linux-kernel - Re: [PATCH 1/3] crypto: sm4 - create SM4 library based on sm4 generic code

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Date:   Thu, 10 Jun 2021 16:19:36 -0700
From:   Eric Biggers <ebiggers@...nel.org>
To:     Tianjia Zhang <tianjia.zhang@...ux.alibaba.com>
Cc:     Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Gilad Ben-Yossef <gilad@...yossef.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        "Markku-Juhani O . Saarinen" <mjos@....fi>,
        Jussi Kivilinna <jussi.kivilinna@....fi>, x86@...nel.org,
        linux-crypto@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] crypto: sm4 - create SM4 library based on sm4
 generic code

On Thu, Jun 10, 2021 at 09:44:57PM +0800, Tianjia Zhang wrote:
> Take the existing small footprint and mostly time invariant C code

It is using an S-box without any prefetching.  That doesn't look very
"time invariant" to me.

> diff --git a/lib/crypto/sm4.c b/lib/crypto/sm4.c
> new file mode 100644
> index 000000000000..cbdd14a254d0
[..]
> +/**
> + * crypto_sm4_expand_key - Expands the SM4 key as described in GB/T 32907-2016
> + * @ctx:	The location where the computed key will be stored.
> + * @in_key:	The supplied key.
> + * @key_len:	The length of the supplied key.
> + *
> + * Returns 0 on success. The function fails only if an invalid key size (or
> + * pointer) is supplied.
> + */
> +int crypto_sm4_expand_key(struct crypto_sm4_ctx *ctx, const u8 *in_key,
> +			  unsigned int key_len)
[...]
> +/**
> + * crypto_sm4_do_crypt - Encrypt or decrypt a single SM4 block
> + * @rk:		The rkey_enc for encrypt or rkey_dec for decrypt
> + * @out:	Buffer to store output data
> + * @in: 	Buffer containing the input data
> + */
> +void crypto_sm4_do_crypt(const u32 *rk, u8 *out, const u8 *in)

Calling these "sm4_expandkey()" and "sm4_crypt_block()" would be more consistent
with the other lib/crypto/ functions such as the AES ones.  The other
lib/crypto/ functions don't have a "crypto_" prefix, as that is used for
functions related to the traditional crypto API rather than the library API.

- Eric