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Re: iptables and tor

M wrote:
Hash: SHA1

On Sat, Feb 09, 2008 at 07:07:26PM -0500, dante@xxxxxxxxxxxxxxxxxxx wrote 0.8K bytes in 21 lines about:
: Has anyone given any thought as to what firewall rules to use on a linux
: system running a tor server?  Besides the usual attacks against the
In general, how would you protect a server with a public IP without tor?

Common "default deny and allow only specified" rules which is used by
any admin who has common sense? Can't think of anything else.

Only allow incoming tcp traffic to Tor's dir- and listeningport and deny
everything else?

The packets coming in on Tor TLS tunnels are destined for your node. They go up the stack through TCP and TLS to the Tor application itself. Tor does its AES CTR encryption on the cells coming out of these streams, and puts them in other streams based on the circuit labels. Here they get TLS'd, packed into TCP segments and go out. This means that packets going out after relaying have nothing to do with packets coming in, so I don't think marking makes any difference. This is clearly a positive point of Tor.

What you could do is to allow Tor's ports (defaults or the ones defined in your torrc) to pass through your firewall, and deny/shadow others. You can also do some TCP stuff on these ports, trying to add some DoS resistance, change priority (see the post http://archives.seul.org/or/talk/Feb-2008/msg00047.html ), correct some TCP misbehavior ,etc.

Otherwise, configure your exit policy well in the torrc, and hope that Tor respects it ;-) ... OK, it is open source, so you can even be sure about it :-)