linux-kernel - Re: [PATCH] Re: [PATCH] drivers/net: remove network drivers' last few uses of IRQF_SAMPLE

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Message-ID: <20080518125759.GA18812@tsunami.ccur.com>
Date:	Sun, 18 May 2008 08:57:59 -0400
From:	Joe Korty <joe.korty@...r.com>
To:	Theodore Tso <tytso@....edu>, Andi Kleen <andi@...stfloor.org>,
	Arjan van de Ven <arjan@...radead.org>,
	Chris Peterson <cpeterso@...terso.com>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Jeff Garzik <jeff@...zik.org>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Brandeburg, Jesse" <jesse.brandeburg@...el.com>,
	tpmdd-devel@...ts.sourceforge.net, tpm@...horst.net
Subject: Re: [PATCH] Re: [PATCH] drivers/net: remove network drivers' last few uses of IRQF_SAMPLE_RANDOM

On Sun, May 18, 2008 at 07:26:57AM -0400, Theodore Tso wrote:
> On Sun, May 18, 2008 at 12:13:35PM +0200, Andi Kleen wrote:
> > We don't use it for most long term keys, e.g. ssh host keys. That is
> > because even on high entropy systems /dev/random usually doesn't work
> > during distribution installation because the system has not run long
> > enough to collect significant entropy yet.
>  ...
> Hence, if you don't think the system hasn't run long enough to collect
> significant entropy, you need to distinguish between "has run long
> enough to collect entropy which is causes the entropy credits using a
> somewhat estimation system where we try to be conservative such that
> /dev/random will let you extract the number of bits you need", and
> "has run long enough to collect entropy which is unpredictable by an
> outside attacker such that host keys generated by /dev/urandom really
> are secure".
> ...
> If distributions really cared, they could very well introduce keyboard
> banging as part of the install process; but no, being able to do an
> unmanned, "turnkey" install is considered more important.  That says
> something about how much they care about security right there.

If the World really cared about security, every cpu chip
would supply a true source of random bits based on the
sampling some easily accessable quantum on-chip state,
such as the tiny fluctuations in current flow across
a resistance.  I suspect supplying this would be about
as expensive as supplying a true TSC driven directly by
the external clock -- that is, so close to zero as to
not matter.

Joe
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