import sys
import ctypes
import ctypes.wintypes

#####################################################
#script to query windows 8.x OEM key from PC firmware
#ACPI -> table MSDM -> raw content -> byte offset 56 to end
#ck, 03-Jan-2014 (christian@korneck.de)
#####################################################

#for ref: common STR to DWORD conversions: ACPI: 1094930505 - FIRM: 1179210317 - RSMB: 1381190978 - FACP: 1178682192 - PCAF: 1346584902 - MSDM: 1297302605 - MDSM  1296323405

def EnumAcpiTables():
#returns a list of the names of the ACPI tables on this system
	FirmwareTableProviderSignature=ctypes.wintypes.DWORD(1094930505)
	pFirmwareTableBuffer=ctypes.create_string_buffer(0)
	BufferSize=ctypes.wintypes.DWORD(0)
	#http://msdn.microsoft.com/en-us/library/windows/desktop/ms724259
	EnumSystemFirmwareTables=ctypes.WinDLL("Kernel32").EnumSystemFirmwareTables
	ret=EnumSystemFirmwareTables(FirmwareTableProviderSignature, pFirmwareTableBuffer, BufferSize)
	pFirmwareTableBuffer=None
	pFirmwareTableBuffer=ctypes.create_string_buffer(ret)
	BufferSize.value=ret
	ret2=EnumSystemFirmwareTables(FirmwareTableProviderSignature, pFirmwareTableBuffer, BufferSize)
	return [pFirmwareTableBuffer.value[i:i+4] for i in range(0, len(pFirmwareTableBuffer.value), 4)]

def FindAcpiTable(table):
#checks if specific ACPI table exists and returns True/False
	tables = EnumAcpiTables()
	if table in tables:
		return True
	else:
		return False

def GetAcpiTable(table,TableDwordID):
#returns raw contents of ACPI table
	#http://msdn.microsoft.com/en-us/library/windows/desktop/ms724379x
	GetSystemFirmwareTable=ctypes.WinDLL("Kernel32").GetSystemFirmwareTable
	FirmwareTableProviderSignature=ctypes.wintypes.DWORD(1094930505)
	FirmwareTableID=ctypes.wintypes.DWORD(int(TableDwordID))
	pFirmwareTableBuffer=ctypes.create_string_buffer(0)
	BufferSize=ctypes.wintypes.DWORD(0)
	ret = GetSystemFirmwareTable(FirmwareTableProviderSignature, FirmwareTableID, pFirmwareTableBuffer, BufferSize)
	pFirmwareTableBuffer=None
	pFirmwareTableBuffer=ctypes.create_string_buffer(ret)
	BufferSize.value=ret
	ret2 = GetSystemFirmwareTable(FirmwareTableProviderSignature, FirmwareTableID, pFirmwareTableBuffer, BufferSize)
	return pFirmwareTableBuffer.raw
	
def GetWindowsKey():
	#returns Windows Key as string
	table=b"MSDM"
	TableDwordID=1296323405
	if FindAcpiTable(table)==True:
		try:
			rawtable = GetAcpiTable(table, TableDwordID)
			#http://msdn.microsoft.com/library/windows/hardware/hh673514
			#byte offset 36 from beginning = Microsoft 'software licensing data structure' / 36 + 20 bytes offset from beginning = Win Key
			return rawtable[56:len(rawtable)].decode("utf-8")
		except:
			return False
	else:
		print("[ERR] - ACPI table " + str(table) + " not found on this system")
		return False
	
try:	
	WindowsKey=GetWindowsKey()
	if WindowsKey==False:
		print("unexpected error")
		sys.exit(1)
	else:
		print(str(WindowsKey))
except:
	print("unexpected error")
	sys.exit(1)