Re: [tor-talk] Orbot v14 alpha: obfsclient, Tor 0.2.5.3-alpha

[George Kadianakis <desnacked@xxxxxxxxxx>]

Nathan Freitas <nathan@xxxxxxxxxxx> writes:

> On May 3, 2014 4:18:28 PM EDT, George Kadianakis <desnacked@xxxxxxxxxx> wrote:
>>George Kadianakis <desnacked@xxxxxxxxxx> writes:
>>
>>> Nathan Freitas <nathan@xxxxxxxxxxx> writes:
>>>
>>>> On May 3, 2014 6:10:58 AM EDT, George Kadianakis
>><desnacked@xxxxxxxxxx> wrote:
>>>>>Nathan Freitas <nathan@xxxxxxxxxxx> writes:
>>>>>
>>>>>> Orbot now supports Obfs3 and Scramblesuit, thanks to Yawning's
>>help.
>>>>>>
>>>>>
>>>>>Great news! Thanks!
>>>>>
>>>>>BTW, how are obfs3 bridges supposed to be used?
>>>>
>>>> This is the string I use for scramblesuit, copied directly from the
>>bridges.tp.o page:
>>>>
>>>> scramblesuit xxx.xxx.xxx.xxx:xxxxx fingerprintxxx
>>password=sharedsecretxxx
>>>>
>>>>>I installed Orbot-v14.0.0-ALPHA-2a.apk and checked the Preferences
>>>>>menu. There used to be an option called 'Obfuscated Bridges' that
>>it's
>>>>>not there anymore. I assumed that I just have to specify a bridge,
>>and
>>>>>then prefix it with the transport name, like you do in the torrc.
>>>>
>>>> Yes.
>>>>
>>>>>
>>>>>So I clicked on 'Bridges' and then inserted 'obfs3 <ip>:<port>'
>>(with
>>>>>my own <ip> and <port>) and started up Orbot. Unfortunately, I think
>>>>>that it didn't work very well. In the logs I got:
>>>>>""""
>>>>>Adding bridge: obfs3 <ip>:<port>
>>>>
>>>> Hmm.... Add a fingerprint perhaps?
>>>>
>>>
>>> Hm, I just tried that bridge again (without adding a fingerprint),
>>and
>>> now I'm getting the usual PT error:
>>> "We were supposed to connect to bridge '<ip>:<port>' using pluggable
>>> transport 'obfs3', but we can't find a pluggable transport proxy
>>> supporting 'obfs2'. ..."
>>>
>>> I'm not sure why I'm getting this today instead of the error I was
>>> getting yesterday [0]. I don't remember rebooting or changing
>>> anything.
>>>
>>> In any case, this new message usually means that obfsproxy crashed
>>> early: before being configured to be a Pluggable Transport. The same
>>> should be true for obfsclient too. Could it be a permission issue?
>>>
>>
>>We played a bit with Yawning on this.
>>
>>Are we sure that the ClientTransportPlugin is even set at all?
>>
>>Because looking at
>>https://gitweb.torproject.org/orbot.git/blob/HEAD:/src/org/torproject/android/service/TorService.java#l1713
>>it seems that it depends on the boolean PREF_BRIDGES_OBFUSCATED which
>>apparently is never set since commit 147b57af4.
>>
>>This seems to agree with my experience since I'm getting the log
>>message "Using standard bridges" which is on the 'else' codepath.
>>
>>Or maybe we are missing something.
>
> Wow, I just realized that I removed that preference UI, but on my test device it was already set to TRUE, since I did not do a clean install.
>
> Thanks for the testing, and will push a new release our in next 24 hours with that fixed.

Thanks!

BTW, I'd suggest to parse the Bridge lines to figure out if PTs are
used and only then insert a ClientTransportPlugin line (in contrast,
to always adding a ClientTransportPlugin line). That's to avoid issues
like #11658.

You can check if a Bridge line uses PTs, by checking if its second
element is a C-identifier as the pt-spec.txt suggests. An IP:PORT is
not a C-identifier because of the colon.
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