Provided by: libiptables-chainmgr-perl_1.5-1_all 
NAME
IPTables::ChainMgr - Perl extension for manipulating iptables and ip6tables policies
SYNOPSIS
use IPTables::ChainMgr;
my $ipt_bin = '/sbin/iptables'; # can set this to /sbin/ip6tables
my %opts = (
'use_ipv6' => 0, # can set to 1 to force ip6tables usage
'ipt_rules_file' => '', # optional file path from
# which to read iptables rules
'iptout' => '/tmp/iptables.out',
'ipterr' => '/tmp/iptables.err',
'debug' => 0,
'verbose' => 0
### advanced options
'ipt_alarm' => 5, ### max seconds to wait for iptables execution.
'ipt_exec_style' => 'waitpid', ### can be 'waitpid',
### 'system', or 'popen'.
'ipt_exec_sleep' => 1, ### add in time delay between execution of
### iptables commands (default is 0).
);
my $ipt_obj = IPTables::ChainMgr->new(%opts)
or die "[*] Could not acquire IPTables::ChainMgr object";
my $rv = 0;
my $out_ar = [];
my $errs_ar = [];
# check to see if the 'CUSTOM' chain exists in the filter table
($rv, $out_ar, $errs_ar) = $ipt_obj->chain_exists('filter', 'CUSTOM');
if ($rv) {
print "CUSTOM chain exists.\n";
### flush all rules from the chain
$ipt_obj->flush_chain('filter', 'CUSTOM');
### now delete the chain (along with any jump rule in the
### INPUT chain)
$ipt_obj->delete_chain('filter', 'INPUT', 'CUSTOM');
}
# set the policy on the FORWARD table to DROP
$ipt_obj->set_chain_policy('filter', 'FORWARD', 'DROP');
# create new iptables chain in the 'filter' table
$ipt_obj->create_chain('filter', 'CUSTOM');
# translate a network into the same representation that iptables or
# ip6tables uses (e.g. '10.1.2.3/24' is properly represented as '10.1.2.0/24',
# and '0000:0000:00AA:0000:0000:AA00:0000:0001/64' = '0:0:aa::/64')
$normalized_net = $ipt_obj->normalize_net('10.1.2.3/24');
# add rule to jump packets from the INPUT chain into CUSTOM at the
# 4th rule position
$ipt_obj->add_jump_rule('filter', 'INPUT', 4, 'CUSTOM');
# find rule that allows all traffic from 10.1.2.0/24 to 192.168.1.2
($rule_num, $chain_rules) = $ipt_obj->find_ip_rule('10.1.2.0/24', '192.168.1.2',
'filter', 'INPUT', 'ACCEPT', {'normalize' => 1});
# find rule that allows all TCP port 80 traffic from 10.1.2.0/24 to
# 192.168.1.1
($rule_num, $chain_rules) = $ipt_obj->find_ip_rule('10.1.2.0/24', '192.168.1.2',
'filter', 'INPUT', 'ACCEPT', {'normalize' => 1, 'protocol' => 'tcp',
's_port' => 0, 'd_port' => 80});
# add rule at the 5th rule position to allow all traffic from
# 10.1.2.0/24 to 192.168.1.2 via the INPUT chain in the filter table
($rv, $out_ar, $errs_ar) = $ipt_obj->add_ip_rule('10.1.2.0/24',
'192.168.1.2', 5, 'filter', 'INPUT', 'ACCEPT', {});
# add rule at the 4th rule position to allow all traffic from
# 10.1.2.0/24 to 192.168.1.2 over TCP port 80 via the CUSTOM chain
# in the filter table
($rv, $out_ar, $errs_ar) = $ipt_obj->add_ip_rule('10.1.2.0/24',
'192.168.1.2', 4, 'filter', 'CUSTOM', 'ACCEPT',
{'protocol' => 'tcp', 's_port' => 0, 'd_port' => 80});
# append rule at the end of the CUSTOM chain in the filter table to
# allow all traffic from 10.1.2.0/24 to 192.168.1.2 via port 80
($rv, $out_ar, $errs_ar) = $ipt_obj->append_ip_rule('10.1.2.0/24',
'192.168.1.2', 'filter', 'CUSTOM', 'ACCEPT',
{'protocol' => 'tcp', 's_port' => 0, 'd_port' => 80});
# for each of the examples above, here are ip6tables analogs
# (requires instantiating the IPTables::ChainMgr object with
# /sbin/ip6tables): find rule that allows all traffic from fe80::200:f8ff:fe21:67cf
# to 0:0:aa::/64
($rule_num, $chain_rules) = $ipt_obj->find_ip_rule('fe80::200:f8ff:fe21:67cf', '0:0:aa::/64',
