Copyright © 2005, 2007 Thomas M. Eastep
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2009/06/08
Table of Contents
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.
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).
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,norfc1918,tcpflags,upnpIf your fw->loc policy is not ACCEPT then you need this rule:
#ACTION SOURCE DEST allowoutUPnP $FW loc
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:
#ACTION SOURCE DEST PROTO DEST PORT(S) SOURCE ORIGINAL RATE USER/ # PORT(S) DESTINATION LIMIT GROUP ACCEPT $FW loc all - - - - root
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.