shorewall_code/Shorewall-docs2/OPENVPN.xml

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<article id="OPENVPN">
  <!--$Id$-->

  <articleinfo>
    <title>OpenVPN Tunnels</title>

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

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

      <author>
        <firstname>Simon</firstname>

        <surname>Mater</surname>
      </author>
    </authorgroup>

    <pubdate>2004-10-12</pubdate>

    <copyright>
      <year>2003</year>

      <holder>Thomas M. Eastep</holder>

      <holder>Simon Mater</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>

  <para>OpenVPN is a robust and highly configurable VPN (Virtual Private
  Network) daemon which can be used to securely link two or more private
  networks using an encrypted tunnel over the internet. OpenVPN is an Open
  Source project and is <ulink
  url="http://openvpn.sourceforge.net/license.html">licensed under the
  GPL</ulink>. OpenVPN can be downloaded from <ulink
  url="http://openvpn.sourceforge.net/">http://openvpn.sourceforge.net/</ulink>.</para>

  <para>OpenVPN support was added to Shorewall in version 1.3.14.</para>

  <section>
    <title>Bridging two Masqueraded Networks</title>

    <para>Suppose that we have the following situation:</para>

    <graphic fileref="images/TwoNets1.png" />

    <para>We want systems in the 192.168.1.0/24 subnetwork to be able to
    communicate with the systems in the 10.0.0.0/8 network. This is
    accomplished through use of the
    <filename>/etc/shorewall/tunnels</filename> file and the
    <filename>/etc/shorewall/policy file</filename> and OpenVPN.</para>

    <para>While it was possible to use the Shorewall start and stop script to
    start and stop OpenVPN, I decided to use the init script of OpenVPN to
    start and stop it.</para>

    <para>On each firewall, you will need to declare a zone to represent the
    remote subnet. We'll assume that this zone is called <quote>vpn</quote>
    and declare it in <filename>/etc/shorewall/zones</filename> on both
    systems as follows.</para>

    <blockquote>
      <para><filename>/etc/shorewall/zones</filename> — Systems A &amp;
      B</para>

      <programlisting>#ZONE           DISPLAY           COMMENTS
vpn             VPN               Remote subnet</programlisting>
    </blockquote>

    <para>On system A, the 10.0.0.0/8 will comprise the <emphasis
    role="bold">vpn</emphasis> zone.</para>

    <blockquote>
      <para>In <filename>/etc/shorewall/interfaces</filename> on system
      A:</para>

      <programlisting>#ZONE      INTERFACE        BROADCAST     OPTIONS
vpn        tun0</programlisting>
    </blockquote>

    <para>In <filename>/etc/shorewall/tunnels</filename> on system A, we need
    the following:</para>

    <blockquote>
      <programlisting>#TYPE         ZONE           GATEWAY        GATEWAY ZONE
openvpn       net            134.28.54.2</programlisting>
    </blockquote>

    <note>
      <para>Some OpenVPN clients (notabley on <trademark>Windows</trademark>)
      do not use the same source and destination ports which can cause
      problems. If system B is a Windows system or if you find that Shorewall
      is blocking the UDP port 5000 traffic from the remote gateway, then you
      will want the following entry in
      <filename>/etc/shorewall/tunnels</filename> instead of the one
      above:</para>

      <programlisting>#TYPE                  ZONE           GATEWAY        GATEWAY ZONE
generic:udp:5000       net            134.28.54.2</programlisting>
    </note>

    <para>This entry in <filename>/etc/shorewall/tunnels</filename> opens the
    firewall so that OpenVPN traffic on the default port 5000/udp will be
    accepted to/from the remote gateway. If you change the port used by
    OpenVPN to 7777, you can define /etc/shorewall/tunnels like this:</para>

    <blockquote>
      <para>/etc/shorewall/tunnels with port 7777:</para>

      <programlisting>#TYPE             ZONE           GATEWAY         GATEWAY ZONE
openvpn:7777      net            134.28.54.2</programlisting>
    </blockquote>

    <para>This is the OpenVPN config on system A:</para>

    <blockquote>
      <programlisting>dev tun
local 206.162.148.9
remote 134.28.54.2
ifconfig 192.168.99.1 192.168.99.2
up ./route-a.up
tls-server
dh dh1024.pem
ca ca.crt
cert my-a.crt
key my-a.key
comp-lzo
verb 5</programlisting>
    </blockquote>

    <para>Similarly, On system B the 192.168.1.0/24 subnet will comprise the
    <emphasis role="bold">vpn</emphasis> zone</para>

    <blockquote>
      <para>In <filename>/etc/shorewall/interfaces</filename> on system
      B:</para>

      <programlisting>#ZONE      INTERFACE        BROADCAST     OPTIONS
vpn        tun0             192.168.1.255</programlisting>
    </blockquote>

    <para>In <filename>/etc/shorewall/tunnels</filename> on system B, we
    have:</para>

    <blockquote>
      <programlisting>#TYPE         ZONE           GATEWAY        GATEWAY ZONE
openvpn       net            206.191.148.9</programlisting>
    </blockquote>

    <para>And in the OpenVPN config on system B:</para>

    <blockquote>
      <programlisting>dev tun
local 134.28.54.2
remote 206.162.148.9
ifconfig 192.168.99.2 192.168.99.1
up ./route-b.up
tls-client
ca ca.crt
cert my-b.crt
key my-b.key
comp-lzo
verb 5</programlisting>
    </blockquote>

    <para>You will need to allow traffic between the <quote>vpn</quote> zone
    and the <quote>loc</quote> zone on both systems -- if you simply want to
    admit all traffic in both directions, you can use the policy file:</para>

    <blockquote>
      <para><filename>/etc/shorewall/policy </filename>on systems A &amp;
      B</para>

      <programlisting>#SOURCE        DEST          POLICY          LOG LEVEL
loc            vpn           ACCEPT
vpn            loc           ACCEPT</programlisting>
    </blockquote>

    <para>On both systems, restart Shorewall and start OpenVPN. The systems in
    the two masqueraded subnetworks can now talk to each other.</para>
  </section>
</article>