Re: [PATCH v4 01/12] crypto: ecdsa - Convert byte arrays with key coordinates to digits

Lukas Wunner
2024-03-02T21:34:29Z

On Thu, Feb 29, 2024 at 09:19:56PM -0500, Stefan Berger wrote:
> --- a/crypto/ecdsa.c
> +++ b/crypto/ecdsa.c
> @@ -222,9 +222,8 @@ static int ecdsa_ecc_ctx_reset(struct ecc_ctx *ctx)
> static int ecdsa_set_pub_key(struct crypto_akcipher *tfm, const void *key, unsigned int keylen)
> {
> struct ecc_ctx *ctx = akcipher_tfm_ctx(tfm);
> + unsigned int digitlen, ndigits;
> const unsigned char *d = key;
> - const u64 *digits = (const u64 *)&d[1];
> - unsigned int ndigits;
> int ret;
>
> ret = ecdsa_ecc_ctx_reset(ctx);

Hm, the removal of digits isn't strictly necessary. If you would keep it,
the patch would become simpler (fewer lines changes).

> @@ -238,12 +237,17 @@ static int ecdsa_set_pub_key(struct crypto_akcipher *tfm, const void *key, unsig
> return -EINVAL;
>
> keylen--;
> - ndigits = (keylen >> 1) / sizeof(u64);
> + digitlen = keylen >> 1;
> +
> + ndigits = DIV_ROUND_UP(digitlen, sizeof(u64));

Instead of introducing an additional digitlen variable, you could just
use keylen. It seems it's not used in the remainder of the function,
so modifying it is harmless:

keylen--;
+ keylen >>= 1;
- ndigits = (keylen >> 1) / sizeof(u64);
+ ndigits = DIV_ROUND_UP(digitlen, sizeof(u64));

Just a suggestion.

Thanks,

Lukas