refactor code, support multiple mqtt packets in one tcp message, support other mqtt packets

1 files changed, 351 insertions, 0 deletions

diff --git a/mqtt.py b/mqtt.py
new file mode 100644
index 0000000..b2cbb33
--- /dev/null
+++ b/mqtt.py
@@ -0,0 +1,351 @@
+from mitmproxy.utils import strutils
+from typing import List
+
+import struct
+
+
+class MQTTControlPacket:
+    # Packet types
+    (
+        CONNECT,
+        CONNACK,
+        PUBLISH,
+        PUBACK,
+        PUBREC,
+        PUBREL,
+        PUBCOMP,
+        SUBSCRIBE,
+        SUBACK,
+        UNSUBSCRIBE,
+        UNSUBACK,
+        PINGREQ,
+        PINGRESP,
+        DISCONNECT,
+    ) = range(1, 15)
+
+    # http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.html#_Table_2.1_-
+    NAMES = [
+        "reserved",
+        "CONNECT",
+        "CONNACK",
+        "PUBLISH",
+        "PUBACK",
+        "PUBREC",
+        "PUBREL",
+        "PUBCOMP",
+        "SUBSCRIBE",
+        "SUBACK",
+        "UNSUBSCRIBE",
+        "UNSUBACK",
+        "PINGREQ",
+        "PINGRESP",
+        "DISCONNECT",
+        "reserved",
+    ]
+
+    # http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.html#_Table_3.1_-
+    CONNECT_RETURN_CODES = [
+        "Connection Accepted",
+        "Connection Refused, unacceptable protocol version",
+        "Connection Refused, identifier rejected",
+        "Connection Refused, Server unavailable",
+        "Connection Refused, bad user name or password",
+        "Connection Refused, not authorized",
+    ]
+
+    SUBACK_RETURN_CODES = {
+        0x00: "Success - Maximum QoS 0",
+        0x01: "Success - Maximum QoS 1",
+        0x02: "Success - Maximum QoS 2",
+        0x80: "Failure",
+    }
+
+    PACKETS_WITH_IDENTIFIER = [
+        PUBACK,
+        PUBREC,
+        PUBREL,
+        PUBCOMP,
+        SUBSCRIBE,
+        SUBACK,
+        UNSUBSCRIBE,
+        UNSUBACK,
+    ]
+
+    def __init__(self, buf: bytes, packet_type: int, packet_flags: int, length: int, length_size=1):
+        self.buf = buf
+        self.packet_type = packet_type
+        self.packet_type_human = self.NAMES[self.packet_type]
+        self.packet_flags = packet_flags
+        self.remaining_length = length
+        self.remaining_length_size = length_size
+        self.packet_identifier = None
+        self.payload = {}
+
+        self.dup, self.qos, self.retain = self._parse_flags()
+
+    def parse(self):
+        # Variable header & Payload
+        # http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.html#_Toc398718024
+        # http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.html#_Toc398718026
+        if self.packet_type == self.CONNECT:
+            self._parse_connect_variable_headers()
+            self._parse_connect_payload()
+
+        elif self.packet_type == self.CONNACK:
+            self._parse_connack_variable_headers()
+
+        elif self.packet_type == self.PUBLISH:
+            self._parse_publish_variable_headers()
+            self._parse_publish_payload()
+
+        elif self.packet_type in (self.SUBSCRIBE, self.UNSUBSCRIBE):
+            flags = self.packet_flags
+            if flags != 0x2:
+                raise Exception(f'Packet is malformed: flags = {flags} != 0x2')
+
+            self._parse_packet_identifier()
+            self._parse_subscribe_payload(with_qos=(self.packet_type == self.SUBSCRIBE))
+
+        elif self.packet_type == self.SUBACK:
+            self._parse_packet_identifier()
+            self._parse_suback_payload()
+
+        elif self.packet_type == self.UNSUBACK:
+            self._parse_packet_identifier()
+
+        elif self.packet_type == self.PUBACK:
+            self._parse_packet_identifier()
+
+        elif self.packet_type == self.UNSUBSCRIBE:
+            pass
+
+        # else:
+        #     self.payload = None
+
+    def pprint(self):
+        pid = f' {self.packet_identifier:04x}' if self.packet_identifier is not None else ''
+        s = f'[{self.NAMES[self.packet_type]}{pid}]'
+
+        if self.packet_type == self.CONNECT:
+            s += f"""
+Protocol Level: {self.variable_headers['ProtocolLevel'][0]}
+Client Id: {self.payload['ClientId']}
