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Date: Wed, 31 Jul 2013 10:46:14 -0700
From: "David O'Brien" <obrien@FreeBSD.org>
To: Andrey Chernov <ache@freebsd.org>
Subject: Re: svn commit: r253786 - in head/sys: dev/random
 modules/padlock_rng modules/rdrand_rng modules/yarrow_rng
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On Wed, Jul 31, 2013 at 05:58:43AM +0400, Andrey Chernov wrote:
> On 31.07.2013 4:07, David O'Brien wrote:
> > I believe you're talking about this code in
> > sys/libkern/arc4random.c:arc4rand()
> > 
> > 	if (atomic_cmpset_int(&arc4rand_iniseed_state, ARC4_ENTR_HAVE,
> > 	    ARC4_ENTR_SEED) || reseed ||
> > 	   (arc4_numruns > ARC4_RESEED_BYTES) ||
> > 	   (tv.tv_sec > arc4_t_reseed))
> > 		arc4_randomstir();
> > 
> > Without setting 'arc4rand_iniseed_state' from ARC4_ENTR_NONE ->
> > ARC4_ENTR_HAVE, we would still call arc4_randomstir() periodically due
> > to (tv.tv_sec > arc4_t_reseed) and (arc4_numruns > ARC4_RESEED_BYTES).
> 
> The whole problem is that arc4 is poorly initialized right after boot,
> but immediately used in many places like tcp. It reseeds again only
> after 5 minutes after boot making vulnerability window at this interval.

I realize the motivation for your r249631 change.

But as it relates to the change I committed, there is no change in
behavior in this.  If one is using a hardware RNG, yarrow is not
initialized and so the ARC4_ENTR_NONE -> ARC4_ENTR_HAVE transition
does not happen.

-- 
-- David  (obrien@FreeBSD.org)