How to use the impacket.dcerpc.v5.dtypes.NULL function in impacket

else:
            lmhash = ''
            nthash = ''
        if hasattr(rpctransport, 'set_credentials'):
            # This method exists only for selected protocol sequences.
            rpctransport.set_credentials(self.username,self.password, self.domain, lmhash, nthash)
        dce = rpctransport.get_dce_rpc()
        #dce.set_auth_level(RPC_C_AUTHN_LEVEL_PKT_INTEGRITY)
        dce.connect()
        dce.bind(lsat.MSRPC_UUID_LSAT, transfer_syntax = self.ts)
        request = lsat.LsarOpenPolicy2()
        request['SystemName'] = NULL
        request['ObjectAttributes']['RootDirectory'] = NULL
        request['ObjectAttributes']['ObjectName'] = NULL
        request['ObjectAttributes']['SecurityDescriptor'] = NULL
        request['ObjectAttributes']['SecurityQualityOfService'] = NULL
        request['DesiredAccess'] = MAXIMUM_ALLOWED | lsat.POLICY_LOOKUP_NAMES
        resp = dce.request(request)

        return dce, rpctransport, resp['PolicyHandle']

def test_hRpcEnumPrinters(self):
        dce, rpctransport = self.connect()
        resp = rprn.hRpcEnumPrinters(dce, rprn.PRINTER_ENUM_LOCAL, NULL, 1)
        hexdump(b''.join(resp['pPrinterEnum']))

def hLsarLookupSids2(dce, policyHandle, sids, lookupLevel = LSAP_LOOKUP_LEVEL.LsapLookupWksta, lookupOptions=0x00000000, clientRevision=0x00000001):
    request = LsarLookupSids2()
    request['PolicyHandle'] = policyHandle
    request['SidEnumBuffer']['Entries'] = len(sids)
    for sid in sids:
        itemn = LSAPR_SID_INFORMATION()
        itemn['Sid'].fromCanonical(sid)
        request['SidEnumBuffer']['SidInfo'].append(itemn)

    request['TranslatedNames']['Names'] = NULL
    request['LookupLevel'] = lookupLevel
    request['LookupOptions'] = lookupOptions
    request['ClientRevision'] = clientRevision

    return dce.request(request)

def __wmiExec(self, command):
        # Convert command to wmi exec friendly format
        command = command.replace('%COMSPEC%', 'cmd.exe')
        username, password, domain, lmhash, nthash, aesKey, _, _ = self.__smbConnection.getCredentials()
        dcom = DCOMConnection(self.__smbConnection.getRemoteHost(), username, password, domain, lmhash, nthash, aesKey,
                              oxidResolver=False, doKerberos=self.__doKerberos, kdcHost=self.__kdcHost)
        iInterface = dcom.CoCreateInstanceEx(wmi.CLSID_WbemLevel1Login,wmi.IID_IWbemLevel1Login)
        iWbemLevel1Login = wmi.IWbemLevel1Login(iInterface)
        iWbemServices= iWbemLevel1Login.NTLMLogin('//./root/cimv2', NULL, NULL)
        iWbemLevel1Login.RemRelease()

        win32Process,_ = iWbemServices.GetObject('Win32_Process')
        win32Process.Create(command, '\\', None)

        dcom.disconnect()

request['pmsgIn']['V8']['ulFlags'] =  drsuapi.DRS_INIT_SYNC | drsuapi.DRS_WRIT_REP
        request['pmsgIn']['V8']['cMaxObjects'] = 1
        request['pmsgIn']['V8']['cMaxBytes'] = 0
        request['pmsgIn']['V8']['ulExtendedOp'] = drsuapi.EXOP_REPL_OBJ
        if self.__ppartialAttrSet is None:
            self.__prefixTable = []
            self.__ppartialAttrSet = drsuapi.PARTIAL_ATTR_VECTOR_V1_EXT()
            self.__ppartialAttrSet['dwVersion'] = 1
            self.__ppartialAttrSet['cAttrs'] = len(NTDSHashes.ATTRTYP_TO_ATTID)
            for attId in NTDSHashes.ATTRTYP_TO_ATTID.values():
                self.__ppartialAttrSet['rgPartialAttr'].append(drsuapi.MakeAttid(self.__prefixTable , attId))
        request['pmsgIn']['V8']['pPartialAttrSet'] = self.__ppartialAttrSet
        request['pmsgIn']['V8']['PrefixTableDest']['PrefixCount'] = len(self.__prefixTable)
        request['pmsgIn']['V8']['PrefixTableDest']['pPrefixEntry'] = self.__prefixTable
        request['pmsgIn']['V8']['pPartialAttrSetEx1'] = NULL

        return self.__drsr.request(request)

def hOpenCurrentConfig(dce, samDesired = MAXIMUM_ALLOWED):
    request = OpenCurrentConfig()
    request['ServerName'] = NULL
    request['samDesired'] = samDesired
    return dce.request(request)

