[tor-talk] WebRTC to uncover local IP

[Aymeric Vitte]

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.

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.

-- 
Peersm : http://www.peersm.com
torrent-live: https://github.com/Ayms/torrent-live
node-Tor : https://www.github.com/Ayms/node-Tor
GitHub : https://www.github.com/Ayms