[tor-dev] Proposal 190: Password-based Bridge Client Authorization

[Robert Ransom]

On 2012-01-17, Ian Goldberg <iang at cs.uwaterloo.ca> wrote:
> On Tue, Jan 17, 2012 at 08:43:00PM +0200, George Kadianakis wrote:
>> [0]: Did the Telex people clean up the patch, generalize it, and post
>> it in openssl-dev? Having configurable {Server,Client}Hello.Random in
>> a future version of OpenSSL would be neat.
>
> At USENIX Security, Adam opined that openssl's callback mechanism should
> be able to do this with no patches to the source.  (I think there was
> one part of Telex that would still need patches to openssl, but I don't
> think that was it.)  You basically request a callback right after the
> clienthello.random is generated, and in the callback, overwrite the
> value.  Or something like that; I don't remember exactly.

In a Telex TLS connection, the client's DH secret key is derived from
the ECDH shared secret between the client's Telex ECDH key and the
Telex server's ECDH key.  (This has the unfortunate side effect that a
client attempting to find Telex servers gives up forward secrecy for
its TLS connections.)  This may be the part of Telex which requires an
OpenSSL patch.


Robert Ransom