text: /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
   * All rights reserved.
   *
   * This package is an SSL implementation written
   * by Eric Young (eay@cryptsoft.com).
   * The implementation was written so as to conform with Netscapes SSL.
   *
   * This library is free for commercial and non-commercial use as long as
   * the following conditions are aheared to.  The following conditions
   * apply to all code found in this distribution, be it the RC4, RSA,
   * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
   * included with this distribution is covered by the same copyright terms
   * except that the holder is Tim Hudson (tjh@cryptsoft.com).
   *
   * Copyright remains Eric Young's, and as such any Copyright notices in
   * the code are not to be removed.
   * If this package is used in a product, Eric Young should be given attribution
   * as the author of the parts of the library used.
   * This can be in the form of a textual message at program startup or
   * in documentation (online or textual) provided with the package.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 1. Redistributions of source code must retain the copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   * 3. All advertising materials mentioning features or use of this software
   *    must display the following acknowledgement:
   *    "This product includes cryptographic software written by
   *     Eric Young (eay@cryptsoft.com)"
   *    The word 'cryptographic' can be left out if the rouines from the library
   *    being used are not cryptographic related :-).
   * 4. If you include any Windows specific code (or a derivative thereof) from
   *    the apps directory (application code) you must include an acknowledgement:
   *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
   *
   * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
   * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   * SUCH DAMAGE.
   *
   * The licence and distribution terms for any publically available version or
   * derivative of this code cannot be changed.  i.e. this code cannot simply be
   * copied and put under another distribution licence
   * [including the GNU Public Licence.] */
  
  #include <CNIOBoringSSL_dh.h>
  
  #include <string.h>
  
  #include <CNIOBoringSSL_bn.h>
  #include <CNIOBoringSSL_buf.h>
  #include <CNIOBoringSSL_err.h>
  #include <CNIOBoringSSL_ex_data.h>
  #include <CNIOBoringSSL_mem.h>
  #include <CNIOBoringSSL_thread.h>
  
  #include "../internal.h"
  
  
  #define OPENSSL_DH_MAX_MODULUS_BITS 10000
  
  static CRYPTO_EX_DATA_CLASS g_ex_data_class = CRYPTO_EX_DATA_CLASS_INIT;
  
  DH *DH_new(void) {
    DH *dh = OPENSSL_malloc(sizeof(DH));
    if (dh == NULL) {
      OPENSSL_PUT_ERROR(DH, ERR_R_MALLOC_FAILURE);
      return NULL;
    }
  
    OPENSSL_memset(dh, 0, sizeof(DH));
  
    CRYPTO_MUTEX_init(&dh->method_mont_p_lock);
  
    dh->references = 1;
    CRYPTO_new_ex_data(&dh->ex_data);
  
    return dh;
  }
  
  void DH_free(DH *dh) {
    if (dh == NULL) {
      return;
    }
  
    if (!CRYPTO_refcount_dec_and_test_zero(&dh->references)) {
      return;
    }
  
    CRYPTO_free_ex_data(&g_ex_data_class, dh, &dh->ex_data);
  
    BN_MONT_CTX_free(dh->method_mont_p);
    BN_clear_free(dh->p);
    BN_clear_free(dh->g);
    BN_clear_free(dh->q);
    BN_clear_free(dh->j);
    OPENSSL_free(dh->seed);
    BN_clear_free(dh->counter);
    BN_clear_free(dh->pub_key);
    BN_clear_free(dh->priv_key);
    CRYPTO_MUTEX_cleanup(&dh->method_mont_p_lock);
  
    OPENSSL_free(dh);
  }
  
  void DH_get0_key(const DH *dh, const BIGNUM **out_pub_key,
                   const BIGNUM **out_priv_key) {
    if (out_pub_key != NULL) {
      *out_pub_key = dh->pub_key;
    }
    if (out_priv_key != NULL) {
      *out_priv_key = dh->priv_key;
    }
  }
  
  int DH_set0_key(DH *dh, BIGNUM *pub_key, BIGNUM *priv_key) {
    if (pub_key != NULL) {
      BN_free(dh->pub_key);
      dh->pub_key = pub_key;
    }
  
    if (priv_key != NULL) {
      BN_free(dh->priv_key);
      dh->priv_key = priv_key;
    }
  
    return 1;
  }
  
  void DH_get0_pqg(const DH *dh, const BIGNUM **out_p, const BIGNUM **out_q,
                   const BIGNUM **out_g) {
    if (out_p != NULL) {
      *out_p = dh->p;
    }
    if (out_q != NULL) {
      *out_q = dh->q;
    }
    if (out_g != NULL) {
      *out_g = dh->g;
    }
  }
  
  int DH_set0_pqg(DH *dh, BIGNUM *p, BIGNUM *q, BIGNUM *g) {
    if ((dh->p == NULL && p == NULL) ||
        (dh->g == NULL && g == NULL)) {
      return 0;
    }
  
