mirror of
https://gitlab.com/shorewall/code.git
synced 2024-12-04 21:41:15 +01:00
2ee1d11f94
Signed-off-by: Tom Eastep <teastep@shorewall.net>
461 lines
19 KiB
XML
461 lines
19 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
|
|
<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN"
|
|
"http://www.oasis-open.org/docbook/xml/4.4/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><?dbtimestamp format="Y/m/d"?></pubdate>
|
|
|
|
<copyright>
|
|
<year>2003-2008</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>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>
|
|
|
|
<caution>
|
|
<para><emphasis role="bold">This article applies to Shorewall 4.0 and
|
|
later. If you are running a version of Shorewall earlier than Shorewall
|
|
4.0.0 then please see the documentation for that
|
|
release.</emphasis></para>
|
|
</caution>
|
|
|
|
<section id="Transparent">
|
|
<title>Squid as a Transparent (Interception) Proxy</title>
|
|
|
|
<important>
|
|
<para>This section gives instructions for transparent proxying of HTTP.
|
|
HTTPS (normally TCP port 443) <emphasis role="bold">cannot</emphasis> be
|
|
proxied transparently (stop and think about it for a minute; if HTTPS
|
|
could be transparently proxied, then how secure would it be?).</para>
|
|
</important>
|
|
|
|
<caution>
|
|
<para>Please observe the following general requirements:</para>
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>In all cases, Squid should be configured to run as a
|
|
transparent proxy as described at <ulink
|
|
url="http://wiki.squid-cache.org/SquidFaq/InterceptionProxy">http://wiki.squid-cache.org/SquidFaq/InterceptionProxy</ulink>.</para>
|
|
|
|
<para>The bottom line of that article is that if you are running
|
|
<emphasis role="bold">Squid 2.6 or later</emphasis>, then you simply
|
|
need to add the word <firstterm>transparent</firstterm> to your
|
|
http_port specification:</para>
|
|
|
|
<programlisting>http_port 3128 transparent</programlisting>
|
|
|
|
<para>In <emphasis role="bold">earlier Squid versions</emphasis>,
|
|
you need to set several options:</para>
|
|
|
|
<programlisting>http_port 3128
|
|
httpd_accel_host virtual
|
|
httpd_accel_port 80
|
|
httpd_accel_with_proxy on
|
|
httpd_accel_uses_host_header on</programlisting>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Depending on your distribution, other Squid configuration
|
|
changes may be required. These changes typically consist of:</para>
|
|
|
|
<orderedlist>
|
|
<listitem>
|
|
<para>Adding an ACL that represents the clients on your local
|
|
network.</para>
|
|
|
|
<para>Example:</para>
|
|
|
|
<programlisting>ACL my_networks src 192.168.1.0/24 192.168.2.0/24</programlisting>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Allowing HTTP access to that ACL.</para>
|
|
|
|
<para>Example:</para>
|
|
|
|
<programlisting>http_access allow my_networks</programlisting>
|
|
</listitem>
|
|
</orderedlist>
|
|
|
|
<para>See your distribution's Squid documentation and <ulink
|
|
url="http://www.squid-cache.org/">http://www.squid-cache.org/</ulink>
|
|
for details.</para>
|
|
|
|
<para>It is a good idea to get Squid working as a <link
|
|
linkend="Manual">manual proxy</link> first before you try
|
|
transparent proxying.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>The following instructions mention the file
|
|
/etc/shorewall/start - if you don't have that file, simply create
|
|
it.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>When the Squid server is 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>
|
|
</itemizedlist>
