[12418] in bugtraq
Sendmail 8.x.x - any user may rebuild aliases database
daemon@ATHENA.MIT.EDU (Michal Zalewski)
Wed Nov 3 15:23:03 1999
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Message-Id: <lcamtuf.4.05.9912122118210.4246-100000@nimue.ids.pl>
Date: Sun, 12 Dec 1999 21:31:30 +0100
Reply-To: Michal Zalewski <lcamtuf@IDS.PL>
From: Michal Zalewski <lcamtuf@IDS.PL>
X-To: BUGTRAQ@SECURITYFOCUS.COM
To: BUGTRAQ@SECURITYFOCUS.COM
Sendmail up to recent 8.9.x versions - any user may pass -bi parameter to
/usr/sbin/sendmail. This will result in aliases database rebuild. IMHO
there's no reason to allow such things, but no matter - something rather
stupid is done during rebuild:
5366 open("/etc/aliases.db", O_RDWR|O_TRUNC) = 6
What a bad luck! There's approx 0.1 sec delay due to /etc/aliases
processing (on my system). Meantime, luser might deliver any signals
to sendmail process... SIGKILL is quite good. After that, /etc/aliases.db
will be left in unusable state (no EOF marker), causing DoS:
220 Marchew ESMTP Mail Service at nimue.ids.pl ready.
mail from: myself
451 Cannot open hash database /etc/aliases: Invalid argument
rcpt to: lcamtuf
503 Need MAIL before RCPT
Exploit is trivial.
_______________________________________________________________________
Michal Zalewski [lcamtuf@ids.pl] [link / marchew] [dione.ids.pl SYSADM]
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