/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
/**
 * Copyright (c) 2017-2020, Regents of the University of California.
 *
 * This file is part of ndncert, a certificate management system based on NDN.
 *
 * ndncert is free software: you can redistribute it and/or modify it under the terms
 * of the GNU General Public License as published by the Free Software Foundation, either
 * version 3 of the License, or (at your option) any later version.
 *
 * ndncert is distributed in the hope that it will be useful, but WITHOUT ANY
 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
 * PARTICULAR PURPOSE.  See the GNU General Public License for more details.
 *
 * You should have received copies of the GNU General Public License along with
 * ndncert, e.g., in COPYING.md file.  If not, see <http://www.gnu.org/licenses/>.
 *
 * See AUTHORS.md for complete list of ndncert authors and contributors.
 */

#ifndef NDNCERT_PROTOCOL_DETAIL_CRYPTO_HELPER_HPP
#define NDNCERT_PROTOCOL_DETAIL_CRYPTO_HELPER_HPP

#include "ndncert-common.hpp"

namespace ndn {
namespace ndncert {

static const int INFO_LEN = 10;
static const uint8_t INFO[] = {0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7, 0xf8, 0xf9};
static const int AES_128_KEY_LEN = 16;

class ECDHState
{
public:
  ECDHState();
  ~ECDHState();

  std::string
  getBase64PubKey();

  uint8_t*
  deriveSecret(const std::string& peerKeyStr);

  uint8_t m_publicKey[256];
  size_t m_publicKeyLen;
  uint8_t m_sharedSecret[256];
  size_t m_sharedSecretLen;

PUBLIC_WITH_TESTS_ELSE_PRIVATE:
  uint8_t*
  deriveSecret(const uint8_t* peerkey, int peerKeySize);

  uint8_t*
  getRawSelfPubKey();

private:
  struct ECDH_CTX;
  unique_ptr<ECDH_CTX> context;
};

/**
 * HMAC based key derivation function (HKDF)
 * @p secret, intput, the input to the HKDF
 * @p secretLen, intput, the length of the secret
 * @p salt, intput, the salt used in HKDF
 * @p saltLen, intput, the length of the salt
 * @p output, output, the output of the HKDF
 * @p output_len, intput, the length of expected output
 * @p info, intput, the additional information used in HKDF
 * @p info_len, intput, the additional information used in HKDF
 * @return the length of the derived key if successful, -1 if failed
 */
int
hkdf(const uint8_t* secret, int secret_len,
     const uint8_t* salt, int salt_len,
     uint8_t* output, int output_len,
     const uint8_t* info = INFO, int info_len = INFO_LEN);

/**
 * HMAC based on SHA-256
 * @p data, intput, the array to hmac
 * @p data_length, intput, the length of the array
 * @p key, intput, the key for the function
 * @p key_len, intput, the length of the key
 * @p result, output, result of the HMAC. Enough memory (32 Bytes) must be allocated beforehands
 * @throw runtime_error when an error occurred in the underlying HMAC.
 */
void
hmac_sha256(const uint8_t* data, const unsigned data_length,
            const uint8_t* key, const unsigned key_length,
            uint8_t* result);

/**
 * Authenticated GCM 128 Encryption with associated data
 * @p plaintext, input, plaintext
 * @p plaintext_len, input, size of plaintext
 * @p associated, input, associated authentication data
 * @p associated_len, input, size of associated authentication data
 * @p key, input, 16 bytes AES key
 * @p iv, input, 12 bytes IV
 * @p ciphertext, output, enough memory must be allocated beforehands
 * @p tag, output, 16 bytes tag
 * @return the size of ciphertext
 * @throw runtime_error when there is an error in the process of encryption
 */
int
aes_gcm_128_encrypt(const uint8_t* plaintext, size_t plaintext_len, const uint8_t* associated, size_t associated_len,
                    const uint8_t* key, const uint8_t* iv, uint8_t* ciphertext, uint8_t* tag);

/**
 * Authenticated GCM 128 Decryption with associated data
 * @p ciphertext, input, ciphertext
 * @p ciphertext_len, input, size of ciphertext
 * @p associated, input, associated authentication data
 * @p associated_len, input, size of associated authentication data
 * @p tag, input, 16 bytes tag
 * @p key, input, 16 bytes AES key
 * @p iv, input, 12 bytes IV
 * @p plaintext, output, enough memory must be allocated beforehands
 * @return the size of plaintext or -1 if the verification fails
 * @throw runtime_error when there is an error in the process of encryption
 */
int
aes_gcm_128_decrypt(const uint8_t* ciphertext, size_t ciphertext_len, const uint8_t* associated, size_t associated_len,
                    const uint8_t* tag, const uint8_t* key, const uint8_t* iv, uint8_t* plaintext);

/**
 * Encode the payload into TLV block with Authenticated GCM 128 Encryption
 * @p tlv::type, intput, the TLV TYPE of the encoded block, either ApplicationParameters or Content
 * @p key, intput, 16 Bytes, the AES key used for encryption
 * @p payload, input, the plaintext payload
 * @p payloadSize, input, the size of the plaintext payload
 * @p associatedData, input, associated data used for authentication
 * @p associatedDataSize, input, the size of associated data
 * @return the TLV block with @p tlv::type TLV TYPE
 */
Block
encodeBlockWithAesGcm128(uint32_t tlv_type, const uint8_t* key, const uint8_t* payload, size_t payloadSize,
                         const uint8_t* associatedData, size_t associatedDataSize);

/**
 * Decode the payload from TLV block with Authenticated GCM 128 Encryption
 * @p block, intput, the TLV block in the format of NDNCERT protocol
 * @p key, intput, 16 Bytes, the AES key used for encryption
 * @p associatedData, input, associated data used for authentication
 * @p associatedDataSize, input, the size of associated data
 * @return the plaintext buffer
 */
Buffer
decodeBlockWithAesGcm128(const Block& block, const uint8_t* key,
                         const uint8_t* associatedData, size_t associatedDataSize);

} // namespace ndncert
} // namespace ndn

#endif // NDNCERT_PROTOCOL_DETAIL_CRYPTO_HELPER_HPP