I was just playing through a mock attack sequence in my head and I realized that I was wrong about it being an issue for the hmac signature implementation. The nonces and time stamps do indeed protect that.
I think the only affected implementation is the plain text signature, which I really never thought should have been part of the standard in the first place. Does anyone actually use that? So the question is can you 'trick' a provider into accepting plaintext signatures? If you can you are vulnerable. I think the Ruby implementation by default only supports hmac-sha1. I will test this and see. P On Fri, Aug 14, 2009 at 3:44 PM, Mike Malone<[email protected]> wrote: > > I'm no security expert, but I'm gunna go ahead and say that (IMO) this > attack is at best a theoretical attack for the vast majority of OAuth > installs. > >> Blaine or Kellan threw out a question about this vulnerability in an >> OAuth context that I haven't had the time (nor do I have the >> qualifications) to answer: do the use of a nonce and timestamp >> mitigate the risk? > > Seth, I actually think that enforcing nonces should make this attack > impossible for guessing OAuth signatures (assuming you enforce nonces > for malformed requests). If you can only get a good/bad response once > then you're out of luck. > > In practice few people actually check nonces, but checking time stamps > should make this attack _extremely_ infeasible if not impossible. If > you only allowed timestamps that are <= 15 minutes old, for example, > an attacker would have to determine your signature within 15 minutes > (which means making many millions of requests in that period of time). > > Coda suggested that researches were able to determine 20µs differences > with a few hundred (or thousand?) measurements. As a point of > reference, here are some measurements from my machine (using Python): > >>>> timeit.Timer("'aa' == 'bb'").timeit(10000000) > 0.74933886528015137 >>>> timeit.Timer("'aa' == 'ab'").timeit(10000000) > 0.80185294151306152 > > Mike > > > > -- http://agree2.com - Reach Agreement! http://extraeagle.com - Solutions for the electronic Extra Legal world http://stakeventures.com - Bootstrapping blog --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "OAuth" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/oauth?hl=en -~----------~----~----~----~------~----~------~--~---
