/* 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 <openssl/dh.h>

#include <string.h>

#include <openssl/bn.h>
#include <openssl/err.h>
#include <openssl/digest.h>
#include <openssl/mem.h>
#include <openssl/thread.h>

#include "internal.h"
#include "../../internal.h"
#include "../bn/internal.h"


#define OPENSSL_DH_MAX_MODULUS_BITS 10000

DH *DH_new(void) {
  DH *dh = OPENSSL_malloc(sizeof(DH));
  if (dh == NULL) {
    return NULL;
  }

  OPENSSL_memset(dh, 0, sizeof(DH));

  CRYPTO_MUTEX_init(&dh->method_mont_p_lock);

  dh->references = 1;

  return dh;
}

DH *DH_new_by_nid(int nid) {
  switch (nid) {
    case NID_ffdhe2048:
      return DH_get_rfc7919_2048();
    case NID_ffdhe4096:
      return DH_get_rfc7919_4096();
    default:
      OPENSSL_PUT_ERROR(DH, DH_R_INVALID_NID);
      return NULL;
  }
}

void DH_free(DH *dh) {
  if (dh == NULL) {
    return;
  }

  if (!CRYPTO_refcount_dec_and_test_zero(&dh->references)) {
    return;
  }

  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->pub_key);
  BN_clear_free(dh->priv_key);
  CRYPTO_MUTEX_cleanup(&dh->method_mont_p_lock);

  OPENSSL_free(dh);
}

unsigned DH_bits(const DH *dh) { return BN_num_bits(dh->p); }

const BIGNUM *DH_get0_pub_key(const DH *dh) { return dh->pub_key; }

const BIGNUM *DH_get0_priv_key(const DH *dh) { return dh->priv_key; }

const BIGNUM *DH_get0_p(const DH *dh) { return dh->p; }

const BIGNUM *DH_get0_q(const DH *dh) { return dh->q; }

const BIGNUM *DH_get0_g(const DH *dh) { return dh->g; }

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;
  }
}

void DH_clear_flags(DH *dh, int flags) {
  (void) dh;
  (void) flags;
}

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;
  }

  // Invalidate the cached Montgomery parameters.
  BN_MONT_CTX_free(dh->method_mont_p);
  dh->method_mont_p = NULL;
  return 1;
}

int DH_set_length(DH *dh, unsigned priv_length) {
  dh->priv_length = priv_length;
  return 1;
}

int DH_generate_key(DH *dh) {
  boringssl_ensure_ffdh_self_test();

  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;
}

static int dh_compute_key(DH *dh, BIGNUM *out_shared_key,
                          const BIGNUM *peers_key, BN_CTX *ctx) {
  if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) {
    OPENSSL_PUT_ERROR(DH, DH_R_MODULUS_TOO_LARGE);
    return 0;
  }

  if (dh->priv_key == NULL) {
    OPENSSL_PUT_ERROR(DH, DH_R_NO_PRIVATE_VALUE);
    return 0;
  }

  int check_result;
  if (!DH_check_pub_key(dh, peers_key, &check_result) || check_result) {
    OPENSSL_PUT_ERROR(DH, DH_R_INVALID_PUBKEY);
    return 0;
  }

  int ret = 0;
  BN_CTX_start(ctx);
  BIGNUM *p_minus_1 = BN_CTX_get(ctx);

  if (!p_minus_1 ||
      !BN_MONT_CTX_set_locked(&dh->method_mont_p, &dh->method_mont_p_lock,
                              dh->p, ctx)) {
    goto err;
  }

  if (!BN_mod_exp_mont_consttime(out_shared_key, peers_key, dh->priv_key, dh->p,
                                 ctx, dh->method_mont_p) ||
      !BN_copy(p_minus_1, dh->p) ||
      !BN_sub_word(p_minus_1, 1)) {
    OPENSSL_PUT_ERROR(DH, ERR_R_BN_LIB);
    goto err;
  }

  // This performs the check required by SP 800-56Ar3 section 5.7.1.1 step two.
  if (BN_cmp_word(out_shared_key, 1) <= 0 ||
      BN_cmp(out_shared_key, p_minus_1) == 0) {
    OPENSSL_PUT_ERROR(DH, DH_R_INVALID_PUBKEY);
    goto err;
  }

  ret = 1;

 err:
  BN_CTX_end(ctx);
  return ret;
}

int dh_compute_key_padded_no_self_test(unsigned char *out,
                                       const BIGNUM *peers_key, DH *dh) {
  BN_CTX *ctx = BN_CTX_new();
  if (ctx == NULL) {
    return -1;
  }
  BN_CTX_start(ctx);

  int dh_size = DH_size(dh);
  int ret = -1;
  BIGNUM *shared_key = BN_CTX_get(ctx);
  if (shared_key &&
      dh_compute_key(dh, shared_key, peers_key, ctx) &&
      BN_bn2bin_padded(out, dh_size, shared_key)) {
    ret = dh_size;
  }