|
|
</caution>
|
|
|
|
<caution>
|
|
<para>In the instructions below, only TCP Port 80 is opened from the
|
|
system running Squid to the Internet. If your users require browsing
|
|
sites that use a port other than 80 (e.g.,
|
|
http://www.domain.tld:<emphasis role="bold">8080</emphasis>) then you
|
|
must open those ports as well.</para>
|
|
</caution>
|
|
|
|
<section id="Configurations">
|
|
<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 DPORT SPORT ORIGDEST
|
|
ACCEPT $FW net tcp www
|
|
REDIRECT loc 3128 tcp www - !206.124.146.177
|
|
</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 needed, you may just add the additional hosts/networks to the
|
|
ORIGDEST column in your REDIRECT rule.</para>
|
|
|
|
<para><filename>/etc/shorewall/rules</filename>:<programlisting>#ACTION SOURCE DEST PROTO DPORT SPORT ORIGDEST
|
|
REDIRECT loc 3128 tcp www - !206.124.146.177,130.252.100.0/24</programlisting></para>
|
|
|
|
<para>People frequently ask <emphasis>How can I exclude certain
|
|
internal systems from using the proxy? I want to allow those systems
|
|
to go directly to the net</emphasis>.</para>
|
|
|
|
<para>Suppose that you want to exclude 192.168.1.5 and 192.168.1.33
|
|
from the proxy. Your rules would then be:</para>
|
|
|
|
<programlisting>#ACTION SOURCE DEST PROTO DPORT SPORT ORIGDEST
|
|
ACCEPT $FW net tcp www
|
|
REDIRECT loc:!192.168.1.5,192.168.1.33\
|
|
3128 tcp www - !206.124.146.177,130.252.100.0/24
|
|
ACCEPT loc net tcp www</programlisting>
|
|
|
|
<para>The last rule may be omitted if your loc->net policy is
|
|
ACCEPT.</para>
|
|
|
|
<para>In some cases (when running an LTSP server on the Shorewall
|
|
system), you might want to transparently proxy web connections that
|
|
originate on the firewall itself. This requires care to ensure that
|
|
Squid's own web connections are not proxied.</para>
|
|
|
|
<para>First, determine the user id that Squid is running under:</para>
|
|
|
|
<programlisting>gateway:/etc/shorewall# <emphasis role="bold">ps aux | fgrep -i squid | fgrep -v fgrep</emphasis>
|
|
root 10085 0.0 0.0 23864 700 ? Ss Apr22 0:00 /usr/sbin/squid -D -YC
|
|
<emphasis role="bold">proxy</emphasis> 10088 0.0 0.9 40512 19192 ? S Apr22 10:58 <emphasis
|
|
role="bold">(squid)</emphasis> -D -YC
|
|
gateway:/etc/shorewall# </programlisting>
|
|
|
|
<para>In this case, the proxy process <emphasis
|
|
role="bold">(squid)</emphasis> is running under the <emphasis
|
|
role="bold">proxy</emphasis> user Id. We add these rules:</para>
|
|
|
|
<programlisting>#ACTION SOURCE DEST PROTO DPORT SPORT ORIGDEST RATE USER
|
|
ACCEPT $FW net tcp www
|
|
REDIRECT $FW 3128 tcp www - - - <emphasis
|
|
role="bold"> !proxy</emphasis></programlisting>
|
|
</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>Add this entry to your /etc/shorewall/providers file.</para>
|
|
|
|
<programlisting>#NAME NUMBER MARK DUPLICATE INTERFACE GATEWAY OPTIONS
|
|
Squid 1 202 - eth1 192.168.1.3 loose,notrack</programlisting>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>In <filename>/etc/shorewall/mangle</filename> add:</para>
|
|
|
|
<programlisting>#ACTION SOURCE DEST PROTO DPORT SPORT ORIGDEST
|
|
MARK(202):P eth1:!192.168.1.3 0.0.0.0/0 tcp 80</programlisting>
|
|
|
|
<para>If you are still using a tcrules file, you should consider
|
|
switching to using a mangle file (<command>shorewall update
|
|
-t</command> (<command>shorewall update</command> on Shorewall 5.0
|
|
and later) will do that for you). Corresponding
|
|
/etc/shorewall/tcrules entries are:</para>
|
|
|
|
<programlisting>#MARK SOURCE DEST PROTO DPORT
