// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
// Mobius Forensic Toolkit
// Copyright (C) 2008,2009,2010,2011,2012,2013,2014,2015,2016,2017,2018,2019,2020,2021,2022,2023,2024,2025 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 "imagefile_impl.h"
#include "reader_impl.h"
#include <mobius/decoder/data_decoder.h>
#include <mobius/exception.inc>
#include <mobius/io/file.h>
#include <mobius/io/reader.h>
#include <stdexcept>

namespace
{
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
// Constants
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
static constexpr int SECTOR_SIZE = 512;		// always 512 bytes
static constexpr int DISK_TYPE_FIXED = 2;
static constexpr int DISK_TYPE_DYNAMIC = 3;
static constexpr int DISK_TYPE_DIFFERENCING = 4;
static constexpr int PAYLOAD_BLOCK_NOT_PRESENT = 0;
static constexpr int PAYLOAD_BLOCK_UNDEFINED = 1;
static constexpr int PAYLOAD_BLOCK_ZERO = 2;
static constexpr int PAYLOAD_BLOCK_UNMAPPED = 3;
static constexpr int PAYLOAD_BLOCK_FULLY_PRESENT = 6;
static constexpr int PAYLOAD_BLOCK_PARTIALLY_PRESENT = 7;

} // namespace

// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
//! \brief Check if file is an instance of imagefile vhd
//! \param f File object
//! \return True/false
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
bool
imagefile_impl::is_instance (const mobius::io::file& f)
{
  bool is_instance = false;

  if (f && f.exists ())
    {
      auto reader = f.new_reader ();

      if (reader)
        {
          auto data = reader.read (8);
          is_instance = data == "vhdxfile";
        }
    }

  return is_instance;
}

// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
//! \brief Constructor
//! \param f File object
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
imagefile_impl::imagefile_impl (const mobius::io::file& f)
  : file_ (f)
{
}

// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
//! \brief Get attribute
//! \param name Attribute name
//! \return Attribute value
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
mobius::pod::data
imagefile_impl::get_attribute (const std::string& name) const
{
  _load_metadata ();
  return attributes_.get (name);
}

// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
//! \brief Set attribute
//! \param name Attribute name
//! \param value Attribute value
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
void
imagefile_impl::set_attribute (
  const std::string&,
  const mobius::pod::data&
)
{
  throw std::runtime_error (mobius::MOBIUS_EXCEPTION_MSG ("set_attribute not implemented"));
}

// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
//! \brief Get attributes
//! \return Attributes
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
mobius::pod::map
imagefile_impl::get_attributes () const
{
  _load_metadata ();
  return attributes_;
}

// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
//! \brief Create new reader for imagefile
//! \return reader
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
mobius::io::reader
imagefile_impl::new_reader () const
{
  _load_metadata ();

  if (disk_type_ == DISK_TYPE_FIXED || disk_type_ == DISK_TYPE_DYNAMIC)
    return mobius::io::reader (
             std::make_shared <reader_impl> (*this)
           );

  else
    throw std::runtime_error (mobius::MOBIUS_EXCEPTION_MSG ("unsupported disk type"));
}

// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
//! \brief Create new writer for imagefile
//! \return writer
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
mobius::io::writer
imagefile_impl::new_writer () const
{
  throw std::runtime_error (mobius::MOBIUS_EXCEPTION_MSG ("writer not implemented"));
}

// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
//! \brief Get Block Allocation Table
//! \return Table
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
imagefile_impl::bat_type
imagefile_impl::get_block_allocation_table () const
{
  _load_metadata ();

  if (disk_type_ != DISK_TYPE_DYNAMIC)
    throw std::runtime_error (mobius::MOBIUS_EXCEPTION_MSG ("disk type has no Block Allocation Table"));

  _load_block_allocation_table ();
  return block_allocation_table_;
}

// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
//! \brief Load metadata from imagefile
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
void
imagefile_impl::_load_metadata () const
{
  if (metadata_loaded_)
    return;

  if (!file_ || !file_.exists ())
    throw std::runtime_error (mobius::MOBIUS_EXCEPTION_MSG ("image file not found"));

  // decode metadata
  auto reader = file_.new_reader ();

