Hello,
We have been operating a moderately successful public tor relay for a while now. Having read about how TOR works back a couple of years ago, I was more or less sold on the idea that if traffic originating on your local network uses your own TOR relay as the first hop (entry node), then by the time your traffic has left your tor relay, people in the middle can't tell the difference between traffic originating from your network and other (relayed) traffic passing through your TOR relay.
I also understand that this still doesn't protect you from an exit node being able to see your traffic (and why you should use HTTPS with a high-quality cipher if it's really important), and that there are other ways your traffic can be analyzed -- but all in all, I would rather our TOR traffic enter the TOR network through a relay I *KNOW* I can trust (mine!) than leave it to chance.
We have polipo running on our public TOR relay, configured to accept traffic from our local subnets. We've basically followed the info in this TOR doco:
https://trac.torproject.org/projects/tor/wiki/doc/CentralizedTorServer
The TOR browser bundle appears to function correctly, ie, it is able to start up, open circuits, etc. and we get the expected Congratulations! page opening a new browser window. But when clicking the green onion to show the circuit of relays handling the browser's connection, our relay is never the first hop.
I'm using TBB 5.01a on one particular system, and for an example, it shows this for the circuit:
- This browser - Austria (aa.bb.cc.dd) - Germany (ee.ff.gg.hh) - Guatemala (ii.jj.kk.ll) - Internet
I have tried defining an EntryNodes statement with the $fingerprint of our TOR relay and setting StrictNodes 1 in the TBB's torrc file, but it can't ever establish a circuit when I try this. We get messages like this logged on the browser's tor:
05/20/2015 04:21:20.700 [WARN] Failed to find node for hop 0 of our path. Discarding this circuit. 05/20/2015 04:21:20.700 [WARN] Failed to find node for hop 0 of our path. Discarding this circuit. 05/20/2015 04:21:20.900 [NOTICE] Closing no-longer-configured Socks listener on 127.0.0.1:9150 05/20/2015 04:21:20.900 [NOTICE] DisableNetwork is set. Tor will not make or accept non-control network connections. Shutting down all existing connections. 05/20/2015 04:21:20.900 [NOTICE] Closing old Socks listener on 127.0.0.1:9150 05/20/2015 04:21:21.700 [NOTICE] Delaying directory fetches: DisableNetwork is set.
Is it possible to define your desired entry node via IP address and port, or some other way that does not require a successful directory connection/circuit first? (so it can find the relay by its fingerprint)? It seems like a chicken vs. egg problem... Or what about defining a directory for the client to use by its IP/port? We are operating a public directory as well.
I can't find any info about this or other approaches anywhere.
So I always end up removing the EntryNodes and StrictNodes statement from TBB's torrc file, leaving only the HTTPSProxy aa.bb.cc.dd:<polipo-listen-port> statement in there with the DataDirectory, GeoIPFile, and GeoIPv6File statements. It gets the TBB's on our network to the local polipo proxy, which in turn forwards the traffic to our public TOR relay. TBB works fine, but I don't think our TOR relay is the one getting to see our traffic with the original source address with this setup.
It is definitely possible, likely even, that I am misunderstanding parts of how this is supposed to work or how a central TOR relay/proxy is supposed to be configured. But it doesn't seem to me that proxying our local network's TBB clients' traffic through the polipo instance on our public TOR relay means that our TOR traffic is being "anonymized" as to where it originated from before it gets to the first node in the circuit - or we would be seeing our TOR relay as the first hop when we look at the circuit in "the green onion button".
If I'm wrong about this, that's great - I'd love to see some documentation to explain it better if you have any links handy. But if I'm right, how can I configure our TBB clients to actually MAKE them use our TOR proxy as their entry node?
Thanks, Tor User