text: /*
   * Copyright 2002-2017 The OpenSSL Project Authors. All Rights Reserved.
   *
   * 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 <string.h>
  #include <openssl/err.h>
  #include <openssl/obj_mac.h>
  #include <openssl/bn.h>
  #include <openssl/rand.h>
  #include <openssl/ec.h>
  #include "ec_lcl.h"
  
  int ossl_ecdsa_sign(int type, const unsigned char *dgst, int dlen,
                      unsigned char *sig, unsigned int *siglen,
                      const BIGNUM *kinv, const BIGNUM *r, EC_KEY *eckey)
  {
      ECDSA_SIG *s;
      RAND_seed(dgst, dlen);
      s = ECDSA_do_sign_ex(dgst, dlen, kinv, r, eckey);
      if (s == NULL) {
          *siglen = 0;
          return 0;
      }
      *siglen = i2d_ECDSA_SIG(s, &sig);
      ECDSA_SIG_free(s);
      return 1;
  }
  
  static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in,
                              BIGNUM **kinvp, BIGNUM **rp,
                              const unsigned char *dgst, int dlen)
  {
      BN_CTX *ctx = NULL;
      BIGNUM *k = NULL, *r = NULL, *X = NULL;
      const BIGNUM *order;
      EC_POINT *tmp_point = NULL;
      const EC_GROUP *group;
      int ret = 0;
      int order_bits;
  
      if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL) {
          ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_PASSED_NULL_PARAMETER);
          return 0;
      }
  
      if (!EC_KEY_can_sign(eckey)) {
          ECerr(EC_F_ECDSA_SIGN_SETUP, EC_R_CURVE_DOES_NOT_SUPPORT_SIGNING);
          return 0;
      }
  
      if (ctx_in == NULL) {
          if ((ctx = BN_CTX_new()) == NULL) {
              ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_MALLOC_FAILURE);
              return 0;
          }
      } else
          ctx = ctx_in;
  
      k = BN_new();               /* this value is later returned in *kinvp */
      r = BN_new();               /* this value is later returned in *rp */
      X = BN_new();
      if (k == NULL || r == NULL || X == NULL) {
          ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_MALLOC_FAILURE);
          goto err;
      }
      if ((tmp_point = EC_POINT_new(group)) == NULL) {
          ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
          goto err;
      }
      order = EC_GROUP_get0_order(group);
      if (order == NULL) {
          ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
          goto err;
      }
  
      /* Preallocate space */
      order_bits = BN_num_bits(order);
      if (!BN_set_bit(k, order_bits)
          || !BN_set_bit(r, order_bits)
          || !BN_set_bit(X, order_bits))
          goto err;
  
      do {
          /* get random k */
          do
              if (dgst != NULL) {
                  if (!BN_generate_dsa_nonce
                      (k, order, EC_KEY_get0_private_key(eckey), dgst, dlen,
                       ctx)) {
                      ECerr(EC_F_ECDSA_SIGN_SETUP,
                               EC_R_RANDOM_NUMBER_GENERATION_FAILED);
                      goto err;
                  }
              } else {
                  if (!BN_rand_range(k, order)) {
                      ECerr(EC_F_ECDSA_SIGN_SETUP,
                               EC_R_RANDOM_NUMBER_GENERATION_FAILED);
                      goto err;
                  }
              }
          while (BN_is_zero(k));
  
          /*
           * We do not want timing information to leak the length of k, so we
           * compute G*k using an equivalent scalar of fixed bit-length.
           *
           * We unconditionally perform both of these additions to prevent a
           * small timing information leakage.  We then choose the sum that is
           * one bit longer than the order.  This guarantees the code
           * path used in the constant time implementations elsewhere.
           *
           * TODO: revisit the BN_copy aiming for a memory access agnostic
           * conditional copy.
           */
          if (!BN_add(r, k, order)
              || !BN_add(X, r, order)
              || !BN_copy(k, BN_num_bits(r) > order_bits ? r : X))
              goto err;
  
