shorewall_code/docs/UPnP.xml

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<?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>
<!--$Id$-->
<articleinfo>
<title>Shorewall and UPnP</title>
<authorgroup>
<author>
<firstname>Tom</firstname>
<surname>Eastep</surname>
</author>
</authorgroup>
<pubdate><?dbtimestamp format="Y/m/d"?></pubdate>
<copyright>
<year>2005</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>
<section id="UPnP">
<title>UPnP</title>
<para>Shorewall includes support for UPnP (Universal Plug and Play) using
linux-igd (<ulink
url="http://linux-igd.sourceforge.net">http://linux-igd.sourceforge.net</ulink>).
UPnP is required by a number of popular applications including MSN
IM.</para>
<warning>
<para>From a security architecture viewpoint, UPnP is a disaster. It
assumes that:</para>
<orderedlist numeration="loweralpha">
<listitem>
<para>All local systems and their users are completely
trustworthy.</para>
</listitem>
<listitem>
<para>No local system is infected with any worm or trojan.</para>
</listitem>
</orderedlist>
<para>If either of these assumptions are not true then UPnP can be used
to totally defeat your firewall and to allow incoming connections to
arbitrary local systems on any port whatsoever. In short: USE
UPnP<emphasis> </emphasis> <emphasis role="bold">AT YOUR OWN
RISK.</emphasis></para>
</warning>
<warning>
<para>The linux-igd project was inactive for a long time and has just
been resurrected. I haven't tried to build using the current code (as of
2006-07-22) but the last time I did, I found that building and
installing linux-igd was not for the faint of heart. You must download
the source from CVS and I had to do quite a bit of fiddling with the
include files from libupnp (which is required to build and/or run
linux-igd).</para>
</warning>
<para></para>
</section>
<section id="linux-igd">
<title>linux-igd Configuration</title>
<para>In /etc/upnpd.conf, you will want:</para>
<programlisting>insert_forward_rules = yes
prerouting_chain_name = UPnP
forward_chain_name = forwardUPnP</programlisting>
</section>
<section id="Shorewall">
<title>Shorewall Configuration</title>
<para>In <filename>/etc/shorewall/interfaces</filename>, you need the
'upnp' option on your external interface.</para>
<para>Example:</para>
<programlisting>#ZONE INTERFACE BROADCAST OPTIONS
net eth1 detect dhcp,routefilter,tcpflags,<emphasis
role="bold">upnp</emphasis></programlisting>
<para>If your fw-&gt;loc policy is not ACCEPT then you need this
rule:</para>
<programlisting>#ACTION SOURCE DEST
allowoutUPnP $FW loc</programlisting>
<note>
<para>To use 'allowoutUPnP', your iptables and kernel must support the
'owner match' feature (see the output of "shorewall show capabilities")
and you may not be running kernel version 2.6.14 or later. If you are
running 2.6.14 or later, then replace the above rule with:</para>
</note>
<blockquote>
<programlisting>#ACTION SOURCE DEST PROTO DEST PORT(S) SOURCE ORIGINAL RATE USER/
# PORT(S) DESTINATION LIMIT GROUP
ACCEPT $FW loc all - - - - root</programlisting>
</blockquote>
<para>If your loc-&gt;fw policy is not ACCEPT then you need this
rule:</para>
<programlisting>#ACTION SOURCE DEST
allowinUPnP loc $FW</programlisting>
<para>You MUST have this rule:</para>
<programlisting>#ACTION SOURCE DEST
forwardUPnP net loc</programlisting>
<para>You must also ensure that you have a route to 224.0.0.0/4 on your
internal (local) interface as described in the linux-igd
documentation.</para>
</section>
</article>