linux-kernel - Re: [PATCH v13 02/12] pkcs7: Allow the signing algo to calculate the digest itself

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Message-ID: <aXSxI9dxfAJ0tj14@kernel.org>
Date: Sat, 24 Jan 2026 13:46:43 +0200
From: Jarkko Sakkinen <jarkko@...nel.org>
To: David Howells <dhowells@...hat.com>
Cc: Lukas Wunner <lukas@...ner.de>, Ignat Korchagin <ignat@...udflare.com>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Eric Biggers <ebiggers@...nel.org>,
	Luis Chamberlain <mcgrof@...nel.org>,
	Petr Pavlu <petr.pavlu@...e.com>,
	Daniel Gomez <da.gomez@...nel.org>,
	Sami Tolvanen <samitolvanen@...gle.com>,
	"Jason A . Donenfeld" <Jason@...c4.com>,
	Ard Biesheuvel <ardb@...nel.org>,
	Stephan Mueller <smueller@...onox.de>, linux-crypto@...r.kernel.org,
	keyrings@...r.kernel.org, linux-modules@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v13 02/12] pkcs7: Allow the signing algo to calculate the
 digest itself

On Wed, Jan 21, 2026 at 12:31:35PM +0000, David Howells wrote:
> Jarkko Sakkinen <jarkko@...nel.org> wrote:
> 
> > I'd use the wording you used already in commit message, which
> > factors more descriptive than what you have here. E.g., name
> > it "external_digest".
> 
> ML-DSA uses "external" to mean that the caller does the
> digestion/hashing/XOF-ing/whatever Eric wants to call it, but the caller also
> has to put other stuff into the digest/hash/XOF/thing that then gets passed to
> ML-DSA if it does this.
> 
> For added confusion, the NIST FIPS tests seem to consider what this patch does
> as 'external' but an "external mu" as 'internal':
> 
> 	"tgId": 1,
> 	"testType": "AFT",
> 	"parameterSet": "ML-DSA-44",
> 	"signatureInterface": "external",
> 	"preHash": "pure",
> 
> vs:
> 
> 	"tgId": 7,
> 	"testType": "AFT",
> 	"parameterSet": "ML-DSA-44",
> 	"signatureInterface": "internal",
> 	"externalMu": true,
> 
> I haven't come up with a better name that particularly describes this.  Maybe
> use "no_prehash" or "algo_takes_hash" or "algo_takes_data"?
> 
> Maybe better than using a true/false value, use an enum?
> 
> 	enum public_key_hash {
> 		ALGO_SIGNS_HASH, /* RSA, ECDSA, ... */
> 		ALGO_SIGNS_DATA, /* MLDSA, ... */
> 	};

I think this would be better idea, as it makes the states more explicit.

And I was actually considering to suggest enum so yeah, I'm on board
with this suggestion.

> 
> David
> 

BR, Jarkko