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368 lines
13 KiB
HTML
368 lines
13 KiB
HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<html>
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<head>
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<meta http-equiv="Content-Type"
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content="text/html; charset=windows-1252">
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<title>Shorewall IPSec Tunneling</title>
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<meta name="GENERATOR" content="Microsoft FrontPage 5.0">
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<meta name="ProgId" content="FrontPage.Editor.Document">
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</head>
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<body>
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<table border="0" cellpadding="0" cellspacing="0"
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style="border-collapse: collapse;" bordercolor="#111111" width="100%"
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id="AutoNumber1" bgcolor="#400169" height="90">
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<tbody>
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<tr>
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<td width="100%">
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<h1 align="center"><font color="#ffffff">IPSEC Tunnels</font></h1>
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</td>
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</tr>
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</tbody>
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</table>
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<h2><font color="#660066">Configuring FreeS/Wan</font></h2>
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There is an excellent guide to configuring IPSEC tunnels at<a
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href="http://jixen.tripod.com"> http://jixen.tripod.com</a> . I highly recommend
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that you consult that site for information about confuring FreeS/Wan.
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<p><font color="#ff6633"><b>Warning: </b></font>Do not use Proxy ARP and
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FreeS/Wan on the same system unless you are prepared to suffer the consequences.
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If you start or restart Shorewall with an IPSEC tunnel active, the proxied
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IP addresses are mistakenly assigned to the IPSEC tunnel device (ipsecX)
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rather than to the interface that you specify in the INTERFACE column of
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/etc/shorewall/proxyarp. I haven't had the time to debug this problem so I
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can't say if it is a bug in the Kernel or in FreeS/Wan. </p>
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<p>You <b>might</b> be able to work around this problem using the following
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(I haven't tried it):</p>
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<p>In /etc/shorewall/init, include:</p>
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<p> qt service ipsec stop</p>
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<p>In /etc/shorewall/start, include:</p>
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<p> qt service ipsec start</p>
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<h2> <font color="#660066">IPSec Gateway on the Firewall System </font></h2>
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<p>Suppose that we have the following sutuation:</p>
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<font color="#660066">
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<p align="center"><font face="Century Gothic, Arial, Helvetica"> <img
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src="images/TwoNets1.png" width="745" height="427">
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</font></p>
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</font>
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<p align="left">We want systems in the 192.168.1.0/24 sub-network to be able
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to communicate with systems in the 10.0.0.0/8 network.</p>
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<p align="left">To make this work, we need to do two things:</p>
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<p align="left">a) Open the firewall so that the IPSEC tunnel can be established
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(allow the ESP and AH protocols and UDP Port 500). </p>
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<p align="left">b) Allow traffic through the tunnel.</p>
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<p align="left">Opening the firewall for the IPSEC tunnel is accomplished
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by adding an entry to the /etc/shorewall/tunnels file.</p>
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<p align="left">In /etc/shorewall/tunnels on system A, we need the following </p>
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<blockquote>
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<table border="2" cellpadding="2" style="border-collapse: collapse;">
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<tbody>
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<tr>
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<td><strong> TYPE</strong></td>
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<td><strong> ZONE</strong></td>
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<td><strong> GATEWAY</strong></td>
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<td><strong> GATEWAY ZONE</strong></td>
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</tr>
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<tr>
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<td>ipsec</td>
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<td>net</td>
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<td>134.28.54.2</td>
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<td> </td>
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</tr>
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</tbody>
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</table>
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</blockquote>
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<p align="left">In /etc/shorewall/tunnels on system B, we would have:</p>
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<blockquote>
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<table border="2" cellpadding="2" style="border-collapse: collapse;">
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<tbody>
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<tr>
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<td><strong> TYPE</strong></td>
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<td><strong> ZONE</strong></td>
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<td><strong> GATEWAY</strong></td>
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<td><strong> GATEWAY ZONE</strong></td>
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</tr>
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<tr>
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<td>ipsec</td>
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<td>net</td>
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<td>206.161.148.9</td>
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<td> </td>
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</tr>
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</tbody>
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</table>
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</blockquote>
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<p align="left"><b>Note: </b>If either of the endpoints is behind a NAT gateway
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then the tunnels file entry on the <u><b>other</b></u> endpoint should specify
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a tunnel type of <i>ipsecnat</i> rather than <i>ipsec</i> and the GATEWAY
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address should specify the external address of the NAT gateway.<br>
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</p>
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<p align="left">You need to define a zone for the remote subnet or include