+Will Topic: {self.payload.get('WillTopic')}
+Will Message: {strutils.bytes_to_escaped_str(self.payload.get('WillMessage', b'None'))}
+User Name: {self.payload.get('UserName')}
+Password: {strutils.bytes_to_escaped_str(self.payload.get('Password', b'None'))}
+"""
+
+        elif self.packet_type == self.CONNACK:
+            rc = self.connack_headers["ReturnCode"]
+            rc_desc = self.CONNECT_RETURN_CODES[rc] if rc < len(self.CONNECT_RETURN_CODES) else f'{rc:02x}'
+            s += f" SessionPresent: {self.connack_headers['SessionPresent']}. {rc_desc}"
+
+        elif self.packet_type in (self.SUBSCRIBE, self.UNSUBSCRIBE):
+            s += " sent topic filters: "
+            s += ", ".join([f"'{tf}'" for tf in self.topic_filters])
+
+        elif self.packet_type == self.SUBACK:
+            rc = self.payload['ReturnCode']
+            s += " "
+            s += self.SUBACK_RETURN_CODES[rc] if rc in self.SUBACK_RETURN_CODES else f'{rc:02xs}'
+
+        elif self.packet_type == self.PUBLISH:
+            topic_name = strutils.bytes_to_escaped_str(self.topic_name)
+            payload = strutils.bytes_to_escaped_str(self.payload)
+
+            s += f" '{payload}' to topic '{topic_name}'"
+
+        elif self.packet_type in (self.PINGREQ, self.PINGRESP, self.UNSUBACK, self.PUBACK, self.DISCONNECT):
+            # just print packet type with packet identifier (if any)
+            pass
+
+        else:
+            s = f"Packet type {self.NAMES[self.packet_type]} is not supported yet!"
+
+        return s
+
+    def _parse_length_prefixed_bytes(self, offset):
+        field_length_bytes = self.buf[offset: offset + 2]
+        field_length = struct.unpack("!H", field_length_bytes)[0]
+        offset += 2
+
+        field_content_bytes = self.buf[offset: offset + field_length]
+
+        return field_length + 2, field_content_bytes
+
+    def _parse_publish_variable_headers(self):
+        offset = len(self.buf) - self.remaining_length
+
+        field_length, field_content_bytes = self._parse_length_prefixed_bytes(offset)
+        self.topic_name = field_content_bytes
+
+        if self.qos in [0x01, 0x02]:
+            offset += field_length
+            self.packet_identifier = self.buf[offset: offset + 2][0]
+
+    def _parse_publish_payload(self):
+        fixed_header_length = len(self.buf) - self.remaining_length
+        variable_header_length = 2 + len(self.topic_name)
+
+        if self.qos in [0x01, 0x02]:
+            variable_header_length += 2
+
+        offset = fixed_header_length + variable_header_length
+
+        self.payload = self.buf[offset:]
+
+    def _parse_subscribe_payload(self, with_qos=True):
+        # skip packet identifier
+        offset = self.remaining_length_size
+        offset += 1 # fixed header
+        offset += 2 # packet identifier
+
+        self.topic_filters = []
+
+        while len(self.buf) - offset > 0:
+            field_length, topic_filter_bytes = self._parse_length_prefixed_bytes(offset)
+            offset += field_length
+
+            topic_filter = {
+                'topic': topic_filter_bytes.decode("utf-8")
+            }
+
+            if with_qos:
+                topic_filter['qos'] = self.buf[offset: offset + 1][0] & 0x3
+                offset += 1
+
+            self.topic_filters.append(topic_filter)
+
+    def _parse_suback_payload(self):
+        offset = len(self.buf) - self.remaining_length + 2
+        rc = self.buf[offset]
+        self.payload['ReturnCode'] = rc
+
+    # http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.html#_Toc398718030
+    def _parse_connect_variable_headers(self):
+        offset = len(self.buf) - self.remaining_length
+
+        self.variable_headers = {}
+        self.connect_flags = {}
+
+        self.variable_headers["ProtocolName"] = self.buf[offset: offset + 6]
+        self.variable_headers["ProtocolLevel"] = self.buf[offset + 6: offset + 7]
+        self.variable_headers["ConnectFlags"] = self.buf[offset + 7: offset + 8]
+        self.variable_headers["KeepAlive"] = self.buf[offset + 8: offset + 10]
+
+        # http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.html#_Toc385349229
+        self.connect_flags["CleanSession"] = bool(self.variable_headers["ConnectFlags"][0] & 0x02)
