Commit d67c96fb authored by Stefan Berger's avatar Stefan Berger Committed by Herbert Xu
Browse files

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



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: default avatarLukas Wunner <lukas@wunner.de>
Tested-by: default avatarLukas Wunner <lukas@wunner.de>
Reviewed-by: default avatarJarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: default avatarStefan Berger <stefanb@linux.ibm.com>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
parent 526d23fc

crypto/ecdsa.c

+9 −5
Original line number Diff line number Diff line
@@ -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;

include/crypto/internal/ecc.h

+21 −0
Original line number Diff line number Diff line
@@ -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

 *