Re: OpenID/Debian PRNG/DNS Cache poisoning advisory

["Ben Laurie" <benl () google com>]

On Fri, Aug 8, 2008 at 5:57 PM, Eric Rescorla <ekr () networkresonance com> wrote:
> At Fri, 8 Aug 2008 17:31:15 +0100,
> Dave Korn wrote:
> > Eric Rescorla wrote on 08 August 2008 16:06:
> >
> > > At Fri, 8 Aug 2008 11:50:59 +0100,
> > > Ben Laurie wrote:
> > > > However, since the CRLs will almost certainly not be checked, this
> > > > means the site will still be vulnerable to attack for the lifetime of
> > > > the certificate (and perhaps beyond, depending on user
> > > > behaviour). Note that shutting down the site DOES NOT prevent the attack.
> > > >
> > > > Therefore mitigation falls to other parties.
> > > >
> > > > 1. Browsers must check CRLs by default.
> > >
> > > Isn't this a good argument for blacklisting the keys on the client
> > > side?
> >
> >   Isn't that exactly what "Browsers must check CRLs" means in this context
> > anyway?  What alternative client-side blacklisting mechanism do you suggest?
>
> It's easy to compute all the public keys that will be generated
> by the broken PRNG. The clients could embed that list and refuse
> to accept any certificate containing one of them. So, this
> is distinct from CRLs in that it doesn't require knowing
> which servers have which cert...

It also only fixes this single type of key compromise. Surely it is
time to stop ignoring CRLs before something more serious goes wrong?