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From:   Krzysztof Kozlowski <krzk@kernel.org>
Date:   Tue, 20 Aug 2019 13:48:50 +0200
Message-ID: <CAJKOXPfR_L4z=sE8ETUB3_6sVV=ab=vntqh-_KvNmsKacEa4qQ@mail.gmail.com>
Subject: Re: [PATCH 2/2] crypto: s5p - use correct block size of 1 for ctr(aes)
To:     Kamil Konieczny <k.konieczny@partner.samsung.com>
Cc:     Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        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>
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On Tue, 20 Aug 2019 at 13:39, Kamil Konieczny
<k.konieczny@partner.samsung.com> wrote:
>
>
>
> 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.

Buffer alignment is different thing and it is defined in cra_alignmask.
I am talking about req->nbytes which should be aligned according to
s5p_aes_crypt(). But if blocksize is 1 byte, then what possible values
for req->nbytes?

Best regards,
Krzysztof