Catch MQTT encoding errors (#3749)

* added error handling to mqtt message receive if payload is not utf-8 unicode
added mqtt test for above code as well

* change permission back to 644

* attempting to test new code

* changed exception to AttributeError
fixed test for above

* fixed lint errors I made in tests....mqtt/test_init.py

* more lint fixes for my added test

* remove dual decode of MQTT payload

* convert if to try, except, else statement for mqtt payload decode

* rework mqtt unicode testing code to properly check for log file entriy on unicode decode exception

* fixed lint error

* Update test_init.py

homeassistant/components/mqtt/__init__.py

@@ -401,13 +401,20 @@ class MQTT(object):
 
     def _mqtt_on_message(self, _mqttc, _userdata, msg):
         """Message received callback."""
-        _LOGGER.debug("received message on %s: %s",
-                      msg.topic, msg.payload.decode('utf-8'))
-        self.hass.bus.fire(EVENT_MQTT_MESSAGE_RECEIVED, {
-            ATTR_TOPIC: msg.topic,
-            ATTR_QOS: msg.qos,
-            ATTR_PAYLOAD: msg.payload.decode('utf-8'),
-        })
+        try:
+            payload = msg.payload.decode('utf-8')
+        except AttributeError:
+            _LOGGER.error("Illegal utf-8 unicode payload from "
+                          "MQTT topic: %s, Payload: %s", msg.topic,
+                          msg.payload)
+        else:
+            _LOGGER.debug("received message on %s: %s",
+                          msg.topic, payload)
+            self.hass.bus.fire(EVENT_MQTT_MESSAGE_RECEIVED, {
+                ATTR_TOPIC: msg.topic,
+                ATTR_QOS: msg.qos,
+                ATTR_PAYLOAD: payload,
+            })
 
     def _mqtt_on_unsubscribe(self, _mqttc, _userdata, mid, granted_qos):
         """Unsubscribe successful callback."""

tests/components/mqtt/test_init.py

@@ -316,3 +316,27 @@ class TestMQTTCallbacks(unittest.TestCase):
     def test_invalid_mqtt_topics(self):
         self.assertRaises(vol.Invalid, mqtt.valid_publish_topic, 'bad+topic')
         self.assertRaises(vol.Invalid, mqtt.valid_subscribe_topic, 'bad\0one')
+
+    def test_receiving_non_utf8_message_gets_logged(self):
+        """Test receiving a non utf8 encoded message."""
+        calls = []
+
+        def record(event):
+            """Helper to record calls."""
+            calls.append(event)
+
+        payload = 0x9a
+        topic = 'test_topic'
+        self.hass.bus.listen_once(mqtt.EVENT_MQTT_MESSAGE_RECEIVED, record)
+        MQTTMessage = namedtuple('MQTTMessage', ['topic', 'qos', 'payload'])
+        message = MQTTMessage(topic, 1, payload)
+        with self.assertLogs(level='ERROR') as test_handle:
+            mqtt.MQTT_CLIENT._mqtt_on_message(
+                None,
+                {'hass': self.hass},
+                message)
+            self.hass.block_till_done()
+            self.assertIn(
+                "ERROR:homeassistant.components.mqtt:Illegal utf-8 unicode "
+                "payload from MQTT topic: %s, Payload: " % topic,
+                test_handle.output[0])