Tom Eastep 2005 2010 Thomas M. Eastep 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 GNU Free Documentation License.

Shorewall includes support for UPnP (Universal Plug and Play) using linux-igd (http://linux-igd.sourceforge.net). UPnP is required by a number of popular applications including MSN IM. From a security architecture viewpoint, UPnP is a disaster. It assumes that: All local systems and their users are completely trustworthy. No local system is infected with any worm or trojan. 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 AT YOUR OWN RISK.

In /etc/upnpd.conf, you will want: create_forward_rules = yes prerouting_chain_name = UPnP forward_chain_name = forwardUPnP

In /etc/shorewall/interfaces, you need the 'upnp' option on your external interface. Example: #ZONE INTERFACE BROADCAST OPTIONS net eth1 detect dhcp,routefilter,tcpflags,upnp If your loc->fw policy is not ACCEPT then you need this rule: #ACTION SOURCE DEST allowinUPnP loc $FW You MUST have this rule: #ACTION SOURCE DEST forwardUPnP net loc 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. The init script included with the Debian linux-idg package adds this route during start and deletes it during stop.

It is sometimes desirable to run UPnP-enabled client programs like Transmission (BitTorrent client) on a Shorewall-protected system. Shorewall provides support for UPnP client access in the form of the upnpclient option in shorewall-interfaces (5). The upnpclient option causes Shorewall to detect the default gateway through the interface and to accept UDP packets from that gateway. Note that, like all aspects of UPnP, this is a security hole so use this option at your own risk. Note that when multiple clients behind the firewall use UPnP, they must configure their applications to use unique ports.