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Message-ID: <e1b3ccb744d67e6214cf206ba8480cb3e35694cf.camel@redhat.com>
Subject: Re: jitterentropy vs. simulation
From: Simo Sorce <simo@redhat.com>
To: Johannes Berg <johannes@sipsolutions.net>, Anton Ivanov
	 <anton.ivanov@kot-begemot.co.uk>, linux-um@lists.infradead.org
Cc: linux-crypto@vger.kernel.org, Stephan =?ISO-8859-1?Q?M=FCller?=
	 <smueller@chronox.de>
Date: Fri, 01 Dec 2023 14:25:37 -0500
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On Fri, 2023-12-01 at 19:35 +0100, Johannes Berg wrote:
> [I guess we should keep the CCs so other see it]
>=20
> > Looking at the stuck check it will be bogus in simulations.
>=20
> True.
>=20
> > You might as well ifdef that instead.
> >=20
> > If a simulation is running insert the entropy regardless and do not com=
pute the derivatives used in the check.
>=20
> Actually you mostly don't want anything inserted in that case, so it's
> not bad to skip it.
>=20
> I was mostly thinking this might be better than adding a completely
> unrelated ifdef. Also I guess in real systems with a bad implementation
> of random_get_entropy(), the second/third derivates might be
> constant/zero for quite a while, so may be better to abort?
>=20
> In any case, I couldn't figure out any way to not configure this into
> the kernel when any kind of crypto is also in ...

Doesn't this imply the simulation is not complete and you need to add
clock jitter for the simulation to be more useful?

You can use the host rng to add random jitter to the simulation clock.

Simo.

--=20
Simo Sorce,
DE @ RHEL Crypto Team,
Red Hat, Inc