Full Disclosure mailing list archives
Re: OpenID/Debian PRNG/DNS Cache poisoning advisory
From: Eric Rescorla <ekr () networkresonance com>
Date: Fri, 08 Aug 2008 11:20:15 -0700
At Fri, 08 Aug 2008 10:43:53 -0700, Dan Kaminsky wrote:
Eric Rescorla wrote: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.
Why do you say a couple of megabytes? 99% of the value would be 1024-bit RSA keys. There are ~32,000 such keys. If you devote an 80-bit hash to each one (which is easily large enough to give you a vanishingly small false positive probability; you could probably get away with 64 bits), that's 320KB. Given that the smallest Firefox build (Windows) is 7.1 MB, this doesn't sound like a nonstarter to me at all, especially since the browser could download it in the background.
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.
Yes, there are a number of approaches to more efficient CRL checking, I think that's a separate issue. -Ekr _______________________________________________ Full-Disclosure - We believe in it. Charter: http://lists.grok.org.uk/full-disclosure-charter.html Hosted and sponsored by Secunia - http://secunia.com/
Current thread:
- Re: OpenID/Debian PRNG/DNS Cache poisoning advisory, (continued)
- Re: OpenID/Debian PRNG/DNS Cache poisoning advisory Paul Hoffman (Aug 08)
- Re: OpenID/Debian PRNG/DNS Cache poisoning advisory Nicolas Williams (Aug 08)
- Re: [OpenID] OpenID/Debian PRNG/DNS Cache poisoning advisory Dick Hardt (Aug 08)
- Re: [OpenID] OpenID/Debian PRNG/DNS Cache poisoning advisory Gerald Beuchelt (Aug 08)
- Re: [OpenID] OpenID/Debian PRNG/DNS Cache poisoning advisory Eddy Nigg (StartCom Ltd.) (Aug 08)
- Re: OpenID/Debian PRNG/DNS Cache poisoning advisory Dave Korn (Aug 08)
- Re: OpenID/Debian PRNG/DNS Cache poisoning advisory Dan Guido (Aug 08)
- Re: OpenID/Debian PRNG/DNS Cache poisoning advisory Jin Sei (Aug 08)
- Re: OpenID/Debian PRNG/DNS Cache poisoning advisory Peter Gutmann (Aug 08)
- Re: OpenID/Debian PRNG/DNS Cache poisoning advisory Dan Kaminsky (Aug 08)
- Re: OpenID/Debian PRNG/DNS Cache poisoning advisory Eric Rescorla (Aug 08)
- Re: OpenID/Debian PRNG/DNS Cache poisoning advisory Florian Weimer (Aug 08)
- Re: OpenID/Debian PRNG/DNS Cache poisoning advisory Nicolas Williams (Aug 08)
- Re: OpenID/Debian PRNG/DNS Cache poisoning advisory Leichter, Jerry (Aug 08)
- Re: OpenID/Debian PRNG/DNS Cache poisoning advisory Eric Rescorla (Aug 08)
- Re: OpenID/Debian PRNG/DNS Cache poisoning advisory Leichter, Jerry (Aug 08)
- Re: OpenID/Debian PRNG/DNS Cache poisoning advisory Forrest J. Cavalier III (Aug 09)
- Re: OpenID/Debian PRNG/DNS Cache poisoning advisory Seth Breidbart (Aug 13)
- key blacklisting & file size (was: OpenID/Debian PRNG/DNS Cache poisoning advisory) Solar Designer (Aug 08)
- Re: OpenID/Debian PRNG/DNS Cache poisoning advisory Tim Dierks (Aug 08)
- Re: OpenID/Debian PRNG/DNS Cache poisoning advisory Ben Laurie (Aug 08)