GIPTables Firewall <= v1.1 insecure temporary file creation

[ZATAZ Audits <exploits@xxxxxxxxx>]

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GIPTables Firewall insecure temporary file creation

Vendor: http://www.giptables.org/
Advisory: http://www.zataz.net/adviso/giptables-05222005.txt
Vendor informed: yes
Exploit available: yes
Impact : medium
Exploitation : low

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

It is also possible to cause a Denial of Service by manipulating the
ip adresses present into the temporary file

The exploitation require that the root configure or reconfigure his
firewall rules.

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Versions:
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GIPTables Firewall <= v1.1

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Solution:
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non solution yet.

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Timeline:
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Discovered : 2005-05-22
Vendor notified : 2005-05-22
Vendor response : no response
Vendor fix : no fix
Disclosure : 2005-06-06

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Technical details :
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Vulnerable code :
- - -----------------

# Network Ghouls

[ "$NETWORK_GHOULS" == "yes" ] && \
[ "$DEBUG" = "on" ] && echo -e "\n# Network Ghouls"

if [ "$NETWORK_GHOULS" == "yes" ] && [ -f
"$GIPTABLES_BLOCKED_FILE" ]; then

     deny_file="$GIPTABLES_BLOCKED_FILE"
     temp_file="/tmp/temp.ip.addresses"
     cat $deny_file | sed -n -e "s/^[ ]*\([0-9.]*\).*$/\1/p" | awk '
$1 ' > $temp_file
     while read ip_addr
     do

         drop_ipaddr interface0_in source $ip_addr && \
         drop_ipaddr interface0_out destination $ip_addr

         [ -n "$INTERFACE1" ] &&  \
         drop_ipaddr interface1_in source $ip_addr && \
         drop_ipaddr interface1_out destination $ip_addr

         [ -n "$INTERFACE1" ] &&  \
         drop_ipaddr network1_in source $ip_addr && \
         drop_ipaddr network1_out destination $ip_addr

     done < $temp_file
     rm -f $temp_file > /dev/null 2>&1
     unset temp_file
     unset deny_file

fi

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Related :
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nothing related

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Possible fix :
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deny_file="$GIPTABLES_BLOCKED_FILE"

if mkdir "/tmp/.giptables.$$"; then
        chmod 700 /tmp/.giptables.$$
        temp_file="/tmp/.giptables.$$/temp.ip.addresses"
        else
        echo "$Error: failed to create temporary file" 1>&2
        exit 1
    fi
    temp_file="/tmp/.giptables.$$/temp.ip.addresses"


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Credits :
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Eric Romang (eromang@xxxxxxxxx - ZATAZ Audit)