          /* compute r the x-coordinate of generator * k */
          if (!EC_POINT_mul(group, tmp_point, k, NULL, NULL, ctx)) {
              ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
              goto err;
          }
          if (EC_METHOD_get_field_type(EC_GROUP_method_of(group)) ==
              NID_X9_62_prime_field) {
              if (!EC_POINT_get_affine_coordinates_GFp
                  (group, tmp_point, X, NULL, ctx)) {
                  ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
                  goto err;
              }
          }
  #ifndef OPENSSL_NO_EC2M
          else {                  /* NID_X9_62_characteristic_two_field */
  
              if (!EC_POINT_get_affine_coordinates_GF2m(group,
                                                        tmp_point, X, NULL,
                                                        ctx)) {
                  ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
                  goto err;
              }
          }
  #endif
          if (!BN_nnmod(r, X, order, ctx)) {
              ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
              goto err;
          }
      }
      while (BN_is_zero(r));
  
      /* compute the inverse of k */
      if (EC_GROUP_get_mont_data(group) != NULL) {
          /*
           * We want inverse in constant time, therefore we utilize the fact
           * order must be prime and use Fermats Little Theorem instead.
           */
          if (!BN_set_word(X, 2)) {
              ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
              goto err;
          }
          if (!BN_mod_sub(X, order, X, order, ctx)) {
              ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
              goto err;
          }
          BN_set_flags(X, BN_FLG_CONSTTIME);
          if (!BN_mod_exp_mont_consttime
              (k, k, X, order, ctx, EC_GROUP_get_mont_data(group))) {
              ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
              goto err;
          }
      } else {
          if (!BN_mod_inverse(k, k, order, ctx)) {
              ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
              goto err;
          }
      }
  
      /* clear old values if necessary */
      BN_clear_free(*rp);
      BN_clear_free(*kinvp);
      /* save the pre-computed values  */
      *rp = r;
      *kinvp = k;
      ret = 1;
   err:
      if (!ret) {
          BN_clear_free(k);
          BN_clear_free(r);
      }
      if (ctx != ctx_in)
          BN_CTX_free(ctx);
      EC_POINT_free(tmp_point);
      BN_clear_free(X);
      return (ret);
  }
  
  int ossl_ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp,
                            BIGNUM **rp)
  {
      return ecdsa_sign_setup(eckey, ctx_in, kinvp, rp, NULL, 0);
  }
  
  ECDSA_SIG *ossl_ecdsa_sign_sig(const unsigned char *dgst, int dgst_len,
                                 const BIGNUM *in_kinv, const BIGNUM *in_r,
                                 EC_KEY *eckey)
  {
      int ok = 0, i;
      BIGNUM *kinv = NULL, *s, *m = NULL, *tmp = NULL, *blind = NULL;
      BIGNUM *blindm = NULL;
      const BIGNUM *order, *ckinv;
      BN_CTX *ctx = NULL;
      const EC_GROUP *group;
      ECDSA_SIG *ret;
      const BIGNUM *priv_key;
  
      group = EC_KEY_get0_group(eckey);
      priv_key = EC_KEY_get0_private_key(eckey);
  
      if (group == NULL || priv_key == NULL) {
          ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_PASSED_NULL_PARAMETER);
          return NULL;
      }
  
      if (!EC_KEY_can_sign(eckey)) {
          ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, EC_R_CURVE_DOES_NOT_SUPPORT_SIGNING);
          return NULL;
      }
  
      ret = ECDSA_SIG_new();
      if (ret == NULL) {
          ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_MALLOC_FAILURE);
          return NULL;
      }
      ret->r = BN_new();
      ret->s = BN_new();
      if (ret->r == NULL || ret->s == NULL) {
          ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_MALLOC_FAILURE);
          goto err;
      }
      s = ret->s;
  
      ctx = BN_CTX_secure_new();
      if (ctx == NULL) {
          ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_MALLOC_FAILURE);
          goto err;
      }
  
