1IPTables::ChainMgr(3) User Contributed Perl DocumentationIPTables::ChainMgr(3)
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NAME

6       IPTables::ChainMgr - Perl extension for manipulating iptables and
7       ip6tables policies
8

SYNOPSIS

10         use IPTables::ChainMgr;
11
12         my $ipt_bin = '/sbin/iptables'; # can set this to /sbin/ip6tables
13
14         my %opts = (
15             'use_ipv6' => 0,         # can set to 1 to force ip6tables usage
16             'ipt_rules_file' => '',  # optional file path from
17                                      # which to read iptables rules
18             'debug'    => 0,
19             'verbose'  => 0
20
21             ### advanced options
22             'ipt_alarm' => 5,  ### max seconds to wait for iptables execution.
23             'ipt_exec_style' => 'waitpid',  ### can be 'waitpid',
24                                             ### 'system', or 'popen'.
25             'ipt_exec_sleep' => 1, ### add in time delay between execution of
26                                    ### iptables commands (default is 0).
27         );
28
29         my $ipt_obj = IPTables::ChainMgr->new(%opts)
30             or die "[*] Could not acquire IPTables::ChainMgr object";
31
32         my $rv = 0;
33         my $out_ar = [];
34         my $errs_ar = [];
35
36         # check to see if the 'CUSTOM' chain exists in the filter table
37         ($rv, $out_ar, $errs_ar) = $ipt_obj->chain_exists('filter', 'CUSTOM');
38         if ($rv) {
39             print "CUSTOM chain exists.\n";
40
41             ### flush all rules from the chain
42             $ipt_obj->flush_chain('filter', 'CUSTOM');
43
44             ### now delete the chain (along with any jump rule in the
45             ### INPUT chain)
46             $ipt_obj->delete_chain('filter', 'INPUT', 'CUSTOM');
47         }
48
49         # set the policy on the FORWARD table to DROP
50         $ipt_obj->set_chain_policy('filter', 'FORWARD', 'DROP');
51
52         # create new iptables chain in the 'filter' table
53         $ipt_obj->create_chain('filter', 'CUSTOM');
54
55         # translate a network into the same representation that iptables or
56         # ip6tables uses (e.g. '10.1.2.3/24' is properly represented as '10.1.2.0/24',
57         # and '0000:0000:00AA:0000:0000:AA00:0000:0001/64' = '0:0:aa::/64')
58         $normalized_net = $ipt_obj->normalize_net('10.1.2.3/24');
59
60         # add rule to jump packets from the INPUT chain into CUSTOM at the
61         # 4th rule position
62         $ipt_obj->add_jump_rule('filter', 'INPUT', 4, 'CUSTOM');
63
64         # find rule that allows all traffic from 10.1.2.0/24 to 192.168.1.2
65         ($rule_num, $chain_rules) = $ipt_obj->find_ip_rule('10.1.2.0/24', '192.168.1.2',
66             'filter', 'INPUT', 'ACCEPT', {'normalize' => 1});
67
68         # find rule that allows all TCP port 80 traffic from 10.1.2.0/24 to
69         # 192.168.1.1
70         ($rule_num, $chain_rules) = $ipt_obj->find_ip_rule('10.1.2.0/24', '192.168.1.2',
71             'filter', 'INPUT', 'ACCEPT', {'normalize' => 1, 'protocol' => 'tcp',
72             's_port' => 0, 'd_port' => 80});
73
74         # add rule at the 5th rule position to allow all traffic from
75         # 10.1.2.0/24 to 192.168.1.2 via the INPUT chain in the filter table
76         ($rv, $out_ar, $errs_ar) = $ipt_obj->add_ip_rule('10.1.2.0/24',
77             '192.168.1.2', 5, 'filter', 'INPUT', 'ACCEPT', {});
78
79         # add rule at the 4th rule position to allow all traffic from
80         # 10.1.2.0/24 to 192.168.1.2 over TCP port 80 via the CUSTOM chain
81         # in the filter table
82         ($rv, $out_ar, $errs_ar) = $ipt_obj->add_ip_rule('10.1.2.0/24',
83             '192.168.1.2', 4, 'filter', 'CUSTOM', 'ACCEPT',
84             {'protocol' => 'tcp', 's_port' => 0, 'd_port' => 80});
85
86         # append rule at the end of the CUSTOM chain in the filter table to
87         # allow all traffic from 10.1.2.0/24 to 192.168.1.2 via port 80
88         ($rv, $out_ar, $errs_ar) = $ipt_obj->append_ip_rule('10.1.2.0/24',
89             '192.168.1.2', 'filter', 'CUSTOM', 'ACCEPT',
90             {'protocol' => 'tcp', 's_port' => 0, 'd_port' => 80});
91
92         # for each of the examples above, here are ip6tables analogs
93         # (requires instantiating the IPTables::ChainMgr object with
94         # /sbin/ip6tables): find rule that allows all traffic from fe80::200:f8ff:fe21:67cf
95         # to 0:0:aa::/64
96         ($rule_num, $chain_rules) = $ipt_obj->find_ip_rule('fe80::200:f8ff:fe21:67cf', '0:0:aa::/64',
97             'filter', 'INPUT', 'ACCEPT', {'normalize' => 1});
98
99         # find rule that allows all TCP port 80 traffic from fe80::200:f8ff:fe21:67c to 0:0:aa::/64
100         ($rule_num, $chain_rules) = $ipt_obj->find_ip_rule('fe80::200:f8ff:fe21:67cf', '0:0:aa::/64',
101             'filter', 'INPUT', 'ACCEPT', {'normalize' => 1, 'protocol' => 'tcp',
102             's_port' => 0, 'd_port' => 80});
103
104         # add rule at the 5th rule position to allow all traffic from
105         # fe80::200:f8ff:fe21:67c to 0:0:aa::/64 via the INPUT chain in the filter table
106         ($rv, $out_ar, $errs_ar) = $ipt_obj->add_ip_rule('fe80::200:f8ff:fe21:67cf',
107             '0:0:aa::/64', 5, 'filter', 'INPUT', 'ACCEPT', {});
108
109         # add rule at the 4th rule position to allow all traffic from
110         # fe80::200:f8ff:fe21:67c to 0:0:aa::/64 over TCP port 80 via the CUSTOM chain
111         # in the filter table
112         ($rv, $out_ar, $errs_ar) = $ipt_obj->add_ip_rule('fe80::200:f8ff:fe21:67cf',
113             '0:0:aa::/64', 4, 'filter', 'CUSTOM', 'ACCEPT',
114             {'protocol' => 'tcp', 's_port' => 0, 'd_port' => 80});
115
116         # append rule at the end of the CUSTOM chain in the filter table to
117         # allow all traffic from fe80::200:f8ff:fe21:67c to 0:0:aa::/64 via port 80
118         ($rv, $out_ar, $errs_ar) = $ipt_obj->append_ip_rule('fe80::200:f8ff:fe21:67cf',
119             '0:0:aa::/64', 'filter', 'CUSTOM', 'ACCEPT',
120             {'protocol' => 'tcp', 's_port' => 0, 'd_port' => 80});
121
122         # run an arbitrary iptables command and collect the output
123         ($rv, $out_ar, $errs_ar) = $ipt_obj->run_ipt_cmd(
124                 '/sbin/iptables -v -n -L');
125

