Re: Suspicious Circuits

[Roger Dingledine <arma@xxxxxxx>]

On Sun, Dec 09, 2007 at 09:19:53PM -0800, Kyle Williams wrote:
> I've been having problems getting to hidden services the last couple of
> days.
> I noticed something odd in Vidalia the other day, but it was gone before I
> could take a screenshot.
> However this evening, I was having a lot of problems with .onion addresses,
> and Vidalia was showing several (more than 6) nodes in a circuit almost
> every time I tried to reach any hidden service, including my own.

Exciting. Looks like a bug of some sort.

> These circuits have more than 3 nodes, and as shown in the picture, has the
> same node more than once in the circuit.  Correct me if I'm wrong, but I
> thought circuits are not allowed to have the same node more than once.

We make an exception for client-side introduction circuits: the first
three hops ensure your anonymity, and after that we try one random
node at a time out of the set of introduction points listed in the
hidden service descriptor. If one of the intro points doesn't cooperate
(for example because the hidden service is no longer connected to that
introduction point, so they *can't* help), then we move on to the next.
We keep reusing the same circuit (just extending it another hop each time)
so we don't waste a lot of time making new circuits.

But we're *supposed* to be marking each intro point down when it
isn't helpful, so the fact that we're extending back to it (repeatedly
sometimes, based on your jpgs!) is definitely a bug of some sort. Can
you get me a debug-level log from when this happens?

Also, you mentioned that the bug doesn't happen on 0.1.2.8-alpha. What
about 0.1.2.18?

Thanks,
--Roger