RSnake wrote:
>> The point is - someone with shared IP is vulnerable ONLY to an
>> attacker with the same IP. Which makes attacks much less generic and
>> much more painful. Rock solid it ain't, but I think it's a pretty
>> good band-aid until all (hmmm...) clients upgrade to Acrobat Reader 8.0.
>>
>> -Amit
>
> Sorry for responding late, I've been doing some consulting work.
>
> After talking with some people on my blog I don't believe that is the
> case (at least not in theory). Let's say Alice has an account with
> Bob's website. Cathy is an attacker who owns a website that uses
> anti-DNS pinning.
Of course anti-DNS pinning would work against my algorithm, but anti-DNS
pinning is a larger problem, one that is out of scope here. I mean - so
many things are broken when anti-DNS pinning is introduced... especially
any IP-based security techniques. Anti-DNS pinning should be solved by
browser vendors (if possible), regardless of the PDF problem. And at any
rate, I feel that my algorithm makes the attack harder because it forces
it to involve anti-DNS pinning.

Anyway, if you worry about the current anti-DNS pinning techniques, you
may simply serve your PDF files in HTTPS only. I believe this will
defeat the present day anti-DNS pinning techniques (in the sense that
the user under anti-DNS pinning attack will get a certificate error
before being served the PDF).

-Amit

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