Method packet_handler

dshell/plugins/tftp/tftp.py:114–234

Handles each UDP packet. It checks the TFTP opcode and parses accordingly.

(self, pkt)

            self.__closeStream(k, "POSSIBLY INCOMPLETE")

    def packet_handler(self, pkt):
        """
        Handles each UDP packet. It checks the TFTP opcode and parses
        accordingly.
        """
        udpp = pkt.pkt.upper_layer
        while not isinstance(udpp, udp.UDP):
            try:
                udpp = udpp.upper_layer
            except AttributeError:
                # There doesn't appear to be a UDP layer, for some reason
                return

        data = udpp.body_bytes

        try:
            flag = struct.unpack("!H", data[:2])[0]
        except struct.error:
            return   # awful small packet
        data = data[2:]
        if flag == self.RRQ:
            # this packet is requesting to read a file from the server
            try:
                filename, mode = data.split(b"\x00")[0:2]
            except ValueError:
                return  # probably not TFTP
            clientIP, clientPort, serverIP, serverPort = pkt.sip, udpp.sport, pkt.dip, udpp.dport
            self.unset_read_streams[(clientIP, clientPort, serverIP)] = {
                'filename': filename,
                'mode': mode,
                'readwrite': 'read',
                'closed_connection': False,
                'filedata': {},
                'timestamp': pkt.ts
            }

        elif flag == self.WRQ:
            # this packet is requesting to write a file to the server
            try:
                filename, mode = data.split(b"\x00")[0:2]
            except ValueError:
                return  # probably not TFTP
            # in this case, we are writing to the "server"
            clientIP, clientPort, serverIP, serverPort = pkt.sip, udpp.sport, pkt.dip, udpp.dport
            self.unset_write_streams[(clientIP, clientPort, serverIP)] = {
                'filename': filename,
                'mode': mode,
                'readwrite': 'write',
                'closed_connection': False,
                'filedata': {},
                'timestamp': pkt.ts
            }

        elif flag == self.DATA:
            # this packet is sending a chunk of data
            clientIP, clientPort, serverIP, serverPort = pkt.sip, udpp.sport, pkt.dip, udpp.dport
            key = (clientIP, clientPort, serverIP, serverPort)
            if key not in self.open_streams: