Date: Fri, 20 Jan 2012 09:58:23 +0400 From: Andrey Chernov <ache@FreeBSD.ORG> To: Mark Murray <markm@FreeBSD.ORG> Cc: svn-src-head@FreeBSD.ORG, David Schultz <das@FreeBSD.ORG>, src-committers@FreeBSD.ORG, svn-src-all@FreeBSD.ORG Subject: Re: svn commit: r230230 - head/sys/dev/random Message-ID: <20120120055823.GA28177@vniz.net> In-Reply-To: <E1Rny2A-000C3x-O6@groundzero.grondar.org> References: <201201162018.q0GKIADK050161@svn.freebsd.org> <20120118061943.GA80874@vniz.net> <E1Rny2A-000C3x-O6@groundzero.grondar.org>
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On Thu, Jan 19, 2012 at 07:52:30PM +0000, Mark Murray wrote: > Andrey Chernov writes: > > On Mon, Jan 16, 2012 at 08:18:10PM +0000, David Schultz wrote: > > > Author: das > > > Date: Mon Jan 16 20:18:10 2012 > > > New Revision: 230230 > > > URL: http://svn.freebsd.org/changeset/base/230230 > > > > > > Log: > > > Generate a warning if the kernel's arc4random() is seeded with bogus entropy. > > > > While you are here, could you review/commit my patch to fix bad 31bit > > arc4rand() seeding, please? > > > > --- yarrow.c.bak 2011-09-26 07:35:48.000000000 +0400 > > +++ yarrow.c 2012-01-18 10:13:47.000000000 +0400 > > This is the wrong place for this; it may achieve the desired result, but > the file is where the Yarrow algorithm is implepeneted; ARC4 reseeds are > not a part of that, which makes this proposal a layering violation at > best, and an unwarranted dependancy at worst. > > Look at the function random_yarrow_unblock(). Thats where yopu want to > be doing this. This function is where the random device is unblocked > once safely seeded. Thanx for your hint, but I fear one moment using random_yarrow_unblock(). It is called under mtx_lock(&random_reseed_mtx) in reseed(). And when arc4rand() seeding is called, it uses read_random(), so I see possible deadlock can happens. In my version arc4rand() seeding happens only when this lock is released, so no blocking is possible. But perhaps I oversight something, correct me if I am wrong, please. -- http://ache.vniz.net/
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