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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Using Shorewall with Squid</title><meta name="generator" content="DocBook XSL Stylesheets V1.62.4" /></head><body><div class="article" lang="en" xml:lang="en"><div class="titlepage"><div><div><h1 class="title"><a id="Shorewall_Squid_Usage"></a>Using Shorewall with Squid</h1></div><div><div class="authorgroup"><div class="author"><h3 class="author"><span class="firstname">Tom</span> <span class="surname">Eastep</span></h3></div></div></div><div><p class="copyright">Copyright © 2003-2004 Thomas M. Eastep</p></div><div><div class="legalnotice"><p>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
“<span class="quote"><a href="GnuCopyright.htm" target="_self">GNU Free Documentation License</a></span>”.</p></div></div><div><p class="pubdate">2004-02-04</p></div></div><div></div><hr /></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="section"><a href="#id2807725">Squid as a Transparent Proxy</a></span></dt><dt><span class="section"><a href="#id2807811">Configurations</a></span></dt><dd><dl><dt><span class="section"><a href="#Firewall">Squid (transparent) Running on the Firewall</a></span></dt><dt><span class="section"><a href="#Local">Squid (transparent) Running in the local network</a></span></dt><dt><span class="section"><a href="#DMZ">Squid (transparent) Running in the DMZ</a></span></dt></dl></dd><dt><span class="section"><a href="#id2859624">Squid as a Manual Proxy</a></span></dt></dl></div><p></p><p>This page covers Shorewall configuration to use with <a href="http://www.squid-cache.org" target="_self">Squid</a> running as a Transparent
Proxy or as a Manual Proxy.</p><p>If you are running Shorewall 1.3, please see <a href="1.3/Shorewall_Squid_Usage.html" target="_self">this documentation</a>.</p><div class="section" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="id2807725"></a>Squid as a Transparent Proxy</h2></div></div><div></div></div><div class="caution" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Caution</h3><p>Please observe the following general requirements:</p><div class="itemizedlist"><ul type="disc"><li><p>In all cases, Squid should be configured to run as a transrent
proxy as described at
http://tldp.org/HOWTO/mini/TransparentProxy.html.</p></li><li><p>The following instructions mention the files
/etc/shorewall/start and /etc/shorewall/init -- if you don't
have those files, siimply create them.</p></li><li><p>When the Squid server is in the DMZ zone or in the local zone,
that zone must be defined ONLY by its interface -- no
/etc/shorewall/hosts file entries. That is because the packets being
routed to the Squid server still have their original destination IP
addresses.</p></li><li><p>You must have iptables installed on your Squid server.</p></li><li><p>If you run a Shorewall version earlier than 1.4.6, you must
have NAT and MANGLE enabled in your /etc/shorewall/conf file</p><table border="0" bgcolor="#E0E0E0"><tr><td><pre class="programlisting">NAT_ENABLED=Yes
MANGLE_ENABLED=Yes</pre></td></tr></table></li></ul></div></div></div><div class="section" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="id2807811"></a>Configurations</h2></div></div><div></div></div><p>Three different configurations are covered:</p><table class="simplelist" border="0" summary="Simple list"><tr><td>Squid (transparent) Running on the Firewall</td></tr><tr><td>Squid (transparent) Running in the local Network</td></tr><tr><td>Squid (transparent) Running in a DMZ</td></tr></table><div class="section" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="Firewall"></a>Squid (transparent) Running on the Firewall</h3></div></div><div></div></div><p>You want to redirect all local www connection requests EXCEPT
those to your own http server (206.124.146.177) to a Squid transparent
proxy running on the firewall and listening on port 3128. Squid will of
course require access to remote web servers.</p><p>In <tt class="filename">/etc/shorewall/rules</tt>:</p><table border="0" bgcolor="#E0E0E0"><tr><td><pre class="programlisting">#ACTION SOURCE DEST PROTO DEST PORT(S) SOURCE ORIGINAL
# PORT(S) DEST
REDIRECT loc 3228 tcp www - !206.124.146.177
ACCEPT fw net tcp www</pre></td></tr></table><p>There may be a requirement to exclude additional destination hosts
or networks from being redirected. For example, you might also want
