merge: testing → main (reconcile 2-week divergence)

decnet/templates/mqtt/server.py

@@ -0,0 +1,340 @@
+#!/usr/bin/env python3
+"""
+MQTT server (port 1883).
+Parses MQTT CONNECT packets, extracts client_id, etc.
+Responds with CONNACK.
+Supports dynamic topics and retained publishes.
+Logs PUBLISH commands sent by clients.
+"""
+
+import asyncio
+import json
+import os
+import random
+import struct
+
+import instance_seed as _seed
+from syslog_bridge import (
+    encode_secret,
+    forward_syslog,
+    syslog_line,
+    write_syslog_file,
+)
+
+NODE_NAME = os.environ.get("NODE_NAME", "mqtt-broker")
+SERVICE_NAME   = "mqtt"
+LOG_TARGET = os.environ.get("LOG_TARGET", "")
+PORT = int(os.environ.get("PORT", "1883"))
+
+# Default to auth-required. A broker that accepts literally anyone with any
+# client_id / username was realistic for devices on a flat OT LAN pre-2018,
+# but in 2024+ it's a tell. Operators who *want* the anonymous-broker decoy
+# still set MQTT_ACCEPT_ALL=1 explicitly.
+MQTT_ACCEPT_ALL = os.environ.get("MQTT_ACCEPT_ALL", "0") == "1"
+# Optional cred list (user:pass comma-separated). If set, only those combos
+# succeed even when ACCEPT_ALL is off — lets operators plant credential bait.
+_MQTT_CREDS: set[tuple[str, str]] = set()
+for combo in os.environ.get("MQTT_CREDS", "").split(","):
+    combo = combo.strip()
+    if ":" in combo:
+        u, _, p = combo.partition(":")
+        _MQTT_CREDS.add((u, p))
+
+_PERSONA_CHOICES = ["water_plant", "building_hvac", "solar_farm", "factory_line"]
+MQTT_PERSONA = os.environ.get("MQTT_PERSONA") or _seed.pick(_PERSONA_CHOICES)
+MQTT_CUSTOM_TOPICS = os.environ.get("MQTT_CUSTOM_TOPICS", "")
+
+# Fleet-diverse broker ID. Real mosquitto versions in the wild right now.
+_BROKER_VERSION = os.environ.get("MQTT_BROKER_VERSION") or _seed.pick([
+    "mosquitto version 1.6.9",
+    "mosquitto version 2.0.11",
+    "mosquitto version 2.0.15",
+    "mosquitto version 2.0.17",
+    "mosquitto version 2.0.18",
+    "HiveMQ CE 2024.4",
+    "EMQX 5.3.2",
+])
+
+_CONNACK_ACCEPTED = b"\x20\x02\x00\x00"
+_CONNACK_NOT_AUTH = b"\x20\x02\x00\x05"
+
+
+def _log(event_type: str, severity: int = 6, **kwargs) -> None:
+    line = syslog_line(SERVICE_NAME, NODE_NAME, event_type, severity, **kwargs)
+    write_syslog_file(line)
+    forward_syslog(line, LOG_TARGET)
+
+
+def _read_utf8(data: bytes, pos: int):
+    """Read MQTT UTF-8 string (2-byte length prefix). Returns (string, next_pos)."""
+    if pos + 2 > len(data):
+        return "", pos
+    length = struct.unpack(">H", data[pos:pos + 2])[0]
+    pos += 2
+    return data[pos:pos + length].decode(errors="replace"), pos + length
+
+
+def _parse_connect(payload: bytes):
+    pos = 0
+    proto_name, pos = _read_utf8(payload, pos)
+    if pos >= len(payload):
+        return {}, pos
+    _proto_level = payload[pos]
+    pos += 1
+    if pos >= len(payload):
+        return {}, pos
+    flags = payload[pos]
+    pos += 1
+    pos += 2  # Keep alive
+    client_id, pos = _read_utf8(payload, pos)
+    result = {"client_id": client_id, "proto": proto_name}
+    if flags & 0x04:
+        _, pos = _read_utf8(payload, pos)
+        _, pos = _read_utf8(payload, pos)
+    if flags & 0x80:
+        username, pos = _read_utf8(payload, pos)
+        result["username"] = username
+    if flags & 0x40:
+        password, pos = _read_utf8(payload, pos)
+        result["password"] = password
+    return result
+
+
+def _parse_subscribe(payload: bytes):
+    """Returns (packet_id, [(topic, qos), ...])"""
