linux-kernel - Re: [PATCH] crypto: extend ansi_cprng to allow resetting of DT value

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Date:	Tue, 4 Nov 2008 16:04:24 -0500
From:	Jarod Wilson <jarod@...hat.com>
To:	Neil Horman <nhorman@...driver.com>
Cc:	herbert@...dor.apana.org.au, davem@...emloft.net,
	linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] crypto: extend ansi_cprng to allow resetting of DT value

On Monday 03 November 2008 16:22:40 Neil Horman wrote:
> Hey all-
> 	This is a patch that was sent to me by Jarod Wilson, marking off my
> outstanding todo to allow the ansi cprng to set/reset the DT counter value
> in a cprng instance.  Currently crytpo_rng_reset accepts a seed byte array
> which is interpreted by the ansi_cprng as a {V key} tuple.  This patch
> extends that tuple to now be {V key DT}, with DT an optional value during
> reset.  This patch also fixes  a bug we noticed in which the offset of the
> key area of the seed is started at DEFAULT_PRNG_KSZ rather than
> DEFAULT_BLK_SZ as it should be.
>
> Regards
> Neil
>
> Signed-off-by: Neil Horman <nhorman@...driver.com>

Even better than my original version, since it lets providing a DT value be 
optional. Go ahead and slap this on there too:

Signed-off-by: Jarod Wilson <jarod@...hat.com>


>  ansi_cprng.c |   16 +++++++++++++---
>  1 file changed, 13 insertions(+), 3 deletions(-)
>
>
> diff --git a/crypto/ansi_cprng.c b/crypto/ansi_cprng.c
> index 72db0fd..486aa93 100644
> --- a/crypto/ansi_cprng.c
> +++ b/crypto/ansi_cprng.c
> @@ -349,15 +349,25 @@ static int cprng_get_random(struct crypto_rng *tfm,
> u8 *rdata, return get_prng_bytes(rdata, dlen, prng);
>  }
>
> +/*
> + *  This is the cprng_registered reset method the seed value is
> + *  interpreted as the tuple { V KEY DT}
> + *  V and KEY are required during reset, and DT is optional, detected
> + *  as being present by testing the length of the seed
> + */
>  static int cprng_reset(struct crypto_rng *tfm, u8 *seed, unsigned int
> slen) {
>  	struct prng_context *prng = crypto_rng_ctx(tfm);
> -	u8 *key = seed + DEFAULT_PRNG_KSZ;
> +	u8 *key = seed + DEFAULT_BLK_SZ;
> +	u8 *dt = NULL;
>
>  	if (slen < DEFAULT_PRNG_KSZ + DEFAULT_BLK_SZ)
>  		return -EINVAL;
>
> -	reset_prng_context(prng, key, DEFAULT_PRNG_KSZ, seed, NULL);
> +	if (slen >= (2 * DEFAULT_BLK_SZ + DEFAULT_PRNG_KSZ))
> +		dt = key + DEFAULT_PRNG_KSZ;
> +
> +	reset_prng_context(prng, key, DEFAULT_PRNG_KSZ, seed, dt);
>
>  	if (prng->flags & PRNG_NEED_RESET)
>  		return -EINVAL;
> @@ -379,7 +389,7 @@ static struct crypto_alg rng_alg = {
>  		.rng = {
>  			.rng_make_random	= cprng_get_random,
>  			.rng_reset		= cprng_reset,
> -			.seedsize = DEFAULT_PRNG_KSZ + DEFAULT_BLK_SZ,
> +			.seedsize = DEFAULT_PRNG_KSZ + 2*DEFAULT_BLK_SZ,
>  		}
>  	}
>  };

-- 
Jarod Wilson
jarod@...hat.com

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