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From:   Stephan =?ISO-8859-1?Q?M=FCller?= <smueller@chronox.de>
To:     Florian Weimer <fw@deneb.enyo.de>
Cc:     Arnd Bergmann <arnd@arndb.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-crypto@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
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        "Eric W. Biederman" <ebiederm@xmission.com>,
        "Alexander E. Patrakov" <patrakov@gmail.com>,
        "Ahmed S. Darwish" <darwish.07@gmail.com>,
        "Theodore Y. Ts'o" <tytso@mit.edu>, Willy Tarreau <w@1wt.eu>,
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        William Jon McCann <mccann@jhu.edu>,
        zhangjs <zachary@baishancloud.com>,
        Andy Lutomirski <luto@kernel.org>,
        Florian Weimer <fweimer@redhat.com>,
        Lennart Poettering <mzxreary@0pointer.de>,
        Nicolai Stange <nstange@suse.de>,
        "Peter, Matthias" <matthias.peter@bsi.bund.de>,
        Marcelo Henrique Cerri <marcelo.cerri@canonical.com>,
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        Neil Horman <nhorman@redhat.com>
Subject: Re: [PATCH v24 00/12] /dev/random - a new approach with full SP800-90B compliance
Date:   Tue, 12 Nov 2019 23:43:42 +0100
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Am Dienstag, 12. November 2019, 14:23:10 CET schrieb Florian Weimer:

Hi Florian,

> * Stephan M=FCller:
> > * support deactivation of TRNG (i.e. blocking behavior of /dev/random)
> >=20
> >   at compile time. If deactivated, /dev/random behaves like
> >   getrandom(2).
>=20
> I don't quite understand this comment.  Doesn't getrandom with the
> GRND_RANDOM always behave like /dev/random?  Presumably, without the
> TRNG tap, the GRND_RANDOM flag for getrandom is ignored, and reading
> from /dev/random behaves like reading from /dev/urandom.

Absolutely. Apologies for the imprecision here. I will correct that.

The idea is that the constant blocking behavior of /dev/random and GRND_RAN=
DOM=20
is replaced with the blocking behavior of getrandom(2) without the GRND_RAN=
DOM=20
flag (i.e. the interface waits until the LRNG thinks it is completely seede=
d=20
before it provides ulimited data).
>=20
> Anyway, reading the accompanying PDF, this looks rather impressive:
> the userspace bootstrapping problem is gone (the issue where waiting
> for more entropy prevents the collection of more entropy), *and* we
> can still make the standards people happy.
>=20
> (Replying from my other account due to mail issues, sorry.)


Ciao
Stephan