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Date: Tue, 04 Jun 2024 19:31:33 +0300
Message-Id: <D1RDKBAGB7DD.CML0Z8K8Z5KI@kernel.org>
Cc: <linux-kernel@vger.kernel.org>, <lukas@wunner.de>
Subject: Re: [PATCH 1/2] crypto: ecdsa - Use ecc_digits_from_bytes to create
 hash digits array
From: "Jarkko Sakkinen" <jarkko@kernel.org>
To: "Stefan Berger" <stefanb@linux.ibm.com>, <keyrings@vger.kernel.org>,
 <linux-crypto@vger.kernel.org>, <herbert@gondor.apana.org.au>,
 <davem@davemloft.net>
References: <20240529230827.379111-1-stefanb@linux.ibm.com>
 <20240529230827.379111-2-stefanb@linux.ibm.com>
 <D1MQBJSYUBRS.12KH2S8FUK0XS@kernel.org>
 <899c3637-dc2a-4c73-9b8a-91e7b4da1638@linux.ibm.com>
In-Reply-To: <899c3637-dc2a-4c73-9b8a-91e7b4da1638@linux.ibm.com>

On Thu May 30, 2024 at 3:24 PM EEST, Stefan Berger wrote:
>
>
> On 5/30/24 01:28, Jarkko Sakkinen wrote:
> > On Thu May 30, 2024 at 2:08 AM EEST, Stefan Berger wrote:
> >> Since ecc_digits_from_bytes will provide zeros when an insufficient nu=
mber
> >> of bytes are passed in the input byte array, use it to create the hash
> >> digits directly from the input byte array. This avoids going through a=
n
> >> intermediate byte array (rawhash) that has the first few bytes filled =
with
> >> zeros.
> >>
> >> Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
> >> ---
> >>   crypto/ecdsa.c | 17 ++++-------------
> >>   1 file changed, 4 insertions(+), 13 deletions(-)
> >>
> >> diff --git a/crypto/ecdsa.c b/crypto/ecdsa.c
> >> index 258fffbf623d..fa029f36110b 100644
> >> --- a/crypto/ecdsa.c
> >> +++ b/crypto/ecdsa.c
> >> @@ -142,10 +142,8 @@ static int ecdsa_verify(struct akcipher_request *=
req)
> >>   	struct ecdsa_signature_ctx sig_ctx =3D {
> >>   		.curve =3D ctx->curve,
> >>   	};
> >> -	u8 rawhash[ECC_MAX_BYTES];
> >>   	u64 hash[ECC_MAX_DIGITS];
> >>   	unsigned char *buffer;
> >> -	ssize_t diff;
> >>   	int ret;
> >>  =20
> >>   	if (unlikely(!ctx->pub_key_set))
> >> @@ -164,18 +162,11 @@ static int ecdsa_verify(struct akcipher_request =
*req)
> >>   	if (ret < 0)
> >>   		goto error;
> >>  =20
> >> -	/* if the hash is shorter then we will add leading zeros to fit to n=
digits */
> >> -	diff =3D bufsize - req->dst_len;
> >> -	if (diff >=3D 0) {
> >> -		if (diff)
> >> -			memset(rawhash, 0, diff);
> >> -		memcpy(&rawhash[diff], buffer + req->src_len, req->dst_len);
> >> -	} else if (diff < 0) {
> >> -		/* given hash is longer, we take the left-most bytes */
> >> -		memcpy(&rawhash, buffer + req->src_len, bufsize);
> >> -	}
> >> +	if (bufsize > req->dst_len)
> >> +		bufsize =3D req->dst_len;
> >>  =20
> >> -	ecc_swap_digits((u64 *)rawhash, hash, ctx->curve->g.ndigits);
> >> +	ecc_digits_from_bytes(buffer + req->src_len, bufsize,
> >> +			      hash, ctx->curve->g.ndigits);
> >>  =20
> >>   	ret =3D _ecdsa_verify(ctx, hash, sig_ctx.r, sig_ctx.s);
> >>  =20
> >=20
> > Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
> >=20
> > I don't think it'd be even nit-picking to say that the function
> > called would really need kdoc. I had to spend about 20 minutes
> > to reacall ecc_digits_from_bytes().
>
> Here's the file with all the kdocs:=20
> https://elixir.bootlin.com/linux/v6.10-rc1/source/include/crypto/internal=
/ecc.h#L67

LOL, sorry I forgot this. I think this was the 2nd time I complained
about this ;-) I'm sorry, yeah that WFM.

Just not used to this convention but I don't mind actually if it is
that way.

BR, Jarkko