/*
* Copyright 2017-2019 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 "crypto/sm2.h"
#include "crypto/sm2err.h"
#include "crypto/ec.h" /* ec_group_do_inverse_ord() */
#include "internal/numbers.h"
#include <openssl/err.h>
#include <openssl/evp.h>
#include <openssl/err.h>
#include <openssl/bn.h>
#include <string.h>
int sm2_compute_z_digest(uint8_t *out,
const EVP_MD *digest,
const uint8_t *id,
const size_t id_len,
const EC_KEY *key)
{
int rc = 0;
const EC_GROUP *group = EC_KEY_get0_group(key);
BN_CTX *ctx = NULL;
EVP_MD_CTX *hash = NULL;
BIGNUM *p = NULL;
BIGNUM *a = NULL;
BIGNUM *b = NULL;
BIGNUM *xG = NULL;
BIGNUM *yG = NULL;
BIGNUM *xA = NULL;
BIGNUM *yA = NULL;
int p_bytes = 0;
uint8_t *buf = NULL;
uint16_t entl = 0;
uint8_t e_byte = 0;
hash = EVP_MD_CTX_new();
ctx = BN_CTX_new();
if (hash == NULL || ctx == NULL) {
SM2err(SM2_F_SM2_COMPUTE_Z_DIGEST, ERR_R_MALLOC_FAILURE);
goto done;
}
p = BN_CTX_get(ctx);
a = BN_CTX_get(ctx);
b = BN_CTX_get(ctx);
xG = BN_CTX_get(ctx);
yG = BN_CTX_get(ctx);
xA = BN_CTX_get(ctx);
yA = BN_CTX_get(ctx);
if (yA == NULL) {
SM2err(SM2_F_SM2_COMPUTE_Z_DIGEST, ERR_R_MALLOC_FAILURE);
goto done;
}
if (!EVP_DigestInit(hash, digest)) {
SM2err(SM2_F_SM2_COMPUTE_Z_DIGEST, ERR_R_EVP_LIB);
goto done;
}
/* Z = h(ENTL || ID || a || b || xG || yG || xA || yA) */
if (id_len >= (UINT16_MAX / 8)) {
/* too large */
SM2err(SM2_F_SM2_COMPUTE_Z_DIGEST, SM2_R_ID_TOO_LARGE);
goto done;
}
entl = (uint16_t)(8 * id_len);
e_byte = entl >> 8;
if (!EVP_DigestUpdate(hash, &e_byte, 1)) {
SM2err(SM2_F_SM2_COMPUTE_Z_DIGEST, ERR_R_EVP_LIB);
goto done;
}
e_byte = entl & 0xFF;
if (!EVP_DigestUpdate(hash, &e_byte, 1)) {
SM2err(SM2_F_SM2_COMPUTE_Z_DIGEST, ERR_R_EVP_LIB);
goto done;
}
if (id_len > 0 && !EVP_DigestUpdate(hash, id, id_len)) {
SM2err(SM2_F_SM2_COMPUTE_Z_DIGEST, ERR_R_EVP_LIB);
goto done;
}
if (!EC_GROUP_get_curve(group, p, a, b, ctx)) {
SM2err(SM2_F_SM2_COMPUTE_Z_DIGEST, ERR_R_EC_LIB);
goto done;
}
p_bytes = BN_num_bytes(p);
buf = OPENSSL_zalloc(p_bytes);
if (buf == NULL) {
SM2err(SM2_F_SM2_COMPUTE_Z_DIGEST, ERR_R_MALLOC_FAILURE);
goto done;
}
if (BN_bn2binpad(a, buf, p_bytes) < 0
|| !EVP_DigestUpdate(hash, buf, p_bytes)
|| BN_bn2binpad(b, buf, p_bytes) < 0
|| !EVP_DigestUpdate(hash, buf, p_bytes)
|| !EC_POINT_get_affine_coordinates(group,
EC_GROUP_get0_generator(group),
xG, yG, ctx)
|| BN_bn2binpad(xG, buf, p_bytes) < 0
|| !EVP_DigestUpdate(hash, buf, p_bytes)
|| BN_bn2binpad(yG, buf, p_bytes) < 0
|| !EVP_DigestUpdate(hash, buf, p_bytes)
|| !EC_POINT_get_affine_coordinates(group,
EC_KEY_get0_public_key(key),
xA, yA, ctx)
|| BN_bn2binpad(xA, buf, p_bytes) < 0
|| !EVP_DigestUpdate(hash, buf, p_bytes)