      BN_CTX_start(ctx);
      tmp = BN_CTX_get(ctx);
      m = BN_CTX_get(ctx);
      blind = BN_CTX_get(ctx);
      blindm = BN_CTX_get(ctx);
      if (blindm == NULL) {
          ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_MALLOC_FAILURE);
          goto err;
      }
  
      order = EC_GROUP_get0_order(group);
      if (order == NULL) {
          ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_EC_LIB);
          goto err;
      }
      i = BN_num_bits(order);
      /*
       * Need to truncate digest if it is too long: first truncate whole bytes.
       */
      if (8 * dgst_len > i)
          dgst_len = (i + 7) / 8;
      if (!BN_bin2bn(dgst, dgst_len, m)) {
          ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
          goto err;
      }
      /* If still too long truncate remaining bits with a shift */
      if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) {
          ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
          goto err;
      }
      do {
          if (in_kinv == NULL || in_r == NULL) {
              if (!ecdsa_sign_setup(eckey, ctx, &kinv, &ret->r, dgst, dgst_len)) {
                  ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_ECDSA_LIB);
                  goto err;
              }
              ckinv = kinv;
          } else {
              ckinv = in_kinv;
              if (BN_copy(ret->r, in_r) == NULL) {
                  ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_MALLOC_FAILURE);
                  goto err;
              }
          }
  
          /*
           * The normal signature calculation is:
           *
           *   s := k^-1 * (m + r * priv_key) mod order
           *
           * We will blind this to protect against side channel attacks
           *
           *   s := k^-1 * blind^-1 * (blind * m + blind * r * priv_key) mod order
           */
  
          /* Generate a blinding value */
          do {
              if (!BN_rand(blind, BN_num_bits(order) - 1, BN_RAND_TOP_ANY,
                           BN_RAND_BOTTOM_ANY))
                  goto err;
          } while (BN_is_zero(blind));
          BN_set_flags(blind, BN_FLG_CONSTTIME);
          BN_set_flags(blindm, BN_FLG_CONSTTIME);
          BN_set_flags(tmp, BN_FLG_CONSTTIME);
  
          /* tmp := blind * priv_key * r mod order */
          if (!BN_mod_mul(tmp, blind, priv_key, order, ctx)) {
              ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
              goto err;
          }
          if (!BN_mod_mul(tmp, tmp, ret->r, order, ctx)) {
              ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
              goto err;
          }
  
          /* blindm := blind * m mod order */
          if (!BN_mod_mul(blindm, blind, m, order, ctx)) {
              ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
              goto err;
          }
  
          /* s : = (blind * priv_key * r) + (blind * m) mod order */
          if (!BN_mod_add_quick(s, tmp, blindm, order)) {
              ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
              goto err;
          }
  
          /* s:= s * blind^-1 mod order */
          if (BN_mod_inverse(blind, blind, order, ctx) == NULL) {
              ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
              goto err;
          }
          if (!BN_mod_mul(s, s, blind, order, ctx)) {
              ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
              goto err;
          }
  
          /* s := s * k^-1 mod order */
          if (!BN_mod_mul(s, s, ckinv, order, ctx)) {
              ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
              goto err;
          }
  
          if (BN_is_zero(s)) {
              /*
               * if kinv and r have been supplied by the caller don't to
               * generate new kinv and r values
               */
              if (in_kinv != NULL && in_r != NULL) {
                  ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, EC_R_NEED_NEW_SETUP_VALUES);
                  goto err;
              }
          } else
              /* s != 0 => we have a valid signature */
              break;
      }
      while (1);
  
      ok = 1;
   err:
      if (!ok) {
          ECDSA_SIG_free(ret);
          ret = NULL;
      }
      BN_CTX_end(ctx);
      BN_CTX_free(ctx);
      BN_clear_free(kinv);
      return ret;
  }
  
  /*-
   * returns
   *      1: correct signature
   *      0: incorrect signature
   *     -1: error
   */
  int ossl_ecdsa_verify(int type, const unsigned char *dgst, int dgst_len,
                        const unsigned char *sigbuf, int sig_len, EC_KEY *eckey)
  {
      ECDSA_SIG *s;
      const unsigned char *p = sigbuf;
      unsigned char *der = NULL;
      int derlen = -1;
      int ret = -1;
  
      s = ECDSA_SIG_new();
      if (s == NULL)
          return (ret);
      if (d2i_ECDSA_SIG(&s, &p, sig_len) == NULL)
          goto err;
      /* Ensure signature uses DER and doesn't have trailing garbage */
      derlen = i2d_ECDSA_SIG(s, &der);
      if (derlen != sig_len || memcmp(sigbuf, der, derlen) != 0)
          goto err;
      ret = ECDSA_do_verify(dgst, dgst_len, s, eckey);
   err:
      OPENSSL_clear_free(der, derlen);
      ECDSA_SIG_free(s);
      return (ret);
  }
  
