linux-kernel - Re: [PATCH] ELF: implement AT

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Message-ID: <20081006220759.GM10357@outflux.net>
Date:	Mon, 6 Oct 2008 15:07:59 -0700
From:	Kees Cook <kees.cook@...onical.com>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Roland McGrath <roland@...hat.com>, linux-kernel@...r.kernel.org,
	Jakub Jelinek <jakub@...hat.com>,
	Ulrich Drepper <drepper@...hat.com>, libc-alpha@...rceware.org
Subject: Re: [PATCH] ELF: implement AT_RANDOM for future glibc use

On Mon, Oct 06, 2008 at 09:26:41PM +0200, Andi Kleen wrote:
> > We're already using get_random* for stack, heap, and brk.  Also,
> > get_random* uses the nonblocking pool, so this is the same as if userspace
> > had tried to pull bytes out of /dev/urandom, which (as I understand it)
> 
> Yes exactly that's the problem. Think about it: do you really 
> need the same cryptographic strength for your mmap placement
> as you need for your SSL session keys?
> 
> And if you need true entropy for your session keys do you
> still get it when it was all used for low security 
> purposes first?

Off-list I was just shown random32().  If AT_RANDOM used that instead,
would that be acceptable?

-- 
Kees Cook
Ubuntu Security Team
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