text: /* ====================================================================
   * Copyright 2002 Sun Microsystems, Inc. ALL RIGHTS RESERVED.
   *
   * The Elliptic Curve Public-Key Crypto Library (ECC Code) included
   * herein is developed by SUN MICROSYSTEMS, INC., and is contributed
   * to the OpenSSL project.
   *
   * The ECC Code is licensed pursuant to the OpenSSL open source
   * license provided below.
   *
   * The ECDH software is originally written by Douglas Stebila of
   * Sun Microsystems Laboratories.
   *
   */
  /* ====================================================================
   * Copyright (c) 1998-2003 The OpenSSL Project.  All rights reserved.
   *
   * 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 above 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 acknowledgment:
   *    "This product includes software developed by the OpenSSL Project
   *    for use in the OpenSSL Toolkit. (http://www.OpenSSL.org/)"
   *
   * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
   *    endorse or promote products derived from this software without
   *    prior written permission. For written permission, please contact
   *    openssl-core@OpenSSL.org.
   *
   * 5. Products derived from this software may not be called "OpenSSL"
   *    nor may "OpenSSL" appear in their names without prior written
   *    permission of the OpenSSL Project.
   *
   * 6. Redistributions of any form whatsoever must retain the following
   *    acknowledgment:
   *    "This product includes software developed by the OpenSSL Project
   *    for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)"
   *
   * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
   * EXPRESSED 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 OpenSSL PROJECT OR
   * ITS 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.
   * ====================================================================
   *
   * This product includes cryptographic software written by Eric Young
   * (eay@cryptsoft.com).  This product includes software written by Tim
   * Hudson (tjh@cryptsoft.com).
   *
   */
  
  #include <string.h>
  #include <limits.h>
  
  #include "internal/cryptlib.h"
  
  #include <openssl/err.h>
  #include <openssl/bn.h>
  #include <openssl/objects.h>
  #include <openssl/ec.h>
  #include "ec_lcl.h"
  
  int ossl_ecdh_compute_key(unsigned char **psec, size_t *pseclen,
                            const EC_POINT *pub_key, const EC_KEY *ecdh)
  {
      if (ecdh->group->meth->ecdh_compute_key == NULL) {
          ECerr(EC_F_OSSL_ECDH_COMPUTE_KEY, EC_R_CURVE_DOES_NOT_SUPPORT_ECDH);
          return -1;
      }
  
      return ecdh->group->meth->ecdh_compute_key(psec, pseclen, pub_key, ecdh);
  }
  
  /*-
   * This implementation is based on the following primitives in the IEEE 1363 standard:
   *  - ECKAS-DH1
   *  - ECSVDP-DH
   */
  int ecdh_simple_compute_key(unsigned char **pout, size_t *poutlen,
                              const EC_POINT *pub_key, const EC_KEY *ecdh)
  {
      BN_CTX *ctx;
      EC_POINT *tmp = NULL;
      BIGNUM *x = NULL, *y = NULL;
      const BIGNUM *priv_key;
      const EC_GROUP *group;
      int ret = 0;
      size_t buflen, len;
      unsigned char *buf = NULL;
  
      if ((ctx = BN_CTX_new()) == NULL)
          goto err;
      BN_CTX_start(ctx);
      x = BN_CTX_get(ctx);
      y = BN_CTX_get(ctx);
  
      priv_key = EC_KEY_get0_private_key(ecdh);
      if (priv_key == NULL) {
          ECerr(EC_F_ECDH_SIMPLE_COMPUTE_KEY, EC_R_NO_PRIVATE_VALUE);
          goto err;
      }
  
      group = EC_KEY_get0_group(ecdh);
  
      if (EC_KEY_get_flags(ecdh) & EC_FLAG_COFACTOR_ECDH) {
          if (!EC_GROUP_get_cofactor(group, x, NULL) ||
              !BN_mul(x, x, priv_key, ctx)) {
              ECerr(EC_F_ECDH_SIMPLE_COMPUTE_KEY, ERR_R_MALLOC_FAILURE);
              goto err;
          }
          priv_key = x;
      }
  
      if ((tmp = EC_POINT_new(group)) == NULL) {
          ECerr(EC_F_ECDH_SIMPLE_COMPUTE_KEY, ERR_R_MALLOC_FAILURE);
          goto err;
      }
  
      if (!EC_POINT_mul(group, tmp, NULL, pub_key, priv_key, ctx)) {
          ECerr(EC_F_ECDH_SIMPLE_COMPUTE_KEY, EC_R_POINT_ARITHMETIC_FAILURE);
          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, x, y, ctx)) {
              ECerr(EC_F_ECDH_SIMPLE_COMPUTE_KEY, EC_R_POINT_ARITHMETIC_FAILURE);
              goto err;
          }
      }
  #ifndef OPENSSL_NO_EC2M
      else {
          if (!EC_POINT_get_affine_coordinates_GF2m(group, tmp, x, y, ctx)) {
              ECerr(EC_F_ECDH_SIMPLE_COMPUTE_KEY, EC_R_POINT_ARITHMETIC_FAILURE);
              goto err;
          }
      }
  #endif
  
      buflen = (EC_GROUP_get_degree(group) + 7) / 8;
      len = BN_num_bytes(x);
      if (len > buflen) {
          ECerr(EC_F_ECDH_SIMPLE_COMPUTE_KEY, ERR_R_INTERNAL_ERROR);
          goto err;
      }
      if ((buf = OPENSSL_malloc(buflen)) == NULL) {
          ECerr(EC_F_ECDH_SIMPLE_COMPUTE_KEY, ERR_R_MALLOC_FAILURE);
          goto err;
      }
  
      memset(buf, 0, buflen - len);
      if (len != (size_t)BN_bn2bin(x, buf + buflen - len)) {
          ECerr(EC_F_ECDH_SIMPLE_COMPUTE_KEY, ERR_R_BN_LIB);
          goto err;
      }
  
      *pout = buf;
      *poutlen = buflen;
      buf = NULL;
  
      ret = 1;
  
   err:
      EC_POINT_free(tmp);
      if (ctx)
          BN_CTX_end(ctx);
      BN_CTX_free(ctx);
      OPENSSL_free(buf);
      return ret;
  }
  