  int ossl_ecdsa_verify_sig(const unsigned char *dgst, int dgst_len,
                            const ECDSA_SIG *sig, EC_KEY *eckey)
  {
      int ret = -1, i;
      BN_CTX *ctx;
      const BIGNUM *order;
      BIGNUM *u1, *u2, *m, *X;
      EC_POINT *point = NULL;
      const EC_GROUP *group;
      const EC_POINT *pub_key;
  
      /* check input values */
      if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL ||
          (pub_key = EC_KEY_get0_public_key(eckey)) == NULL || sig == NULL) {
          ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, EC_R_MISSING_PARAMETERS);
          return -1;
      }
  
      if (!EC_KEY_can_sign(eckey)) {
          ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, EC_R_CURVE_DOES_NOT_SUPPORT_SIGNING);
          return -1;
      }
  
      ctx = BN_CTX_new();
      if (ctx == NULL) {
          ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_MALLOC_FAILURE);
          return -1;
      }
      BN_CTX_start(ctx);
      u1 = BN_CTX_get(ctx);
      u2 = BN_CTX_get(ctx);
      m = BN_CTX_get(ctx);
      X = BN_CTX_get(ctx);
      if (X == NULL) {
          ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
          goto err;
      }
  
      order = EC_GROUP_get0_order(group);
      if (order == NULL) {
          ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_EC_LIB);
          goto err;
      }
  
      if (BN_is_zero(sig->r) || BN_is_negative(sig->r) ||
          BN_ucmp(sig->r, order) >= 0 || BN_is_zero(sig->s) ||
          BN_is_negative(sig->s) || BN_ucmp(sig->s, order) >= 0) {
          ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, EC_R_BAD_SIGNATURE);
          ret = 0;                /* signature is invalid */
          goto err;
      }
      /* calculate tmp1 = inv(S) mod order */
      if (!BN_mod_inverse(u2, sig->s, order, ctx)) {
          ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
          goto err;
      }
      /* digest -> m */
      i = BN_num_bits(order);
      /*
       * Need to truncate digest if it is too long: first truncate whole bytes.
       */
      if (8 * dgst_len > i)
          dgst_len = (i + 7) / 8;
      if (!BN_bin2bn(dgst, dgst_len, m)) {
          ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
          goto err;
      }
      /* If still too long truncate remaining bits with a shift */
      if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) {
          ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
          goto err;
      }
      /* u1 = m * tmp mod order */
      if (!BN_mod_mul(u1, m, u2, order, ctx)) {
          ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
          goto err;
      }
      /* u2 = r * w mod q */
      if (!BN_mod_mul(u2, sig->r, u2, order, ctx)) {
          ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
          goto err;
      }
  
      if ((point = EC_POINT_new(group)) == NULL) {
          ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_MALLOC_FAILURE);
          goto err;
      }
      if (!EC_POINT_mul(group, point, u1, pub_key, u2, ctx)) {
          ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_EC_LIB);
          goto err;
      }
      if (EC_METHOD_get_field_type(EC_GROUP_method_of(group)) ==
          NID_X9_62_prime_field) {
          if (!EC_POINT_get_affine_coordinates_GFp(group, point, X, NULL, ctx)) {
              ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_EC_LIB);
              goto err;
          }
      }
  #ifndef OPENSSL_NO_EC2M
      else {                      /* NID_X9_62_characteristic_two_field */
  
          if (!EC_POINT_get_affine_coordinates_GF2m(group, point, X, NULL, ctx)) {
              ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_EC_LIB);
              goto err;
          }
      }
  #endif
      if (!BN_nnmod(u1, X, order, ctx)) {
          ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
          goto err;
      }
      /*  if the signature is correct u1 is equal to sig->r */
      ret = (BN_ucmp(u1, sig->r) == 0);
   err:
      BN_CTX_end(ctx);
      BN_CTX_free(ctx);
      EC_POINT_free(point);
      return ret;
  }
  