[130166] in cryptography@c2.net mail archive
Re: OpenID/Debian PRNG/DNS Cache poisoning advisory
daemon@ATHENA.MIT.EDU (Dan Kaminsky)
Fri Aug 8 13:59:30 2008
Date: Fri, 08 Aug 2008 10:43:53 -0700
From: Dan Kaminsky <dan@doxpara.com>
To: Eric Rescorla <ekr@networkresonance.com>
CC: Dave Korn <dave.korn@artimi.com>, "'Ben Laurie'" <benl@google.com>,
bugtraq@securityfocus.com, security@openid.net,
"'OpenID List'" <general@openid.net>, cryptography@metzdowd.com,
full-disclosure@lists.grok.org.uk
In-Reply-To: <20080808165730.7761450846@romeo.rtfm.com>
Eric Rescorla 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...
Funnily enough I was just working on this -- and found that we'd end up
adding a couple megabytes to every browser. #DEFINE NONSTARTER. I am
curious about the feasibility of a large bloom filter that fails back to
online checking though. This has side effects but perhaps they can be
made statistically very unlikely, without blowing out the size of a browser.
Updating the filter could then be something we do on a 24 hour
autoupdate basis. Doing either this, or doing revocation checking over
DNS (seriously), is not necessarily a bad idea. We need to do better
than we've been.
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