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it in your local zone. In this example, we'll assume that you have created
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a zone called "vpn" to represent the remote subnet.</p>
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<blockquote>
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<table border="2" cellpadding="2" style="border-collapse: collapse;">
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<tbody>
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<tr>
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<td><strong>ZONE</strong></td>
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<td><strong>DISPLAY</strong></td>
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<td><strong>COMMENTS</strong></td>
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</tr>
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<tr>
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<td>vpn</td>
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<td>VPN</td>
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<td>Remote Subnet</td>
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</tr>
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</tbody>
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</table>
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</blockquote>
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<p align="left">At both systems, ipsec0 would be included in /etc/shorewall/interfaces
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as a "vpn" interface:</p>
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<blockquote>
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<table border="2" cellpadding="2" style="border-collapse: collapse;">
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<tbody>
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<tr>
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<td><strong> ZONE</strong></td>
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<td><strong> INTERFACE</strong></td>
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<td><strong> BROADCAST</strong></td>
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<td><strong> OPTIONS</strong></td>
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</tr>
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<tr>
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<td>vpn</td>
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<td>ipsec0</td>
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<td> </td>
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<td> </td>
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</tr>
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</tbody>
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</table>
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</blockquote>
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<p align="left"> You will need to allow traffic between the "vpn" zone and
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the "loc" zone -- if you simply want to admit all traffic in both
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directions, you can use the policy file:</p>
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<blockquote>
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<table border="2" cellpadding="2" style="border-collapse: collapse;">
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<tbody>
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<tr>
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<td><strong>SOURCE</strong></td>
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<td><strong>DEST</strong></td>
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<td><strong>POLICY</strong></td>
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<td><strong>LOG LEVEL</strong></td>
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</tr>
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<tr>
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<td>loc</td>
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<td>vpn</td>
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<td>ACCEPT</td>
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<td> </td>
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</tr>
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<tr>
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<td>vpn</td>
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<td>loc</td>
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<td>ACCEPT</td>
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<td> </td>
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</tr>
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</tbody>
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</table>
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</blockquote>
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<p align="left"> Once you have these entries in place, restart Shorewall (type
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shorewall restart); you are now ready to configure the tunnel in <a
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href="http://www.xs4all.nl/%7Efreeswan/"> FreeS/WAN</a> .</p>
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<h2><font color="#660066"><a name="RoadWarrior"></a> Mobile System (Road
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Warrior)</font></h2>
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<p>Suppose that you have a laptop system (B) that you take with you when you
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travel and you want to be able to establish a secure connection back to your
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local network.</p>
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<p align="center"><strong><font face="Century Gothic, Arial, Helvetica">
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<img src="images/Mobile.png" width="677" height="426">
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</font></strong></p>
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<p align="left">You need to define a zone for the laptop or include it in
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your local zone. In this example, we'll assume that you have created
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a zone called "vpn" to represent the remote host.</p>
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<blockquote>
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<table border="2" cellpadding="2" style="border-collapse: collapse;">
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<tbody>
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<tr>
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<td><strong>ZONE</strong></td>
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<td><strong>DISPLAY</strong></td>
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<td><strong>COMMENTS</strong></td>
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</tr>
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<tr>
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<td>vpn</td>
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<td>VPN</td>
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<td>Remote Subnet</td>
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</tr>
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</tbody>
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</table>
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</blockquote>
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<p align="left"> In this instance, the mobile system (B) has IP address 134.28.54.2
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but that cannot be determined in advance. In the /etc/shorewall/tunnels file
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on system A, the following entry should be made:</p>
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<blockquote>
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<table border="2" cellpadding="2" style="border-collapse: collapse;">
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<tbody>
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<tr>
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<td><strong> TYPE</strong></td>
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<td><strong> ZONE</strong></td>
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<td><strong> GATEWAY</strong></td>
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<td><strong> GATEWAY ZONE</strong></td>
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</tr>
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<tr>
