linux-kernel - Re: [PATCH v2] crypto: sun4i-ss: support the Security System PRNG

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Message-ID: <20161208092400.GA9743@Red>
Date:   Thu, 8 Dec 2016 10:24:00 +0100
From:   Corentin Labbe <clabbe.montjoie@...il.com>
To:     Herbert Xu <herbert@...dor.apana.org.au>
Cc:     davem@...emloft.net, maxime.ripard@...e-electrons.com,
        wens@...e.org, linux-kernel@...r.kernel.org,
        linux-crypto@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2] crypto: sun4i-ss: support the Security System PRNG

On Thu, Dec 08, 2016 at 05:06:18PM +0800, Herbert Xu wrote:
> On Wed, Dec 07, 2016 at 01:51:27PM +0100, Corentin Labbe wrote:
> > 
> > So I must expose it as a crypto_rng ?
> 
> If it is to be exposed at all then algif_rng would be the best
> place.
> 

I have badly said my question.
So I need to use the HW PRNG in a crypto_rng "provider" that could be thereafter used from user space via algif_rng. right ?

> > Could you explain why PRNG must not be used as hw_random ?
> 
> The hwrng interface was always meant to be an interface for real
> hardware random number generators.  People rely on that so we
> should not provide bogus entropy sources through this interface.
> 

Why not adding a KCONFIG HW_RANDOM_ACCEPT_ALSO_PRNG with big warning ?
Or a HW_PRNG Kconfig which do the same than hwrandom with /dev/prng ?
With that it will be much easier to convert in-tree PRNG that you want to remove.

Regards
Corentin Labbe