[tor-relays] Port for obfsproxy

[George Kadianakis]

dardok <dardok at riseup.net> writes:

> George Kadianakis:
>> "GDR!" <gdr at gdr.name> writes:
>> 
>>> On 07.10.2013 21:11, dardok wrote:
>>>> I guess that you misunderstood the concept of obfsproxy. It is 
>>>> useful to obfuscate the communication between a client  within 
>>>> a censorship zone and a tor bridge. The obfsproxy doesn't 
>>>> emulate a HTTP protocol communication, instead it is designed 
>>>> to look random (and the packets are encypted). So if you try
>>>> to run this service over the HTTP port 80 and the packets are 
>>>> random and not looking like a HTTP communication, it will be 
>>>> more suspicious than running this service over any other port.
>>> 
>>> Thank you. I understood the concept but not the implementation.
>>> 
>>> "For example, there MIGHT be a HTTP transport which transforms 
>>> Tor traffic to look like regular HTTP traffic."
>>> 
>>> I missed the "MIGHT" part. Too bad this doesn't exist.
>> 
>> Ha, you caught us! That website sentence is indeed an advertisement
>> trick!  Obfsproxy does *not* have an HTTP module yet, 
>> unfortunately.
>> 
>> The funny thing about HTTP transports is that it's easy to write a
>>  simple but trivially detectable HTTP transport, and quite hard to
>>  write an actually good HTTP transport. We have open tickets for 
>> both ideas and would appreciate coding help: 
>> https://trac.torproject.org/projects/tor/ticket/5625 
>> https://trac.torproject.org/projects/tor/ticket/8676
>> 
>> Also see 
>> https://github.com/sjmurdoch/http-transport/blob/master/design.md 
>> for things to consider when writing your HTTP transport.
>> 
>> (I CC'ed dardok who recently appeared in tor-talk and wanted to 
>> contribute to pluggable transports development.)
>> 
>
> George Kadianakis, thanks for the links. I've been reading some papers
> and the conclusion that I drew is that it would be good to try to run
> a real service or program in both parts of communication, i.e. a
> browser binary in the client side and a server binary in the bridge
> side, to perfectly mimick the HTTP communication protocol and be able
> to hide inside these packets the TOR traffic. Is there some private
> list or chat about PTs? Is there some advanced work on this field,
> that's related to running real HTTP services and wrapping the TOR
> traffic into them?

Greetings dardok,

if you want to chat about PTs development, the tor-dev mailing list
might be a good place (OTOH this mailing list is not a very good
place). If you fancy synchronous communication, you can try dropping
by the #tor-dev IRC channel in OFTC.

Furthermore, every 2 weeks we are having PT meetings where many PT
developers come together and talk to each other. If I'm not mistaken,
the next such meeting will be on the 25th of October.

As far as "advanced work" on the field of HTTP PTs is concerned, the
links I posted on my previous mail are a good start. 

(
You might also want to check out the 'stegotorus' transport. It's a
transport proxy capable of simulating multiple protocols (including
HTTP) but it's main implementation is closed source (it also doesn't
use an actual browser). There is an open source version of it, but
it's codebase is huge and it needs tons of work to be deployable. If
you want to make a new HTTP PT, I would suggest to start a new
project. Please get in touch with us before you start hacking :)
)

If you want to continue this development discussion, I would suggest
to CC tor-dev instead of tor-relays :)

Cheers!