Class: FilesHunter::Decoders::CAB

Inherits:
BeginPatternDecoder show all
Defined in:
lib/fileshunter/Decoders/CAB.rb

Constant Summary collapse

BEGIN_PATTERN_CAB = 
"MSCF\x00\x00\x00\x00".force_encoding(Encoding::ASCII_8BIT)
END_STRING_TERMINATOR = 
"\x00".force_encoding(Encoding::ASCII_8BIT)
AUTHENTICODE_ID = 
"\x30\x82".force_encoding(Encoding::ASCII_8BIT)

Instance Method Summary collapse

Methods inherited from BeginPatternDecoder

#find_segments

Methods inherited from FilesHunter::Decoder

#segments_found, #setup

Instance Method Details

#decode(offset) ⇒ Object 



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# File 'lib/fileshunter/Decoders/CAB.rb', line 17

def decode(offset)

  # CFHEADER
  cabinet_size = BinData::Uint32le.read(@data[offset+8..offset+11])
  invalid_data("@#{offset} - Invalid CAB header.") if (BinData::Uint32le.read(@data[offset+12..offset+15]) != 0)
  #cf_file_offset = BinData::Uint32le.read(@data[offset+16..offset+19])
  invalid_data("@#{offset} - Invalid CAB header.") if (BinData::Uint32le.read(@data[offset+20..offset+23]) != 0)
  minor_version = @data[offset+24].ord
  major_version = @data[offset+25].ord
  nbr_cf_folders = BinData::Uint16le.read(@data[offset+26..offset+27])
  nbr_cf_files = BinData::Uint16le.read(@data[offset+28..offset+29])
  flags = BinData::Uint16le.read(@data[offset+30..offset+31])
  flag_prev_cabinet = ((flags & 0b00000000_00000001) != 0)
  flag_next_cabinet = ((flags & 0b00000000_00000010) != 0)
  flag_reserve_present = ((flags & 0b00000000_00000100) != 0)
  set_id = BinData::Uint16le.read(@data[offset+32..offset+33])
  idx_cabinet = BinData::Uint16le.read(@data[offset+34..offset+35])
  cursor = offset + 36
  reserve_field_size_in_folder = 0
  reserve_field_size_in_data = 0
  if flag_reserve_present
    reserve_field_size_in_header = BinData::Uint16le.read(@data[offset+36..offset+37])
    invalid_data("@#{offset} - Invalid reserve_field_size_in_header (#{reserve_field_size_in_header})") if (reserve_field_size_in_header > 60000)
    reserve_field_size_in_folder = @data[offset+38].ord
    reserve_field_size_in_data = @data[offset+39].ord
    cursor += 4 + reserve_field_size_in_header
  end
  if flag_prev_cabinet
    idx_terminator = @data.index(END_STRING_TERMINATOR, cursor)
    invalid_data("@#{cursor} - Unable to read previous cabinet name") if (idx_terminator == nil)
    cursor = idx_terminator + 1
    idx_terminator = @data.index(END_STRING_TERMINATOR, cursor)
    invalid_data("@#{cursor} - Unable to read previous disk name") if (idx_terminator == nil)
    cursor = idx_terminator + 1
  end
  if flag_next_cabinet
    idx_terminator = @data.index(END_STRING_TERMINATOR, cursor)
    invalid_data("@#{cursor} - Unable to read next cabinet name") if (idx_terminator == nil)
    cursor = idx_terminator + 1
    idx_terminator = @data.index(END_STRING_TERMINATOR, cursor)
    invalid_data("@#{cursor} - Unable to read next disk name") if (idx_terminator == nil)
    cursor = idx_terminator + 1
  end
  progress(cursor)
  found_relevant_data([:cab, :msu, :mzz])
  metadata(
    :cabinet_size => cabinet_size,
    :minor_version => minor_version,
    :major_version => major_version,
    :nbr_cf_folders => nbr_cf_folders,
    :nbr_cf_files => nbr_cf_files,
    :set_id => set_id,
    :idx_cabinet => idx_cabinet,
    :flag_prev_cabinet => flag_prev_cabinet,
    :flag_next_cabinet => flag_next_cabinet,
    :flag_reserve_present => flag_reserve_present
  )

  # CFFOLDER
  data_blocks = []
  log_debug "@#{cursor} - Beginning of #{nbr_cf_folders} CFFOLDER structures"
  nbr_cf_folders.times do |idx_cf_folder|
    first_data_offset = BinData::Uint32le.read(@data[cursor..cursor+3])
    nbr_data_blocks = BinData::Uint16le.read(@data[cursor+4..cursor+5])
    data_blocks << [ first_data_offset, nbr_data_blocks ]
    # compression_type = BinData::Uint16le.read(@data[cursor+6..cursor+7])
    cursor += 8 + reserve_field_size_in_folder
    progress(cursor)
  end

  # CFFILE
  log_debug "@#{cursor} - Beginning of #{nbr_cf_files} CFFILE structures"
  nbr_cf_files.times do |idx_cf_file|
    # file_size = BinData::Uint32le.read(@data[cursor..cursor+3])
    # file_offset = BinData::Uint32le.read(@data[cursor+4..cursor+7])
    # idx_file_in_folder = BinData::Uint16le.read(@data[cursor+8..cursor+9])
    # file_date = BinData::Uint16le.read(@data[cursor+10..cursor+11])
    # file_time = BinData::Uint16le.read(@data[cursor+12..cursor+13])
    # file_attrs = BinData::Uint16le.read(@data[cursor+14..cursor+15])
    cursor += 16
    idx_terminator = @data.index(END_STRING_TERMINATOR, cursor)
    invalid_data("@#{cursor} - Unable to read file name") if (idx_terminator == nil)
    cursor = idx_terminator + 1
    progress(cursor)
  end

  # CFDATA
  log_debug "@#{cursor} - Beginning of CFDATA"
  while (!data_blocks.empty?)
    # We should be on the first data block
    first_datablock_offset, nbr_datablocks = data_blocks.shift
    invalid_data("@#{cursor} - We should be on the next data block offset (#{offset+first_datablock_offset})") if (cursor-offset != first_datablock_offset)
    nbr_datablocks.times do |idx_datablock|
      # data_crc = BinData::Uint32le.read(@data[cursor..cursor+3])
      nbr_compressed_bytes = BinData::Uint16le.read(@data[cursor+4..cursor+5])
      # nbr_uncompressed_bytes = BinData::Uint16le.read(@data[cursor+6..cursor+7])
      cursor += 8 + reserve_field_size_in_data + nbr_compressed_bytes
      progress(cursor)
    end
  end
  invalid_data("@#{cursor} - We should be on at the end of the CAB file (#{offset+cabinet_size})") if (cursor-offset != cabinet_size)

  # Check if it is signed digitally using Authenticode
  if ((cursor+4 < @end_offset) and
      (@data[cursor..cursor+1] == AUTHENTICODE_ID))
    # Read the size
    authenticode_size = BinData::Uint16be.read(@data[cursor+2..cursor+3])
    log_debug "@#{cursor} - Found authenticode data of size #{authenticode_size}"
    cursor += 4 + authenticode_size
    # Eat eventually up to 4 "\x00" bytes
    while ((cursor < @end_offset) and
           (@data[cursor] == "\x00"))
      cursor += 1
    end
  end

  return cursor
end

#get_begin_pattern ⇒ Object 



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# File 'lib/fileshunter/Decoders/CAB.rb', line 13

def get_begin_pattern
  return BEGIN_PATTERN_CAB, { :offset_inc => 4 }
end