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Re: [tor-talk] WebRTC to uncover local IP



On 30/01/15 11:36, Aymeric Vitte wrote:

Le 29/01/2015 22:20, isis a écrit :
Even better than disabling it, the Tor Browser Team really needs help
from
someone with a really strong knowledge of WebRTC and its potential
privacy
caveats to help us assess which parts of WebRTC (if any) that we might
be able
to safely allow.  The reason it's entirely disabled is because we know
some
parts are unsafe, and sadly we didn't have the time/resources to sort out
which parts are which. :/

I thought that the Tor project team had already a strong knowledge of
WebRTC since recently we saw that the future might be flashproxy
combined with uProxy (then WebRTC) to do something unstoppable.

Some time ago I made [1], this drawing is supposed to explain simply how
WebRTC works and at that time just leaded to the conclusion that the
signaling servers are the perfect MITM and that the STUN servers can
correlate the connections, then the IPs.

You forgot to give the url.


But the signaling servers are not mandatory finally, WebRTC peers can
introduce each others, but you still need some servers accessed usually
via WebSockets to bootstrap the process, these are the concepts of
projects like Peersm (which at the same time solves the issue of WebRTC
DTLS self signed certificates) and WebTorrent.

I did not study it deeply but in the strict context of the current Tor
Browser, I think that nothing is safe in WebRTC, and it should be
entirely disabled.

Another more interesting idea that I have repeatedly posted without
getting any feedback would be to allow to set the browser's proxy to an
interface, like WebSockets or WebRTC.

Example: let's take the proxy auto config mechanism, the pac file (let's
forget about the security aspects to retrieve it here) which contains
findproxyforurl is sandboxed and executed inside browsers, it is called
by the proxy and returns an url.

Instead of returning an url, you could have the Tor protocol inside the
pac file (so sandboxed too) and it could return an Object, the Tor
protocol would establish circuits via WebSockets or WebRTC with the Tor
network or between browsers, the proxy would use the Object to write to
those circuits and read from them (like a duplex stream
proxy.pipe(Object).pipe(proxy))

The interest would be to have Tor on any device, I am not saying that
the pac file could be a solution, that's just an example of how this
could work based on what exists today, now still remains the issue of
implementing all of what the Tor Browser is doing, but it's still
interesting to study, it certainly applies to projects mentioned above
and plenty of others, now or later.


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