'filter', 'INPUT', 'ACCEPT', {'normalize' => 1});
# find rule that allows all TCP port 80 traffic from fe80::200:f8ff:fe21:67c to 0:0:aa::/64
($rule_num, $chain_rules) = $ipt_obj->find_ip_rule('fe80::200:f8ff:fe21:67cf', '0:0:aa::/64',
'filter', 'INPUT', 'ACCEPT', {'normalize' => 1, 'protocol' => 'tcp',
's_port' => 0, 'd_port' => 80});
# add rule at the 5th rule position to allow all traffic from
# fe80::200:f8ff:fe21:67c to 0:0:aa::/64 via the INPUT chain in the filter table
($rv, $out_ar, $errs_ar) = $ipt_obj->add_ip_rule('fe80::200:f8ff:fe21:67cf',
'0:0:aa::/64', 5, 'filter', 'INPUT', 'ACCEPT', {});
# add rule at the 4th rule position to allow all traffic from
# fe80::200:f8ff:fe21:67c to 0:0:aa::/64 over TCP port 80 via the CUSTOM chain
# in the filter table
($rv, $out_ar, $errs_ar) = $ipt_obj->add_ip_rule('fe80::200:f8ff:fe21:67cf',
'0:0:aa::/64', 4, 'filter', 'CUSTOM', 'ACCEPT',
{'protocol' => 'tcp', 's_port' => 0, 'd_port' => 80});
# append rule at the end of the CUSTOM chain in the filter table to
# allow all traffic from fe80::200:f8ff:fe21:67c to 0:0:aa::/64 via port 80
($rv, $out_ar, $errs_ar) = $ipt_obj->append_ip_rule('fe80::200:f8ff:fe21:67cf',
'0:0:aa::/64', 'filter', 'CUSTOM', 'ACCEPT',
{'protocol' => 'tcp', 's_port' => 0, 'd_port' => 80});
# run an arbitrary iptables command and collect the output
($rv, $out_ar, $errs_ar) = $ipt_obj->run_ipt_cmd(
'/sbin/iptables -v -n -L');
DESCRIPTION
The "IPTables::ChainMgr" package provides an interface to manipulate iptables and
ip6tables policies on Linux systems through the direct execution of iptables/ip6tables
commands. Note that the 'firewalld' infrastructure on Fedora21 is also supported through
execution of the 'firewall-cmd' binary. Although making a perl extension of libiptc
provided by the Netfilter project is possible (and has been done by the IPTables::libiptc
module available from CPAN), it is also easy enough to just execute iptables/ip6tables
commands directly in order to both parse and change the configuration of the policy.
Further, this simplifies installation since the only external requirement is (in the
spirit of scripting) to be able to point IPTables::ChainMgr at an installed iptables or
ip6tables binary instead of having to compile against a library.
FUNCTIONS
The IPTables::ChainMgr extension provides an object interface to the following functions:
chain_exists($table, $chain)
This function tests whether or not a chain (e.g. 'INPUT') exists within the specified
table (e.g. 'filter'). This is most useful to test whether a custom chain has been
added to the running iptables/ip6tables policy. The return values are (as with many
IPTables::ChainMgr functions) an array of three things: a numeric value, and both the
stdout and stderr of the iptables or ip6tables command in the form of array
references. So, an example invocation of the chain_exists() function would be:
($rv, $out_ar, $errs_ar) = $ipt_obj->chain_exists('filter', 'CUSTOM');
If $rv is 1, then the CUSTOM chain exists in the filter table, and 0 otherwise. The
$out_ar array reference contains the output of the command "/sbin/iptables -t filter
-v -n -L CUSTOM", which will contain the rules in the CUSTOM chain (if it exists) or
nothing (if not). The $errs_ar array reference contains the stderr of the iptables
command. As with all IPTables::ChainMgr functions, if the IPTables::ChainMgr object
was instantiated with the ip6tables binary path, then the above command would become
"/sbin/ip6tables -t filter -v -n -L CUSTOM".
