// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
// Mobius Forensic Toolkit
// Copyright (C) 2008,2009,2010,2011,2012,2013,2014,2015,2016,2017,2018,2019,2020,2021 Eduardo Aguiar
//
// This program 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 2, or (at your option) any later
// version.
//
// This program 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 a copy of the GNU General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
#include "pkcs5.h"
#include "hash.h"
#include "hmac.h"
#include <mobius/exception.inc>
#include <stdexcept>

namespace mobius
{
namespace crypt
{
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
//! \brief Unpad plain text
//! \param data Plain text data
//! \return Unpadded data
//! \see RFC 2898 (section 6.1.1.4)
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
mobius::bytearray
pkcs5_unpad (const mobius::bytearray& data)
{
  mobius::bytearray unpad_data;

  if (data)
    {
      auto pad_size = data[data.size () - 1];

      if (pad_size < data.size ())
        unpad_data = data.slice (0, data.size () - pad_size - 1);
    }

  return unpad_data;
}

// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
//! \brief PBKDF1 key derivation function
//! \param hash_id Hash algorithm (either "md2", "md5" or "sha1")
//! \param key Key
//! \param salt Salt
//! \param count Iterations
//! \param dklen Derived key length in bytes
//! \see RFC 2898
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
mobius::bytearray
pbkdf1 (
  const std::string& hash_id,
  const mobius::bytearray& key,
  const mobius::bytearray& salt,
  std::uint32_t count,
  std::uint16_t dklen
  )
{
  // Validate input parameters
  if (dklen == 0)
    throw std::out_of_range (MOBIUS_EXCEPTION_MSG ("Derived key length must be > 0"));

  if (hash_id == "sha1")
    {
      if (dklen > 20)
        throw std::out_of_range (MOBIUS_EXCEPTION_MSG ("Derived key too long"));
    }

  else if (hash_id == "md2" || hash_id == "md5")
    {
      if (dklen > 16)
        throw std::out_of_range (MOBIUS_EXCEPTION_MSG ("Derived key too long"));
    }

  else
    throw std::out_of_range (MOBIUS_EXCEPTION_MSG ("Invalid hash algorithm"));

  // Calculate derived key
  mobius::crypt::hash h (hash_id);
  h.update (key);
  h.update (salt);
  mobius::bytearray t = h.get_digest ();

  for (std::uint32_t i = 1; i < count; i++)
    {
      mobius::crypt::hash h2 (hash_id);
      h2.update (t);
      t = h2.get_digest ();
    }

  return t.slice (0, dklen - 1);
}

// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
//! \brief PBKDF2 key derivation function (with HMAC)
//! \param hash_id hash algorithm (e.g. "md2", "md5", "sha1")
//! \param key Key
//! \param salt Salt
//! \param count Iterations
//! \param dklen Derived key length in bytes
//! \see RFC 2898
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
mobius::bytearray
pbkdf2_hmac (
  const std::string& hash_id,
  const mobius::bytearray& key,
  const mobius::bytearray& salt,
  std::uint32_t count,
  std::uint16_t dklen
  )
{
  // Validate input parameters
  if (dklen == 0)
    throw std::out_of_range (MOBIUS_EXCEPTION_MSG ("Derived key length must be > 0"));

  // Calculate derived key
  std::uint32_t i = 1;
  mobius::bytearray dk;
  mobius::crypt::hmac hmac (key, hash_id);

  while (dk.size () < dklen)
    {
      hmac.reset ();
      hmac.update (salt);
      hmac.update (
      {
        static_cast <uint8_t> (i >> 24),
        static_cast <uint8_t> (i >> 16),
        static_cast <uint8_t> (i >> 8),
        static_cast <uint8_t> (i)
      });

      auto t = hmac.get_digest ();
      auto u = t;

      for (std::uint32_t j = 1; j < count; j++)
        {
          hmac.reset ();
          hmac.update (u);
          u = hmac.get_digest ();
          t ^= u;
        }

      dk += t;
      ++i;
    }

  return dk.slice (0, dklen - 1);
}

} // namespace crypt
} // namespace mobius
