Question

I am currently writing a security tool in python that runs as a daemon on a host computer. Whenever a usb storage device is detected, it will copy all of the files from the usb to some dir on the host computer. Is there any easy way to do this sort of usb detection / interface? Thanks in advance!

Answer 1

Yes, you need to use the RegisterDeviceNotification Windows API call. As far as I know, there is no Python module that wraps this functionality, so you have to use ctypes to call this function.

Fortunately, you are not the first person who has wanted to do this, so there are some code samples floating around the web. WxPython provides a code sample, but as you are writing a daemon this may not interest you. You might want to try the following code sample, which relies on both ctypes and pywin32, lifted shameless from Tim Golden:

import win32serviceutil
import win32service
import win32event
import servicemanager

import win32gui
import win32gui_struct
struct = win32gui_struct.struct
pywintypes = win32gui_struct.pywintypes
import win32con

GUID_DEVINTERFACE_USB_DEVICE = "{A5DCBF10-6530-11D2-901F-00C04FB951ED}"
DBT_DEVICEARRIVAL = 0x8000
DBT_DEVICEREMOVECOMPLETE = 0x8004

import ctypes

#
# Cut-down clone of UnpackDEV_BROADCAST from win32gui_struct, to be
# used for monkey-patching said module with correct handling
# of the "name" param of DBT_DEVTYPE_DEVICEINTERFACE
#
def _UnpackDEV_BROADCAST (lparam):
  if lparam == 0: return None
  hdr_format = "iii"
  hdr_size = struct.calcsize (hdr_format)
  hdr_buf = win32gui.PyGetMemory (lparam, hdr_size)
  size, devtype, reserved = struct.unpack ("iii", hdr_buf)
  # Due to x64 alignment issues, we need to use the full format string over
  # the entire buffer.  ie, on x64:
  # calcsize('iiiP') != calcsize('iii')+calcsize('P')
  buf = win32gui.PyGetMemory (lparam, size)

  extra = {}
  if devtype == win32con.DBT_DEVTYP_DEVICEINTERFACE:
    fmt = hdr_format + "16s"
    _, _, _, guid_bytes = struct.unpack (fmt, buf[:struct.calcsize(fmt)])
    extra['classguid'] = pywintypes.IID (guid_bytes, True)
    extra['name'] = ctypes.wstring_at (lparam + struct.calcsize(fmt))
  else:
    raise NotImplementedError("unknown device type %d" % (devtype,))
  return win32gui_struct.DEV_BROADCAST_INFO(devtype, **extra)
win32gui_struct.UnpackDEV_BROADCAST = _UnpackDEV_BROADCAST

class DeviceEventService (win32serviceutil.ServiceFramework):

  _svc_name_ = "DevEventHandler"
  _svc_display_name_ = "Device Event Handler"
  _svc_description_ = "Handle device notification events"

  def __init__(self, args):
    win32serviceutil.ServiceFramework.__init__ (self, args)
    self.hWaitStop = win32event.CreateEvent (None, 0, 0, None)
    #
    # Specify that we're interested in device interface
    # events for USB devices
    #
    filter = win32gui_struct.PackDEV_BROADCAST_DEVICEINTERFACE (
      GUID_DEVINTERFACE_USB_DEVICE
    )
    self.hDevNotify = win32gui.RegisterDeviceNotification (
      self.ssh, # copy of the service status handle
      filter,
      win32con.DEVICE_NOTIFY_SERVICE_HANDLE
    )

  #
  # Add to the list of controls already handled by the underlying
  # ServiceFramework class. We're only interested in device events
  #
  def GetAcceptedControls(self):
    rc = win32serviceutil.ServiceFramework.GetAcceptedControls (self)
    rc |= win32service.SERVICE_CONTROL_DEVICEEVENT
    return rc

  #
  # Handle non-standard service events (including our device broadcasts)
  # by logging to the Application event log
  #
  def SvcOtherEx(self, control, event_type, data):
    if control == win32service.SERVICE_CONTROL_DEVICEEVENT:
      info = win32gui_struct.UnpackDEV_BROADCAST(data)
      #
      # This is the key bit here where you'll presumably
      # do something other than log the event. Perhaps pulse
      # a named event or write to a secure pipe etc. etc.
      #
      if event_type == DBT_DEVICEARRIVAL:
        servicemanager.LogMsg (
          servicemanager.EVENTLOG_INFORMATION_TYPE,
          0xF000,
          ("Device %s arrived" % info.name, '')
        )
      elif event_type == DBT_DEVICEREMOVECOMPLETE:
        servicemanager.LogMsg (
          servicemanager.EVENTLOG_INFORMATION_TYPE,
          0xF000,
          ("Device %s removed" % info.name, '')
        )

  #
  # Standard stuff for stopping and running service; nothing
  # specific to device notifications
  #
  def SvcStop(self):
    self.ReportServiceStatus (win32service.SERVICE_STOP_PENDING)
    win32event.SetEvent (self.hWaitStop)

  def SvcDoRun(self):
    win32event.WaitForSingleObject (self.hWaitStop, win32event.INFINITE)
    servicemanager.LogMsg (
      servicemanager.EVENTLOG_INFORMATION_TYPE,
      servicemanager.PYS_SERVICE_STOPPED,
      (self._svc_name_, '')
    )

if __name__=='__main__':
  win32serviceutil.HandleCommandLine (DeviceEventService)