|| BN_bn2binpad(yA, buf, p_bytes) < 0
|| !EVP_DigestUpdate(hash, buf, p_bytes)
|| !EVP_DigestFinal(hash, out, NULL)) {
SM2err(SM2_F_SM2_COMPUTE_Z_DIGEST, ERR_R_INTERNAL_ERROR);
goto done;
}
rc = 1;
done:
OPENSSL_free(buf);
BN_CTX_free(ctx);
EVP_MD_CTX_free(hash);
return rc;
}
static BIGNUM *sm2_compute_msg_hash(const EVP_MD *digest,
const EC_KEY *key,
const uint8_t *id,
const size_t id_len,
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 *z = NULL;
BIGNUM *e = NULL;
if (md_size < 0) {
SM2err(SM2_F_SM2_COMPUTE_MSG_HASH, SM2_R_INVALID_DIGEST);
goto done;
}
z = OPENSSL_zalloc(md_size);
if (hash == NULL || z == NULL) {
SM2err(SM2_F_SM2_COMPUTE_MSG_HASH, ERR_R_MALLOC_FAILURE);
goto done;
}
if (!sm2_compute_z_digest(z, digest, id, id_len, key)) {
/* SM2err already called */
goto done;
}
if (!EVP_DigestInit(hash, digest)
|| !EVP_DigestUpdate(hash, z, md_size)
|| !EVP_DigestUpdate(hash, msg, msg_len)
/* reuse z buffer to hold H(Z || M) */
|| !EVP_DigestFinal(hash, z, NULL)) {
SM2err(SM2_F_SM2_COMPUTE_MSG_HASH, ERR_R_EVP_LIB);
goto done;
}
e = BN_bin2bn(z, md_size, NULL);
if (e == NULL)
SM2err(SM2_F_SM2_COMPUTE_MSG_HASH, ERR_R_INTERNAL_ERROR);
done:
OPENSSL_free(z);
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);
ctx = BN_CTX_new();
if (kG == NULL || ctx == NULL) {
SM2err(SM2_F_SM2_SIG_GEN, ERR_R_MALLOC_FAILURE);
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) {
SM2err(SM2_F_SM2_SIG_GEN, ERR_R_MALLOC_FAILURE);
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) {
SM2err(SM2_F_SM2_SIG_GEN, ERR_R_MALLOC_FAILURE);
goto done;
}
for (;;) {
if (!BN_priv_rand_range(k, order)) {
SM2err(SM2_F_SM2_SIG_GEN, ERR_R_INTERNAL_ERROR);
goto done;
}
if (!EC_POINT_mul(group, kG, k, NULL, NULL, ctx)
|| !EC_POINT_get_affine_coordinates(group, kG, x1, NULL,
ctx)
|| !BN_mod_add(r, e, x1, order, ctx)) {
SM2err(SM2_F_SM2_SIG_GEN, ERR_R_INTERNAL_ERROR);
goto done;
}
/* try again if r == 0 or r+k == n */
if (BN_is_zero(r))
continue;
if (!BN_add(rk, r, k)) {
SM2err(SM2_F_SM2_SIG_GEN, ERR_R_INTERNAL_ERROR);
goto done;
}
if (BN_cmp(rk, order) == 0)
continue;
if (!BN_add(s, dA, BN_value_one())
|| !ec_group_do_inverse_ord(group, s, s, ctx)
|| !BN_mod_mul(tmp, dA, r, order, ctx)
|| !BN_sub(tmp, k, tmp)
|| !BN_mod_mul(s, s, tmp, order, ctx)) {
SM2err(SM2_F_SM2_SIG_GEN, ERR_R_BN_LIB);
goto done;
}
sig = ECDSA_SIG_new();
if (sig == NULL) {
SM2err(SM2_F_SM2_SIG_GEN, ERR_R_MALLOC_FAILURE);
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();
pt = EC_POINT_new(group);
if (ctx == NULL || pt == NULL) {
SM2err(SM2_F_SM2_SIG_VERIFY, ERR_R_MALLOC_FAILURE);
goto done;
}
BN_CTX_start(ctx);
t = BN_CTX_get(ctx);
x1 = BN_CTX_get(ctx);
