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) 2000-2002 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
   *    licensing@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 <openssl/ecdh.h>
  
  #include <limits.h>
  #include <string.h>
  
  #include <openssl/bn.h>
  #include <openssl/ec.h>
  #include <openssl/ec_key.h>
  #include <openssl/err.h>
  #include <openssl/mem.h>
  #include <openssl/sha.h>
  
  #include "../ec/internal.h"
  
  
  int ECDH_compute_key_fips(uint8_t *out, size_t out_len, const EC_POINT *pub_key,
                            const EC_KEY *priv_key) {
    if (priv_key->priv_key == NULL) {
      OPENSSL_PUT_ERROR(ECDH, ECDH_R_NO_PRIVATE_VALUE);
      return 0;
    }
    const EC_SCALAR *const priv = &priv_key->priv_key->scalar;
  
    BN_CTX *ctx = BN_CTX_new();
    if (ctx == NULL) {
      return 0;
    }
    BN_CTX_start(ctx);
  
    int ret = 0;
    size_t buflen = 0;
    uint8_t *buf = NULL;
  
    const EC_GROUP *const group = EC_KEY_get0_group(priv_key);
    EC_POINT *shared_point = EC_POINT_new(group);
    if (shared_point == NULL) {
      OPENSSL_PUT_ERROR(ECDH, ERR_R_MALLOC_FAILURE);
      goto err;
    }
  
    if (!ec_point_mul_scalar(group, shared_point, NULL, pub_key, priv, ctx)) {
      OPENSSL_PUT_ERROR(ECDH, ECDH_R_POINT_ARITHMETIC_FAILURE);
      goto err;
    }
  
    BIGNUM *x = BN_CTX_get(ctx);
    if (!x) {
      OPENSSL_PUT_ERROR(ECDH, ERR_R_MALLOC_FAILURE);
      goto err;
    }
  
    if (!EC_POINT_get_affine_coordinates_GFp(group, shared_point, x, NULL, ctx)) {
      OPENSSL_PUT_ERROR(ECDH, ECDH_R_POINT_ARITHMETIC_FAILURE);
      goto err;
    }
  
    buflen = (EC_GROUP_get_degree(group) + 7) / 8;
    buf = OPENSSL_malloc(buflen);
    if (buf == NULL) {
      OPENSSL_PUT_ERROR(ECDH, ERR_R_MALLOC_FAILURE);
      goto err;
    }
  
    if (!BN_bn2bin_padded(buf, buflen, x)) {
      OPENSSL_PUT_ERROR(ECDH, ERR_R_INTERNAL_ERROR);
      goto err;
    }
  
    switch (out_len) {
      case SHA224_DIGEST_LENGTH:
        SHA224(buf, buflen, out);
        break;
      case SHA256_DIGEST_LENGTH:
        SHA256(buf, buflen, out);
        break;
      case SHA384_DIGEST_LENGTH:
        SHA384(buf, buflen, out);
        break;
      case SHA512_DIGEST_LENGTH:
        SHA512(buf, buflen, out);
        break;
      default:
        OPENSSL_PUT_ERROR(ECDH, ECDH_R_UNKNOWN_DIGEST_LENGTH);
        goto err;
    }
  
    ret = 1;
  
  err:
    OPENSSL_free(buf);
    EC_POINT_free(shared_point);
    BN_CTX_end(ctx);
    BN_CTX_free(ctx);
    return ret;
  }
  