import logging import struct import ctypes from coapthon.messages.request import Request from coapthon.messages.response import Response from coapthon.messages.option import Option from coapthon import defines from coapthon.messages.message import Message __author__ = 'Giacomo Tanganelli' logger = logging.getLogger(__name__) class Serializer(object): """ Serializer class to serialize and deserialize CoAP message to/from udp streams. """ @staticmethod def deserialize(datagram, source): """ De-serialize a stream of byte to a message. :param datagram: the incoming udp message :param source: the source address and port (ip, port) :return: the message :rtype: Message """ try: fmt = "!BBH" pos = struct.calcsize(fmt) s = struct.Struct(fmt) values = s.unpack_from(datagram) first = values[0] code = values[1] mid = values[2] version = (first & 0xC0) >> 6 message_type = (first & 0x30) >> 4 token_length = (first & 0x0F) if Serializer.is_response(code): message = Response() message.code = code elif Serializer.is_request(code): message = Request() message.code = code else: message = Message() message.source = source message.destination = None message.version = version message.type = message_type message.mid = mid if token_length > 0: message.token = datagram[pos:pos+token_length] else: message.token = None pos += token_length current_option = 0 values = datagram[pos:] length_packet = len(values) pos = 0 while pos < length_packet: next_byte = struct.unpack("B", values[pos].to_bytes(1, "big"))[0] pos += 1 if next_byte != int(defines.PAYLOAD_MARKER): # the first 4 bits of the byte represent the option delta # delta = self._reader.read(4).uint num, option_length, pos = Serializer.read_option_value_len_from_byte(next_byte, pos, values) logger.debug("option value (delta): %d len: %d", num, option_length) current_option += num # read option try: option_item = defines.OptionRegistry.LIST[current_option] except KeyError: (opt_critical, _, _) = defines.OptionRegistry.get_option_flags(current_option) if opt_critical: raise AttributeError("Critical option %s unknown" % current_option) else: # If the non-critical option is unknown # (vendor-specific, proprietary) - just skip it logger.warning("unrecognized option %d", current_option) else: if option_length == 0: value = None elif option_item.value_type == defines.INTEGER: tmp = values[pos: pos + option_length] value = 0 for b in tmp: value = (value << 8) | struct.unpack("B", b.to_bytes(1, "big"))[0] elif option_item.value_type == defines.OPAQUE: tmp = values[pos: pos + option_length] value = tmp else: value = values[pos: pos + option_length] option = Option() option.number = current_option option.value = Serializer.convert_to_raw(current_option, value, option_length) message.add_option(option) if option.number == defines.OptionRegistry.CONTENT_TYPE.number: message.payload_type = option.value finally: pos += option_length else: if length_packet <= pos: # log.err("Payload Marker with no payload") raise AttributeError("Packet length %s, pos %s" % (length_packet, pos)) message.payload = "" payload = values[pos:] if hasattr(message, 'payload_type') and message.payload_type in [ defines.Content_types["application/octet-stream"], defines.Content_types["application/exi"], defines.Content_types["application/cbor"] ]: message.payload = payload else: try: message.payload = payload.decode("utf-8") except AttributeError: message.payload = payload pos += len(payload) return message except AttributeError: return defines.Codes.BAD_REQUEST.number except struct.error: return defines.Codes.BAD_REQUEST.number except UnicodeDecodeError as e: logger.debug(e) return defines.Codes.BAD_REQUEST.number @staticmethod def serialize(message): """ Serialize a message to a udp packet :type message: Message :param message: the message to be serialized :rtype: stream of byte :return: the message serialized """ fmt = "!BBH" if message.token is None: tkl = 0 else: tkl = len(message.token) tmp = (defines.VERSION << 2) tmp |= message.type tmp <<= 4 tmp |= tkl values = [tmp, message.code, message.mid] if message.token is not None and tkl > 0: fmt += "%ss" % tkl values.append(message.token) options = Serializer.as_sorted_list(message.options) # already sorted lastoptionnumber = 0 for option in options: # write 4-bit option delta optiondelta = option.number - lastoptionnumber optiondeltanibble = Serializer.get_option_nibble(optiondelta) tmp = (optiondeltanibble << defines.OPTION_DELTA_BITS) # write 4-bit option length optionlength = option.length optionlengthnibble = Serializer.get_option_nibble(optionlength) tmp |= optionlengthnibble fmt += "B" values.append(tmp) # write extended option delta field (0 - 2 bytes) if optiondeltanibble == 13: fmt += "B" values.append(optiondelta - 13) elif optiondeltanibble == 14: fmt += "H" values.append(optiondelta - 269) # write extended option length field (0 - 2 bytes) if optionlengthnibble == 13: fmt += "B" values.append(optionlength - 13) elif optionlengthnibble == 14: fmt += "H" values.append(optionlength - 269) # write option