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crypto: ecdsa - Use ecc_digits_from_bytes to convert signature

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Since ecc_digits_from_bytes will provide zeros when an insufficient number
of bytes are passed in the input byte array, use it to convert the r and s
components of the signature to digits directly from the input byte
array. This avoids going through an intermediate byte array that has the
first few bytes filled with zeros.

Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Stefan Berger 2024-05-29 19:08:27 -04:00 committed by Herbert Xu
parent 2fd2a82ccb
commit 546ce0bdc9
1 changed files with 2 additions and 10 deletions
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12
crypto/ecdsa.c
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@ -38,7 +38,6 @@ static int ecdsa_get_signature_rs(u64 *dest, size_t hdrlen, unsigned char tag,
size_t bufsize = ndigits * sizeof(u64);
ssize_t diff = vlen - bufsize;
const char *d = value;
u8 rs[ECC_MAX_BYTES];
if (!value || !vlen)
return -EINVAL;
@ -46,7 +45,7 @@ static int ecdsa_get_signature_rs(u64 *dest, size_t hdrlen, unsigned char tag,
/* diff = 0: 'value' has exacly the right size
* diff > 0: 'value' has too many bytes; one leading zero is allowed that
* makes the value a positive integer; error on more
* diff < 0: 'value' is missing leading zeros, which we add
* diff < 0: 'value' is missing leading zeros
*/
if (diff > 0) {
/* skip over leading zeros that make 'value' a positive int */
@ -61,14 +60,7 @@ static int ecdsa_get_signature_rs(u64 *dest, size_t hdrlen, unsigned char tag,
if (-diff >= bufsize)
return -EINVAL;
if (diff) {
/* leading zeros not given in 'value' */
memset(rs, 0, -diff);
}
memcpy(&rs[-diff], d, vlen);
ecc_swap_digits((u64 *)rs, dest, ndigits);
ecc_digits_from_bytes(d, vlen, dest, ndigits);
return 0;
}