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From:   Krzysztof Kozlowski <krzk@kernel.org>
Date:   Tue, 20 Aug 2019 12:24:08 +0200
Message-ID: <CAJKOXPevJjBuRJjUX=6BfuMZSLUyqP3fpi7_eWDF170RfPvL+g@mail.gmail.com>
Subject: Re: [PATCH 2/2] crypto: s5p - use correct block size of 1 for ctr(aes)
To:     Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc:     linux-crypto@vger.kernel.org, herbert@gondor.apana.org.au,
        Vladimir Zapolskiy <vz@mleia.com>,
        Kamil Konieczny <k.konieczny@partner.samsung.com>,
        "linux-samsung-soc@vger.kernel.org" 
        <linux-samsung-soc@vger.kernel.org>
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On Mon, 19 Aug 2019 at 16:24, Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote:
>
> Align the s5p ctr(aes) implementation with other implementations
> of the same mode, by setting the block size to 1.
>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> ---
>  drivers/crypto/s5p-sss.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/crypto/s5p-sss.c b/drivers/crypto/s5p-sss.c
> index ef90c58edb1f..010f1bb20dad 100644
> --- a/drivers/crypto/s5p-sss.c
> +++ b/drivers/crypto/s5p-sss.c
> @@ -2173,7 +2173,7 @@ static struct crypto_alg algs[] = {
>                 .cra_flags              = CRYPTO_ALG_TYPE_ABLKCIPHER |
>                                           CRYPTO_ALG_ASYNC |
>                                           CRYPTO_ALG_KERN_DRIVER_ONLY,
> -               .cra_blocksize          = AES_BLOCK_SIZE,
> +               .cra_blocksize          = 1,

This makes sense but I wonder how does it work later with
s5p_aes_crypt() and its check for request length alignment
(AES_BLOCK_SIZE). With block size of 1 byte, I understand that
req->nbytes can be for example 4 bytes which is not AES block
aligned... If my reasoning is correct, then the CTR mode in s5p-sss is
not fully working.

Best regards,
Krzysztof