shorewall_code/Shorewall-docs/OPENVPN.html
2003-07-16 18:59:33 +00:00

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<title>OpenVPN Tunnels</title>
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<h1 align="center"><font color="#ffffff">OpenVPN Tunnels</font></h1>
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<h3><br>
</h3>
<p>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 <a href="http://openvpn.sourceforge.net/license.html">licensed under
the GPL</a>. OpenVPN can be downloaded from <a
href="http://openvpn.sourceforge.net/">http://openvpn.sourceforge.net/</a>.<br>
</p>
<p>OpenVPN support was added to Shorewall in version 1.3.14.<br>
</p>
<h2>Bridging two Masqueraded Networks</h2>
<p>Suppose that we have the following situation:</p>
<p align="center"><img border="0" src="images/TwoNets1.png" width="745"
height="427">
</p>
<p align="left">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 /etc/shorewall/tunnels file and the /etc/shorewall/policy
file and OpenVPN.</p>
<p align="left">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.</p>
<p align="left">On each firewall, you will need to declare a zone to represent
the remote subnet. We'll assume that this zone is called 'vpn' and declare
it in /etc/shorewall/zones on both systems as follows.</p>
<blockquote>
<table border="2" cellpadding="2" style="border-collapse: collapse;">
<tbody>
<tr>
<td><strong>ZONE</strong></td>
<td><strong>DISPLAY</strong></td>
<td><strong>COMMENTS</strong></td>
</tr>
<tr>
<td>vpn</td>
<td>VPN</td>
<td>Remote Subnet</td>
</tr>
</tbody>
</table>
</blockquote>
<p align="left">On system A, the 10.0.0.0/8 will comprise the <b>vpn</b> zone.
In /etc/shorewall/interfaces:</p>
<blockquote>
<table border="2" cellpadding="2" style="border-collapse: collapse;">
<tbody>
<tr>
<td><b>ZONE</b></td>
<td><b>INTERFACE</b></td>
<td><b>BROADCAST</b></td>
<td><b>OPTIONS</b></td>
</tr>
<tr>
<td>vpn</td>
<td>tun0</td>
<td><br>
</td>
<td><EFBFBD></td>
</tr>
</tbody>
</table>
</blockquote>
<p align="left">In /etc/shorewall/tunnels on system A, we need the following:</p>
<blockquote>
<table border="2" cellpadding="2" style="border-collapse: collapse;">
<tbody>
<tr>
<td><b>TYPE</b></td>
<td><b>ZONE</b></td>
<td><b>GATEWAY</b></td>
<td><b>GATEWAY ZONE</b></td>
</tr>
<tr>
<td>openvpn</td>
<td>net</td>
<td>134.28.54.2</td>
<td><EFBFBD></td>
</tr>
</tbody>
</table>
</blockquote>
<p>This entry in /etc/shorewall/tunnels 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<6E>/etc/shorewall/tunnels
like this:<br>
</p>
<blockquote>
<table border="2" cellpadding="2" style="border-collapse: collapse;">
<tbody>
<tr>
<td><b>TYPE</b></td>
<td><b>ZONE</b></td>
<td><b>GATEWAY</b></td>
<td><b>GATEWAY ZONE</b></td>
</tr>
<tr>
<td>openvpn:7777</td>
<td>net</td>
<td>134.28.54.2</td>
<td><EFBFBD></td>
</tr>
</tbody>
</table>
</blockquote>
<p>This is the OpenVPN config on system A:</p>
<blockquote>
<p></p>
</blockquote>
<blockquote>
<p>dev tun<br>
local 206.162.148.9<br>
remote 134.28.54.2<br>
ifconfig 192.168.99.1 192.168.99.2<br>
up ./route-a.up<br>
tls-server<br>
dh dh1024.pem<br>
ca ca.crt<br>
cert my-a.crt<br>
key my-a.key<br>
comp-lzo<br>
verb 5<br>
</p>
</blockquote>
<p>Similarly, On system B the 192.168.1.0/24 subnet will comprise the <b>vpn</b>
zone. In /etc/shorewall/interfaces:</p>
<blockquote>
<table border="2" cellpadding="2" style="border-collapse: collapse;">
<tbody>
<tr>
<td><b>ZONE</b></td>
<td><b>INTERFACE</b></td>
<td><b>BROADCAST</b></td>
<td><b>OPTIONS</b></td>
</tr>
<tr>
<td>vpn</td>
<td>tun0</td>
<td>192.168.1.255</td>
<td><EFBFBD></td>
</tr>
</tbody>
</table>
</blockquote>
<p>In /etc/shorewall/tunnels on system B, we have:</p>
<blockquote>
<table border="2" cellpadding="2" style="border-collapse: collapse;">
<tbody>
<tr>
<td><b>TYPE</b></td>
<td><b>ZONE</b></td>
<td><b>GATEWAY</b></td>
<td><b>GATEWAY ZONE</b></td>
</tr>
<tr>
<td>openvpn</td>
<td>net</td>
<td>206.191.148.9</td>
<td><EFBFBD></td>
</tr>
</tbody>
</table>
</blockquote>
<p>And in the<68>OpenVPN config on system B:</p>
<blockquote>
<p>dev tun<br>
local 134.28.54.2<br>
remote 206.162.148.9<br>
ifconfig 192.168.99.2 192.168.99.1<br>
up ./route-b.up<br>
tls-client<br>
ca ca.crt<br>
cert my-b.crt<br>
key my-b.key<br>
comp-lzo<br>
verb 5<br>
</p>
</blockquote>
<p align="left">You will need to allow traffic between the "vpn" zone and
the "loc" zone on both systems -- if you simply want to admit all traffic
in both directions, you can use the policy file:</p>
<blockquote>
<table border="2" cellpadding="2" style="border-collapse: collapse;">
<tbody>
<tr>
<td><strong>SOURCE</strong></td>
<td><strong>DEST</strong></td>
<td><strong>POLICY</strong></td>
<td><strong>LOG LEVEL</strong></td>
</tr>
<tr>
<td>loc</td>
<td>vpn</td>
<td>ACCEPT</td>
<td><EFBFBD></td>
</tr>
<tr>
<td>vpn</td>
<td>loc</td>
<td>ACCEPT</td>
<td><EFBFBD></td>
</tr>
</tbody>
</table>
</blockquote>
<p>On both systems, restart Shorewall and start OpenVPN. The systems in the
two masqueraded subnetworks can now talk to each other.</p>
<p><font size="2">Updated 2/4/2003 - <a href="support.htm">Tom Eastep</a></font>
<small>and Simon Mater</small><br>
</p>
<p><font size="2"> </font></p>
<p><font face="Trebuchet MS"><a href="copyright.htm"><font size="2">Copyright</font>
<20> <font size="2">2003 Thomas M. Eastep. and Simon Mater<br>
</font></a></font></p>
<br>
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