+    if len(payload) < 2:
+        return 0, []
+    pos = 0
+    packet_id = struct.unpack(">H", payload[pos:pos+2])[0]
+    pos += 2
+    topics = []
+    while pos < len(payload):
+        topic, pos = _read_utf8(payload, pos)
+        if pos >= len(payload):
+            break
+        qos = payload[pos] & 0x03
+        pos += 1
+        topics.append((topic, qos))
+    return packet_id, topics
+
+
+def _suback(packet_id: int, granted_qos: list[int]) -> bytes:
+    payload = struct.pack(">H", packet_id) + bytes(granted_qos)
+    return bytes([0x90, len(payload)]) + payload
+
+
+def _publish(topic: str, value: str, retain: bool = True) -> bytes:
+    topic_bytes = topic.encode()
+    topic_len   = struct.pack(">H", len(topic_bytes))
+    payload     = str(value).encode()
+    fixed = 0x31 if retain else 0x30
+    remaining = len(topic_len) + len(topic_bytes) + len(payload)
+
+    # variable length encoding
+    rem_bytes = []
+    while remaining > 0:
+        encoded = remaining % 128
+        remaining = remaining // 128
+        if remaining > 0:
+            encoded = encoded | 128
+        rem_bytes.append(encoded)
+    if not rem_bytes:
+        rem_bytes = [0]
+
+    return bytes([fixed]) + bytes(rem_bytes) + topic_len + topic_bytes + payload
+
+
+def _parse_publish(payload: bytes, qos: int):
+    pos = 0
+    topic, pos = _read_utf8(payload, pos)
+    packet_id = 0
+    if qos > 0:
+        if pos + 2 <= len(payload):
+            packet_id = struct.unpack(">H", payload[pos:pos+2])[0]
+            pos += 2
+    data = payload[pos:]
+    return topic, packet_id, data
+
+
+def _generate_topics() -> dict:
+    topics: dict = {}
+    if MQTT_CUSTOM_TOPICS:
+        try:
+            topics = json.loads(MQTT_CUSTOM_TOPICS)
+            return topics
+        except Exception as e:
+            _log("config_error", severity=4, error=str(e))
+
+    if MQTT_PERSONA == "water_plant":
+        site = _seed.pick(["north", "south", "east", "west", "plant-a", "plant-b"])
+        topics.update({
+            f"{site}/water/tank1/level": f"{random.uniform(60.0, 80.0):.1f}",
+            f"{site}/water/tank1/pressure": f"{random.uniform(2.5, 3.0):.2f}",
+            f"{site}/water/pump1/status": "RUNNING",
+            f"{site}/water/pump1/rpm": f"{int(random.uniform(1400, 1450))}",
+            f"{site}/water/pump2/status": "STANDBY",
+            f"{site}/water/chlorine/dosing": f"{random.uniform(1.1, 1.3):.1f}",
+            f"{site}/water/chlorine/residual": f"{random.uniform(0.7, 0.9):.1f}",
+            f"{site}/water/valve/inlet/state": "OPEN",
+            f"{site}/water/valve/drain/state": "CLOSED",
+            f"{site}/alarm/high_pressure": "0",
+            f"{site}/alarm/low_chlorine": "0",
+            f"{site}/alarm/pump_fault": "0",
+        })
+    elif MQTT_PERSONA == "building_hvac":
+        floor = _seed.rng.randint(1, 12)
+        for i in range(_seed.rng.randint(4, 10)):
+            topics[f"bldg/floor{floor}/zone{i}/temp"] = f"{random.uniform(20.0, 24.5):.1f}"
+            topics[f"bldg/floor{floor}/zone{i}/setpoint"] = f"{random.uniform(21.0, 23.0):.1f}"
+        topics[f"bldg/floor{floor}/ahu/status"] = _seed.pick(["RUNNING", "RUNNING", "IDLE"])
+    elif MQTT_PERSONA == "solar_farm":
+        for arr in range(1, _seed.rng.randint(4, 9)):
+            topics[f"solar/array{arr}/power_kw"] = f"{random.uniform(40.0, 180.0):.1f}"
+            topics[f"solar/array{arr}/irradiance"] = f"{random.uniform(500, 950):.0f}"
+    elif MQTT_PERSONA == "factory_line":
+        line = _seed.pick(["A", "B", "C"])
+        for m in range(1, _seed.rng.randint(3, 7)):
+            topics[f"line{line}/machine{m}/state"] = _seed.pick(["RUN", "RUN", "IDLE", "FAULT"])
+            topics[f"line{line}/machine{m}/cycle_count"] = str(_seed.rng.randint(1000, 999_999))
+    if not topics:
+        topics = {
+            "device/status": "online",
+            "device/uptime": str(_seed.uptime_seconds()),
+        }
+    # $SYS keys match every real broker.
