Re: [TLS] Confirmation of Consensus on Removing Compression from TLS 1.3

On Wed, Mar 26, 2014 at 6:02 PM, Martin Rex <mrex@sap.com> wrote:
> Paterson, Kenny wrote:
>>
>> Really? I assume you know about CRIME??
>
> Yes, I do.  Similar to BEAST, it is *NOT* an attack.
> It is a pretty boring demonstration of the principle of operation
> of querying an encryption oracle (BEAST) or compression oracle (CRIME).
>
> None of the alleged "fixes" against BEAST and CRIME addresses the
> real vulnerability.  Even with compression disabled and TLSv1.1+ or
> AEAD cipher suites, the vulnerability is WIDE OPEN.  The attackers
> code could, rather than performing a demonstration of a boring
> principle, submit any attacker-desired nefarious request to the
> server, the Browser will blissfully insert the authentication-credentials
> into that nefarious request, and the server will blissfully execute
> the request.  No matter what fancy stuff the TLS WG puts into TLSv1.3,
> the attack will continue to work as long as the browser keeps doing
> the stupid stuff: volutarily and blissfully inserting authentication
> credentials into requests that the browser performs on the attackers
> behalf.

This is called a CSRF, and has been known for a long time. The
solution is to use capability-like URLs, with unguessable content.

BEAST goes further: it exposes to the adversary credentials, rather
than letting the adversary use some of them through controllable
means. Sometimes you need to take advantage of this browser behavior:
OAuth I believe relies on being able to make cross-site requests with
the user credentials, as does single-sign-on.

Furthermore, BEAST also affects VPNs built on TLS, where you don't
have an option but to pass possibly adversarially influenced traffic.

Sincerely,
Watson Ladd
>
>
> -Martin
>
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