linux-kernel - Re: [PATCH 1/9] crypto: add hmac IPAD/OPAD constant

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Message-ID: <20170518041045.GA32127@gondor.apana.org.au>
Date:   Thu, 18 May 2017 12:10:45 +0800
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Corentin Labbe <clabbe.montjoie@...il.com>
Cc:     davem@...emloft.net, thomas.lendacky@....com, gary.hook@....com,
        boris.brezillon@...e-electrons.com, arno@...isbad.org,
        matthias.bgg@...il.com, giovanni.cabiddu@...el.com,
        salvatore.benedetto@...el.com, linux-crypto@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, qat-linux@...el.com
Subject: Re: [PATCH 1/9] crypto: add hmac IPAD/OPAD constant

On Mon, Apr 24, 2017 at 04:16:21PM +0200, Corentin Labbe wrote:
> Many HMAC users directly use directly 0x36/0x5c values.
> It's better with crypto to use a name instead of directly some crypto
> constant.
> 
> This patch simply add HMAC_IPAD_VALUE/HMAC_OPAD_VALUE defines.
> 
> Signed-off-by: Corentin Labbe <clabbe.montjoie@...il.com>
> ---
>  crypto/hmac.c         | 4 ++--
>  include/crypto/hash.h | 3 +++
>  2 files changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/crypto/hmac.c b/crypto/hmac.c
> index 72e38c0..4a997ce 100644
> --- a/crypto/hmac.c
> +++ b/crypto/hmac.c
> @@ -74,8 +74,8 @@ static int hmac_setkey(struct crypto_shash *parent,
>  	memcpy(opad, ipad, bs);
>  
>  	for (i = 0; i < bs; i++) {
> -		ipad[i] ^= 0x36;
> -		opad[i] ^= 0x5c;
> +		ipad[i] ^= HMAC_IPAD_VALUE;
> +		opad[i] ^= HMAC_OPAD_VALUE;
>  	}
>  
>  	return crypto_shash_init(shash) ?:
> diff --git a/include/crypto/hash.h b/include/crypto/hash.h
> index b5727bc..0f51ff1 100644
> --- a/include/crypto/hash.h
> +++ b/include/crypto/hash.h
> @@ -922,4 +922,7 @@ static inline void shash_desc_zero(struct shash_desc *desc)
>  			 sizeof(*desc) + crypto_shash_descsize(desc->tfm));
>  }
>  
> +#define HMAC_IPAD_VALUE 0x36
> +#define HMAC_OPAD_VALUE 0x5c
> +
>  #endif	/* _CRYPTO_HASH_H */

I think this should go into a header file specific to hmac.  Since
I don't see an existing hmac header file you should create one for it.

Thanks,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt