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IPTables::Parse.3pm

NAME

IPTables::Parse - Perl extension for parsing iptables firewall rulesets

SYNOPSIS

   use IPTables::Parse;
 
   my %opts = (
       'iptables' => '/sbin/iptables',
       'iptout'   => '/tmp/iptables.out',
       'ipterr'   => '/tmp/iptables.err',
       'debug'    => 0,
       'verbose'  => 0
   );
 
   my $ipt_obj = new IPTables::Parse(%opts)
       or die "[*] Could not acquire IPTables::Parse object";
 
   my $rv = 0;
 
   my $table = 'filter';
   my $chain = 'INPUT';
 
   my ($ipt_hr, $rv) = $ipt_obj->default_drop($table, $chain);
   if ($rv) {
       if (defined $ipt_hr->{'all'}) {
           print "The INPUT chain has a default DROP rule for all protocols.\n";
       } else {
           for my $proto qw/tcp udp icmp/ {
               if (defined $ipt_hr->{$proto}) {
                   print "The INPUT chain drops $proto by default.\n";
               }
           }
       }
   } else {
       print "[-] Could not parse iptables policy\n";
   }
 
   ($ipt_hr, $rv) = $ipt_obj->default_log($table, $chain);
   if ($rv) {
       if (defined $ipt_hr->{'all'}) {
           print "The INPUT chain has a default LOG rule for all protocols.\n";
       } else {
           for my $proto qw/tcp udp icmp/ {
               if (defined $ipt_hr->{$proto}) {
                   print "The INPUT chain logs $proto by default.\n";
               }
           }
       }
   } else {
       print "[-] Could not parse iptables policy\n";
   }
 
 

DESCRIPTION

The "IPTables::Parse" package provides an interface to parse iptables rules on Linux systems through the direct execution of iptables commands, or from parsing a file that contains an iptables policy listing. You can get the current policy applied to a table/chain, look for a specific user-defined chain, check for a default DROP policy, or determing whether or not logging rules exist.

FUNCTIONS

The IPTables::Parse extension provides an object interface to the following functions:

chain_policy($table, $chain)

This function returns the policy (e.g. 'DROP', 'ACCEPT', etc.) for the specified table and chain:

   print "INPUT policy: ", $ipt_obj->chain_policy('filter', 'INPUT'), "\n";
 
 

chain_rules($table, $chain)

This function parses the specified chain and table and returns an array reference for all rules in the chain. Each element in the array reference is a hash with the following keys (that contain values depending on the rule): "src", "dst", "protocol", "s_port", "d_port", "target", "packets", "bytes", "intf_in", "intf_out", "to_ip", "to_port", "state", "raw", and "extended". The "extended" element contains the rule output past the protocol information, and the "raw" element contains the complete rule itself as reported by iptables.

default_drop($table, $chain)

This function parses the running iptables policy in order to determine if the specified chain contains a default DROP rule. Two values are returned, a hash reference whose keys are the protocols that are dropped by default if a global ACCEPT rule has not accepted matching packets first, along with a return value that tells the caller if parsing the iptables policy was successful. Note that if all protocols are dropped by default, then the hash key 'all' will be defined.

   ($ipt_hr, $rv) = $ipt_obj->default_drop('filter', 'INPUT');
 
 

default_log($table, $chain)

This function parses the running iptables policy in order to determine if the specified chain contains a default LOG rule. Two values are returned, a hash reference whose keys are the protocols that are logged by default if a global ACCEPT rule has not accepted matching packets first, along with a return value that tells the caller if parsing the iptables policy was successful. Note that if all protocols are logged by default, then the hash key 'all' will be defined. An example invocation is:

   ($ipt_hr, $rv) = $ipt_obj->default_log('filter', 'INPUT');
 
 

AUTHOR

Michael Rash, <mbr@cipherdyne.org>

SEE ALSO

The IPTables::Parse is used by the IPTables::ChainMgr extension in support of the psad, fwsnort, and fwknop projects to parse iptables policies (see the psad(8), fwsnort(8), and fwknop(8) man pages). As always, the iptables(8) provides the best information on command line execution and theory behind iptables.

Although there is no mailing that is devoted specifically to the IPTables::Parse extension, questions about the extension will be answered on the following lists:

   The psad mailing list: http://lists.sourceforge.net/lists/listinfo/psad-discuss
   The fwknop mailing list: http://lists.sourceforge.net/lists/listinfo/fwknop-discuss
   The fwsnort mailing list: http://lists.sourceforge.net/lists/listinfo/fwsnort-discuss
 
 

The latest version of the IPTables::Parse extension can be found at:

http://www.cipherdyne.org/modules/

CREDITS

Thanks to the following people:

   Franck Joncourt <franck.mail@dthconnex.com>
   Grant Ferley
 
 

AUTHOR

The IPTables::Parse extension was written by Michael Rash <mbr@cipherdyne.org> to support the psad, fwknop, and fwsnort projects. Please send email to this address if there are any questions, comments, or bug reports.

COPYRIGHT AND LICENSE

Copyright (C) 2005-2008 by Michael Rash

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.8.5 or, at your option, any later version of Perl 5 you may have available.