|
|
202:P eth1:!192.168.1.3 0.0.0.0/0 tcp 80</programlisting>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>In <filename> <filename>/etc/shorewall/interfaces</filename>
|
|
</filename>:</para>
|
|
|
|
<programlisting>#ZONE INTERFACE OPTIONS
|
|
loc eth1 <emphasis role="bold">routeback,routefilter=0,logmartians=0</emphasis> </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 > /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 system in your DMZ with IP address
|
|
192.0.2.177. You want to run both a web server and Squid on that
|
|
system.</para>
|
|
</section>
|
|
|
|
<section>
|
|
<title>Simple Configuration</title>
|
|
|
|
<para>In <filename>/etc/shorewall/rules</filename>:</para>
|
|
|
|
<programlisting>#ACTION SOURCE DEST PROTO DPORT SPORT ORIGDEST
|
|
DNAT loc dmz:192.0.2.177:3128 tcp 80 - !192.0.2.177</programlisting>
|
|
</section>
|
|
|
|
<section>
|
|
<title>More Complex configuration</title>
|
|
|
|
<para>Assume that the dmz is connected through eth2 and that your
|
|
local lan interfaces through eth1</para>
|
|
|
|
<orderedlist>
|
|
<listitem>
|
|
<para>Add this entry to your /etc/shorewall/providers file.</para>
|
|
|
|
<programlisting>#NAME NUMBER MARK DUPLICATE INTERFACE GATEWAY OPTIONS
|
|
Squid 1 202 - eth2 192.0.2.177 loose,notrack</programlisting>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>In <filename>/etc/shorewall/mangle</filename> add:</para>
|
|
|
|
<programlisting>#ACTION SOURCE DEST PROTO DPORT
|
|
MARK(202):P eth1 0.0.0.0/0 tcp 80</programlisting>
|
|
|
|
<para>Corresponding /etc/shorewall/tcrules entries are:</para>
|
|
|
|
<programlisting>#MARK SOURCE DEST PROTO DPORT
|
|
202:P eth1 0.0.0.0/0 tcp 80</programlisting>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>In <filename> <filename>/etc/shorewall/interfaces</filename>
|
|
</filename>:</para>
|
|
|
|
<programlisting>#ZONE INTERFACE OPTIONS
|
|
loc eth2 <emphasis role="bold">routefilter=0,logmartians=0</emphasis> </programlisting>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>On 172.0.2.177, 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 > /etc/sysconfig/iptables
|
|
chkconfig --level 35 iptables on</command> </programlisting>
|
|
</listitem>
|
|
</orderedlist>
|
|
</section>
|
|
</section>
|
|
</section>
|
|
|
|
<section id="Manual">
|
|
<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 DPORT
|
|
ACCEPT Z SZ tcp SP
|
|
ACCEPT SZ net tcp 80,443</programlisting>
|
|
|
|
<example id="Example1">
|
|
<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 DPORT
|
|
ACCEPT loc $FW tcp 8080
|
|
ACCEPT $FW net tcp 80,443</programlisting></para>
|
|
</example>
|
|
</section>
|
|
|
|
<section id="TPROXY">
|
|
<title>Squid3 as a Transparent Proxy with TPROXY</title>
|
|
|
|
<para>Shorewall 4.5.4 contains support for TPROXY. TPROXY differs from
|
|
REDIRECT in that it does not modify the IP header and requires Squid 3 or
|
|
later. Because the IP header stays intact, TPROXY requires policy routing
|
|
to direct the packets to the proxy server running on the firewall. This
|
|
approach requires TPROXY support in your kernel and iptables and Squid 3.
|
|
See <ulink
|
|
url="http://wiki.squid-cache.org/Features/Tproxy4">http://wiki.squid-cache.org/Features/Tproxy4</ulink>.</para>
|
|
|
|
<note>
|
|
<para>Support for the TPROXY action in shorewall-tcrules(5) and the
|
|
<option>local</option> option in shorewall-providers(5) has been
|
|
available since Shoreall 4.4.7. That support required additional rules
|
|
to be added in the 'start' extention script to make it work reliably.