DESCRIPTION

127       The "IPTables::ChainMgr" package provides an interface to manipulate
128       iptables and ip6tables policies on Linux systems through the direct
129       execution of iptables/ip6tables commands. Note that the 'firewalld'
130       infrastructure on Fedora21 is also supported through execution of the
131       'firewall-cmd' binary.  Although making a perl extension of libiptc
132       provided by the Netfilter project is possible (and has been done by the
133       IPTables::libiptc module available from CPAN), it is also easy enough
134       to just execute iptables/ip6tables commands directly in order to both
135       parse and change the configuration of the policy.  Further, this
136       simplifies installation since the only external requirement is (in the
137       spirit of scripting) to be able to point IPTables::ChainMgr at an
138       installed iptables or ip6tables binary instead of having to compile
139       against a library.
140

FUNCTIONS

142       The IPTables::ChainMgr extension provides an object interface to the
143       following functions:
144
145       chain_exists($table, $chain)
146           This function tests whether or not a chain (e.g. 'INPUT') exists
147           within the specified table (e.g. 'filter').  This is most useful to
148           test whether a custom chain has been added to the running
149           iptables/ip6tables policy.  The return values are (as with many
150           IPTables::ChainMgr functions) an array of three things: a numeric
151           value, and both the stdout and stderr of the iptables or ip6tables
152           command in the form of array references.  So, an example invocation
153           of the chain_exists() function would be:
154
155             ($rv, $out_ar, $errs_ar) = $ipt_obj->chain_exists('filter', 'CUSTOM');
156
157           If $rv is 1, then the CUSTOM chain exists in the filter table, and
158           0 otherwise.  The $out_ar array reference contains the output of
159           the command "/sbin/iptables -t filter -v -n -L CUSTOM", which will
160           contain the rules in the CUSTOM chain (if it exists) or nothing (if
161           not).  The $errs_ar array reference contains the stderr of the
162           iptables command.  As with all IPTables::ChainMgr functions, if the
163           IPTables::ChainMgr object was instantiated with the ip6tables
164           binary path, then the above command would become "/sbin/ip6tables
165           -t filter -v -n -L CUSTOM".
166
167       create_chain($table, $chain)
168           This function creates a chain within the specified table.  Again,
169           three return values are given like so:
170
171             ($rv, $out_ar, $errs_ar) = $ipt_obj->create_chain('filter', 'CUSTOM');
172
173           Behind the scenes, the create_chain() function in the example above
174           runs the iptables command "/sbin/iptables -t filter -N CUSTOM", or
175           for ip6tables "/sbin/ip6tables -t filter -N CUSTOM".
176
177       flush_chain($table, $chain)
178           This function flushes all rules from chain in the specified table,
179           and three values are returned:
180
181             ($rv, $out_ar, $errs_ar) = $ipt_obj->flush_chain('filter', 'CUSTOM');
182
183           The flush_chain() function in the example above executes the
184           command "/sbin/iptables -t filter -F CUSTOM" or "/sbin/ip6tables -t
185           filter -F CUSTOM".
186
187       set_chain_policy($table, $chain, $target)
188           This function sets the policy of a built-in chain
189           (iptables/ip6tables does not allow this for non built-in chains) to
190           the specified target:
191
192             ($rv, $out_ar, $errs_ar) = $ipt_obj->set_chain_policy('filter', 'FORWARD', 'DROP');
193
194           In this example, the following command is executed behind the
195           scenes: "/sbin/iptables -t filter -P FORWARD DROP" or
196           "/sbin/ip6tables -t filter -P FORWARD DROP".
197
198       delete_chain($table, $jump_from_chain, $chain)
199           This function deletes a chain from the specified table along with
200           any jump rule to which packets are jumped into this chain:
201
202             ($rv, $out_ar, $errs_ar) = $ipt_obj->delete_chain('filter', 'INPUT', 'CUSTOM');
203
204           Internally a check is performed to see whether the chain exists
205           within the table, and global jump rules are removed from the jump
206           chain before deletion (a chain cannot be deleted until there are no
207           references to it).  In the example above, the CUSTOM chain is
208           deleted after any jump rule to this chain from the INPUT chain is
209           also deleted.
210
211       find_ip_rule($src, $dst, $table, $chain, $target, %extended_info)
212           This function parses the specified chain to see if there is a rule
213           that matches the $src, $dst, $target, and (optionally) any
