// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
// Mobius Forensic Toolkit
// Copyright (C) 2008,2009,2010,2011,2012,2013,2014,2015,2016,2017,2018 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 <mobius/imagefile/ewf/segment_decoder.h>
#include <mobius/decoder/data_decoder.h>
#include <mobius/datetime/conv_unix_timestamp.h>
#include <mobius/io/reader_evaluator.h>
#include <mobius/crypt/hash_functor.h>
#include <mobius/crypt/hash_adler32.h>
#include <mobius/string_functions.h>
#include <mobius/zlib_functions.h>
#include <mobius/charset.h>

// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
// constants
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
static constexpr int FILE_HEADER_SIZE = 13;
static constexpr int SECTION_HEADER_SIZE = 76;

namespace mobius
{
namespace imagefile
{
namespace ewf
{
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
//! \brief convert an Adler-32 digest from bytearray to uint32_t
//! \param digest bytearray digest (4 bytes length)
//! \return std::uint32_t
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
static std::uint32_t
digest_to_uint32_t (const mobius::bytearray& digest)
{
  return std::uint32_t (digest[0]) << 24 |
         std::uint32_t (digest[1]) << 16 |
         std::uint32_t (digest[2]) << 8 |
         std::uint32_t (digest[3]);
}

// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
//! \brief iterator constructor
//! \param reader reader object
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
segment_decoder::const_iterator::const_iterator (const segment_decoder *decoder, offset_type offset)
 : decoder_ (decoder)
{
  section_ = decoder_->decode_section (offset);
}

// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
//! \brief check if two iterators are equal
//! \param i iterator
//! \return true/false
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
bool
segment_decoder::const_iterator::operator== (const const_iterator& i)
{
  return section_.get_offset () == i.section_.get_offset ();
}

// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
//! \brief operator++
//! \return reference to object
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
segment_decoder::const_iterator&
segment_decoder::const_iterator::operator++ ()
{
  auto offset = section_.get_offset ();
  auto next_offset = section_.get_next_offset ();
  
  if (offset == next_offset)
    section_ = section ();
  
  else
    section_ = decoder_->decode_section (next_offset);

  return *this;
}

// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
//! \brief constructor
//! \see EWCF 2.1.1
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
segment_decoder::segment_decoder (mobius::io::reader reader)
 : reader_ (reader)
{
  const mobius::bytearray EWF_SIGNATURE = {'E', 'V', 'F', 0x09, 0x0d, 0x0a, 0xff, 0x00};

  mobius::decoder::data_decoder decoder (reader);
  mobius::bytearray signature = decoder.get_bytearray_by_size (EWF_SIGNATURE.size ());

  if (signature == EWF_SIGNATURE)
    {
      decoder.skip (1);
      segment_number_ = decoder.get_uint32_le ();
      is_valid_ = true;
    }
}

// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
//! \brief get first section
//! \return section
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
segment_decoder::const_iterator
segment_decoder::begin () const
{
  return const_iterator (this, FILE_HEADER_SIZE);
}

// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
//! \brief get ending section
//! \return section
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
segment_decoder::const_iterator
segment_decoder::end () const
{
  return const_iterator ();
}

// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
//! \brief decode generic section
//! \param offset offset from the beginning of data
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
const section
segment_decoder::decode_section (offset_type offset) const
{
  mobius::crypt::hash_functor <mobius::crypt::hash_adler32> hash_functor;
  auto reader = mobius::io::reader_evaluator (reader_, hash_functor);

  mobius::decoder::data_decoder decoder (reader);
  decoder.seek (offset);

  section sec;
  sec.set_offset (offset);
  sec.set_name (decoder.get_string_by_size (16));
  sec.set_next_offset (decoder.get_uint64_le ());
  sec.set_size (decoder.get_uint64_le ());
  decoder.get_bytearray_by_size (40);           // padding

  std::uint32_t calculated_adler32 = digest_to_uint32_t (hash_functor.get_digest ());
  sec.set_calculated_adler32 (calculated_adler32);

  sec.set_adler32 (decoder.get_uint32_le ());

  return sec;
}

// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
//! \brief decode <header> and <header2> sections
//! \return header_section
//! \see EWCF 3.4
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
const header_section
segment_decoder::decode_header_section (const section& arg_section) const
{
  mobius::decoder::data_decoder decoder (reader_);
  decoder.seek (arg_section.get_offset () + SECTION_HEADER_SIZE);

  // create header_section
  header_section section (arg_section);

  // get data from header section  
  mobius::bytearray data = decoder.get_bytearray_by_size (section.get_size () - SECTION_HEADER_SIZE);
  data = zlib_decompress (data);
  const std::string text = conv_charset_to_utf8 (data, section.get_name () == "header2" ? "UTF-16" : "ASCII");

