1-ca.pugleaf.net!utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!rutgers!psuvax1!flee
References: <28952@ucbvax.BERKELEY.EDU>

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Path: arc1-ca.pugleaf.net!utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!rutgers!psuvax1!flee
From: flee@shire.cs.psu.edu (Felix Lee)
Newsgroups: comp.mail.sendmail,comp.unix.wizards
Subject: Another Sendmail security problem
Message-ID: <FLEE.89Apr28231830@shire.cs.psu.edu>
Date: 29 Apr 89 03:18:30 GMT
References: <28952@ucbvax.BERKELEY.EDU>
Sender: news@psuvax1.cs.psu.edu
Organization: Penn State University Computer Science
Lines: 27