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Subject: Re: [PATCH 2/2] crypto: s5p - use correct block size of 1 for
 ctr(aes)
To:     Krzysztof Kozlowski <krzk@kernel.org>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc:     linux-crypto@vger.kernel.org, herbert@gondor.apana.org.au,
        Vladimir Zapolskiy <vz@mleia.com>,
        "linux-samsung-soc@vger.kernel.org" 
        <linux-samsung-soc@vger.kernel.org>
From:   Kamil Konieczny <k.konieczny@partner.samsung.com>
Message-ID: <1f932022-0335-1d00-b651-83c82d77fa7a@partner.samsung.com>
Date:   Tue, 20 Aug 2019 13:39:33 +0200
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On 20.08.2019 12:24, Krzysztof Kozlowski wrote:
> 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.

As I remember this case there are allocated buffers with len aligned up
AES_BLOCK_SIZE, source data copy to one buf, hw encrypts full block, 
then nbytes are copy back.

-- 
Best regards,
Kamil Konieczny
Samsung R&D Institute Poland