text: /*
   * Copyright 1995-2017 The OpenSSL Project Authors. All Rights Reserved.
   *
   * 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 <stdio.h>
  #include "internal/cryptlib.h"
  #include <openssl/bn.h>
  #include "dh_locl.h"
  
  /*-
   * Check that p and g are suitable enough
   *
   * p is odd
   * 1 < g < p - 1
   */
  int DH_check_params_ex(const DH *dh)
  {
      int errflags = 0;
  
      (void)DH_check_params(dh, &errflags);
  
      if ((errflags & DH_CHECK_P_NOT_PRIME) != 0)
          DHerr(DH_F_DH_CHECK_PARAMS_EX, DH_R_CHECK_P_NOT_PRIME);
      if ((errflags & DH_NOT_SUITABLE_GENERATOR) != 0)
          DHerr(DH_F_DH_CHECK_PARAMS_EX, DH_R_NOT_SUITABLE_GENERATOR);
  
      return errflags == 0;
  }
  
  int DH_check_params(const DH *dh, int *ret)
  {
      int ok = 0;
      BIGNUM *tmp = NULL;
      BN_CTX *ctx = NULL;
  
      *ret = 0;
      ctx = BN_CTX_new();
      if (ctx == NULL)
          goto err;
      BN_CTX_start(ctx);
      tmp = BN_CTX_get(ctx);
      if (tmp == NULL)
          goto err;
  
      if (!BN_is_odd(dh->p))
          *ret |= DH_CHECK_P_NOT_PRIME;
      if (BN_is_negative(dh->g) || BN_is_zero(dh->g) || BN_is_one(dh->g))
          *ret |= DH_NOT_SUITABLE_GENERATOR;
      if (BN_copy(tmp, dh->p) == NULL || !BN_sub_word(tmp, 1))
          goto err;
      if (BN_cmp(dh->g, tmp) >= 0)
          *ret |= DH_NOT_SUITABLE_GENERATOR;
  
      ok = 1;
   err:
      BN_CTX_end(ctx);
      BN_CTX_free(ctx);
      return ok;
  }
  
  /*-
   * Check that p is a safe prime and
   * if g is 2, 3 or 5, check that it is a suitable generator
   * where
   * for 2, p mod 24 == 11
   * for 3, p mod 12 == 5
   * for 5, p mod 10 == 3 or 7
   * should hold.
   */
  int DH_check_ex(const DH *dh)
  {
      int errflags = 0;
  
      (void)DH_check(dh, &errflags);
  
      if ((errflags & DH_NOT_SUITABLE_GENERATOR) != 0)
          DHerr(DH_F_DH_CHECK_EX, DH_R_NOT_SUITABLE_GENERATOR);
      if ((errflags & DH_CHECK_Q_NOT_PRIME) != 0)
          DHerr(DH_F_DH_CHECK_EX, DH_R_CHECK_Q_NOT_PRIME);
      if ((errflags & DH_CHECK_INVALID_Q_VALUE) != 0)
          DHerr(DH_F_DH_CHECK_EX, DH_R_CHECK_INVALID_Q_VALUE);
      if ((errflags & DH_CHECK_INVALID_J_VALUE) != 0)
          DHerr(DH_F_DH_CHECK_EX, DH_R_CHECK_INVALID_J_VALUE);
      if ((errflags & DH_UNABLE_TO_CHECK_GENERATOR) != 0)
          DHerr(DH_F_DH_CHECK_EX, DH_R_UNABLE_TO_CHECK_GENERATOR);
      if ((errflags & DH_CHECK_P_NOT_PRIME) != 0)
          DHerr(DH_F_DH_CHECK_EX, DH_R_CHECK_P_NOT_PRIME);
      if ((errflags & DH_CHECK_P_NOT_SAFE_PRIME) != 0)
          DHerr(DH_F_DH_CHECK_EX, DH_R_CHECK_P_NOT_SAFE_PRIME);
  
      return errflags == 0;
  }
  
  int DH_check(const DH *dh, int *ret)
  {
      int ok = 0, r;
      BN_CTX *ctx = NULL;
      BN_ULONG l;
      BIGNUM *t1 = NULL, *t2 = NULL;
  