if (x1 == NULL) {
SM2err(SM2_F_SM2_SIG_VERIFY, ERR_R_MALLOC_FAILURE);
goto done;
}
/*
* B1: verify whether r' in [1,n-1], verification failed if not
* B2: verify 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, verification pass if yes, otherwise failed
*/
ECDSA_SIG_get0(sig, &r, &s);
if (BN_cmp(r, BN_value_one()) < 0
|| BN_cmp(s, BN_value_one()) < 0
|| BN_cmp(order, r) <= 0
|| BN_cmp(order, s) <= 0) {
SM2err(SM2_F_SM2_SIG_VERIFY, SM2_R_BAD_SIGNATURE);
goto done;
}
if (!BN_mod_add(t, r, s, order, ctx)) {
SM2err(SM2_F_SM2_SIG_VERIFY, ERR_R_BN_LIB);
goto done;
}
if (BN_is_zero(t)) {
SM2err(SM2_F_SM2_SIG_VERIFY, SM2_R_BAD_SIGNATURE);
goto done;
}
if (!EC_POINT_mul(group, pt, s, EC_KEY_get0_public_key(key), t, ctx)
|| !EC_POINT_get_affine_coordinates(group, pt, x1, NULL, ctx)) {
SM2err(SM2_F_SM2_SIG_VERIFY, ERR_R_EC_LIB);
goto done;
}
if (!BN_mod_add(t, e, x1, order, ctx)) {
SM2err(SM2_F_SM2_SIG_VERIFY, ERR_R_BN_LIB);
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 uint8_t *id,
const size_t id_len,
const uint8_t *msg, size_t msg_len)
{
BIGNUM *e = NULL;
ECDSA_SIG *sig = NULL;
e = sm2_compute_msg_hash(digest, key, id, id_len, msg, msg_len);
if (e == NULL) {
/* SM2err already called */
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 uint8_t *id,
const size_t id_len,
const uint8_t *msg, size_t msg_len)
{
BIGNUM *e = NULL;
int ret = 0;
e = sm2_compute_msg_hash(digest, key, id, id_len, msg, msg_len);
if (e == NULL) {
/* SM2err already called */
goto done;
}
ret = sm2_sig_verify(key, sig, e);
done:
BN_free(e);
return ret;
}
int sm2_sign(const unsigned char *dgst, int dgstlen,
unsigned char *sig, unsigned int *siglen, EC_KEY *eckey)
{
BIGNUM *e = NULL;
ECDSA_SIG *s = NULL;
int sigleni;
int ret = -1;
e = BN_bin2bn(dgst, dgstlen, NULL);
if (e == NULL) {
SM2err(SM2_F_SM2_SIGN, ERR_R_BN_LIB);
goto done;
}
s = sm2_sig_gen(eckey, e);
sigleni = i2d_ECDSA_SIG(s, &sig);
if (sigleni < 0) {
SM2err(SM2_F_SM2_SIGN, ERR_R_INTERNAL_ERROR);
goto done;
}
*siglen = (unsigned int)sigleni;
ret = 1;
done:
ECDSA_SIG_free(s);
BN_free(e);
return ret;
}
int sm2_verify(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;
s = ECDSA_SIG_new();
if (s == NULL) {
SM2err(SM2_F_SM2_VERIFY, ERR_R_MALLOC_FAILURE);
goto done;
}
if (d2i_ECDSA_SIG(&s, &p, sig_len) == NULL) {
SM2err(SM2_F_SM2_VERIFY, SM2_R_INVALID_ENCODING);
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) {
SM2err(SM2_F_SM2_VERIFY, SM2_R_INVALID_ENCODING);
goto done;
}
e = BN_bin2bn(dgst, dgstlen, NULL);
if (e == NULL) {
SM2err(SM2_F_SM2_VERIFY, ERR_R_BN_LIB);
goto done;
}
ret = sm2_sig_verify(eckey, s, e);
done:
OPENSSL_free(der);
BN_free(e);
ECDSA_SIG_free(s);
return ret;
}