Re: [rtcweb] Security implications of host candidates

[Harald Alvestrand <[e-mail]>]

Thoughts:

- If I want to find out that I'm on the same host as another context
that I can communicate with in *any* fashion, I've got lots of games I
can play.

Example: Measure memory pressure, allocate 1 Gbyte in one context,
measure memory pressure again. This works for any measurement that's
available to both contexts and relates to the whole system.
Example: Measure the local clock's skew compared to some reference clock
(NTP-fashion). If the skew is the same down to the nanosecond, same host
is likely.
Example: Allocate any resource that can only be accessed from one
context at a time. Loop, asking for it, in the other context. Release it
in the first context, and check the timing on when the other one gets it.

In general, anything that can potentially be used as a covert channel
can be used more easily to figure out if we're on the same host.

My conclusion: Defending against this attack isn't worth the trouble.
We've already lost.

- Nevertheless, we're finding that the MDNS mode has implications that
we don't perceive fully yet.

My conclusion: This is an additional mode, not a replacement for one of
the other modes. We should continue to specify both.


On 07/10/2018 02:24 AM, Justin Uberti wrote:
>
>
> On Mon, Jul 9, 2018 at 4:35 PM youenn fablet <[e-mail]
> <mailto:[e-mail]>> wrote:
>
>
>     > The reason for the different treatment is that it could be
>     argued that v6 addresses, being already public and unique, don't
>     constitute a new signal. That makes the tradeoff with datachannel
>     impact less clear.
>
>
>     If they are public, cannot they be discovered and exposed as srflx?
>
>
> That's a good point; I had forgotten about NAT64. v6 STUN isn't widely
> deployed, but if we did want to hide NAT64 v6 addresses, we could make
> this work.
>
> However, if we consider NAT64 to be an entirely temporary situation,
> this may not make sense.
>
>
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