      *ret = 0;
      ctx = BN_CTX_new();
      if (ctx == NULL)
          goto err;
      BN_CTX_start(ctx);
      t1 = BN_CTX_get(ctx);
      t2 = BN_CTX_get(ctx);
      if (t2 == NULL)
          goto err;
  
      if (dh->q) {
          if (BN_cmp(dh->g, BN_value_one()) <= 0)
              *ret |= DH_NOT_SUITABLE_GENERATOR;
          else if (BN_cmp(dh->g, dh->p) >= 0)
              *ret |= DH_NOT_SUITABLE_GENERATOR;
          else {
              /* Check g^q == 1 mod p */
              if (!BN_mod_exp(t1, dh->g, dh->q, dh->p, ctx))
                  goto err;
              if (!BN_is_one(t1))
                  *ret |= DH_NOT_SUITABLE_GENERATOR;
          }
          r = BN_is_prime_ex(dh->q, BN_prime_checks, ctx, NULL);
          if (r < 0)
              goto err;
          if (!r)
              *ret |= DH_CHECK_Q_NOT_PRIME;
          /* Check p == 1 mod q  i.e. q divides p - 1 */
          if (!BN_div(t1, t2, dh->p, dh->q, ctx))
              goto err;
          if (!BN_is_one(t2))
              *ret |= DH_CHECK_INVALID_Q_VALUE;
          if (dh->j && BN_cmp(dh->j, t1))
              *ret |= DH_CHECK_INVALID_J_VALUE;
  
      } else if (BN_is_word(dh->g, DH_GENERATOR_2)) {
          l = BN_mod_word(dh->p, 24);
          if (l == (BN_ULONG)-1)
              goto err;
          if (l != 11)
              *ret |= DH_NOT_SUITABLE_GENERATOR;
      } else if (BN_is_word(dh->g, DH_GENERATOR_5)) {
          l = BN_mod_word(dh->p, 10);
          if (l == (BN_ULONG)-1)
              goto err;
          if ((l != 3) && (l != 7))
              *ret |= DH_NOT_SUITABLE_GENERATOR;
      } else
          *ret |= DH_UNABLE_TO_CHECK_GENERATOR;
  
      r = BN_is_prime_ex(dh->p, BN_prime_checks, ctx, NULL);
      if (r < 0)
          goto err;
      if (!r)
          *ret |= DH_CHECK_P_NOT_PRIME;
      else if (!dh->q) {
          if (!BN_rshift1(t1, dh->p))
              goto err;
          r = BN_is_prime_ex(t1, BN_prime_checks, ctx, NULL);
          if (r < 0)
              goto err;
          if (!r)
              *ret |= DH_CHECK_P_NOT_SAFE_PRIME;
      }
      ok = 1;
   err:
      BN_CTX_end(ctx);
      BN_CTX_free(ctx);
      return ok;
  }
  
  int DH_check_pub_key_ex(const DH *dh, const BIGNUM *pub_key)
  {
      int errflags = 0;
  
      (void)DH_check(dh, &errflags);
  
      if ((errflags & DH_CHECK_PUBKEY_TOO_SMALL) != 0)
          DHerr(DH_F_DH_CHECK_PUB_KEY_EX, DH_R_CHECK_PUBKEY_TOO_SMALL);
      if ((errflags & DH_CHECK_PUBKEY_TOO_LARGE) != 0)
          DHerr(DH_F_DH_CHECK_PUB_KEY_EX, DH_R_CHECK_PUBKEY_TOO_LARGE);
      if ((errflags & DH_CHECK_PUBKEY_INVALID) != 0)
          DHerr(DH_F_DH_CHECK_PUB_KEY_EX, DH_R_CHECK_PUBKEY_INVALID);
  
      return errflags == 0;
  }
  
  int DH_check_pub_key(const DH *dh, const BIGNUM *pub_key, int *ret)
  {
      int ok = 0;
      BIGNUM *tmp = NULL;
      BN_CTX *ctx = NULL;
  
      *ret = 0;
      ctx = BN_CTX_new();
      if (ctx == NULL)
          goto err;
      BN_CTX_start(ctx);
      tmp = BN_CTX_get(ctx);
      if (tmp == NULL || !BN_set_word(tmp, 1))
          goto err;
      if (BN_cmp(pub_key, tmp) <= 0)
          *ret |= DH_CHECK_PUBKEY_TOO_SMALL;
      if (BN_copy(tmp, dh->p) == NULL || !BN_sub_word(tmp, 1))
          goto err;
      if (BN_cmp(pub_key, tmp) >= 0)
          *ret |= DH_CHECK_PUBKEY_TOO_LARGE;
  
      if (dh->q != NULL) {
          /* Check pub_key^q == 1 mod p */
          if (!BN_mod_exp(tmp, pub_key, dh->q, dh->p, ctx))
              goto err;
          if (!BN_is_one(tmp))
              *ret |= DH_CHECK_PUBKEY_INVALID;
      }
  
      ok = 1;
   err:
      BN_CTX_end(ctx);
      BN_CTX_free(ctx);
      return ok;
  }
  