create_chain($table, $chain)
This function creates a chain within the specified table. Again, three return values
are given like so:
($rv, $out_ar, $errs_ar) = $ipt_obj->create_chain('filter', 'CUSTOM');
Behind the scenes, the create_chain() function in the example above runs the iptables
command "/sbin/iptables -t filter -N CUSTOM", or for ip6tables "/sbin/ip6tables -t
filter -N CUSTOM".
flush_chain($table, $chain)
This function flushes all rules from chain in the specified table, and three values
are returned:
($rv, $out_ar, $errs_ar) = $ipt_obj->flush_chain('filter', 'CUSTOM');
The flush_chain() function in the example above executes the command "/sbin/iptables
-t filter -F CUSTOM" or "/sbin/ip6tables -t filter -F CUSTOM".
set_chain_policy($table, $chain, $target)
This function sets the policy of a built-in chain (iptables/ip6tables does not allow
this for non built-in chains) to the specified target:
($rv, $out_ar, $errs_ar) = $ipt_obj->set_chain_policy('filter', 'FORWARD', 'DROP');
In this example, the following command is executed behind the scenes: "/sbin/iptables
-t filter -P FORWARD DROP" or "/sbin/ip6tables -t filter -P FORWARD DROP".
delete_chain($table, $jump_from_chain, $chain)
This function deletes a chain from the specified table along with any jump rule to
which packets are jumped into this chain:
($rv, $out_ar, $errs_ar) = $ipt_obj->delete_chain('filter', 'INPUT', 'CUSTOM');
Internally a check is performed to see whether the chain exists within the table, and
global jump rules are removed from the jump chain before deletion (a chain cannot be
deleted until there are no references to it). In the example above, the CUSTOM chain
is deleted after any jump rule to this chain from the INPUT chain is also deleted.
find_ip_rule($src, $dst, $table, $chain, $target, %extended_info)
This function parses the specified chain to see if there is a rule that matches the
$src, $dst, $target, and (optionally) any %extended_info criteria. The return values
are the rule number in the chain (or zero if it doesn't exist), and the total number
of rules in the chain. Below are four examples; the first is to find an ACCEPT rule
for 10.1.2.0/24 to communicate with 192.168.1.2 in the INPUT chain, and the second is
the same except that the rule is restricted to TCP port 80. The third and forth
examples illustrate ip6tables analogs of the first two examples with source IP
fe80::200:f8ff:fe21:67cf/128 and destination network: 0:0:aa::/64
($rulenum, $chain_rules) = $ipt_obj->find_ip_rule('10.1.2.0/24',
'192.168.1.2', 'filter', 'INPUT', 'ACCEPT', {'normalize' => 1});
if ($rulenum) {
print "matched rule $rulenum out of $chain_rules rules\n";
}
($rulenum, $chain_rules) = $ipt_obj->find_ip_rule('10.1.2.0/24',
'192.168.1.2', 'filter', 'INPUT', 'ACCEPT',
{'normalize' => 1, 'protocol' => 'tcp', 's_port' => 0, 'd_port' => 80});
if ($rulenum) {
print "matched rule $rulenum out of $chain_rules rules\n";
}
($rulenum, $chain_rules) = $ipt_obj->find_ip_rule('fe80::200:f8ff:fe21:67cf/128',
'0:0:aa::/64', 'filter', 'INPUT', 'ACCEPT', {'normalize' => 1});
if ($rulenum) {
print "matched rule $rulenum out of $chain_rules rules\n";
}
($rulenum, $chain_rules) = $ipt_obj->find_ip_rule('fe80::200:f8ff:fe21:67cf/128',
'0:0:aa::/64', 'filter', 'INPUT', 'ACCEPT',
{'normalize' => 1, 'protocol' => 'tcp', 's_port' => 0, 'd_port' => 80});
if ($rulenum) {
print "matched rule $rulenum out of $chain_rules rules\n";
}
add_ip_rule($src, $dst, $rulenum, $table, $chain, $target, %extended_info)
This function inserts a rule into the running iptables chain and table at the
specified rule number. Return values are success or failure along with the iptables
stdout and stderr.
