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Date: Sat, 30 Mar 2024 00:04:36 -0700
From: Eric Biggers <ebiggers@kernel.org>
To: Zhang Yiqun <zhangyiqun@phytium.com.cn>
Cc: dhowells@redhat.com, jarkko@kernel.org, corbet@lwn.net,
	keyrings@vger.kernel.org, linux-doc@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org
Subject: Re: [PATCH] KEYS: Add ECDH support
Message-ID: <20240330070436.GA2116@sol.localdomain>
References: <20240330065506.3146-1-zhangyiqun@phytium.com.cn>
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In-Reply-To: <20240330065506.3146-1-zhangyiqun@phytium.com.cn>

[+Cc linux-crypto]

On Sat, Mar 30, 2024 at 02:55:06PM +0800, Zhang Yiqun wrote:
> This patch is to introduce ECDH into keyctl syscall for
> userspace usage, containing public key generation and
> shared secret computation.
> 
> It is mainly based on dh code, so it has the same condition
> to the input which only user keys is supported. The output
> result is storing into the buffer with the provided length.
> 
> Signed-off-by: Zhang Yiqun <zhangyiqun@phytium.com.cn>
> ---
>  Documentation/security/keys/core.rst |  62 ++++++
>  include/linux/compat.h               |   4 +
>  include/uapi/linux/keyctl.h          |  11 +
>  security/keys/Kconfig                |  12 +
>  security/keys/Makefile               |   2 +
>  security/keys/compat_ecdh.c          |  50 +++++
>  security/keys/ecdh.c                 | 318 +++++++++++++++++++++++++++
>  security/keys/internal.h             |  44 ++++
>  security/keys/keyctl.c               |  10 +
>  9 files changed, 513 insertions(+)
>  create mode 100644 security/keys/compat_ecdh.c
>  create mode 100644 security/keys/ecdh.c

Nacked-by: Eric Biggers <ebiggers@google.com>

The existing KEYCTL_PKEY_*, KEYCTL_DH_COMPUTE, and AF_ALG are causing enough
problems.  We do not need any more UAPIs like this.  They are hard to maintain,
break often, not properly documented, increase the kernel's attack surface, and
what they do is better done in userspace.

Please refer to the recent thread
https://lore.kernel.org/linux-crypto/CZSHRUIJ4RKL.34T4EASV5DNJM@matfyz.cz/T/#u
where these issues were discussed in detail.

- Eric