full-disclosure - DLL hijacking on Linux

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Message-Id: <201008250026.23528.timb@nth-dimension.org.uk>
Date: Wed, 25 Aug 2010 00:26:22 +0100
From: Tim Brown <timb@...-dimension.org.uk>
To: full-disclosure@...ts.grok.org.uk, bugtraq@...urityfocus.com
Subject: DLL hijacking on Linux

All,

If you've seen the recent Microsoft advisory.  I put together a nice post on a 
similar DLL hijacking issue that affects Linux (and other POSIX-alikes).  You 
can read the full details on my blog (http://www.nth-
dimension.org.uk/blog.php?id=87) but the key point is that an empty directory 
specification statement in LD_LIBRARY_PATH, PATH (and probably others) is 
equivalent to $CWD.  That is to say that LD_LIBRARY_PATH=":/lib" is equivalent 
to LD_LIBRARY_PATH=".:/lib".  It can occur when a script has 
LD_LIBRARY_PATH="$LD_LIBRARY_PATH:/lib" or similar and LD_LIBRARY_PATH hasn't 
previously been defined.  It's worth checking for this kind of thing in scripts 
that may be run via sudo/su when auditing hosts.  I don't believe it's a 
vulnerability per se, but particular instances of broken scripts may well be.

Tim  
-- 
Tim Brown
<mailto:timb@...-dimension.org.uk>
<http://www.nth-dimension.org.uk/>

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