value if optionlength > 0: opt_type = defines.OptionRegistry.LIST[option.number].value_type if opt_type == defines.INTEGER: words = Serializer.int_to_words(option.value, optionlength, 8) for num in range(0, optionlength): fmt += "B" values.append(words[num]) elif opt_type == defines.STRING: fmt += str(len(bytes(option.value, "utf-8"))) + "s" values.append(bytes(option.value, "utf-8")) else: # OPAQUE for b in option.value: fmt += "B" values.append(b) # update last option number lastoptionnumber = option.number payload = message.payload if payload is not None and len(payload) > 0: # if payload is present and of non-zero length, it is prefixed by # an one-byte Payload Marker (0xFF) which indicates the end of # options and the start of the payload fmt += "B" values.append(defines.PAYLOAD_MARKER) if isinstance(payload, bytes): fmt += str(len(payload)) + "s" values.append(payload) else: fmt += str(len(bytes(payload, "utf-8"))) + "s" values.append(bytes(payload, "utf-8")) datagram = None if values[1] is None: values[1] = 0 if values[2] is None: values[2] = 0 try: s = struct.Struct(fmt) datagram = ctypes.create_string_buffer(s.size) s.pack_into(datagram, 0, *values) except struct.error: # The .exception method will report on the exception encountered # and provide a traceback. logger.debug(fmt) logger.debug(values) logging.exception('Failed to pack structure') return datagram @staticmethod def is_request(code): """ Checks if is request. :return: True, if is request """ return defines.REQUEST_CODE_LOWER_BOUND <= code <= defines.REQUEST_CODE_UPPER_BOUND @staticmethod def is_response(code): """ Checks if is response. :return: True, if is response """ return defines.RESPONSE_CODE_LOWER_BOUND <= code <= defines.RESPONSE_CODE_UPPER_BOUND @staticmethod def read_option_value_len_from_byte(byte, pos, values): """ Calculates the value and length used in the extended option fields. :param byte: 1-byte option header value. :return: the value and length, calculated from the header including the extended fields. """ h_nibble = (byte & 0xF0) >> 4 l_nibble = byte & 0x0F value = 0 length = 0 if h_nibble <= 12: value = h_nibble elif h_nibble == 13: value = struct.unpack("!B", values[pos].to_bytes(1, "big"))[0] + 13 pos += 1 elif h_nibble == 14: s = struct.Struct("!H") value = s.unpack_from(values[pos:pos+2])[0] + 269 pos += 2 else: raise AttributeError("Unsupported option number nibble " + str(h_nibble)) if l_nibble <= 12: length = l_nibble elif l_nibble == 13: length = struct.unpack("!B", values[pos].to_bytes(1, "big"))[0] + 13 pos += 1 elif l_nibble == 14: s = struct.Struct("!H") length = s.unpack_from(values[pos:pos+2])[0] + 269 pos += 2 else: raise AttributeError("Unsupported option length nibble " + str(l_nibble)) return value, length, pos @staticmethod def convert_to_raw(number, value, length): """ Get the value of an option as bytes. :param number: the option number :param value: the option value :param length: the option length :return: the value of an option as a BitArray """ opt_type = defines.OptionRegistry.LIST[number].value_type if length == 0 and opt_type != defines.INTEGER: return bytes() elif length == 0 and opt_type == defines.INTEGER: return 0 elif opt_type == defines.STRING: if isinstance(value, bytes): return value.decode("utf-8") elif opt_type == defines.OPAQUE: if isinstance(value, bytes): return value else: return bytes(value, "utf-8") if isinstance(value, tuple): value = value[0] if isinstance(value, str): value = str(value) if isinstance(value, str): return bytes(value, "utf-8") elif isinstance(value, int): return value else: return bytes(value) @staticmethod def as_sorted_list(options): """ Returns all options in a list sorted according to their option numbers. :return: the sorted list """ if len(options) > 0: options = sorted(options, key=lambda o: o.number) return options @staticmethod def get_option_nibble(optionvalue): """ Returns the 4-bit option header value. :param optionvalue: the option value (delta or length) to be encoded. :return: the 4-bit option header value. """ if optionvalue <= 12: return optionvalue elif optionvalue <= 255 + 13: return 13 elif optionvalue <= 65535 + 269: return 14 else: raise AttributeError("Unsupported option delta " + optionvalue) @staticmethod def int_to_words(int_val, num_words=4, word_size=32): """ Convert a int value to bytes. :param int_val: an arbitrary length Python integer to be split up. Network byte order is assumed. Raises an IndexError if width of integer (in bits) exceeds word_size * num_words. :param num_words: number of words expected in return value tuple. :param word_size: size/width of individual words (in bits). :return: a list of fixed width words based on provided parameters. """ max_int = 2 ** (word_size*num_words) - 1 max_word_size = 2 ** word_size - 1 if not 0 <= int_val <= max_int: raise AttributeError('integer %r is out of bounds!' % hex(int_val)) words = [] for _ in range(num_words): word = int_val & max_word_size words.append(int(word)) int_val >>= word_size words.reverse() return words