+        self.connect_flags["Will"] = bool(self.variable_headers["ConnectFlags"][0] & 0x04)
+        self.will_qos = (self.variable_headers["ConnectFlags"][0] >> 3) & 0x03
+        self.connect_flags["WillRetain"] = bool(self.variable_headers["ConnectFlags"][0] & 0x20)
+        self.connect_flags["Password"] = bool(self.variable_headers["ConnectFlags"][0] & 0x40)
+        self.connect_flags["UserName"] = bool(self.variable_headers["ConnectFlags"][0] & 0x80)
+
+    # http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.html#_Toc398718031
+    def _parse_connect_payload(self):
+        fields = []
+        offset = len(self.buf) - self.remaining_length + 10
+
+        while len(self.buf) - offset > 0:
+            field_length, field_content = self._parse_length_prefixed_bytes(offset)
+            fields.append(field_content)
+            offset += field_length
+
+        self.payload = {}
+
+        for f in fields:
+            # http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.html#_Toc385349242
+            if "ClientId" not in self.payload:
+                try:
+                    self.payload["ClientId"] = f.decode("utf-8")
+                except:
+                    self.payload["ClientId"] = str(f)
+
+            # http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.html#_Toc385349243
+            elif self.connect_flags["Will"] and "WillTopic" not in self.payload:
+                self.payload["WillTopic"] = f.decode("utf-8")
+
+            elif self.connect_flags["Will"] and "WillMessage" not in self.payload:
+                self.payload["WillMessage"] = f
+
+            elif self.connect_flags["UserName"] and "UserName" not in self.payload:
+                self.payload["UserName"] = f.decode("utf-8")
+
+            elif self.connect_flags["Password"] and "Password" not in self.payload:
+                self.payload["Password"] = f
+
+            else:
+                raise Exception("")
+
+    # http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.html#_Toc398718035
+    def _parse_connack_variable_headers(self):
+        self.connack_headers = {}
+
+        offset = len(self.buf) - self.remaining_length
+
+        self.connack_headers["SessionPresent"] = self.buf[offset: offset + 1][0] & 0x01 == 0x01
+        self.connack_headers["ReturnCode"] = self.buf[offset + 1: offset + 2][0]
+
+    # http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.html#_Toc398718022
+    def _parse_flags(self):
+        dup = None
+        qos = None
+        retain = None
+
+        if self.packet_type == self.PUBLISH:
+            dup = (self.buf[0] >> 3) & 0x01
+            qos = (self.buf[0] >> 1) & 0x03
+            retain = self.buf[0] & 0x01
+
+        return dup, qos, retain
+
+    # http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.html#_Table_2.5_-
+    def _parse_packet_identifier(self):
+        offset = 1 + self.remaining_length_size
+        self.packet_identifier = struct.unpack('!H', self.buf[offset: offset + 2])[0]
+
+
+def _get_packet_type(buf: bytes) -> int:
+    return buf[0] >> 4
+
+
+def _get_packet_flags(buf: bytes) -> int:
+    return buf[0] & 0xf
+
+
+def _get_remaining_length(buf: bytes) -> tuple:
+    multiplier = 1
+    value = 0
+    i = 1
+
+    while True:
+        encoded_byte = buf[i-1]
+        value += (encoded_byte & 127) * multiplier
+        multiplier *= 128
+
+        if multiplier > 128 * 128 * 128:
+            raise Exception("Malformed Remaining Length")
+
+        if encoded_byte & 128 == 0:
+            break
+
+        i += 1
+
+    return i, value
+
+
+def read_packets(buf: bytes) -> List[MQTTControlPacket]:
+    packets = []
+    while len(buf) > 0:
+        # Fixed header
+        # http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.html#_Toc398718020
+        packet_type = _get_packet_type(buf)
+        packet_flags = _get_packet_flags(buf)
+        length_size, length = _get_remaining_length(buf[1:])
+
+        packets.append(MQTTControlPacket(buf[:1+length_size+length], packet_type, packet_flags, length, length_size=length_size))
+
+        buf = buf[1+length_size+length:]
+
+    return packets