[tor-dev] RFC: Using `utls` in meek_lite.

[Yawning Angel]

Hello,

I just pushed a change to obfs4proxy master to use `utls` to mask the
ClientHello signature (currently Chrome 70.x).

https://gitlab.com/yawning/obfs4/commit/4d453dab2120082b00bf6e63ab4aaeeda6b8d8a3

I understand that this is being worked on for the original meek (see:
https://bugs.torproject.org/29077), but I felt inspired and it was
relatively easy to get something working.

Caveats:
 * This is only lightly tested, and may be doing something wrong or
   distinct.  It seems to work well enough to watch videos over it.
   YMMV.
 * Azure uses HTTP 2.  Not really a problem.
 * `utls.HelloFirefox_Auto` will fail to handshake with Azure due to an
   incompatible group being negotiated.
 * `utls.HelloChrome_Auto` ironically fails to handshake with
   `google.com` in a standalone test case for me.
 * `utls.HelloIOS_Auto` seems to work in all cases, so I may switch to
   that before I tag.

Questions, comments, feedback appreciated,

-- 
Yawning Angel

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