On Thu May 30, 2024 at 2:08 AM EEST, Stefan Berger wrote:
> Since ecc_digits_from_bytes will provide zeros when an insufficient number
> 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 an
> intermediate byte array (rawhash) that has the first few bytes filled with
> zeros.
>
> Signed-off-by: Stefan Berger <stefanb@xxxxxxxxxxxxx>
> ---
> 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 = {
> .curve = ctx->curve,
> };
> - u8 rawhash[ECC_MAX_BYTES];
> u64 hash[ECC_MAX_DIGITS];
> unsigned char *buffer;
> - ssize_t diff;
> int ret;
>
> if (unlikely(!ctx->pub_key_set))
> @@ -164,18 +162,11 @@ static int ecdsa_verify(struct akcipher_request *req)
> if (ret < 0)
> goto error;
>
> - /* if the hash is shorter then we will add leading zeros to fit to ndigits */
> - diff = bufsize - req->dst_len;
> - if (diff >= 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 = req->dst_len;
>
> - ecc_swap_digits((u64 *)rawhash, hash, ctx->curve->g.ndigits);
> + ecc_digits_from_bytes(buffer + req->src_len, bufsize,
> + hash, ctx->curve->g.ndigits);
>
> ret = _ecdsa_verify(ctx, hash, sig_ctx.r, sig_ctx.s);
>
Reviewed-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx>
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().
Like something to remind what, how and why... So that you can
recap quickly. Once I got grip of it (for the 2nd time) the
code itself was just fine, no complains on that.
BR, Jarkko