214           %extended_info criteria.  The return values are the rule number in
215           the chain (or zero if it doesn't exist), and the total number of
216           rules in the chain.  Below are four examples; the first is to find
217           an ACCEPT rule for 10.1.2.0/24 to communicate with 192.168.1.2 in
218           the INPUT chain, and the second is the same except that the rule is
219           restricted to TCP port 80.  The third and forth examples illustrate
220           ip6tables analogs of the first two examples with source IP
221           fe80::200:f8ff:fe21:67cf/128 and destination network: 0:0:aa::/64
222
223             ($rulenum, $chain_rules) = $ipt_obj->find_ip_rule('10.1.2.0/24',
224                 '192.168.1.2', 'filter', 'INPUT', 'ACCEPT', {'normalize' => 1});
225             if ($rulenum) {
226                 print "matched rule $rulenum out of $chain_rules rules\n";
227             }
228
229             ($rulenum, $chain_rules) = $ipt_obj->find_ip_rule('10.1.2.0/24',
230                 '192.168.1.2', 'filter', 'INPUT', 'ACCEPT',
231                 {'normalize' => 1, 'protocol' => 'tcp', 's_port' => 0, 'd_port' => 80});
232             if ($rulenum) {
233                 print "matched rule $rulenum out of $chain_rules rules\n";
234             }
235
236             ($rulenum, $chain_rules) = $ipt_obj->find_ip_rule('fe80::200:f8ff:fe21:67cf/128',
237               '0:0:aa::/64', 'filter', 'INPUT', 'ACCEPT', {'normalize' => 1});
238             if ($rulenum) {
239                 print "matched rule $rulenum out of $chain_rules rules\n";
240             }
241
242             ($rulenum, $chain_rules) = $ipt_obj->find_ip_rule('fe80::200:f8ff:fe21:67cf/128',
243                 '0:0:aa::/64', 'filter', 'INPUT', 'ACCEPT',
244                 {'normalize' => 1, 'protocol' => 'tcp', 's_port' => 0, 'd_port' => 80});
245             if ($rulenum) {
246                 print "matched rule $rulenum out of $chain_rules rules\n";
247             }
248
249       add_ip_rule($src, $dst, $rulenum, $table, $chain, $target,
250       %extended_info)
251           This function inserts a rule into the running iptables chain and
252           table at the specified rule number.  Return values are success or
253           failure along with the iptables stdout and stderr.
254
255       append_ip_rule($src, $dst, $table, $chain, $target, %extended_info)
256           This function appends a rule at the end of the iptables chain in
257           the specified table.  Return values are success or failure along
258           with the iptables stdout and stderr.
259
260       delete_ip_rule($src, $dst, $table, $chain, $target, %extended_info)
261           This function searches for and then deletes a matching rule within
262           the specified chain.  Return values are success or failure along
263           with the iptables stdout and stderr.
264
265       add_jump_rule($table, $from_chain, $rulenum, $to_chain)
266           This function adds a jump rule (after making sure it doesn't
267           already exist) into the specified chain.  The $rulenum variable
268           tells the function where within the calling chain the new jump rule
269           should be placed.  Here is an example to force all packets
270           regardless of source or destination to be jumped to the CUSTOM
271           chain from the INPUT chain at rule 4:
272
273             ($rv, $out_ar, $errs_ar) = $ipt_obj->add_jump_rule('filter', 'INPUT', 4, 'CUSTOM');
274
275       normalize_net($net)
276           This function translates an IP/network into the same representation
277           that iptables or ip6tables uses upon listing a policy.  The first
278           example shows an IPv4 network and how iptables lists it, and the
279           second is an IPv6 network:
280
281             print $ipt_obj->normalize_net('10.1.2.3/24'), "\n" # prints '10.1.2.0/24'
282             print $ipt_obj->normalize_net('0000:0000:00AA:0000:0000:AA00:0000:0001/64'), "\n" # prints '0:0:aa::/64'
283
284       run_ipt_cmd($cmd)
285           This function is a generic work horse function for executing
286           iptables commands, and is used internally by IPTables::ChainMgr
287           functions.  It can also be used by a script that imports the
288           IPTables::ChainMgr extension to provide a consistent mechanism for
289           executing iptables.  Three return values are given: success (1) or
290           failure (0) of the iptables command (yes, this backwards from the
291           normal exit status of Linux/*NIX binaries), and array references to
292           the iptables stdout and stderr.  Here is an example to list all
293           rules in the user-defined chain "CUSTOM":
294
295             ($rv, $out_ar, $errs_ar) = $ipt_obj->run_ipt_cmd('/sbin/iptables -t filter -v -n -L CUSTOM');
296             if ($rv) {
297                 print "rules:\n";
298                 print for @$out_ar;
299             }
300