requests destined for 130.252.100.0/24 to not be routed to Squid.</p><p>If you are running Shorewall version 1.4.5 or later, you may just
add the additional hosts/networks to the ORIGINAL DEST column in your
REDIRECT rule.</p><p><tt class="filename">/etc/shorewall/rules</tt>:</p><table border="0" bgcolor="#E0E0E0"><tr><td><pre class="programlisting">#ACTION SOURCE DEST PROTO DEST PORT(S) SOURCE ORIGINAL
# PORT(S) DEST
REDIRECT loc 3228 tcp www - !206.124.146.177,130.252.100.0/24</pre></td></tr></table><p>If you are running a Shorewall version earlier than 1.4.5, you
must add a manual rule in /etc/shorewall/start:</p><table border="0" bgcolor="#E0E0E0"><tr><td><pre class="programlisting"><span><b class="command">run_iptables -t nat -I loc_dnat -p tcp --dport www -d 130.252.100.0/24 -j RETURN</b></span></pre></td></tr></table><p>To exclude additional hosts or networks, just add additional
similar rules.</p></div><div class="section" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="Local"></a>Squid (transparent) Running in the local network</h3></div></div><div></div></div><p>You want to redirect all local www connection requests to a Squid
transparent proxy running in your local zone at 192.168.1.3 and
listening on port 3128. Your local interface is eth1. There may also be
a web server running on 192.168.1.3. It is assumed that web access is
already enabled from the local zone to the internet..</p><div class="orderedlist"><ol type="1"><li><p>* On your firewall system, issue the following command</p><table border="0" bgcolor="#E0E0E0"><tr><td><pre class="programlisting"><span><b class="command">echo 202 www.out &gt;&gt; /etc/iproute2/rt_tables</b></span></pre></td></tr></table></li><li><p>In /etc/shorewall/init, put:</p><table border="0" bgcolor="#E0E0E0"><tr><td><pre class="programlisting"><span><b class="command">if [ -z &quot;`ip rule list | grep www.out`&quot; ] ; then
ip rule add fwmark 202 table www.out
ip route add default via 192.168.1.3 dev eth1 table www.out
ip route flush cache
echo 0 &gt; /proc/sys/net/ipv4/conf/eth1/send_redirects
fi</b></span></pre></td></tr></table></li><li><div class="important" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Important</h3><p>If you are running Shorewall 1.4.1 or Shorewall 1.4.1a,
please upgrade to Shorewall 1.4.2 or later.</p></div><p>If you are running Shorewall 1.4.2 or later, then in
<tt class="filename">/etc/shorewall/interfaces</tt>:</p><table border="0" bgcolor="#E0E0E0"><tr><td><pre class="programlisting">#ZONE INTERFACE BROADCAST OPTIONS
loc eth1 detect <span class="bold"><b>routeback</b></span> </pre></td></tr></table></li><li><p>In /etc/shorewall/rules:</p><table border="0" bgcolor="#E0E0E0"><tr><td><pre class="programlisting">#ACTION SOURCE DEST PROTO DEST PORT(S)
ACCEPT loc loc tcp www</pre></td></tr></table><div class="orderedlist"><ol type="a"><li><p>Alternativfely, if you are running Shorewall 1.4.0 you can
have the following policy in place of the above rule.</p><p><tt class="filename">/etc/shorewall/policy</tt></p><table border="0" bgcolor="#E0E0E0"><tr><td><pre class="programlisting">#SOURCE DESTINATION POLICY
loc loc ACCEPT</pre></td></tr></table></li></ol></div></li><li><p>In <tt class="filename">/etc/shorewall/start</tt> add:</p><table border="0" bgcolor="#E0E0E0"><tr><td><pre class="programlisting"><span><b class="command">iptables -t mangle -A PREROUTING -i eth1 -s ! 192.168.1.3 -p tcp --dport 80 -j MARK --set-mark 202</b></span></pre></td></tr></table></li><li><p>On 192.168.1.3, arrange for the following command to be
executed after networking has come up</p><table border="0" bgcolor="#E0E0E0"><tr><td><pre class="programlisting"><span><b class="command">iptables -t nat -A PREROUTING -i eth0 -d ! 192.168.1.3 -p tcp --dport 80 -j REDIRECT --to-ports 3128</b></span></pre></td></tr></table><p>If you are running RedHat on the server, you can simply
execute the following commands after you have typed the iptables
command above:</p><table border="0" bgcolor="#E0E0E0"><tr><td><pre class="programlisting"><span><b class="command">iptables-save &gt; /etc/sysconfig/iptables
chkconfig --level 35 iptables on</b></span></pre></td></tr></table></li></ol></div></div><div class="section" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="DMZ"></a>Squid (transparent) Running in the DMZ</h3></div></div><div></div></div><p>You have a single Linux system in your DMZ with IP address
