text: /*
   * Copyright 2017-2020 The OpenSSL Project Authors. All Rights Reserved.
   * Copyright 2017 Ribose Inc. All Rights Reserved.
   * Ported from Ribose contributions from Botan.
   *
   * Licensed under the Apache License 2.0 (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_ex(ec_key_get_libctx(key));
      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;
      EVP_MD *fetched_digest = NULL;
      OSSL_LIB_CTX *libctx = ec_key_get_libctx(key);
      const char *propq = ec_key_get0_propq(key);
  
      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;
      }
  
      fetched_digest = EVP_MD_fetch(libctx, EVP_MD_name(digest), propq);
      if (fetched_digest == NULL) {
          SM2err(SM2_F_SM2_COMPUTE_MSG_HASH, ERR_R_INTERNAL_ERROR);
          goto done;
      }
  
      if (!sm2_compute_z_digest(z, fetched_digest, id, id_len, key)) {
          /* SM2err already called */
          goto done;
      }
  
      if (!EVP_DigestInit(hash, fetched_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:
      EVP_MD_free(fetched_digest);
      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;
      OSSL_LIB_CTX *libctx = ec_key_get_libctx(key);
  
      kG = EC_POINT_new(group);
      ctx = BN_CTX_new_ex(libctx);
      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_ex(k, order, ctx)) {
              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;
      OSSL_LIB_CTX *libctx = ec_key_get_libctx(key);
  
      ctx = BN_CTX_new_ex(libctx);
      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_internal_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(0, ERR_R_BN_LIB);
         goto done;
      }
  
      s = sm2_sig_gen(eckey, e);
      if (s == NULL) {
          SM2err(0, ERR_R_INTERNAL_ERROR);
          goto done;
      }
  
      sigleni = i2d_ECDSA_SIG(s, &sig);
      if (sigleni < 0) {
         SM2err(0, ERR_R_INTERNAL_ERROR);
         goto done;
      }
      *siglen = (unsigned int)sigleni;
  
      ret = 1;
  
   done:
      ECDSA_SIG_free(s);
      BN_free(e);
      return ret;
  }
  
  int sm2_internal_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(0, ERR_R_MALLOC_FAILURE);
          goto done;
      }
      if (d2i_ECDSA_SIG(&s, &p, sig_len) == NULL) {
          SM2err(0, 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(0, SM2_R_INVALID_ENCODING);
          goto done;
      }
  
      e = BN_bin2bn(dgst, dgstlen, NULL);
      if (e == NULL) {
          SM2err(0, 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;
  }
  