|
|
Beginning with Shorewall 4.6.0, TPROXY in <ulink
|
|
url="manpages/shorewall-tcrules.html">shorewall-tcrules</ulink>(5) and
|
|
in <ulink
|
|
url="manpages/shorewall-mangle.html">shorewall-mangle</ulink>(5) work as
|
|
described here.</para>
|
|
</note>
|
|
|
|
<para>The following configuration works with Squid running on the firewall
|
|
itself (assume that Squid is listening on port 3129 for TPROXY
|
|
connections).</para>
|
|
|
|
<para><filename>/etc/shorewall/interfaces:</filename></para>
|
|
|
|
<programlisting>#ZONE INTERFACE OPTIONS
|
|
- lo -</programlisting>
|
|
|
|
<para><filename>/etc/shorewall/providers</filename>:</para>
|
|
|
|
<programlisting>#NAME NUMBER MARK DUPLICATE INTERFACE GATEWAY OPTIONS COPY
|
|
Tproxy 1 - - lo - tproxy</programlisting>
|
|
|
|
<note>
|
|
<para>Notice that the MARK, DUPLICATE and GATEWAY columns are empty and
|
|
that the only option is <option>tproxy</option>.</para>
|
|
</note>
|
|
|
|
<para><filename>/etc/shorewall/mangle</filename> (assume loc interface is
|
|
eth1 and net interface is eth0):</para>
|
|
|
|
<programlisting>#ACTION SOURCE DEST PROTO DPORT SPORT
|
|
DIVERT eth0 0.0.0.0/0 tcp - 80
|
|
TPROXY(3129) eth1 0.0.0.0/0 tcp 80</programlisting>
|
|
|
|
<para>Corresponding <filename>/etc/shorewall/mangle</filename> are:</para>
|
|
|
|
<programlisting>#MARK SOURCE DEST PROTO DPORT SPORT
|
|
DIVERT eth0 0.0.0.0/0 tcp - 80
|
|
TPROXY(3129) eth1 0.0.0.0/0 tcp 80</programlisting>
|
|
|
|
<para>The DIVERT rules are used to avoid unnecessary invocation of TPROXY
|
|
for request packets after the connection is established and to direct
|
|
response packets back to Squid3.</para>
|
|
|
|
<note>
|
|
<para>If you run a web server on the Shorewall system that also listens
|
|
on port 80, then you need to exclude it from TPROXY. Suppose that your
|
|
web server listens on 192.0.2.144; then:</para>
|
|
|
|
<programlisting>#MARK SOURCE DEST PROTO DPORT SPORT
|
|
DIVERT eth0 0.0.0.0/0 tcp - 80
|
|
TPROXY(3129) eth1 !192.0.2.144 tcp 80 -</programlisting>
|
|
</note>
|
|
|
|
<para>/etc/shorewall/rules:</para>
|
|
|
|
<programlisting>#ACTION SOURCE DEST PROTO DPORT
|
|
ACCEPT loc $FW tcp 80
|
|
ACCEPT $FW net tcp 80</programlisting>
|
|
|
|
<para><filename>/etc/squid3/squid.conf</filename>:</para>
|
|
|
|
<programlisting>...
|
|
http_port 3129 tproxy
|
|
...</programlisting>
|
|
|
|
<important>
|
|
<para>If you use TPROXY with both IPv4 and IPv6, then both your local
|
|
hosts and the gateway must have the same DNS view. If a client resolves
|
|
a website URL to an IPv6 address and the server can only resolve to an
|
|
IPv4 address, then Squid will attempt to connect to the IPv4 address
|
|
using the local client's IPv6 address. That clearly doesn't work.</para>
|
|
</important>
|
|
</section>
|
|
</article>
|