/* $OpenBSD: dh_key.c,v 1.37 2022/01/07 09:27:13 tb Exp $ */

/* 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 <stdio.h>

#include <openssl/bn.h>

#include <openssl/dh.h>

#include <openssl/err.h>

#include "bn_lcl.h"

#include "dh_local.h"

static int generate_key(DH *dh);

static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh);

static int dh_bn_mod_exp(const DH *dh, BIGNUM *r, const BIGNUM *a,

      const BIGNUM *p, const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx);

static int dh_init(DH *dh);

static int dh_finish(DH *dh);

int

DH_generate_key(DH *dh)

{

  return dh->meth->generate_key(dh);

}

int

DH_compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)

{

  return dh->meth->compute_key(key, pub_key, dh);

}

static DH_METHOD dh_ossl = {

  .name = "OpenSSL DH Method",

  .generate_key = generate_key,

  .compute_key = compute_key,

  .bn_mod_exp = dh_bn_mod_exp,

  .init = dh_init,

  .finish = dh_finish,

};

const DH_METHOD *

DH_OpenSSL(void)

{

  return &dh_ossl;

}

static int

generate_key(DH *dh)

{

  int ok = 0;

  unsigned l;

  BN_CTX *ctx;

  BN_MONT_CTX *mont = NULL;

  BIGNUM *pub_key = NULL, *priv_key = NULL, *two = NULL;

  if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) {

    DHerror(DH_R_MODULUS_TOO_LARGE);

    return 0;

  }

  ctx = BN_CTX_new();

  if (ctx == NULL)

    goto err;

  if ((priv_key = dh->priv_key) == NULL) {

    if ((priv_key = BN_new()) == NULL)

      goto err;

  }

  if ((pub_key = dh->pub_key) == NULL) {

    if ((pub_key = BN_new()) == NULL)

      goto err;

  }

  if (dh->flags & DH_FLAG_CACHE_MONT_P) {

    mont = BN_MONT_CTX_set_locked(&dh->method_mont_p,

        CRYPTO_LOCK_DH, dh->p, ctx);

    if (!mont)

      goto err;

  }

  if (dh->priv_key == NULL) {

    if (dh->q) {

      if ((two = BN_new()) == NULL)

        goto err;

      if (!BN_add(two, BN_value_one(), BN_value_one()))

        goto err;

      if (!bn_rand_interval(priv_key, two, dh->q))

        goto err;

    } else {

      /* secret exponent length */

      l = dh->length ? dh->length : BN_num_bits(dh->p) - 1;

      if (!BN_rand(priv_key, l, 0, 0))

        goto err;

    }

  }

  if (!dh->meth->bn_mod_exp(dh, pub_key, dh->g, priv_key, dh->p, ctx,

      mont))

    goto err;

  dh->pub_key = pub_key;

  dh->priv_key = priv_key;

  ok = 1;

 err:

  if (ok != 1)

    DHerror(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);

  BN_free(two);

  return ok;

}

static int

compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)

{

  BN_CTX *ctx = NULL;

  BN_MONT_CTX *mont = NULL;

  BIGNUM *tmp;

  int ret = -1;

        int check_result;

  if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) {

    DHerror(DH_R_MODULUS_TOO_LARGE);

    goto err;

  }

  ctx = BN_CTX_new();

  if (ctx == NULL)

    goto err;

  BN_CTX_start(ctx);

  if ((tmp = BN_CTX_get(ctx)) == NULL)

    goto err;

  if (dh->priv_key == NULL) {

    DHerror(DH_R_NO_PRIVATE_VALUE);

    goto err;

  }

  if (dh->flags & DH_FLAG_CACHE_MONT_P) {

    mont = BN_MONT_CTX_set_locked(&dh->method_mont_p,

        CRYPTO_LOCK_DH, dh->p, ctx);

    BN_set_flags(dh->priv_key, BN_FLG_CONSTTIME);

    if (!mont)

      goto err;

  }

        if (!DH_check_pub_key(dh, pub_key, &check_result) || check_result) {

    DHerror(DH_R_INVALID_PUBKEY);

    goto err;

  }

  if (!dh->meth->bn_mod_exp(dh, tmp, pub_key, dh->priv_key, dh->p, ctx,

      mont)) {

    DHerror(ERR_R_BN_LIB);

    goto err;

  }

  ret = BN_bn2bin(tmp, key);

 err:

  if (ctx != NULL) {

    BN_CTX_end(ctx);

    BN_CTX_free(ctx);

  }

  return ret;

}

static int

dh_bn_mod_exp(const DH *dh, BIGNUM *r, const BIGNUM *a, const BIGNUM *p,

    const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx)

{

  return BN_mod_exp_mont_ct(r, a, p, m, ctx, m_ctx);

}

static int

dh_init(DH *dh)

{

  dh->flags |= DH_FLAG_CACHE_MONT_P;

  return 1;

}

static int

dh_finish(DH *dh)

{

  BN_MONT_CTX_free(dh->method_mont_p);

  return 1;

}