+    topics["$SYS/broker/version"] = _BROKER_VERSION
+    topics["$SYS/broker/uptime"] = f"{_seed.uptime_seconds()} seconds"
+    topics["$SYS/broker/clients/connected"] = str(_seed.rng.randint(2, 24))
+    return topics
+
+
+class MQTTProtocol(asyncio.Protocol):
+    def __init__(self):
+        self._transport = None
+        self._peer = None
+        self._buf = b""
+        self._auth = False
+        self._topics = _generate_topics()
+
+    def connection_made(self, transport):
+        self._transport = transport
+        self._peer = transport.get_extra_info("peername", ("?", 0))
+        _log("connect", src=self._peer[0], src_port=self._peer[1])
+
+    def data_received(self, data):
+        self._buf += data
+        try:
+            self._process()
+        except Exception as e:
+            _log("protocol_error", severity=4, error=str(e))
+            if self._transport:
+                self._transport.close()
+
+    def _process(self):
+        while len(self._buf) >= 2:
+            pkt_byte = self._buf[0]
+            pkt_type = (pkt_byte >> 4) & 0x0f
+            flags = pkt_byte & 0x0f
+            qos = (flags >> 1) & 0x03
+
+            # Decode remaining length (variable-length encoding)
+            pos = 1
+            remaining = 0
+            multiplier = 1
+            while pos < len(self._buf):
+                if pos > 4:  # MQTT spec: max 4 bytes for remaining length
+                    self._transport.close()
+                    self._buf = b""
+                    return
+                byte = self._buf[pos]
+                remaining += (byte & 0x7f) * multiplier
+                multiplier *= 128
+                pos += 1
+                if not (byte & 0x80):
+                    break
+            else:
+                return  # incomplete length
+            if len(self._buf) < pos + remaining:
+                return  # incomplete payload
+            payload = self._buf[pos:pos + remaining]
+            self._buf = self._buf[pos + remaining:]
+
+            if pkt_type == 1:  # CONNECT
+                info = _parse_connect(payload)
+                # Migrate auth event to the universal credential SD shape
+                # so the ingester's native branch picks up the row. The
+                # legacy username/password keys are intentionally NOT
+                # forwarded — encode_secret() supplies secret_printable
+                # and secret_b64 in their place.
+                _user = info.get("username", "")
+                _password = info.get("password", "")
+                _passthrough = {k: v for k, v in info.items()
+                                if k not in ("username", "password")}
+                _log("auth", username=_user, principal=_user,
+                     **encode_secret(_password), **_passthrough)
+                # Decide connection: accept-all > cred list > deny.
+                cred = (info.get("username", ""), info.get("password", ""))
+                accepted = (
+                    MQTT_ACCEPT_ALL
+                    or (cred in _MQTT_CREDS if _MQTT_CREDS else False)
+                )
+                if accepted:
+                    self._auth = True
+                    self._transport.write(_CONNACK_ACCEPTED)
+                else:
+                    self._transport.write(_CONNACK_NOT_AUTH)
+                    self._transport.close()
+            elif pkt_type == 8:  # SUBSCRIBE
+                if not self._auth:
+                    self._transport.close()
+                    continue
+                packet_id, subs = _parse_subscribe(payload)
+                granted_qos = [1] * len(subs)  # grant QoS 1 for all
+                self._transport.write(_suback(packet_id, granted_qos))
+
+                # Immediately send retained publishes matching topics
+                for sub_topic, _ in subs:
+                    _log("subscribe", src=self._peer[0], topics=[sub_topic])
+                    for t, v in self._topics.items():
+                        # simple match: if topic ends with #, it matches prefix
+                        if sub_topic.endswith("#"):
+                            prefix = sub_topic[:-1]
+                            if t.startswith(prefix):
+                                self._transport.write(_publish(t, str(v)))
+                        elif sub_topic == t:
+                            self._transport.write(_publish(t, str(v)))
+
+            elif pkt_type == 3:  # PUBLISH
+                if not self._auth:
+                    self._transport.close()
+                    continue
+                topic, packet_id, data = _parse_publish(payload, qos)
+                # Attacker command received!
+                _log("publish", src=self._peer[0], topic=topic, payload=data.decode(errors="replace"))
+
+                if qos == 1:
+                    puback = bytes([0x40, 0x02]) + struct.pack(">H", packet_id)
+                    self._transport.write(puback)
+
+            elif pkt_type == 12:  # PINGREQ
+                self._transport.write(b"\xd0\x00")  # PINGRESP
+            elif pkt_type == 14:  # DISCONNECT
+                self._transport.close()
+            else:
+                _log("packet", src=self._peer[0], pkt_type=pkt_type)
+                self._transport.close()
+
+    def connection_lost(self, exc):
+        _log("disconnect", src=self._peer[0] if self._peer else "?")
+
+
+async def main():
+    _log("startup", msg=f"MQTT server starting as {NODE_NAME}")
+    loop = asyncio.get_running_loop()
+    server = await loop.create_server(MQTTProtocol, "0.0.0.0", PORT)  # nosec B104
+    async with server:
+        await server.serve_forever()
+
+
+if __name__ == "__main__":
+    asyncio.run(main())