shorewall_code/docs/ipsets.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN"
"http://www.oasis-open.org/docbook/xml/4.4/docbookx.dtd">
<article>
  <!--$Id$-->

  <articleinfo>
    <title>Shorewall and Ipsets</title>

    <authorgroup>
      <author>
        <firstname>Tom</firstname>

        <surname>Eastep</surname>
      </author>
    </authorgroup>

    <pubdate><?dbtimestamp format="Y/m/d"?></pubdate>

    <copyright>
      <year>2005</year>

      <year>2008</year>

      <year>2010</year>

      <holder>Thomas M. Eastep</holder>
    </copyright>

    <legalnotice>
      <para>Permission is granted to copy, distribute and/or modify this
      document under the terms of the GNU Free Documentation License, Version
      1.2 or any later version published by the Free Software Foundation; with
      no Invariant Sections, with no Front-Cover, and with no Back-Cover
      Texts. A copy of the license is included in the section entitled
      <quote><ulink url="GnuCopyright.htm">GNU Free Documentation
      License</ulink></quote>.</para>
    </legalnotice>
  </articleinfo>

  <caution>
    <para><emphasis role="bold">This article applies to Shorewall 4.4 and
    later. If you are running a version of Shorewall earlier than Shorewall
    4.4.0 then please see the documentation appropriate for your
    version.</emphasis></para>
  </caution>

  <section id="Ipsets">
    <title>What are Ipsets?</title>

    <para>Ipsets are an extension to Netfilter/iptables that are currently
    available in <ulink
    url="http://xtables-addons.sourceforge.net/">xtables-addons</ulink>.
    Instructions for installing xtables-addons may be found in the <ulink
    url="Dynamic.html">Dynamic Zones article</ulink>.</para>

    <para>Ipset allows you to create one or more named sets of addresses then
    use those sets to define Netfilter/iptables rules. Possible uses of ipsets
    include:</para>

    <orderedlist>
      <listitem>
        <para>Blacklists. Ipsets provide an efficient way to represent large
        sets of addresses and you can maintain the lists without the need to
        restart or even refresh your Shorewall configuration.</para>
      </listitem>

      <listitem>
        <para>Zone definition. Using the /etc/shorewall/hosts file, you can
        <ulink url="Dynamic.html">define a zone based on the (dynamic)
        contents of an ipset</ulink>. Again, you can then add or delete
        addresses to the ipset without restarting Shorewall.</para>
      </listitem>
    </orderedlist>

    <para>See the ipsets site (URL above) for additional information about
    ipsets.</para>
  </section>

  <section id="Support">
    <title>Shorewall Support for Ipsets</title>

    <para>Support for ipsets was introduced in Shorewall version 2.3.0. In
    most places where a host or network address may be used, you may also use
    the name of an ipset prefaced by "+".</para>

    <para>Example: "+Mirrors"</para>

    <para>When using Shorewall, the names of ipsets are restricted as
    follows:</para>

    <itemizedlist>
      <listitem>
        <para>They must begin with a letter (after the '+').</para>
      </listitem>

      <listitem>
        <para>They must be composed of letters, digits or underscores
        ("_").</para>
      </listitem>
    </itemizedlist>

    <para>To generate a negative match, prefix the "+" with "!" as in
    "!+Mirrors".</para>

    <para>Example 1: Blacklist all hosts in an ipset named "blacklist"</para>

    <para><filename>/etc/shorewall/blacklist</filename><programlisting>#ADDRESS/SUBNET         PROTOCOL        PORT
+blacklist</programlisting></para>

    <para>Example 2: Allow SSH from all hosts in an ipset named "sshok:</para>

    <para><filename>/etc/shorewall/rules</filename><programlisting>#ACTION      SOURCE      DEST     PROTO    DEST PORT(S)
ACCEPT       net:+sshok  $FW      tcp      22</programlisting></para>

    <para>The name of the ipset can be optionally followed by a
    comma-separated list of flags enclosed in square brackets ([...]). Each
    flag is either <emphasis role="bold">src</emphasis> or <emphasis
    role="bold">dst</emphasis> and specifies whether it is the SOURCE address
    or port number or the DESTINATION address or port number that should be
    matched. The number of flags must be appropriate for the type of ipset. If
    no flags are given, Shorewall assumes that the set takes a single flag and
    will select the flag based on the context. For example, in the blacklist
    file and when the ipset appears in the SOURCE column of the rules file,
    <emphasis role="bold">src</emphasis> is assumed. If the ipset appears in
    the DEST column of the rules file, <emphasis role="bold">dst</emphasis> is
    assumed. Note that by using <emphasis role="bold">[dst]</emphasis> in the
    blacklist file, you can coerce the rule into matching the destination IP
    address rather than the source.</para>

    <para>Shorewall can save/restore your ipset contents with certain
    restrictions:</para>

    <orderedlist>
      <listitem>
        <para>You must set SAVE_IPSETS=Yes in <ulink
        url="manpages/shorewall.conf.html">shorewall.conf</ulink> (5).</para>
      </listitem>

      <listitem>
        <para>You cannot use an ipset in <ulink
        url="manpages/shorewall-routestopped.html">shorewall-routestopped</ulink>
        (5).</para>
      </listitem>

      <listitem>
        <para>The <command>restore</command> command cannot restore ipset
        contents saved by the <command>save</command> command unless the
        firewall is first stopped.</para>
      </listitem>
    </orderedlist>
  </section>
</article>