On Thu, Sep 20, 2012 at 12:38 PM, Scott Fluhrer (sfluhrer)
<[email protected]> wrote:
> With IPSec, compression happens on a per-packet basis; the contents of 
> previous packets do not affect how this packet is compressed in any way.  
> Hence, there would be a vulnerability only if the attacker can somehow create 
> a single packet that contains both the unknown cookies, as well as his chosen 
> text.  If he can, then likely he could (with sufficient cleverness) figure 
> out a way to exploit it.  However, if his chosen packets contain only what he 
> picked and not the cookies (or whatever else he is interested in), there's no 
> vulnerability.

Indeed, and for the BEAST attack being able to manage buffering (via a
"flush" operation, in that case) was critical to the exploit.  And
such buffering functionality existed, indeed.  If the question is "is
IPsec (ESP) immune to this attack" and the answer is (as I think it
is) "it depends on the application" then the fail-safe thing to do is
to disable compression in IPsec (I'm not necessarily recommending that
though).

Nico
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