[UNIX] LutelWall Insecure Temporary File Creation

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LutelWall Insecure Temporary File Creation
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SUMMARY

" <http://firewall.lutel.pl/index.php> LutelWall is high-level Linux
firewall configuration tool. It uses human-readable and easy to understand
configuration to set up Netfilter in most secure way. Its flexibility
allows firewall administrators build from very simple, single-homed
firewalls, to most complex ones - with multiple subnets, DMZ's and traffic
redirections.

LutelWall firewall stores temporary files in an insecure way, which can be
exploited via symlink attacks to create and overwrite arbitrary files with
the privileges of the user running the affected script.

DETAILS

Vulnerable Systems:
* LutelWall version 0.97 and prior

The exploitation requires that the root try to update the software.

Vulnerable Code:
# Prefix of temporary firewall files
tmp='/tmp/lutelwall'

new_version_check () { # Check for new version of script

if [ "`wget -V 2>&1 >/dev/null`" ]; then
message 3 "Warrning: Wget is required to check for updates."
else
new_ver=`wget -C off -O - -q -t 1 -T 3 -w 3 -U "\`uname -a 2>&1\`"
http://firewall.lutel.pl/ver`
if [ `echo $current_version | gawk '{ gsub("\\\.","") ; print 1$0 }'`
-lt `echo $new_ver | gawk '{ gsub("\\\.","") ; print 1$0 }'` ]; then
echo -e "\nThere is newer version of LutelWall (${new_ver})"
echo -n " Changes since previous version:"
echo `wget -C off -O $tmp-newfeat -q -t 1 -T 3 -w 3
http://firewall.lutel.pl/FEATURES-${new_ver}`
cat $tmp-newfeat
echo "Do you want to update [y/N]? "
read -s -t 5 -n 1 ln
if [ "$ln" = 'y' -o "$ln" = 'Y' ]; then
wget -O $tmp-script -q -T 3 http://firewall.lutel.pl/lutelwall
cat $tmp-script > $0
rm -rf $tmp-script
echo "Your firewall is up to date, exiting after update!"
exit
else
message 5 "Update aborted"
fi
else
message 5 "LutelWall is up-to-date"
fi;
fi;
}

Disclosure Timeline:
* 22.05.05 - Vulnerability discovered
* 22.05.05 - Vendor notified
* 06.06.04 - Public disclosure

ADDITIONAL INFORMATION

The information has been provided by <mailto:exploits@zataz.net> ZATAZ
Audits.
The original article can be found at:
<http://www.zataz.net/adviso/lutelwall-05222005.txt>
http://www.zataz.net/adviso/lutelwall-05222005.txt

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