  // format header metadata lines
  auto lines = mobius::string::split (text, "\n");
  for (auto& line : lines)
    line = mobius::string::rstrip (line, "\r ");

  // check valid header
  if (lines[1] == "main" && lines.size () > 3)
    {
      auto vars = mobius::string::split (lines[2], "\t");
      auto values = mobius::string::split (lines[3], "\t");
      std::string section_text;

      for (std::size_t i = 0;i < vars.size ();i++)
        {
          auto var = vars[i];
          auto value = values[i];

          if (!section_text.empty ())
            section_text += '\n';
          section_text += var + " = " + value;

          if (var == "ov")
            section.set_acquisition_platform (value);
          
          else if (var == "e")
            section.set_acquisition_user (value);

          else if (var == "md")
            section.set_drive_model (value);

          else if (var == "sn")
            section.set_drive_serial_number (value);

          else if (var == "av")
            {
              if (value.length () > 0 && isdigit (value[0]))
                section.set_acquisition_tool ("Encase v" + value);
              else
                section.set_acquisition_tool (value);
            }

          else if (var == "m")
            {
              if (value.find (' ') != std::string::npos)
                {
                  auto d = mobius::string::split (value);
                  section.set_acquisition_time (mobius::datetime::datetime (
                        stoi (d[0]), stoi (d[1]), stoi (d[2]), stoi (d[3]), stoi (d[4]), stoi (d[5])));
                }
              else
                section.set_acquisition_time (mobius::datetime::datetime_from_unix_timestamp (stol (value)));
            }
        }
      section.set_text (section_text);
    }
  else
    for (auto line : lines)
        printf ("INVALID HEADER<%s>\n", line.c_str ());

  return section;
}

// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
//! \brief decode <hash> section
//! \param arg_section generic section
//! \return hash_section
//! \see EWCF 3.18
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
const hash_section
segment_decoder::decode_hash_section (const section& arg_section) const
{
  mobius::decoder::data_decoder decoder (reader_);
  decoder.seek (arg_section.get_offset () + SECTION_HEADER_SIZE);

  hash_section section (arg_section);
  section.set_md5_hash (decoder.get_bytearray_by_size (16).to_hexstring ());
  decoder.skip (16);
  section.set_section_adler32 (decoder.get_uint32_le ());

  return section;
}

// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
//! \brief decode <volume>, <disk> and <data> sections
//! \param arg_section generic section
//! \return volume_section
//! \see EWCF 3.5
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
const volume_section
segment_decoder::decode_volume_section (const section& arg_section) const
{
  mobius::decoder::data_decoder decoder (reader_);
  decoder.seek (arg_section.get_offset () + SECTION_HEADER_SIZE);

  volume_section section (arg_section);
  section.set_media_type (decoder.get_uint32_le ());
  section.set_chunk_count (decoder.get_uint32_le ());
  section.set_chunk_sectors (decoder.get_uint32_le ());
  section.set_sector_size (decoder.get_uint32_le ());
  section.set_sectors (decoder.get_uint64_le ());
  decoder.skip (12); // skip CHS data
  section.set_media_flags (decoder.get_uint32_le ());
  decoder.skip (12);
  section.set_compression_level (decoder.get_uint32_le ());
  decoder.skip (8);
  section.set_guid (decoder.get_bytearray_by_size (16).to_hexstring ());
  decoder.skip (968);
  section.set_section_adler32 (decoder.get_uint32_le ());
  
  return section;
}

// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
//! \brief decode <table> section
//! \param arg_section generic section
//! \return table_section
//! \see EWCF 3.9
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
const table_section
segment_decoder::decode_table_section (const section& arg_section) const
{
  mobius::decoder::data_decoder decoder (reader_);
  decoder.seek (arg_section.get_offset () + SECTION_HEADER_SIZE);

  table_section section (arg_section);
  const auto chunk_count = decoder.get_uint32_le ();
  section.set_chunk_count (chunk_count);
  decoder.skip (4);
  section.set_base_offset (decoder.get_uint64_le ());
  decoder.skip (4);
  section.set_section_adler32 (decoder.get_uint32_le ());

  auto data = decoder.get_bytearray_by_size (4 * chunk_count);

  for (std::uint32_t i = 0;i < chunk_count * 4;i += 4)
    {
      auto offset =
         std::uint32_t (data[i]) |
        (std::uint32_t (data[i+1]) << 8) |
        (std::uint32_t (data[i+2]) << 16) |
        (std::uint32_t (data[i+3]) << 24);

      section.add_offset (offset);
    }

  section.set_table_adler32 (decoder.get_uint32_le ());

  return section;
}

} // namespace ewf
} // namespace imagefile
} // namespace mobius
