// Copyright 2002-2016 The OpenSSL Project Authors. All Rights Reserved.

// Copyright (c) 2002, Oracle and/or its affiliates. All rights reserved.

//

// Licensed under the Apache License, Version 2.0 (the "License");

// you may not use this file except in compliance with the License.

// You may obtain a copy of the License at

//

//     https://www.apache.org/licenses/LICENSE-2.0

//

// Unless required by applicable law or agreed to in writing, software

// distributed under the License is distributed on an "AS IS" BASIS,

// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

// See the License for the specific language governing permissions and

// limitations under the License.

#include <openssl/ecdh.h>

#include <limits.h>

#include <string.h>

#include <openssl/digest.h>

#include <openssl/err.h>

#include <openssl/mem.h>

#include "../fipsmodule/ec/internal.h"

#include "../internal.h"

using namespace bssl;

int ECDH_compute_key(void *out, size_t out_len, const EC_POINT *pub_key,

                     const EC_KEY *priv_key,

                     void *(*kdf)(const void *in, size_t inlen, void *out,

                                  size_t *out_len)) {

  if (FromOpaque(priv_key)->priv_key == nullptr) {

    OPENSSL_PUT_ERROR(ECDH, ECDH_R_NO_PRIVATE_VALUE);

    return -1;

  }

  const EC_SCALAR *const priv = &FromOpaque(priv_key)->priv_key->scalar;

  const EC_GROUP *const group = EC_KEY_get0_group(priv_key);

  if (EC_GROUP_cmp(group, pub_key->group, nullptr) != 0) {

    OPENSSL_PUT_ERROR(EC, EC_R_INCOMPATIBLE_OBJECTS);

    return -1;

  }

  EC_JACOBIAN shared_point;

  uint8_t buf[EC_MAX_BYTES];

  size_t buf_len;

  if (!ec_point_mul_scalar(group, &shared_point, &pub_key->raw, priv) ||

      !ec_get_x_coordinate_as_bytes(group, buf, &buf_len, sizeof(buf),

                                    &shared_point)) {

    OPENSSL_PUT_ERROR(ECDH, ECDH_R_POINT_ARITHMETIC_FAILURE);

    return -1;

  }

  if (kdf != nullptr) {

    if (kdf(buf, buf_len, out, &out_len) == nullptr) {

      OPENSSL_PUT_ERROR(ECDH, ECDH_R_KDF_FAILED);

      return -1;

    }

  } else {

    // no KDF, just copy as much as we can

    if (buf_len < out_len) {

      out_len = buf_len;

    }

    OPENSSL_memcpy(out, buf, out_len);

  }

  if (out_len > INT_MAX) {

    OPENSSL_PUT_ERROR(ECDH, ERR_R_OVERFLOW);

    return -1;

  }

  return (int)out_len;

}