LOG.error('Automation Server does not support type information for this object')
        return {}
    iTypeInfo = iInterface.GetTypeInfo()
    iTypeAttr = iTypeInfo.GetTypeAttr()
    for x in range(iTypeAttr['ppTypeAttr']['cFuncs']):
        funcDesc = iTypeInfo.GetFuncDesc(x)
        names = iTypeInfo.GetNames(funcDesc['ppFuncDesc']['memid'], 255)
        print names['rgBstrNames'][0]['asData']
        funcDesc.dump()
        print '='*80
        if names['pcNames'] > 0:
            name = names['rgBstrNames'][0]['asData']
            methods[name] = {}
            for param in range(1, names['pcNames']):
                methods[name][names['rgBstrNames'][param]['asData']] = ''
        if funcDesc['ppFuncDesc']['elemdescFunc'] != NULL:
            methods[name]['ret'] = funcDesc['ppFuncDesc']['elemdescFunc']['tdesc']['vt']

    return methods

logging.info("SMBv2.1 dialect used")
            else:
                logging.info("SMBv3.0 dialect used")
        else:
            smbConnection = None

        dcom = DCOMConnection(addr, self.__username, self.__password, self.__domain, self.__lmhash, self.__nthash,
                              self.__aesKey, oxidResolver=True, doKerberos=self.__doKerberos, kdcHost=self.__kdcHost)
        try:
            iInterface = dcom.CoCreateInstanceEx(string_to_bin('49B2791A-B1AE-4C90-9B8E-E860BA07F889'), IID_IDispatch)
            iMMC = IDispatch(iInterface)

            resp = iMMC.GetIDsOfNames(('Document',))

            dispParams = DISPPARAMS(None, False)
            dispParams['rgvarg'] = NULL
            dispParams['rgdispidNamedArgs'] = NULL
            dispParams['cArgs'] = 0
            dispParams['cNamedArgs'] = 0
            resp = iMMC.Invoke(resp[0], 0x409, DISPATCH_PROPERTYGET, dispParams, 0, [], [])

            iDocument = IDispatch(self.getInterface(iMMC, resp['pVarResult']['_varUnion']['pdispVal']['abData']))
            resp = iDocument.GetIDsOfNames(('ActiveView',))
            resp = iDocument.Invoke(resp[0], 0x409, DISPATCH_PROPERTYGET, dispParams, 0, [], [])

            iActiveView = IDispatch(self.getInterface(iMMC, resp['pVarResult']['_varUnion']['pdispVal']['abData']))
            pExecuteShellCommand = iActiveView.GetIDsOfNames(('ExecuteShellCommand',))[0]

            pQuit = iMMC.GetIDsOfNames(('Quit',))[0]

            self.shell = RemoteShell(self.__share, (iMMC, pQuit), (iActiveView, pExecuteShellCommand), smbConnection)
            if self.__command != ' ':

logging.info("SMBv1 dialect used")
            elif dialect == SMB2_DIALECT_002:
                logging.info("SMBv2.0 dialect used")
            elif dialect == SMB2_DIALECT_21:
                logging.info("SMBv2.1 dialect used")
            else:
                logging.info("SMBv3.0 dialect used")
        else:
            smbConnection = None

        dcom = DCOMConnection(addr, self.__username, self.__password, self.__domain, self.__lmhash, self.__nthash,
                              self.__aesKey, oxidResolver=True, doKerberos=self.__doKerberos, kdcHost=self.__kdcHost)
        try:
            iInterface = dcom.CoCreateInstanceEx(wmi.CLSID_WbemLevel1Login,wmi.IID_IWbemLevel1Login)
            iWbemLevel1Login = wmi.IWbemLevel1Login(iInterface)
            iWbemServices= iWbemLevel1Login.NTLMLogin('//./root/cimv2', NULL, NULL)
            iWbemLevel1Login.RemRelease()

            win32Process,_ = iWbemServices.GetObject('Win32_Process')

            self.shell = RemoteShell(self.__share, win32Process, smbConnection)
            if self.__command != ' ':
                self.shell.onecmd(self.__command)
            else:
                self.shell.cmdloop()
        except  (Exception, KeyboardInterrupt) as e:
            if logging.getLogger().level == logging.DEBUG:
                import traceback
                traceback.print_exc()
            logging.error(str(e))
            if smbConnection is not None:
                smbConnection.logoff()

def checkNullString(string):
    if string == NULL:
        return string

    if string[-1:] != '\x00':
        return string + '\x00'
    else:
        return string