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

[Stefan Berger]

On 3/2/24 16:34, Lukas Wunner wrote:
> 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.

I would prefer 'digitlen' rather than repurposing keylen and giving it a 
different meaning...

   Stefan
> Thanks,
>
> Lukas