  BN_CTX_end(ctx);
  BN_CTX_free(ctx);
  return ret;
}

int DH_compute_key_padded(unsigned char *out, const BIGNUM *peers_key, DH *dh) {
  boringssl_ensure_ffdh_self_test();

  return dh_compute_key_padded_no_self_test(out, peers_key, dh);
}

int DH_compute_key(unsigned char *out, const BIGNUM *peers_key, DH *dh) {
  boringssl_ensure_ffdh_self_test();

  BN_CTX *ctx = BN_CTX_new();
  if (ctx == NULL) {
    return -1;
  }
  BN_CTX_start(ctx);

  int ret = -1;
  BIGNUM *shared_key = BN_CTX_get(ctx);
  if (shared_key && dh_compute_key(dh, shared_key, peers_key, ctx)) {
    // A |BIGNUM|'s byte count fits in |int|.
    ret = (int)BN_bn2bin(shared_key, out);
  }

  BN_CTX_end(ctx);
  BN_CTX_free(ctx);
  return ret;
}

int DH_compute_key_hashed(DH *dh, uint8_t *out, size_t *out_len,
                          size_t max_out_len, const BIGNUM *peers_key,
                          const EVP_MD *digest) {
  *out_len = (size_t)-1;

  const size_t digest_len = EVP_MD_size(digest);
  if (digest_len > max_out_len) {
    return 0;
  }

  // We have to avoid the underlying |EVP_Digest| services updating the indicator
  // state, so we lock the state here.
  FIPS_service_indicator_lock_state();

  int ret = 0;
  const size_t dh_len = DH_size(dh);
  uint8_t *shared_bytes = OPENSSL_malloc(dh_len);
  unsigned out_len_unsigned;
  if (!shared_bytes ||
      // SP 800-56A is ambiguous about whether the output should be padded prior
      // to revision three. But revision three, section C.1, awkwardly specifies
      // padding to the length of p.
      //
      // Also, padded output avoids side-channels, so is always strongly
      // advisable.
      DH_compute_key_padded(shared_bytes, peers_key, dh) != (int)dh_len ||
      !EVP_Digest(shared_bytes, dh_len, out, &out_len_unsigned, digest, NULL) ||
      out_len_unsigned != digest_len) {
    goto err;
  }

  *out_len = digest_len;
  ret = 1;

 err:
  FIPS_service_indicator_unlock_state();
  OPENSSL_free(shared_bytes);
  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;
}

// All the groups in RFC 7919 are of the form:
// q = (p-1)/2
// g = 2
static DH *calculate_rfc7919_DH_from_p(const BN_ULONG data[], size_t data_len) {
  BIGNUM *const ffdhe_p = BN_new();
  BIGNUM *const ffdhe_q = BN_new();
  BIGNUM *const ffdhe_g = BN_new();
  DH *const dh = DH_new();

  if (!ffdhe_p || !ffdhe_q || !ffdhe_g || !dh) {
    goto err;
  }

  bn_set_static_words(ffdhe_p, data, data_len);

  if (!BN_rshift1(ffdhe_q, ffdhe_p) ||
      !BN_set_word(ffdhe_g, 2) ||
      !DH_set0_pqg(dh, ffdhe_p, ffdhe_q, ffdhe_g)) {
    goto err;
  }

  return dh;

err:
  BN_free(ffdhe_p);
  BN_free(ffdhe_q);
  BN_free(ffdhe_g);
  DH_free(dh);
  return NULL;

}

DH *DH_get_rfc7919_2048(void) {
  // This is the prime from https://tools.ietf.org/html/rfc7919#appendix-A.1,
  // which is specifically approved for FIPS in appendix D of SP 800-56Ar3.
  static const BN_ULONG kFFDHE2048Data[] = {
      TOBN(0xffffffff, 0xffffffff), TOBN(0x886b4238, 0x61285c97),
      TOBN(0xc6f34a26, 0xc1b2effa), TOBN(0xc58ef183, 0x7d1683b2),
      TOBN(0x3bb5fcbc, 0x2ec22005), TOBN(0xc3fe3b1b, 0x4c6fad73),
      TOBN(0x8e4f1232, 0xeef28183), TOBN(0x9172fe9c, 0xe98583ff),
      TOBN(0xc03404cd, 0x28342f61), TOBN(0x9e02fce1, 0xcdf7e2ec),
      TOBN(0x0b07a7c8, 0xee0a6d70), TOBN(0xae56ede7, 0x6372bb19),
      TOBN(0x1d4f42a3, 0xde394df4), TOBN(0xb96adab7, 0x60d7f468),
      TOBN(0xd108a94b, 0xb2c8e3fb), TOBN(0xbc0ab182, 0xb324fb61),
      TOBN(0x30acca4f, 0x483a797a), TOBN(0x1df158a1, 0x36ade735),
      TOBN(0xe2a689da, 0xf3efe872), TOBN(0x984f0c70, 0xe0e68b77),
      TOBN(0xb557135e, 0x7f57c935), TOBN(0x85636555, 0x3ded1af3),
      TOBN(0x2433f51f, 0x5f066ed0), TOBN(0xd3df1ed5, 0xd5fd6561),
      TOBN(0xf681b202, 0xaec4617a), TOBN(0x7d2fe363, 0x630c75d8),
      TOBN(0xcc939dce, 0x249b3ef9), TOBN(0xa9e13641, 0x146433fb),
      TOBN(0xd8b9c583, 0xce2d3695), TOBN(0xafdc5620, 0x273d3cf1),
      TOBN(0xadf85458, 0xa2bb4a9a), TOBN(0xffffffff, 0xffffffff),
  };

  return calculate_rfc7919_DH_from_p(kFFDHE2048Data, OPENSSL_ARRAY_SIZE(kFFDHE2048Data));
}