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<td>ipsec</td>
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<td>net</td>
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<td>0.0.0.0/0</td>
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<td>vpn</td>
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</tr>
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</tbody>
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</table>
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</blockquote>
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<p>Note that the GATEWAY ZONE column contains the name of the zone corresponding
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to peer subnetworks. This indicates that the gateway system itself comprises
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the peer subnetwork; in other words, the remote gateway is a standalone system.</p>
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<p>You will need to configure /etc/shorewall/interfaces and establish
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your "through the tunnel" policy as shown under the first example above.<br>
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</p>
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<h2><a name="Dynamic"></a>Dynamic RoadWarrior Zones</h2>
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Beginning with Shorewall release 1.3.10, you can define multiple VPN zones
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and add and delete remote endpoints dynamically using /sbin/shorewall. In
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/etc/shorewall/zones:<br>
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<br>
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<blockquote>
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<table cellpadding="2" border="2" style="border-collapse: collapse;">
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<tbody>
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<tr>
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<td valign="top"><b>ZONE<br>
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</b></td>
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<td valign="top"><b>DISPLAY<br>
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</b></td>
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<td valign="top"><b>COMMENTS<br>
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</b></td>
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</tr>
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<tr>
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<td valign="top">vpn1<br>
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</td>
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<td valign="top">VPN-1<br>
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</td>
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<td valign="top">First VPN Zone<br>
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</td>
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</tr>
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<tr>
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<td valign="top">vpn2<br>
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</td>
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<td valign="top">VPN-2<br>
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</td>
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<td valign="top">Second VPN Zone<br>
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</td>
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</tr>
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<tr>
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<td valign="top">vpn3<br>
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</td>
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<td valign="top">VPN-3<br>
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</td>
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<td valign="top">Third VPN Zone<br>
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</td>
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</tr>
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</tbody>
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</table>
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<br>
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</blockquote>
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In /etc/shorewall/tunnels:<br>
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<blockquote>
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<table cellpadding="2" cellspacing="" border="2"
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style="border-collapse: collapse;">
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<tbody>
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<tr>
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<td valign="top"><b>TYPE<br>
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</b></td>
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<td valign="top"><b>ZONE<br>
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</b></td>
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<td valign="top"><b>GATEWAY<br>
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</b></td>
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<td valign="top"><b>GATEWAY ZONE<br>
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</b></td>
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</tr>
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<tr>
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<td valign="top">ipsec<br>
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</td>
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<td valign="top">net<br>
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</td>
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<td valign="top">0.0.0.0/0<br>
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</td>
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<td valign="top">vpn1,vpn2,vpn3<br>
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</td>
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</tr>
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</tbody>
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</table>
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<br>
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</blockquote>
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When Shorewall is started, the zones vpn[1-3] will all be empty and Shorewall
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will issue warnings to that effect. These warnings may be safely ignored.
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FreeS/Wan may now be configured to have three different Road Warrior connections
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with the choice of connection being based on X-509 certificates or some other
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means. Each of these connectioins will utilize a different updown script that
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adds the remote station to the appropriate zone when the connection comes
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up and that deletes the remote station when the connection comes down. For
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example, when 134.28.54.2 connects for the vpn2 zone the 'up' part of the
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script will issue the command":<br>
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<br>
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<blockquote>/sbin/shorewall add ipsec0:134.28.54.2 vpn2<br>
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</blockquote>
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and the 'down' part will:<br>
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<blockquote>/sbin/shorewall delete ipsec0:134.28.54.2 vpn</blockquote>
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<p><font size="2">Last updated 10/23/2002 - </font><font size="2">
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<a href="support.htm">Tom Eastep</a></font> </p>
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<p><font face="Trebuchet MS"><a href="copyright.htm"><font size="2">
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Copyright</font> © <font size="2">2001, 2002 Thomas M. Eastep.</font></a></font></p>
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<br>
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<br>
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</body>
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</html>
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