192.0.2.177. You want to run both a web server and Squid on that system.
Your DMZ interface is eth1 and your local interface is eth2.</p><div class="orderedlist"><ol type="1"><li><p>On your firewall system, issue the following command</p><table border="0" bgcolor="#E0E0E0"><tr><td><pre class="programlisting"><span><b class="command">echo 202 www.out &gt;&gt; /etc/iproute2/rt_tables</b></span></pre></td></tr></table></li><li><p>In /etc/shorewall/init, put:</p><table border="0" bgcolor="#E0E0E0"><tr><td><pre class="programlisting"><span><b class="command">if [ -z &quot;`ip rule list | grep www.out`&quot; ] ; then
ip rule add fwmark 202 table www.out
ip route add default via 192.0.2.177 dev eth1 table www.out
ip route flush cache
fi</b></span></pre></td></tr></table></li><li><p>Do <span class="bold"><b>one</b></span> of the following:</p><div class="orderedlist"><ol type="a"><li><p>In <tt class="filename">/etc/shorewall/start</tt> add</p><table border="0" bgcolor="#E0E0E0"><tr><td><pre class="programlisting"><span><b class="command">iptables -t mangle -A PREROUTING -i eth2 -p tcp --dport 80 -j MARK --set-mark 202</b></span></pre></td></tr></table></li><li><p>Set MARK_IN_FORWARD_CHAIN=No in <tt class="filename">/etc/shorewall/shorewall.conf</tt>
and add the following entry in <tt class="filename">/etc/shorewall/tcrules</tt>:</p><table border="0" bgcolor="#E0E0E0"><tr><td><pre class="programlisting">#MARK SOURCE DESTINATION PROTOCOL PORT
202 eth2 0.0.0.0 tcp 80</pre></td></tr></table></li><li><p>Run Shorewall 1.3.14 or later and add the following entry
in <tt class="filename">/etc/shorewall/tcrules</tt>:</p><table border="0" bgcolor="#E0E0E0"><tr><td><pre class="programlisting">#MARK SOURCE DESTINATION PROTOCOL PORT
202:P eth2 0.0.0.0 tcp 80</pre></td></tr></table></li></ol></div></li><li><p>In <tt class="filename">/etc/shorewall/rules</tt>, you will need:</p><table border="0" bgcolor="#E0E0E0"><tr><td><pre class="programlisting">#ACTION SOURCE DEST PROTO DEST PORT(S)
ACCEPT loc dmz tcp 80
ACCEPT dmz net tcp 80</pre></td></tr></table></li><li><p>On 192.0.2.177 (your Web/Squid server), arrange for the
following command to be executed after networking has come up</p><table border="0" bgcolor="#E0E0E0"><tr><td><pre class="programlisting"><span><b class="command">iptables -t nat -A PREROUTING -i eth0 -d ! 192.0.2.177 -p tcp --dport 80 -j REDIRECT --to-ports 3128</b></span></pre></td></tr></table><p>If you are running RedHat on the server, you can simply
execute the following commands after you have typed the iptables
command above:</p><table border="0" bgcolor="#E0E0E0"><tr><td><pre class="programlisting"><span><b class="command">iptables-save &gt; /etc/sysconfig/iptables
chkconfig --level 35 iptables on</b></span></pre></td></tr></table></li></ol></div></div></div><div class="section" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="id2859624"></a>Squid as a Manual Proxy</h2></div></div><div></div></div><p>Assume that Squid is running in zone SZ and listening on port SP;
all web sites that are to be accessed through Squid are in the
“<span class="quote">net</span>” zone. Then for each zone Z that needs access to the
Squid server.</p><p><tt class="filename">/etc/shorewall/rules</tt>:</p><table border="0" bgcolor="#E0E0E0"><tr><td><pre class="programlisting">#ACTION SOURCE DEST PROTO DEST PORT(S)
ACCEPT Z SZ tcp SP
ACCEPT SZ net tcp 80</pre></td></tr></table><div class="example"><a id="id2809851"></a><p class="title"><b>Example 1. Squid on the firewall listening on port 8080 with access from the
“<span class="quote">loc</span>” zone:</b></p><p><tt class="filename">/etc/shorewall/rules:</tt></p><table border="0" bgcolor="#E0E0E0"><tr><td><pre class="programlisting">#ACTION SOURCE DEST PROTO DEST PORT(S)
ACCEPT loc fw tcp 8080
ACCEPT fw net tcp 80</pre></td></tr></table></div></div></div></body></html>
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