DH *DH_get_rfc7919_4096(void) {
    // This is the prime from https://tools.ietf.org/html/rfc7919#appendix-A.3,
    // which is specifically approved for FIPS in appendix D of SP 800-56Ar3.
    static const BN_ULONG kFFDHE4096Data[] = {
        TOBN(0xFFFFFFFF, 0xFFFFFFFF),TOBN(0xC68A007E, 0x5E655F6A),
        TOBN(0x4DB5A851, 0xF44182E1),TOBN(0x8EC9B55A, 0x7F88A46B),
        TOBN(0x0A8291CD, 0xCEC97DCF),TOBN(0x2A4ECEA9, 0xF98D0ACC),
        TOBN(0x1A1DB93D, 0x7140003C),TOBN(0x092999A3, 0x33CB8B7A),
        TOBN(0x6DC778F9, 0x71AD0038),TOBN(0xA907600A, 0x918130C4),
        TOBN(0xED6A1E01, 0x2D9E6832),TOBN(0x7135C886, 0xEFB4318A),
        TOBN(0x87F55BA5, 0x7E31CC7A),TOBN(0x7763CF1D, 0x55034004),
        TOBN(0xAC7D5F42, 0xD69F6D18),TOBN(0x7930E9E4, 0xE58857B6),
        TOBN(0x6E6F52C3, 0x164DF4FB),TOBN(0x25E41D2B, 0x669E1EF1),
        TOBN(0x3C1B20EE, 0x3FD59D7C),TOBN(0x0ABCD06B, 0xFA53DDEF),
        TOBN(0x1DBF9A42, 0xD5C4484E),TOBN(0xABC52197, 0x9B0DEADA),
        TOBN(0xE86D2BC5, 0x22363A0D),TOBN(0x5CAE82AB, 0x9C9DF69E),
        TOBN(0x64F2E21E, 0x71F54BFF),TOBN(0xF4FD4452, 0xE2D74DD3),
        TOBN(0xB4130C93, 0xBC437944),TOBN(0xAEFE1309, 0x85139270),
        TOBN(0x598CB0FA, 0xC186D91C),TOBN(0x7AD91D26, 0x91F7F7EE),
        TOBN(0x61B46FC9, 0xD6E6C907),TOBN(0xBC34F4DE, 0xF99C0238),
        TOBN(0xDE355B3B, 0x6519035B),TOBN(0x886B4238, 0x611FCFDC),
        TOBN(0xC6F34A26, 0xC1B2EFFA),TOBN(0xC58EF183, 0x7D1683B2),
        TOBN(0x3BB5FCBC, 0x2EC22005),TOBN(0xC3FE3B1B, 0x4C6FAD73),
        TOBN(0x8E4F1232, 0xEEF28183),TOBN(0x9172FE9C, 0xE98583FF),
        TOBN(0xC03404CD, 0x28342F61),TOBN(0x9E02FCE1, 0xCDF7E2EC),
        TOBN(0x0B07A7C8, 0xEE0A6D70),TOBN(0xAE56EDE7, 0x6372BB19),
        TOBN(0x1D4F42A3, 0xDE394DF4),TOBN(0xB96ADAB7, 0x60D7F468),
        TOBN(0xD108A94B, 0xB2C8E3FB),TOBN(0xBC0AB182, 0xB324FB61),
        TOBN(0x30ACCA4F, 0x483A797A),TOBN(0x1DF158A1, 0x36ADE735),
        TOBN(0xE2A689DA, 0xF3EFE872),TOBN(0x984F0C70, 0xE0E68B77),
        TOBN(0xB557135E, 0x7F57C935),TOBN(0x85636555, 0x3DED1AF3),
        TOBN(0x2433F51F, 0x5F066ED0),TOBN(0xD3DF1ED5, 0xD5FD6561),
        TOBN(0xF681B202, 0xAEC4617A),TOBN(0x7D2FE363, 0x630C75D8),
        TOBN(0xCC939DCE, 0x249B3EF9),TOBN(0xA9E13641, 0x146433FB),
        TOBN(0xD8B9C583, 0xCE2D3695),TOBN(0xAFDC5620, 0x273D3CF1),
        TOBN(0xADF85458, 0xA2BB4A9A),TOBN(0xFFFFFFFF, 0xFFFFFFFF)
    };

    return calculate_rfc7919_DH_from_p(kFFDHE4096Data, OPENSSL_ARRAY_SIZE(kFFDHE4096Data));
}