Re: [TLS] SSL Renegotiation DOS

I have password protected the post on my blog because of this. I have
confirmed this is an issue and many sites are vulnerable to DOS. I am
reporting to vendor and vulnerable sites. Until then I will keep the post
locked. You can email me individually for the password as this mailing list
is public and I continue to update the post based on feedback and tests.

Best Regards,
Jorge Orchilles

On Wed, Mar 16, 2011 at 3:54 AM, Peter Gutmann <pgut001@cs.auckland.ac.nz>wrote:

> Martin Rex <mrex@sap.com> writes:
>
> >A DoS-client could simply open new connections to the SSL server and
> blindly
> >fire away precompiled static SSL handshake messages, forcing the server to
> do
> >crypto work.  You should be able to make most servers perform RSA decrypts
> on
> >arbitrary data, and a significant number to perform DHE computations.
>
> Exactly.  You can do this with virtually no effort using netcat, I continue
> to
> be surprised that we've never seen this deployed in the wild (not wanting
> to
> give any hints to Anonymous, but LOIC is 1990s script-kiddie technology
> compared to the DoSes you could use if you gave it a few minutes thought).
> What makes it even worse is the Bleichenbacher-attack defense that says you
> have to complete the handshake, at full crypto cost, even if it's obvious
> that
> you're just processing garbage.
>
> (Every time this comes up I'm tempted to release some quick tool to exploit
> the problem, on the basis that if the good guys don't point it out now, the
> bad guys will take advantage of it later.  So far I've resisted the
> temptation...).
>
> Peter.
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