svn commit: r230230 - head/sys/dev/random
Andrey Chernov
ache at FreeBSD.ORG
Fri Jan 20 05:58:27 UTC 2012
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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