Re: [Security] [PATCH] proc: avoid information leaks to non-privileged processes

[Matt Mackall <mpm@selenic.com>]

On Thu, May 07, 2009 at 08:41:36PM +0200, Ingo Molnar wrote:
> 
> * Matt Mackall <mpm@selenic.com> wrote:
> 
> > > As i mentioned it in the previous mail, i'd _really_ like to 
> > > hear your thread model and attack vector description. Does this 
> > > overhead justify the threat? Your change will only result in 
> > > get_random_int() not being considered fast anymore.
> > 
> > My threat model is that someone more clever and with a lot more 
> > expertise attacking systems than either you or me will be able to 
> > leverage the extreme weakness of this hash (O(1) attacks against 
> > the *full* version!) into an attack that incrementally exposes the 
> > hidden RNG state. I've asked a couple such people whether they 
> > think that's likely, and they've said yes.
> 
> My question was whether the variant laced with the cycle counter 
> could be exposable.

In my world, some machines don't have TSCs, so I think this is the
wrong question to be asking.

-- 
Mathematics is the supreme nostalgia of our time.