    if (p != NULL) {
      BN_free(dh->p);
      dh->p = p;
    }
  
    if (q != NULL) {
      BN_free(dh->q);
      dh->q = q;
    }
  
    if (g != NULL) {
      BN_free(dh->g);
      dh->g = g;
    }
  
    return 1;
  }
  
  int DH_generate_parameters_ex(DH *dh, int prime_bits, int generator, BN_GENCB *cb) {
    // We generate DH parameters as follows
    // find a prime q which is prime_bits/2 bits long.
    // p=(2*q)+1 or (p-1)/2 = q
    // For this case, g is a generator if
    // g^((p-1)/q) mod p != 1 for values of q which are the factors of p-1.
    // Since the factors of p-1 are q and 2, we just need to check
    // g^2 mod p != 1 and g^q mod p != 1.
    //
    // Having said all that,
    // there is another special case method for the generators 2, 3 and 5.
    // for 2, p mod 24 == 11
    // for 3, p mod 12 == 5  <<<<< does not work for safe primes.
    // for 5, p mod 10 == 3 or 7
    //
    // Thanks to Phil Karn <karn@qualcomm.com> for the pointers about the
    // special generators and for answering some of my questions.
    //
    // I've implemented the second simple method :-).
    // Since DH should be using a safe prime (both p and q are prime),
    // this generator function can take a very very long time to run.
  
    // Actually there is no reason to insist that 'generator' be a generator.
    // It's just as OK (and in some sense better) to use a generator of the
    // order-q subgroup.
  
    BIGNUM *t1, *t2;
    int g, ok = 0;
    BN_CTX *ctx = NULL;
  
    ctx = BN_CTX_new();
    if (ctx == NULL) {
      goto err;
    }
    BN_CTX_start(ctx);
    t1 = BN_CTX_get(ctx);
    t2 = BN_CTX_get(ctx);
    if (t1 == NULL || t2 == NULL) {
      goto err;
    }
  
    // Make sure |dh| has the necessary elements
    if (dh->p == NULL) {
      dh->p = BN_new();
      if (dh->p == NULL) {
        goto err;
      }
    }
    if (dh->g == NULL) {
      dh->g = BN_new();
      if (dh->g == NULL) {
        goto err;
      }
    }
  
    if (generator <= 1) {
      OPENSSL_PUT_ERROR(DH, DH_R_BAD_GENERATOR);
      goto err;
    }
    if (generator == DH_GENERATOR_2) {
      if (!BN_set_word(t1, 24)) {
        goto err;
      }
      if (!BN_set_word(t2, 11)) {
        goto err;
      }
      g = 2;
    } else if (generator == DH_GENERATOR_5) {
      if (!BN_set_word(t1, 10)) {
        goto err;
      }
      if (!BN_set_word(t2, 3)) {
        goto err;
      }
      // BN_set_word(t3,7); just have to miss
      // out on these ones :-(
      g = 5;
    } else {
      // in the general case, don't worry if 'generator' is a
      // generator or not: since we are using safe primes,
      // it will generate either an order-q or an order-2q group,
      // which both is OK
      if (!BN_set_word(t1, 2)) {
        goto err;
      }
      if (!BN_set_word(t2, 1)) {
        goto err;
      }
      g = generator;
    }
  
    if (!BN_generate_prime_ex(dh->p, prime_bits, 1, t1, t2, cb)) {
      goto err;
    }
    if (!BN_GENCB_call(cb, 3, 0)) {
      goto err;
    }
    if (!BN_set_word(dh->g, g)) {
      goto err;
    }
    ok = 1;
  
  err:
    if (!ok) {
      OPENSSL_PUT_ERROR(DH, ERR_R_BN_LIB);
    }
  
    if (ctx != NULL) {
      BN_CTX_end(ctx);
      BN_CTX_free(ctx);
    }
    return ok;
  }
  
  int DH_generate_key(DH *dh) {
    int ok = 0;
    int generate_new_key = 0;
    BN_CTX *ctx = NULL;
    BIGNUM *pub_key = NULL, *priv_key = NULL;
  
    if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) {
      OPENSSL_PUT_ERROR(DH, DH_R_MODULUS_TOO_LARGE);
      goto err;
    }
  
    ctx = BN_CTX_new();
    if (ctx == NULL) {
      goto err;
    }
  
    if (dh->priv_key == NULL) {
      priv_key = BN_new();
      if (priv_key == NULL) {
        goto err;
      }
      generate_new_key = 1;
    } else {
      priv_key = dh->priv_key;
    }
  
    if (dh->pub_key == NULL) {
      pub_key = BN_new();
      if (pub_key == NULL) {
        goto err;
      }
    } else {
      pub_key = dh->pub_key;
    }
  
    if (!BN_MONT_CTX_set_locked(&dh->method_mont_p, &dh->method_mont_p_lock,
                                dh->p, ctx)) {
      goto err;
    }
  
    if (generate_new_key) {
      if (dh->q) {
        if (!BN_rand_range_ex(priv_key, 2, dh->q)) {
          goto err;
        }
      } else {
        // secret exponent length
        unsigned priv_bits = dh->priv_length;
        if (priv_bits == 0) {
          const unsigned p_bits = BN_num_bits(dh->p);
          if (p_bits == 0) {
            goto err;
          }
  
