// Copyright 1999-2016 The OpenSSL Project Authors. 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/evp.h>

#include <string.h>

#include <openssl/err.h>

#include <openssl/hmac.h>

#include "../internal.h"

using namespace bssl;

int PKCS5_PBKDF2_HMAC(const char *password, size_t password_len,

                      const uint8_t *salt, size_t salt_len, uint32_t iterations,

                      const EVP_MD *digest, size_t key_len, uint8_t *out_key) {

  // See RFC 8018, section 5.2.

  ScopedHMAC_CTX hctx;

  if (!HMAC_Init_ex(hctx.get(), password, password_len, digest, nullptr)) {

    return 0;

  }

  uint32_t i = 1;

  size_t md_len = EVP_MD_size(digest);

  if (key_len > ((uint64_t{1} << 32) - 1) * md_len) {

    OPENSSL_PUT_ERROR(EVP, EVP_R_INVALID_SECRET_LENGTH);

    return 0;

  }

  while (key_len > 0) {

    size_t todo = md_len;

    if (todo > key_len) {

      todo = key_len;

    }

    uint8_t i_buf[4];

    i_buf[0] = (uint8_t)((i >> 24) & 0xff);

    i_buf[1] = (uint8_t)((i >> 16) & 0xff);

    i_buf[2] = (uint8_t)((i >> 8) & 0xff);

    i_buf[3] = (uint8_t)(i & 0xff);

    // Compute U_1.

    uint8_t digest_tmp[EVP_MAX_MD_SIZE];

    if (!HMAC_Init_ex(hctx.get(), nullptr, 0, nullptr, nullptr) ||

        !HMAC_Update(hctx.get(), salt, salt_len) ||

        !HMAC_Update(hctx.get(), i_buf, 4) ||

        !HMAC_Final(hctx.get(), digest_tmp, nullptr)) {

      return 0;

    }

    OPENSSL_memcpy(out_key, digest_tmp, todo);

    for (uint32_t j = 1; j < iterations; j++) {

      // Compute the remaining U_* values and XOR.

      if (!HMAC_Init_ex(hctx.get(), nullptr, 0, nullptr, nullptr) ||

          !HMAC_Update(hctx.get(), digest_tmp, md_len) ||

          !HMAC_Final(hctx.get(), digest_tmp, nullptr)) {

        return 0;

      }

      for (size_t k = 0; k < todo; k++) {

        out_key[k] ^= digest_tmp[k];

      }

    }

    key_len -= todo;

    out_key += todo;

    i++;

  }

  // RFC 8018 describes iterations (c) as being a "positive integer", so a

  // value of 0 is an error.

  //

  // Unfortunately not all consumers of PKCS5_PBKDF2_HMAC() check their return

  // value, expecting it to succeed and unconditionally using `out_key`.  As a

  // precaution for such callsites in external code, the old behavior of

  // iterations < 1 being treated as iterations == 1 is preserved, but

  // additionally an error result is returned.

  //

  // TODO(eroman): Figure out how to remove this compatibility hack, or change

  // the default to something more sensible like 2048.

  if (iterations == 0) {

    return 0;

  }

  return 1;

}

int PKCS5_PBKDF2_HMAC_SHA1(const char *password, size_t password_len,

                           const uint8_t *salt, size_t salt_len,

                           uint32_t iterations, size_t key_len,

                           uint8_t *out_key) {

  return PKCS5_PBKDF2_HMAC(password, password_len, salt, salt_len, iterations,

                           EVP_sha1(), key_len, out_key);

}