linux-kernel - Re: [PATCH 16/17] crypto: jitterentropy

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Message-ID: <20251020212057.GA83624@google.com>
Date: Mon, 20 Oct 2025 21:20:57 +0000
From: Eric Biggers <ebiggers@...nel.org>
To: David Howells <dhowells@...hat.com>
Cc: linux-crypto@...r.kernel.org, Ard Biesheuvel <ardb@...nel.org>,
	"Jason A . Donenfeld" <Jason@...c4.com>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-s390@...r.kernel.org
Subject: Re: [PATCH 16/17] crypto: jitterentropy - use default sha3
 implementation

On Mon, Oct 20, 2025 at 11:35:30AM +0100, David Howells wrote:
> Why don't you take my approach and just call lib/crypto/sha3 directly rather
> than using a crypto/ object as an intermediary if that crypto/ object is just
> going to wrap lib/crypto?

We'll do that, and thanks for writing the patch already!  But that's
something to do in a later patch after adding the library API.  Your
patch description kind of raised a red flag:

    Make the jitterentropy RNG use lib/crypto/sha3 rather than
    crypto/sha3.

    For some reason it goes absolutely wild if crypto/sha3 is
    reimplemented to use lib/crypto/sha3, but it's fine if it uses lib
    directly.

That implies that your changes broke crypto_shash, so you *had* to
convert to the library right away as a workaround for that.

That shouldn't be necessary.  We should generally keep crypto_shash
working for now.  In which case, all jitterentropy should need for now
is a simple substitution s/sha3-256-generic/sha3-256/.

We'll convert jitterentropy to use the library API too.  It's better,
after all.  But it should be done later and because the library API is
better -- not as some sort of workaround.

- Eric