          priv_bits = p_bits - 1;
        }
  
        if (!BN_rand(priv_key, priv_bits, BN_RAND_TOP_ONE, BN_RAND_BOTTOM_ANY)) {
          goto err;
        }
      }
    }
  
    if (!BN_mod_exp_mont_consttime(pub_key, dh->g, priv_key, dh->p, ctx,
                                   dh->method_mont_p)) {
      goto err;
    }
  
    dh->pub_key = pub_key;
    dh->priv_key = priv_key;
    ok = 1;
  
  err:
    if (ok != 1) {
      OPENSSL_PUT_ERROR(DH, ERR_R_BN_LIB);
    }
  
    if (dh->pub_key == NULL) {
      BN_free(pub_key);
    }
    if (dh->priv_key == NULL) {
      BN_free(priv_key);
    }
    BN_CTX_free(ctx);
    return ok;
  }
  
  int DH_compute_key(unsigned char *out, const BIGNUM *peers_key, DH *dh) {
    BN_CTX *ctx = NULL;
    BIGNUM *shared_key;
    int ret = -1;
    int check_result;
  
    if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) {
      OPENSSL_PUT_ERROR(DH, DH_R_MODULUS_TOO_LARGE);
      goto err;
    }
  
    ctx = BN_CTX_new();
    if (ctx == NULL) {
      goto err;
    }
    BN_CTX_start(ctx);
    shared_key = BN_CTX_get(ctx);
    if (shared_key == NULL) {
      goto err;
    }
  
    if (dh->priv_key == NULL) {
      OPENSSL_PUT_ERROR(DH, DH_R_NO_PRIVATE_VALUE);
      goto err;
    }
  
    if (!BN_MONT_CTX_set_locked(&dh->method_mont_p, &dh->method_mont_p_lock,
                                dh->p, ctx)) {
      goto err;
    }
  
    if (!DH_check_pub_key(dh, peers_key, &check_result) || check_result) {
      OPENSSL_PUT_ERROR(DH, DH_R_INVALID_PUBKEY);
      goto err;
    }
  
    if (!BN_mod_exp_mont_consttime(shared_key, peers_key, dh->priv_key, dh->p,
                                   ctx, dh->method_mont_p)) {
      OPENSSL_PUT_ERROR(DH, ERR_R_BN_LIB);
      goto err;
    }
  
    ret = BN_bn2bin(shared_key, out);
  
  err:
    if (ctx != NULL) {
      BN_CTX_end(ctx);
      BN_CTX_free(ctx);
    }
  
    return ret;
  }
  
  int DH_size(const DH *dh) { return BN_num_bytes(dh->p); }
  
  unsigned DH_num_bits(const DH *dh) { return BN_num_bits(dh->p); }
  
  int DH_up_ref(DH *dh) {
    CRYPTO_refcount_inc(&dh->references);
    return 1;
  }
  
  static int int_dh_bn_cpy(BIGNUM **dst, const BIGNUM *src) {
    BIGNUM *a = NULL;
  
    if (src) {
      a = BN_dup(src);
      if (!a) {
        return 0;
      }
    }
  
    BN_free(*dst);
    *dst = a;
    return 1;
  }
  
  static int int_dh_param_copy(DH *to, const DH *from, int is_x942) {
    if (is_x942 == -1) {
      is_x942 = !!from->q;
    }
    if (!int_dh_bn_cpy(&to->p, from->p) ||
        !int_dh_bn_cpy(&to->g, from->g)) {
      return 0;
    }
  
    if (!is_x942) {
      return 1;
    }
  
    if (!int_dh_bn_cpy(&to->q, from->q) ||
        !int_dh_bn_cpy(&to->j, from->j)) {
      return 0;
    }
  
    OPENSSL_free(to->seed);
    to->seed = NULL;
    to->seedlen = 0;
  
    if (from->seed) {
      to->seed = BUF_memdup(from->seed, from->seedlen);
      if (!to->seed) {
        return 0;
      }
      to->seedlen = from->seedlen;
    }
  
    return 1;
  }
  
  DH *DHparams_dup(const DH *dh) {
    DH *ret = DH_new();
    if (!ret) {
      return NULL;
    }
  
    if (!int_dh_param_copy(ret, dh, -1)) {
      DH_free(ret);
      return NULL;
    }
  
    return ret;
  }
  
  int DH_get_ex_new_index(long argl, void *argp, CRYPTO_EX_unused *unused,
                          CRYPTO_EX_dup *dup_unused, CRYPTO_EX_free *free_func) {
    int index;
    if (!CRYPTO_get_ex_new_index(&g_ex_data_class, &index, argl, argp,
                                 free_func)) {
      return -1;
    }
    return index;
  }
  
  int DH_set_ex_data(DH *d, int idx, void *arg) {
    return CRYPTO_set_ex_data(&d->ex_data, idx, arg);
  }
  
  void *DH_get_ex_data(DH *d, int idx) {
    return CRYPTO_get_ex_data(&d->ex_data, idx);
  }
  