linux-kernel - Re: [PATCH] crypto: keywrap - remove unused keywrap algorithm

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Message-ID: <Z3iMnNbcb0WXBGlz@gondor.apana.org.au>
Date: Sat, 4 Jan 2025 09:19:24 +0800
From: Herbert Xu <herbert@...dor.apana.org.au>
To: Eric Biggers <ebiggers@...nel.org>
Cc: linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
	smueller@...onox.de
Subject: Re: [PATCH] crypto: keywrap - remove unused keywrap algorithm

Eric Biggers <ebiggers@...nel.org> wrote:
> From: Eric Biggers <ebiggers@...gle.com>
> 
> The keywrap (kw) algorithm has no in-tree user.  It has never had an
> in-tree user, and the patch that added it provided no justification for
> its inclusion.  Even use of it via AF_ALG is impossible, as it uses a
> weird calling convention where part of the ciphertext is returned via
> the IV buffer, which is not returned to userspace in AF_ALG.
> 
> It's also unclear whether any new code in the kernel that does key
> wrapping would actually use this algorithm.  It is controversial in the
> cryptographic community due to having no clearly stated security goal,
> no security proof, poor performance, and only a 64-bit auth tag.  Later
> work (https://eprint.iacr.org/2006/221) suggested that the goal is
> deterministic authenticated encryption.  But there are now more modern
> algorithms for this, and this is not the same as key wrapping, for which
> a regular AEAD such as AES-GCM usually can be (and is) used instead.
> 
> Therefore, remove this unused code.
> 
> There were several special cases for this algorithm in the self-tests,
> due to its weird calling convention.  Remove those too.
> 
> Cc: Stephan Mueller <smueller@...onox.de>
> Signed-off-by: Eric Biggers <ebiggers@...gle.com>
> ---
> arch/m68k/configs/amiga_defconfig          |   1 -
> arch/m68k/configs/apollo_defconfig         |   1 -
> arch/m68k/configs/atari_defconfig          |   1 -
> arch/m68k/configs/bvme6000_defconfig       |   1 -
> arch/m68k/configs/hp300_defconfig          |   1 -
> arch/m68k/configs/mac_defconfig            |   1 -
> arch/m68k/configs/multi_defconfig          |   1 -
> arch/m68k/configs/mvme147_defconfig        |   1 -
> arch/m68k/configs/mvme16x_defconfig        |   1 -
> arch/m68k/configs/q40_defconfig            |   1 -
> arch/m68k/configs/sun3_defconfig           |   1 -
> arch/m68k/configs/sun3x_defconfig          |   1 -
> arch/mips/configs/decstation_64_defconfig  |   1 -
> arch/mips/configs/decstation_defconfig     |   1 -
> arch/mips/configs/decstation_r4k_defconfig |   1 -
> arch/s390/configs/debug_defconfig          |   1 -
> arch/s390/configs/defconfig                |   1 -
> crypto/Kconfig                             |   8 -
> crypto/Makefile                            |   1 -
> crypto/keywrap.c                           | 319 ---------------------
> crypto/testmgr.c                           |  20 +-
> crypto/testmgr.h                           |  39 ---
> 22 files changed, 1 insertion(+), 403 deletions(-)
> delete mode 100644 crypto/keywrap.c

Patch applied.  Thanks.
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt