sm2_sign.c
/*
* Copyright 2017-2018 The OpenSSL Project Authors. All Rights Reserved.
* Copyright 2017 Ribose Inc. All Rights Reserved.
* Ported from Ribose contributions from Botan.
*
* Licensed under the OpenSSL license (the "License"). You may not use
* this file except in compliance with the License. You can obtain a copy
* in the file LICENSE in the source distribution or at
* https://www.openssl.org/source/license.html
*/
#include <openssl/sm2.h>
#include <openssl/evp.h>
#include <openssl/bn.h>
#include <string.h>
static BIGNUM *compute_msg_hash(const EVP_MD *digest,
const EC_KEY *key,
const char *user_id,
const uint8_t *msg, size_t msg_len)
{
EVP_MD_CTX *hash = EVP_MD_CTX_new();
const int md_size = EVP_MD_size(digest);
uint8_t *za = OPENSSL_zalloc(md_size);
BIGNUM *e = NULL;
if (za == NULL)
goto done;
if (hash == NULL)
goto done;
if (SM2_compute_userid_digest(za, digest, user_id, key) == 0)
goto done;
if (EVP_DigestInit(hash, digest) == 0)
goto done;
if (EVP_DigestUpdate(hash, za, md_size) == 0)
goto done;
if (EVP_DigestUpdate(hash, msg, msg_len) == 0)
goto done;
/* reuse za buffer to hold H(ZA || M) */
if (EVP_DigestFinal(hash, za, NULL) == 0)
goto done;
e = BN_bin2bn(za, md_size, NULL);
done:
OPENSSL_free(za);
EVP_MD_CTX_free(hash);
return e;
}
static
ECDSA_SIG *SM2_sig_gen(const EC_KEY *key, const BIGNUM *e)
{
const BIGNUM *dA = EC_KEY_get0_private_key(key);
const EC_GROUP *group = EC_KEY_get0_group(key);
const BIGNUM *order = EC_GROUP_get0_order(group);
ECDSA_SIG *sig = NULL;
EC_POINT *kG = NULL;
BN_CTX *ctx = NULL;
BIGNUM *k = NULL;
BIGNUM *rk = NULL;
BIGNUM *r = NULL;
BIGNUM *s = NULL;
BIGNUM *x1 = NULL;
BIGNUM *tmp = NULL;
kG = EC_POINT_new(group);
if (kG == NULL)
goto done;
ctx = BN_CTX_new();
if (ctx == NULL)
goto done;
BN_CTX_start(ctx);
k = BN_CTX_get(ctx);
rk = BN_CTX_get(ctx);
x1 = BN_CTX_get(ctx);
tmp = BN_CTX_get(ctx);
if (tmp == NULL)
goto done;
/* These values are returned and so should not be allocated out of the context */
r = BN_new();
s = BN_new();
if (r == NULL || s == NULL)
goto done;
for (;;) {
BN_priv_rand_range(k, order);
if (EC_POINT_mul(group, kG, k, NULL, NULL, ctx) == 0)
goto done;
if (EC_POINT_get_affine_coordinates_GFp(group, kG, x1, NULL, ctx) == 0)
goto done;
if (BN_mod_add(r, e, x1, order, ctx) == 0)
goto done;
/* try again if r == 0 or r+k == n */
if (BN_is_zero(r))
continue;
BN_add(rk, r, k);
if (BN_cmp(rk, order) == 0)
continue;
BN_add(s, dA, BN_value_one());
BN_mod_inverse(s, s, order, ctx);
BN_mod_mul(tmp, dA, r, order, ctx);
BN_sub(tmp, k, tmp);
BN_mod_mul(s, s, tmp, order, ctx);
sig = ECDSA_SIG_new();
if (sig == NULL)
goto done;
/* takes ownership of r and s */
ECDSA_SIG_set0(sig, r, s);
break;
}
done:
if (sig == NULL) {
BN_free(r);
BN_free(s);
}
BN_CTX_free(ctx);
EC_POINT_free(kG);
return sig;
}
static
int SM2_sig_verify(const EC_KEY *key, const ECDSA_SIG *sig, const BIGNUM *e)
{
int ret = 0;
const EC_GROUP *group = EC_KEY_get0_group(key);
const BIGNUM *order = EC_GROUP_get0_order(group);
BN_CTX *ctx = NULL;
EC_POINT *pt = NULL;
BIGNUM *t = NULL;
BIGNUM *x1 = NULL;
const BIGNUM *r = NULL;
const BIGNUM *s = NULL;
ctx = BN_CTX_new();
if (ctx == NULL)
goto done;
pt = EC_POINT_new(group);
if (pt == NULL)
goto done;
BN_CTX_start(ctx);
t = BN_CTX_get(ctx);
x1 = BN_CTX_get(ctx);
if (x1 == NULL)
goto done;
/*
B1: verify whether r' in [1,n-1], verification failed if not
B2: vefify whether s' in [1,n-1], verification failed if not
B3: set M'~=ZA || M'
B4: calculate e'=Hv(M'~)
B5: calculate t = (r' + s') modn, verification failed if t=0
B6: calculate the point (x1', y1')=[s']G + [t]PA
B7: calculate R=(e'+x1') modn, verfication pass if yes, otherwise failed
*/
ECDSA_SIG_get0(sig, &r, &s);
if (BN_cmp(r, BN_value_one()) < 0)
goto done;
if (BN_cmp(s, BN_value_one()) < 0)
goto done;
if (BN_cmp(order, r) <= 0)
goto done;
if (BN_cmp(order, s) <= 0)
goto done;
if (BN_mod_add(t, r, s, order, ctx) == 0)
goto done;
if (BN_is_zero(t) == 1)
goto done;
if (EC_POINT_mul(group, pt, s, EC_KEY_get0_public_key(key), t, ctx) == 0)
goto done;
if (EC_POINT_get_affine_coordinates_GFp(group, pt, x1, NULL, ctx) == 0)
goto done;
if (BN_mod_add(t, e, x1, order, ctx) == 0)
goto done;
if (BN_cmp(r, t) == 0)
ret = 1;
done:
EC_POINT_free(pt);
BN_CTX_free(ctx);
return ret;
}
ECDSA_SIG *SM2_do_sign(const EC_KEY *key,
const EVP_MD *digest,
const char *user_id, const uint8_t *msg, size_t msg_len)
{
BIGNUM *e = NULL;
ECDSA_SIG *sig = NULL;
e = compute_msg_hash(digest, key, user_id, msg, msg_len);
if (e == NULL)
goto done;
sig = SM2_sig_gen(key, e);
done:
BN_free(e);
return sig;
}
int SM2_do_verify(const EC_KEY *key,
const EVP_MD *digest,
const ECDSA_SIG *sig,
const char *user_id, const uint8_t *msg, size_t msg_len)
{
BIGNUM *e = NULL;
int ret = -1;
e = compute_msg_hash(digest, key, user_id, msg, msg_len);
if (e == NULL)
goto done;
ret = SM2_sig_verify(key, sig, e);
done:
BN_free(e);
return ret;
}
int SM2_sign(int type, const unsigned char *dgst, int dgstlen,
unsigned char *sig, unsigned int *siglen, EC_KEY *eckey)
{
BIGNUM *e = NULL;
ECDSA_SIG *s = NULL;
int ret = -1;
if (type != NID_sm3)
goto done;
if (dgstlen != 32) /* expected length of SM3 hash */
goto done;
e = BN_bin2bn(dgst, dgstlen, NULL);
s = SM2_sig_gen(eckey, e);
*siglen = i2d_ECDSA_SIG(s, &sig);
ECDSA_SIG_free(s);
ret = 0;
done:
ECDSA_SIG_free(s);
BN_free(e);
return ret;
}
int SM2_verify(int type, const unsigned char *dgst, int dgstlen,
const unsigned char *sig, int sig_len, EC_KEY *eckey)
{
ECDSA_SIG *s = NULL;
BIGNUM *e = NULL;
const unsigned char *p = sig;
unsigned char *der = NULL;
int derlen = -1;
int ret = -1;
if (type != NID_sm3)
goto done;
s = ECDSA_SIG_new();
if (s == NULL)
goto done;
if (d2i_ECDSA_SIG(&s, &p, sig_len) == NULL)
goto done;
/* Ensure signature uses DER and doesn't have trailing garbage */
derlen = i2d_ECDSA_SIG(s, &der);
if (derlen != sig_len || memcmp(sig, der, derlen) != 0)
goto done;
e = BN_bin2bn(dgst, dgstlen, NULL);
ret = SM2_sig_verify(eckey, s, e);
done:
OPENSSL_free(der);
BN_free(e);
ECDSA_SIG_free(s);
return ret;
}
