Re: [rtcweb] SDP Security Descriptions (RFC 4568) and RTCWeb

[Eric Rescorla <[e-mail]>]

On Thu, Apr 25, 2013 at 9:21 PM, Matthew Kaufman <[e-mail]> wrote:

> On 4/25/2013 4:19 PM, Eric Rescorla wrote:
>
>>
>> It's certainly true that the site has access to the media with DTLS if you
>> don't use identity assertions/isolated streams. However, what it doesn't
>> have is *invisible* access. I.e., it must do something that is user
>> visible,
>> which allows for the detection of cheating by the site. By contrast, if
>> SDES is used
>> then the site can simply passively monitor all your traffic, or at least
>> any that goes through its network and you can't detect it.
>>
>>
> That really depends on what you mean by "user visible" doesn't it? If you
> mean "the user is watching to see that all their packets go to what they
> know is the verified IP address of their buddy" then sure. But if you mean
> "the user is looking at their web browser user interface" or even "the user
> was worried mid-call so checked to see where the packets were going" then I
> think not, as all that needs to happen is for the call to be set up with a
> middlebox in the path that the site claims is necessary for the call to
> work (meets the UI test), keys set with EKT, and then a little ICE
> renegotiation and the middlebox goes away from the path (meets even the
> second test).


What I mean is that you can use fingerprint checks (admittedly
inconvenient) to
detect active attacks. Obviously, current browser UIs don't support that,
but
I expect them to eventually.

-Ekr