linux-kernel - Re: IRQF_SAMPLE

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Message-Id: <1239063404.14392.118.camel@calx>
Date:	Mon, 06 Apr 2009 17:16:44 -0700
From:	Matt Mackall <mpm@...enic.com>
To:	Sven-Haegar Koch <haegar@...net.de>
Cc:	Robin Getz <rgetz@...ckfin.uclinux.org>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Chris Peterson <cpeterso@...terso.com>
Subject: Re: IRQF_SAMPLE_RANDOM question...

On Tue, 2009-04-07 at 00:09 +0200, Sven-Haegar Koch wrote:
> On Mon, 6 Apr 2009, Matt Mackall wrote:
> 
> > On Mon, 2009-04-06 at 14:30 -0400, Robin Getz wrote:
> > > We have lots of embedded headless systems (no keyboard/mouse, no soundcard, no 
> > > video) systems with *no* sources of entropy - and people using SSL.
> > 
> > I'd rather add a random_sample_network call somewhere reasonably central
> > in the network stack. Then we can use the knowledge that the sample is
> > network-connected in the random core to decide how to measure its
> > entropy. The trouble with IRQF_SAMPLE_RANDOM is that many of its users
> > are technically bogus as entropy sources in the current model.
> > 
> > I'm eventually going to move the RNG away from the strict theoretical
> > entropy accounting model to a more pragmatic one which will be much
> > happier with iffy entropy sources, but that's a ways off.
> 
> Btw, perhaps not the perfect question in this thread:
> But what should we use to keep servers running without a hardware rng 
> available and without any external input besides the network?
> After having ssh and openvpn die because of no random and having 
> the machines like dead and unreachable for me I use "ln -sf 
> /dev/urandom /dev/random", but that does not feel so good.

It's fine so long as you're not wearing a tinfoil hat. In fact, as
the /dev/random maintainer, I'd recommend it.

Ted and I have recently been talking about revisiting the design
of /dev/random to avoid these sorts of issues.

-- 
http://selenic.com : development and support for Mercurial and Linux


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