Re: [TLS] New version of Multiple OCSP mode of Certificate Status

[Martin Rex <[e-mail]>]

Adam Langley wrote:
> 
> On Wed, Aug 4, 2010 at 1:47 PM, Martin Rex <[e-mail]> wrote:
> > Using any information in certificates that have not been verified to
> > perform resource-intensive operations is a security problem.  But
> > accessing an arbitrary URL presented in an completely unverified
> > End-Entity certificate is a "Freddy Krueger" waiting for his next victim.
> 
> That seems a little hyperbolic. Accessing completely unverified URLs
> is something that browsers do for every single web page.

There is a difference between something that is an internal part
of the PKI-Software's certificate chain building and the (mis-)behaviour
of applications on top of it.

It it true that the problems is magnitudes worse if the PKI software
does such things in Situations where a user or admin does not
expect this (like when a TLS server requests client certificates and
silently performs AIA retrieval for client certs with incomplete
paths but AIA extension.  Or when you double-click on a
certificate file "something.cer" in Windows explorer and CryptoAPI
does the retrieval secretly.

Anyhow, I think that a PKI-Software that performs intermediate cert
retrieval based on AIA-information of an unverified certificate is
a security nightmare waiting to happen.

-Martin