full-disclosure-uk August 2008 archive
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full-disclosure-uk: Re: [Full-disclosure] OpenID/Debian PRNG/DNS

Re: [Full-disclosure] OpenID/Debian PRNG/DNS Cache poisoning advisory

From: Ben Laurie <benl_at_nospam>
Date: Fri Aug 08 2008 - 17:11:42 GMT
To: "Eric Rescorla" <ekr@networkresonance.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?



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