SEE ALSO

302       The IPTables::ChainMgr extension is closely associated with the
303       IPTables::Parse extension, and both are heavily used by the psad and
304       fwsnort projects to manipulate iptables policies based on various
305       criteria (see the psad(8) and fwsnort(8) man pages).  As always, the
306       iptables(8) man page provides the best information on command line
307       execution and theory behind iptables.
308
309       Although there is no mailing that is devoted specifically to the
310       IPTables::ChainMgr extension, questions about the extension will be
311       answered on the following lists:
312
313         The psad mailing list: http://lists.sourceforge.net/lists/listinfo/psad-discuss
314         The fwsnort mailing list: http://lists.sourceforge.net/lists/listinfo/fwsnort-discuss
315
316       The latest version of the IPTables::ChainMgr extension can be found on
317       CPAN and also here:
318
319         http://www.cipherdyne.org/modules/
320
321       Source control is provided by git:
322
323         http://github.com/mrash/IPTables-ChaingMgr.git
324

CREDITS

326       Thanks to the following people:
327
328         Franck Joncourt <franck.mail@dthconnex.com>
329         Grant Ferley
330         Darien Kindlund
331

AUTHOR

333       The IPTables::ChainMgr extension was written by Michael Rash
334       <mbr@cipherdyne.org> to support the psad and fwsnort projects.  Please
335       send email to this address if there are any questions, comments, or bug
336       reports.
337
339       Copyright (C) 2005-2015 Michael Rash.  All rights reserved.
340
341       This module is free software.  You can redistribute it and/or modify it
342       under the terms of the Artistic License 2.0.  More information can be
343       found here: http://www.perl.com/perl/misc/Artistic.html
344
345       This program is distributed "as is" in the hope that it will be useful,
346       but without any warranty; without even the implied warranty of
347       merchantability or fitness for a particular purpose.
348
349
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351perl v5.32.0                      2020-07-28             IPTables::ChainMgr(3)
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