[UNIX] LutelWall Insecure Temporary File Creation

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  LutelWall Insecure Temporary File Creation
------------------------------------------------------------------------


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:[email protected]> 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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