  _load_file_type_identifier (reader);
  _load_header (reader);
  _load_region_table (reader);

  // other data
  mobius::datetime::datetime acquisition_time = file_.get_modification_time ();
  sectors_ = size_ / sector_size_;

  // fill attributes
  attributes_.set ("physical_sector_size", physical_sector_size_);
  attributes_.set ("block_size", block_size_);
  attributes_.set ("disk_type", disk_type_);
  attributes_.set ("uuid", disk_uuid_);
  attributes_.set ("acquisition_time", acquisition_time);
  attributes_.set ("acquisition_tool", acquisition_tool_);
  attributes_.set ("logfile_guid", logfile_guid_);

  metadata_loaded_ = true;
}

// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
//! \brief Load data from File Type Identifier
//! \param reader Reader object
//! \see MS-VHDX - section 2.2.1
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
void
imagefile_impl::_load_file_type_identifier (mobius::io::reader reader) const
{
  mobius::decoder::data_decoder decoder (reader);
  
  // test signature
  auto signature = decoder.get_string_by_size (8);

  if (signature != "vhdxfile")
    throw std::runtime_error (mobius::MOBIUS_EXCEPTION_MSG ("invalid VHDX signature"));

  // creator
  acquisition_tool_ = decoder.get_string_by_size (512, "utf-16le");
}

// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
//! \brief Load data from Header
//! \param reader Reader object
//! \see MS-VHDX - section 2.2.2
//
// A header is valid if the Signature and Checksum fields both validate
// correctly. A header is current if it is the only valid header or if it is
// valid and its SequenceNumber field is greater than the other header's
// SequenceNumber field. The implementation MUST only use data from the current
// header. If there is no current header, then the VHDX file is corrupt.
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
void
imagefile_impl::_load_header (mobius::io::reader reader) const
{
  mobius::decoder::data_decoder decoder (reader);
  decoder.seek (65536);
  
  std::uint64_t h1_sequence_number = 0;
  std::uint64_t h2_sequence_number = 0;
  
  // test signature - first header
  auto signature_1 = decoder.get_string_by_size (4);

  if (signature_1 == "head")
    {
      decoder.skip (4);		// checksum
      h1_sequence_number = decoder.get_uint64_le ();
    }

  decoder.seek (131072);
  
  // test signature - second header
  auto signature_2 = decoder.get_string_by_size (4);

  if (signature_2 == "head")
    {
      decoder.skip (4);		// checksum
      h2_sequence_number = decoder.get_uint64_le ();
    }

  // check which header is valid
  if (h1_sequence_number == 0 && h2_sequence_number == 0)
    throw std::runtime_error (mobius::MOBIUS_EXCEPTION_MSG ("invalid VHDX header"));

  if (h1_sequence_number >= h2_sequence_number)
    decoder.seek (65536 + 16);

  else
    decoder.seek (131072 + 16);

  // decoder data
  decoder.skip (32);    // FileWriteGuid, DataWriteGuid
  logfile_guid_ = decoder.get_guid ();
  decoder.skip (2);     // LogVersion
  version_ = decoder.get_uint16_le ();
}

// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
//! \brief Load data from Region Table
//! \param reader Reader object
//! \see MS-VHDX - section 2.2.3
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
void
imagefile_impl::_load_region_table (mobius::io::reader reader) const
{
  mobius::decoder::data_decoder decoder (reader);
  decoder.seek (196608);
  
  // test signature
  auto signature = decoder.get_string_by_size (4);

  if (signature != "regi")
    throw std::runtime_error (mobius::MOBIUS_EXCEPTION_MSG ("invalid VHDX Region Table signature"));

  // read Region Table metadata  
  decoder.skip (4);		// checksum
  auto count = decoder.get_uint32_le ();
  decoder.skip (4);		// reserved
  
  // read Regions data
  for (std::uint32_t i = 0;i < count;i++)
    {
      auto guid = decoder.get_guid ();
      auto file_offset = decoder.get_uint64_le ();
      decoder.skip (4);         // length
      auto is_required = decoder.get_uint32_le ();
      
      if (guid == "8B7CA206-4790-4B9A-B8FE-575F050F886E")
        _load_metadata_region (reader, file_offset);

      else if (guid == "2DC27766-F623-4200-9D64-115E9BFD4A08")
         bat_offset_ = file_offset;
         
      else if (is_required)
        throw std::runtime_error (mobius::MOBIUS_EXCEPTION_MSG ("unknown and required Region Table entry"));
    }
}

// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
//! \brief Load data from Metadata Region
//! \param reader Reader object
//! \param file_offset File offset
//! \see MS-VHDX - section 2.6
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
void
imagefile_impl::_load_metadata_region (
  mobius::io::reader reader,
  std::uint64_t file_offset
) const
{
  mobius::decoder::data_decoder decoder (reader);
  decoder.seek (file_offset);
  
  // test signature
  auto signature = decoder.get_string_by_size (8);

  if (signature != "metadata")
    throw std::runtime_error (mobius::MOBIUS_EXCEPTION_MSG ("invalid VHDX Metadata Region signature"));
  
  // read Metadata Table header (section 2.6.1.1)
  decoder.skip (2);		// Reserved
  auto count = decoder.get_uint16_le ();
  decoder.skip (20);		// reserved
  
  // read Metadata Region
  for (std::uint16_t i = 0;i < count;i++)
    {
      auto guid = decoder.get_guid ();
      auto offset = decoder.get_uint32_le ();
      decoder.skip (12);		// length, flags, reserved
      
      auto pos = decoder.tell ();
      decoder.seek (file_offset + offset);

      // File Parameters - section 2.6.2.1
      if (guid == "CAA16737-FA36-4D43-B3B6-33F0AA44E76B")
        {
          block_size_ = decoder.get_uint32_le ();
          auto flags = decoder.get_uint32_le ();

          if (flags & 0x80000000)
            disk_type_ = DISK_TYPE_FIXED;
          
          else if (flags & 0x40000000)     // differencing
            throw std::runtime_error (mobius::MOBIUS_EXCEPTION_MSG ("unsupported disk type"));
            
          else
            disk_type_ = DISK_TYPE_DYNAMIC;
        }

      // Virtual Disk Size - section 2.6.2.2
      else if (guid == "2FA54224-CD1B-4876-B211-5DBED83BF4B8")
        size_ = decoder.get_uint64_le ();

      // Virtual Disk ID - section 2.6.2.3
      else if (guid == "BECA12AB-B2E6-4523-93EF-C309E000C746")
        disk_uuid_ = decoder.get_guid ();

      // Logical Sector Size - section 2.6.2.4
      else if (guid == "8141BF1D-A96F-4709-BA47-F233A8FAAB5F")
        sector_size_ = decoder.get_uint32_le ();

      // Physical Sector Size - section 2.6.2.5
      else if (guid == "CDA348C7-445D-4471-9CC9-E9885251C556")
        physical_sector_size_ = decoder.get_uint32_le ();

      decoder.seek (pos);
    }
}

// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
//! \brief Load block allocation table from imagefile
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
void
imagefile_impl::_load_block_allocation_table () const
{
  if (block_allocation_table_loaded_)
    return;

  // load metadata
  _load_metadata ();

  if (block_size_ == 0)
    throw std::runtime_error (mobius::MOBIUS_EXCEPTION_MSG ("block size must be greater than 0"));

  // decode BAT
  auto reader = file_.new_reader ();
  mobius::decoder::data_decoder decoder (reader);
  decoder.seek (bat_offset_);

  auto chunk_ratio = (std::uint64_t (sector_size_) << 23) / block_size_;
  std::uint64_t block_count = (size_ + block_size_ - 1) / block_size_;
  std::uint64_t i = 0;

  while (block_count > 0)
    {
      auto value = decoder.get_uint64_le ();
      
      // for every chunk_ration data blocks, there is one bitmap block,
      // which we skip for now.
      if (i % (chunk_ratio + 1) != chunk_ratio)
        {
          auto state = value & 0x07;
          auto offset = value & 0xfffffffffff00000;
          
          if (state == PAYLOAD_BLOCK_FULLY_PRESENT)
            block_allocation_table_.push_back (offset);
          else
            block_allocation_table_.push_back (0);

          block_count--;
        }
        
      i++;
    }

  block_allocation_table_loaded_ = true;
}
