Re: [PATCH 4/4] crypto: arm64/chacha - add XChaCha12 support

[Ard Biesheuvel]

On Thu, 29 Nov 2018 at 07:35, Eric Biggers <ebiggers@xxxxxxxxxx> wrote:
>
> From: Eric Biggers <ebiggers@xxxxxxxxxx>
>
> Now that the ARM64 NEON implementation of ChaCha20 and XChaCha20 has
> been refactored to support varying the number of rounds, add support for
> XChaCha12.  This is identical to XChaCha20 except for the number of
> rounds, which is 12 instead of 20.  This can be used by Adiantum.
>
> Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>

Reviewed-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>

> ---
>  arch/arm64/crypto/Kconfig            |  2 +-
>  arch/arm64/crypto/chacha-neon-glue.c | 18 ++++++++++++++++++
>  2 files changed, 19 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/crypto/Kconfig b/arch/arm64/crypto/Kconfig
> index d54ddb8468ef5..d9a523ecdd836 100644
> --- a/arch/arm64/crypto/Kconfig
> +++ b/arch/arm64/crypto/Kconfig
> @@ -101,7 +101,7 @@ config CRYPTO_AES_ARM64_NEON_BLK
>         select CRYPTO_SIMD
>
>  config CRYPTO_CHACHA20_NEON
> -       tristate "ChaCha20 and XChaCha20 stream ciphers using NEON instructions"
> +       tristate "ChaCha20, XChaCha20, and XChaCha12 stream ciphers using NEON instructions"
>         depends on KERNEL_MODE_NEON
>         select CRYPTO_BLKCIPHER
>         select CRYPTO_CHACHA20
> diff --git a/arch/arm64/crypto/chacha-neon-glue.c b/arch/arm64/crypto/chacha-neon-glue.c
> index 4d992029b9121..346eb85498a1e 100644
> --- a/arch/arm64/crypto/chacha-neon-glue.c
> +++ b/arch/arm64/crypto/chacha-neon-glue.c
> @@ -161,6 +161,22 @@ static struct skcipher_alg algs[] = {
>                 .setkey                 = crypto_chacha20_setkey,
>                 .encrypt                = xchacha_neon,
>                 .decrypt                = xchacha_neon,
> +       }, {
> +               .base.cra_name          = "xchacha12",
> +               .base.cra_driver_name   = "xchacha12-neon",
> +               .base.cra_priority      = 300,
> +               .base.cra_blocksize     = 1,
> +               .base.cra_ctxsize       = sizeof(struct chacha_ctx),
> +               .base.cra_module        = THIS_MODULE,
> +
> +               .min_keysize            = CHACHA_KEY_SIZE,
> +               .max_keysize            = CHACHA_KEY_SIZE,
> +               .ivsize                 = XCHACHA_IV_SIZE,
> +               .chunksize              = CHACHA_BLOCK_SIZE,
> +               .walksize               = 4 * CHACHA_BLOCK_SIZE,
> +               .setkey                 = crypto_chacha12_setkey,
> +               .encrypt                = xchacha_neon,
> +               .decrypt                = xchacha_neon,
>         }
>  };
>
> @@ -187,3 +203,5 @@ MODULE_ALIAS_CRYPTO("chacha20");
>  MODULE_ALIAS_CRYPTO("chacha20-neon");
>  MODULE_ALIAS_CRYPTO("xchacha20");
>  MODULE_ALIAS_CRYPTO("xchacha20-neon");
> +MODULE_ALIAS_CRYPTO("xchacha12");
> +MODULE_ALIAS_CRYPTO("xchacha12-neon");
> --
> 2.19.2
>