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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<article id="Shorewall_Squid_Usage">
<!--$Id$-->
<articleinfo>
<title>Using Shorewall with Squid</title>
<authorgroup>
<author>
<firstname>Tom</firstname>
<surname>Eastep</surname>
</author>
</authorgroup>
<pubdate>2004-04-19</pubdate>
<copyright>
<year>2003-2004</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>
<para></para>
<para>This page covers Shorewall configuration to use with <ulink
url="http://www.squid-cache.org">Squid</ulink> running as a Transparent
Proxy or as a Manual Proxy.</para>
<para>If you are running Shorewall 1.3, please see <ulink
url="1.3/Shorewall_Squid_Usage.html">this documentation</ulink>.</para>
<section>
<title>Squid as a Transparent Proxy</title>
<caution>
<para>Please observe the following general requirements:</para>
<itemizedlist>
<listitem>
<para>In all cases, Squid should be configured to run as a transrent
proxy as described at <ulink
url="http://tldp.org/HOWTO/mini/TransparentProxy.html">http://tldp.org/HOWTO/mini/TransparentProxy.html</ulink>.</para>
</listitem>
<listitem>
<para>The following instructions mention the files
/etc/shorewall/start and /etc/shorewall/init -- if you don&#39;t
have those files, siimply create them.</para>
</listitem>
<listitem>
<para>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.</para>
</listitem>
<listitem>
<para>You must have iptables installed on your Squid server.</para>
</listitem>
<listitem>
<para>If you run a Shorewall version earlier than 1.4.6, you must
have NAT and MANGLE enabled in your /etc/shorewall/conf file</para>
<programlisting>NAT_ENABLED=Yes
MANGLE_ENABLED=Yes</programlisting>
</listitem>
</itemizedlist>
</caution>
</section>
<section>
<title>Configurations</title>
<para>Three different configurations are covered:</para>
<simplelist>
<member>Squid (transparent) Running on the Firewall</member>
<member>Squid (transparent) Running in the local Network</member>
<member>Squid (transparent) Running in a DMZ</member>
</simplelist>
<section id="Firewall">
<title>Squid (transparent) Running on the Firewall</title>
<para>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.</para>
<para>In <filename>/etc/shorewall/rules</filename>:</para>
<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</programlisting>
<para>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.</para>
<para>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.</para>
<para><filename>/etc/shorewall/rules</filename>:<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</programlisting></para>
<para>If you are running a Shorewall version earlier than 1.4.5, you
must add a manual rule in /etc/shorewall/start:</para>
<programlisting><command>run_iptables -t nat -I loc_dnat -p tcp --dport www -d 130.252.100.0/24 -j RETURN</command></programlisting>
<para>To exclude additional hosts or networks, just add additional
similar rules.</para>
</section>
<section id="Local">
<title>Squid (transparent) Running in the local network</title>
<para>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..</para>
<orderedlist>
<listitem>
<para>* On your firewall system, issue the following command</para>
<programlisting><command>echo 202 www.out &#62;&#62; /etc/iproute2/rt_tables</command></programlisting>
</listitem>
<listitem>
<para>In /etc/shorewall/init, put:</para>
<programlisting><command>if [ -z &#34;`ip rule list | grep www.out`&#34; ] ; then
ip rule add fwmark CA table www.out # Note 0xCA = 202
ip route add default via 192.168.1.3 dev eth1 table www.out
ip route flush cache
echo 0 &#62; /proc/sys/net/ipv4/conf/eth1/send_redirects
fi</command></programlisting>
</listitem>
<listitem>
<important>
<para>If you are running Shorewall 1.4.1 or Shorewall 1.4.1a,
please upgrade to Shorewall 1.4.2 or later.</para>
</important>
<para>If you are running Shorewall 1.4.2 or later, then in
<filename>/etc/shorewall/interfaces</filename>:</para>
<programlisting>#ZONE INTERFACE BROADCAST OPTIONS
loc eth1 detect <emphasis role="bold">routeback</emphasis> </programlisting>
</listitem>
<listitem>
<para>In /etc/shorewall/rules:</para>
<programlisting>#ACTION SOURCE DEST PROTO DEST PORT(S)
ACCEPT loc loc tcp www</programlisting>
