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

[Martin Rex <[e-mail]>]

Adam Langley wrote:
> 
> That seems a little hyperbolic. Accessing completely unverified URLs
> is something that browsers do for every single web page.

Not really.

Example scenario:

newly booted PC. User logs on, starts the web Browser (about:blank homepage)
and navigates to the HTTPS-url for his online banking.  If HTTPS works
as designed, this should be a safe operation--any "unsafe" content
that the browser would be allowed to serve/access with the consent
of the user is the content served by the online bankings site.

Now if the browser performs AIA retrieval for unverified server
certs, then this scenario is suddenly completely unprotected against
active attacks where the attacker serves a manufactured server
certificate with crafted AIA (but matching the server identity
of the online banking account in the CN= or dNSName SAN.


Essentially, that "safe mode of operation" for your web browser is gone.

-Martin