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Date:   Wed, 3 Jul 2019 21:56:32 +0800
From:   Herbert Xu <herbert@gondor.apana.org.au>
To:     Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc:     linux-crypto@vger.kernel.org, ebiggers@kernel.org,
        horia.geanta@nxp.com
Subject: Re: [PATCH v3 27/30] crypto: des - split off DES library from
 generic DES cipher driver
Message-ID: <20190703135632.cizz77mr7ur3tii7@gondor.apana.org.au>
References: <20190628093529.12281-1-ard.biesheuvel@linaro.org>
 <20190628093529.12281-28-ard.biesheuvel@linaro.org>
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On Fri, Jun 28, 2019 at 11:35:26AM +0200, Ard Biesheuvel wrote:
>
>  static int des_setkey(struct crypto_tfm *tfm, const u8 *key,
>  		      unsigned int keylen)
>  {
>  	struct des_ctx *dctx = crypto_tfm_ctx(tfm);
> -	u32 *flags = &tfm->crt_flags;
> -	u32 tmp[DES_EXPKEY_WORDS];
> -	int ret;
> -
> -	/* Expand to tmp */
> -	ret = des_ekey(tmp, key);
> +	int err;
>  
> -	if (unlikely(ret == 0) && (*flags & CRYPTO_TFM_REQ_FORBID_WEAK_KEYS)) {
> -		*flags |= CRYPTO_TFM_RES_WEAK_KEY;
> -		return -EINVAL;
> +	err = des_expand_key(dctx, key, keylen);
> +	if (err == -ENOKEY) {
> +		if (crypto_tfm_get_flags(tfm) & CRYPTO_TFM_REQ_FORBID_WEAK_KEYS)
> +			err = -EINVAL;
> +		else
> +			err = 0;
>  	}
>  
> -	/* Copy to output */
> -	memcpy(dctx->expkey, tmp, sizeof(dctx->expkey));
> -
> -	return 0;
> +	if (err) {
> +		memzero_explicit(dctx, sizeof(*dctx));

This should use memset as it's not a stack location.  Ditto with
the 3DES version below.  It may not look like a big deal but we
sometimes get bogus patches that convert such memsets to memzeros
and being consistent with our own usage might discourage them.

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