<orderedlist numeration="loweralpha">
<listitem>
<para>Alternativfely, if you are running Shorewall 1.4.0 you can
have the following policy in place of the above rule.</para>
<para><filename>/etc/shorewall/policy</filename></para>
<programlisting>#SOURCE DESTINATION POLICY
loc loc ACCEPT</programlisting>
</listitem>
</orderedlist>
</listitem>
<listitem>
<para>In <filename>/etc/shorewall/start</filename> add:</para>
<programlisting><command>iptables -t mangle -A PREROUTING -i eth1 -s ! 192.168.1.3 -p tcp --dport 80 -j MARK --set-mark 202</command></programlisting>
</listitem>
<listitem>
<para>On 192.168.1.3, arrange for the following command to be
executed after networking has come up</para>
<programlisting><command>iptables -t nat -A PREROUTING -i eth0 -d ! 192.168.1.3 -p tcp --dport 80 -j REDIRECT --to-ports 3128</command></programlisting>
<para>If you are running RedHat on the server, you can simply
execute the following commands after you have typed the iptables
command above:</para>
<programlisting><command>iptables-save &#62; /etc/sysconfig/iptables
chkconfig --level 35 iptables on</command></programlisting>
</listitem>
</orderedlist>
</section>
<section id="DMZ">
<title>Squid (transparent) Running in the DMZ</title>
<para>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.</para>
<orderedlist>
<listitem>
<para>On your firewall system, issue the following command</para>
<programlisting><command>echo 202 www.out &#62;&#62; /etc/iproute2/rt_tables</command></programlisting>
</listitem>
<listitem>
<para>In /etc/shorewall/init, put:</para>
<programlisting><command>if [ -z &#34;`ip rule list | grep www.out`&#34; ] ; then
ip rule add fwmark CA table www.out # Note 0xCA = 202
ip route add default via 192.0.2.177 dev eth1 table www.out
ip route flush cache
fi</command></programlisting>
</listitem>
<listitem>
<para>Do <emphasis role="bold">one</emphasis> of the following:</para>
<orderedlist numeration="loweralpha">
<listitem>
<para>In <filename>/etc/shorewall/start</filename> add</para>
<programlisting><command>iptables -t mangle -A PREROUTING -i eth2 -p tcp --dport 80 -j MARK --set-mark 202</command></programlisting>
</listitem>
<listitem>
<para>Set MARK_IN_FORWARD_CHAIN=No in <filename>/etc/shorewall/shorewall.conf</filename>
and add the following entry in <filename>/etc/shorewall/tcrules</filename>:</para>
<programlisting>#MARK SOURCE DESTINATION PROTOCOL PORT
202 eth2 0.0.0.0 tcp 80</programlisting>
</listitem>
<listitem>
<para>Run Shorewall 1.3.14 or later and add the following entry
in <filename>/etc/shorewall/tcrules</filename>:</para>
<programlisting>#MARK SOURCE DESTINATION PROTOCOL PORT
202:P eth2 0.0.0.0 tcp 80</programlisting>
</listitem>
</orderedlist>
</listitem>
<listitem>
<para>In <filename>/etc/shorewall/rules</filename>, you will need:</para>
<programlisting>#ACTION SOURCE DEST PROTO DEST PORT(S)
ACCEPT loc dmz tcp 80
ACCEPT dmz net tcp 80</programlisting>
</listitem>
<listitem>
<para>On 192.0.2.177 (your Web/Squid server), arrange for the
following command to be executed after networking has come up</para>
<programlisting><command>iptables -t nat -A PREROUTING -i eth0 -d ! 192.0.2.177 -p tcp --dport 80 -j REDIRECT --to-ports 3128</command></programlisting>
<para>If you are running RedHat on the server, you can simply
execute the following commands after you have typed the iptables
command above:</para>
<programlisting><command>iptables-save &#62; /etc/sysconfig/iptables
chkconfig --level 35 iptables on</command></programlisting>
</listitem>
</orderedlist>
</section>
</section>
<section>
<title>Squid as a Manual Proxy</title>
<para>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
<quote>net</quote> zone. Then for each zone Z that needs access to the
Squid server.</para>
<para><filename>/etc/shorewall/rules</filename>:</para>
<programlisting>#ACTION SOURCE DEST PROTO DEST PORT(S)
ACCEPT Z SZ tcp SP
ACCEPT SZ net tcp 80</programlisting>
<example>
<title>Squid on the firewall listening on port 8080 with access from the
<quote>loc</quote> zone:</title>
<para><filename>/etc/shorewall/rules:</filename><programlisting>#ACTION SOURCE DEST PROTO DEST PORT(S)
ACCEPT loc fw tcp 8080
ACCEPT fw net tcp 80</programlisting></para>
</example>
</section>
</article>