Messages in this thread | | | Date | Mon, 6 Oct 2008 16:29:36 -0700 | From | Kees Cook <> | Subject | Re: [PATCH] ELF: implement AT_RANDOM for future glibc use |
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On Tue, Oct 07, 2008 at 01:19:42AM +0200, Andi Kleen wrote: > And you won't deny that session keys are more important than mmap > placement, will you?
Right, I would tend to agree that session key strength is more important than ASLR strength.
> > I'd really love to see this solved. My goal is to get a mainline glibc > > patch for a low-cost randomized stack guard value. > > Your current implementation is high cost. >... > random32() is not a cryptographically strong RNG. I suspect it would > be pretty easy to reverse engineer its seed given some state. It hasn't > been designed to be protected against that.
It's being used for randomness in the networking code, so it's at least mildly random "enough".
> IMHO it needs a new class of random numbers in the kernel that use > some cryptographically strong RNG (there are a couple of candidates > like yarrow) which is very rarely seeded > from the entropy pool[1] and use that for these applications. > A couple of other users in the kernel would benefit that too, > most users of get_random_bytes() probably should be reviewed > for their true requirements.
Sure, but this is a larger (and pre-existing) problem.
> Ideally expose it to userland too so that dumb users like > tmpfile can use it too.
Would you propose that it get hooked to /dev/urandom?
-Kees
-- Kees Cook Ubuntu Security Team
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