[Pkg-telepathy-maintainers] Bug#704234: sends call via Google

Simon McVittie smcv at debian.org
Tue Apr 2 14:25:17 UTC 2013

retitle 704234 misleading debug message implies relaying via Google
severity 704234 minor

> (telepathy-gabble:9974): gabble-DEBUG: gabble_call_stream_constructed
> (call-stream.c:353): Attempting to create Google relay session
> it appears to suggest that calls are relayed through Google's server
> (using TURN?), even though no Google accounts are defined in empathy.
> This may be against the privacy expectations of many users.

The debug message is somewhat misleading. From the source code, this
debug message is emitted whenever a call is using Google's non-standard
ICE variant:

  if (transport == JINGLE_TRANSPORT_GOOGLE_P2P)
      DEBUG ("Attempting to create Google relay session");

but on non-Google accounts, we don't "attempt" very hard: we notice that
we don't have a TURN server, and immediately give up. A few log messages
down you should see this debug message from Wocky (you might need to set
WOCKY_DEBUG=all to see it):

    DEBUG ("No relay server provided, not creating google relay session");

We prefer google-p2p over standard ICE for historical reasons, and
because for Google accounts, it offers the possibility of using Google's
TURN relays in situations where the call would normally fail altogether.
Using Google's TURN servers requires temporary credentials which they
only hand out to users of Google accounts. The practical result is that
we are able to use TURN if either the telepathy-gabble user, or the peer
with whom they are communicating, is on a Google account (if we are, we
have our own credentials, or if the peer is, they use theirs).

Because of the way ICE works, if TURN is available we'll always send a
small amount of data through the relay (to check that it's a valid
"candidate"), but we only send audio or video through the relay on
problematic networks where STUN, etc. have failed. A user's XMPP service
provider is technically able to intercept calls through that provider
regardless of whether we use TURN, so we're only using Google's TURN
relay in situations where Google could already intercept the call if
they wanted to.


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