linux-kernel - Re: [PATCH v3 0/8] crypto, lib/crypto: Add SHAKE128/256 support and move SHA3 to lib/crypto

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Message-ID: <2636609.1759410884@warthog.procyon.org.uk>
Date: Thu, 02 Oct 2025 14:14:44 +0100
From: David Howells <dhowells@...hat.com>
To: Eric Biggers <ebiggers@...nel.org>
Cc: dhowells@...hat.com, "Jason A . Donenfeld" <Jason@...c4.com>,
    Ard Biesheuvel <ardb@...nel.org>,
    Herbert Xu <herbert@...dor.apana.org.au>,
    Stephan Mueller <smueller@...onox.de>, linux-crypto@...r.kernel.org,
    linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 0/8] crypto, lib/crypto: Add SHAKE128/256 support and move SHA3 to lib/crypto

Eric Biggers <ebiggers@...nel.org> wrote:

> Have you had a chance to read this reply?

I have.

You held up your implementation of sha256 and sha224 as an example of how it
perhaps should be implemented:

	It would be worth considering separating the APIs for the different
	algorithms that are part of SHA-3, similar to what I did with SHA-224
	and SHA-256.

so I have followed that.  That defines a type for each, so I'll leave it at
that.

> All I'm really requesting is that we don't create footguns, like the
> following that the API in the v2 patch permitted:

The way you did a separate type for each removed one more footgun - and
arguably a more important one - as the *type* enforces[1] the output buffer
size and the sha3_*_final() function has the same sized-array as the
convenience wrappers.

It also eliminates the need to store the digest size as this is only needed at
the final step for the digest variant algorithms.

David

[1] Inasmuch as this is effective in C.