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crypto: ecdsa - Convert byte arrays with key coordinates to digits

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For NIST P192/256/384 the public key's x and y parameters could be copied
directly from a given array since both parameters filled 'ndigits' of
digits (a 'digit' is a u64). For support of NIST P521 the key parameters
need to have leading zeros prepended to the most significant digit since
only 2 bytes of the most significant digit are provided.

Therefore, implement ecc_digits_from_bytes to convert a byte array into an
array of digits and use this function in ecdsa_set_pub_key where an input
byte array needs to be converted into digits.

Suggested-by: Lukas Wunner <lukas@wunner.de>
Tested-by: Lukas Wunner <lukas@wunner.de>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Stefan Berger 2024-04-04 10:18:45 -04:00 committed by Herbert Xu
parent 526d23fc2d
commit d67c96fb97
2 changed files with 30 additions and 5 deletions
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14
crypto/ecdsa.c
View File

@ -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);
@ -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));
if (ndigits != ctx->curve->g.ndigits)
return -EINVAL;
ecc_swap_digits(digits, ctx->pub_key.x, ndigits);
ecc_swap_digits(&digits[ndigits], ctx->pub_key.y, ndigits);
d++;
ecc_digits_from_bytes(d, digitlen, ctx->pub_key.x, ndigits);
ecc_digits_from_bytes(&d[digitlen], digitlen, ctx->pub_key.y, ndigits);
ret = ecc_is_pubkey_valid_full(ctx->curve, &ctx->pub_key);
ctx->pub_key_set = ret == 0;

21
include/crypto/internal/ecc.h
View File

@ -56,6 +56,27 @@ static inline void ecc_swap_digits(const void *in, u64 *out, unsigned int ndigit
out[i] = get_unaligned_be64(&src[ndigits - 1 - i]);
}
/**
* ecc_digits_from_bytes() - Create ndigits-sized digits array from byte array
* @in: Input byte array
* @nbytes Size of input byte array
* @out Output digits array
* @ndigits: Number of digits to create from byte array
*/
static inline void ecc_digits_from_bytes(const u8 *in, unsigned int nbytes,
u64 *out, unsigned int ndigits)
{
unsigned int o = nbytes & 7;
__be64 msd = 0;
if (o) {
memcpy((u8 *)&msd + sizeof(msd) - o, in, o);
out[--ndigits] = be64_to_cpu(msd);
in += o;
}
ecc_swap_digits(in, out, ndigits);
}
/**
* ecc_is_key_valid() - Validate a given ECDH private key
*