append_ip_rule($src, $dst, $table, $chain, $target, %extended_info)
This function appends a rule at the end of the iptables chain in the specified table.
Return values are success or failure along with the iptables stdout and stderr.
delete_ip_rule($src, $dst, $table, $chain, $target, %extended_info)
This function searches for and then deletes a matching rule within the specified
chain. Return values are success or failure along with the iptables stdout and
stderr.
add_jump_rule($table, $from_chain, $rulenum, $to_chain)
This function adds a jump rule (after making sure it doesn't already exist) into the
specified chain. The $rulenum variable tells the function where within the calling
chain the new jump rule should be placed. Here is an example to force all packets
regardless of source or destination to be jumped to the CUSTOM chain from the INPUT
chain at rule 4:
($rv, $out_ar, $errs_ar) = $ipt_obj->add_jump_rule('filter', 'INPUT', 4, 'CUSTOM');
normalize_net($net)
This function translates an IP/network into the same representation that iptables or
ip6tables uses upon listing a policy. The first example shows an IPv4 network and how
iptables lists it, and the second is an IPv6 network:
print $ipt_obj->normalize_net('10.1.2.3/24'), "\n" # prints '10.1.2.0/24'
print $ipt_obj->normalize_net('0000:0000:00AA:0000:0000:AA00:0000:0001/64'), "\n" # prints '0:0:aa::/64'
run_ipt_cmd($cmd)
This function is a generic work horse function for executing iptables commands, and is
used internally by IPTables::ChainMgr functions. It can also be used by a script that
imports the IPTables::ChainMgr extension to provide a consistent mechanism for
executing iptables. Three return values are given: success (1) or failure (0) of the
iptables command (yes, this backwards from the normal exit status of Linux/*NIX
binaries), and array references to the iptables stdout and stderr. Here is an example
to list all rules in the user-defined chain "CUSTOM":
($rv, $out_ar, $errs_ar) = $ipt_obj->run_ipt_cmd('/sbin/iptables -t filter -v -n -L CUSTOM');
if ($rv) {
print "rules:\n";
print for @$out_ar;
}
SEE ALSO
The IPTables::ChainMgr extension is closely associated with the IPTables::Parse extension,
and both are heavily used by the psad and fwsnort projects to manipulate iptables policies
based on various criteria (see the psad(8) and fwsnort(8) man pages). As always, the
iptables(8) man page provides the best information on command line execution and theory
behind iptables.
Although there is no mailing that is devoted specifically to the IPTables::ChainMgr
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 fwsnort mailing list: http://lists.sourceforge.net/lists/listinfo/fwsnort-discuss
The latest version of the IPTables::ChainMgr extension can be found on CPAN and also here:
http://www.cipherdyne.org/modules/
Source control is provided by git:
http://github.com/mrash/IPTables-ChaingMgr.git
CREDITS
Thanks to the following people:
Franck Joncourt <franck.mail@dthconnex.com>
Grant Ferley
Darien Kindlund
AUTHOR
The IPTables::ChainMgr extension was written by Michael Rash <mbr@cipherdyne.org> to
support the psad and fwsnort projects. Please send email to this address if there are any
questions, comments, or bug reports.
COPYRIGHT AND LICENSE
Copyright (C) 2005-2015 Michael Rash. All rights reserved.
This module is free software. You can redistribute it and/or modify it under the terms of
the Artistic License 2.0. More information can be found here:
http://www.perl.com/perl/misc/Artistic.html
This program is distributed "as is" in the hope that it will be useful, but without any
warranty; without even the implied warranty of merchantability or fitness for a particular
purpose.