On Tue, Aug 2, 2016 at 5:10 PM, Jeremy Rand jeremyrand@airmail.cc wrote:
Nick Mathewson:
Hi, all!
I've seen a couple of emails from people looking into new ways to do naming for onion services. That's great! Before anybody gets too far, I'd like to send this quick note to let you know that integrating stuff like this into Tor is actually easier than you think.
Here's how you do it, using a Tor controller. (See control-spec.txt for protocol documentation. Also see one of the several friendly libraries, like steam, that exist to interface with Tor over this protocol.)
First, you set the Tor option "__LeaveStreamsUnattached". This tells Tor that it shouldn't try to handle new client requests immediately, but it should instead let the controller take responsibility.
In the controller, you make sure that you are watching STREAM events so that you find out about new streams.
Whenever there's a new stream, you check its address. If the address is one that you don't want to rewrite, you just call ATTACHSTREAM on it, with a circuit ID of 0. (The 0 means "Tor, you figure out how to attach this one.".
Otherwise, you do whatever magic dance you do in order to find out the real address for the stream.
If the lookup operation is successful, you say "REDIRECTSTREAM (stream ID) (new address". And then you ATTACHSTREAM as above.
If the lookup operation fails, you call "CLOSESTREAM (stream ID) 2". (The 2 means "resolve failed".
And that's it for the Tor integration! All you need to do now is figure out how the name lookup works.
cheers,
Hi Nick,
Let's say that the name lookup operation will generate network traffic, and therefore should be subject to stream isolation. (This is the case for a subset of Namecoin-based lookup methods.)
How can a Tor controller obtain the needed information to perform stream isolation on the lookup, prior to issuing ATTACHSTREAM?
Conceptually, a controller doesn't isolate streams: the streams are isolated based on their own properties, so that's more of a client thiing.
One of the properties that you can use for isolation here is the SOCKS username and password: two streams with different SOCKS credentials should never be sent over the same circuit. This should make stream isolation happen just fine.
[This is assuming that you use 'ATTACHSTREAM' with a circuit ID of 0, and let Tor make its own isolation decisions.]
Is that about what you wanted to know?
cheers,