LutelWall <= 0.97 insecure temporary file creation

[ZATAZ Audits <exploits@xxxxxxxxx>]

#########################################################

LutelWall insecure temporary file creation

Vendor: http://firewall.lutel.pl/index.php
Advisory: http://www.zataz.net/adviso/lutelwall-05222005.txt
Vendor informed: yes
Exploit available: yes
Impact : medium
Exploitation : low

#########################################################

The vulnerability is caused due to temporary file being created insecurely.
This can be exploited via symlink attacks to create and overwrite 
arbitrary files
with the privileges of the user running the affected script.

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

##########
Versions:
##########

LutelWall <= 0.97

##########
Solution:
##########

non solution yet.

#########
Timeline:
#########

Discovered : 2005-05-22
Vendor notified : 2005-05-22
Vendor response : none
Vendor fix :  no fix
Disclosure : 2005-06-06

#####################
Technical details :
#####################

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;

}

#########
Related :
#########

nothing related

#####################
Credits :
#####################

Eric Romang (eromang@xxxxxxxxx - ZATAZ Audit)