Add option for TLS (#32)

Add support for providing client/CA certs/keys to enable TLS connections to an MQTT broker.

.pep8speaks.yml

@@ -0,0 +1,2 @@
+pycodestyle:  # Same as scanner.linter value. Other option is flake8
+    max-line-length: 120  # Default is 79 in PEP 8 - sorry IBM 3270 terminal users

modbus4mqtt/modbus4mqtt.py

@@ -12,22 +12,29 @@
 
 MAX_DECIMAL_POINTS = 8
 
+
 class mqtt_interface():
-    def __init__(self, hostname, port, username, password, config_file, mqtt_topic_prefix):
+    def __init__(self, hostname, port, username, password, config_file, mqtt_topic_prefix,
+                 use_tls=True, insecure=False, cafile=None, cert=None, key=None):
         self.hostname = hostname
         self._port = port
         self.username = username
         self.password = password
         self.config = self._load_modbus_config(config_file)
+        self.use_tls = use_tls
+        self.insecure = insecure
+        self.cafile = cafile
+        self.cert = cert
+        self.key = key
         if not mqtt_topic_prefix.endswith('/'):
             mqtt_topic_prefix = mqtt_topic_prefix + '/'
         self.prefix = mqtt_topic_prefix
         self.address_offset = self.config.get('address_offset', 0)
         self.registers = self.config['registers']
         for register in self.registers:
             register['address'] += self.address_offset
-        self.modbus_connect_retries = -1 # Retry forever by default
-        self.modbus_reconnect_sleep_interval = 5 # Wait this many seconds between modbus connection attempts
+        self.modbus_connect_retries = -1  # Retry forever by default
+        self.modbus_reconnect_sleep_interval = 5  # Wait this many seconds between modbus connection attempts
 
     def connect(self):
         # Connects to modbus and MQTT.
@@ -65,6 +72,9 @@ def connect_mqtt(self):
         self._mqtt_client._on_disconnect = self._on_disconnect
         self._mqtt_client._on_message = self._on_message
         self._mqtt_client._on_subscribe = self._on_subscribe
+        if self.use_tls:
+            self._mqtt_client.tls_set(ca_certs=self.cafile, certfile=self.cert, keyfile=self.key)
+            self._mqtt_client.tls_insecure_set(self.insecure)
         self._mqtt_client.connect(self.hostname, self._port, 60)
         self._mqtt_client.loop_start()
 
@@ -87,8 +97,9 @@ def poll(self):
         for register in self._get_registers_with('pub_topic'):
             try:
                 value = self._mb.get_value(register.get('table', 'holding'), register['address'])
-            except:
-                logging.warning("Couldn't get value from register {} in table {}".format(register['address'], register.get('table', 'holding')))
+            except Exception:
+                logging.warning("Couldn't get value from register {} in table {}".format(register['address'],
+                                register.get('table', 'holding')))
                 continue
             # Filter the value through the mask, if present.
             value &= register.get('mask', 0xFFFF)
@@ -157,24 +168,28 @@ def _on_message(self, client, userdata, msg):
             if 'value_map' in register:
                 try:
                     value = str(value, 'utf-8')
-                    if not value in register['value_map']:
-                        logging.warning("Value not in value_map. Topic: {}, value: {}, valid values: {}".format(topic, value, register['value_map'].keys()))
+                    if value not in register['value_map']:
+                        logging.warning("Value not in value_map. Topic: {}, value: {}, valid values: {}".format(topic,
+                                        value, register['value_map'].keys()))
                         continue
                     # Map the value from the human-readable form into the raw modbus number
                     value = register['value_map'][value]
                 except UnicodeDecodeError:
-                    logging.warning("Failed to decode MQTT payload as UTF-8. Can't compare it to the value_map for register {}".format(register))
+                    logging.warning("Failed to decode MQTT payload as UTF-8. "
+                                    "Can't compare it to the value_map for register {}".format(register))
                     continue
             try:
                 # Scale the value, if required.
                 value = float(value)
                 value = round(value/register.get('scale', 1))
             except ValueError:
-                logging.error("Failed to convert register value for writing. Bad/missing value_map? Topic: {}, Value: {}".format(topic, value))
+                logging.error("Failed to convert register value for writing. "
+                              "Bad/missing value_map? Topic: {}, Value: {}".format(topic, value))
                 continue
             type = register.get('type', 'uint16')
             value = modbus_interface._convert_from_type_to_uint16(value, type)
-            self._mb.set_value(register.get('table', 'holding'), register['address'], int(value), register.get('mask', 0xFFFF))
+            self._mb.set_value(register.get('table', 'holding'), register['address'], int(value),
+                               register.get('mask', 0xFFFF))
 
     # This throws ValueError exceptions if the imported registers are invalid
     @staticmethod
@@ -197,27 +212,34 @@ def _validate_registers(registers):
                 duplicate_json_keys[register['pub_topic']] = []
                 retain_setting[register['pub_topic']] = set()
             if 'json_key' in register and 'set_topic' in register:
-                raise ValueError("Bad YAML configuration. Register with set_topic '{}' has a json_key specified. This is invalid. See https://github.com/tjhowse/modbus4mqtt/issues/23 for details.".format(register['set_topic']))
+                raise ValueError("Bad YAML configuration. Register with set_topic '{}' has a json_key specified. "
+                                 "This is invalid. See https://github.com/tjhowse/modbus4mqtt/issues/23 for details."
+                                 .format(register['set_topic']))
             all_pub_topics.add(register['pub_topic'])
 
         # Check that all registers with duplicate pub topics have json_keys
         for register in registers:
             if register['pub_topic'] in duplicate_pub_topics:
                 if 'json_key' not in register:
-                    raise ValueError("Bad YAML configuration. pub_topic '{}' duplicated across registers without json_key field. Registers that share a pub_topic must also have a unique json_key.".format(register['pub_topic']))
+                    raise ValueError("Bad YAML configuration. pub_topic '{}' duplicated across registers without "
+                                     "json_key field. Registers that share a pub_topic must also have a unique "
+                                     "json_key.".format(register['pub_topic']))
                 if register['json_key'] in duplicate_json_keys[register['pub_topic']]:
-                    raise ValueError("Bad YAML configuration. pub_topic '{}' duplicated across registers with a duplicated json_key field. Registers that share a pub_topic must also have a unique json_key.".format(register['pub_topic']))
+                    raise ValueError("Bad YAML configuration. pub_topic '{}' duplicated across registers with a "
+                                     "duplicated json_key field. Registers that share a pub_topic must also have "
+                                     "a unique json_key.".format(register['pub_topic']))
                 duplicate_json_keys[register['pub_topic']] += [register['json_key']]
                 if 'retain' in register:
                     retain_setting[register['pub_topic']].add(register['retain'])
         # Check that there are no disagreements as to whether this pub_topic should be retained or not.
         for topic, retain_set in retain_setting.items():
             if len(retain_set) > 1:
-                raise ValueError("Bad YAML configuration. pub_topic '{}' has conflicting retain settings.".format(topic))
+                raise ValueError("Bad YAML configuration. pub_topic '{}' has conflicting retain settings."
+                                 .format(topic))
 
     def _load_modbus_config(self, path):
-        yaml=YAML(typ='safe')
-        result = yaml.load(open(path,'r').read())
+        yaml = YAML(typ='safe')
+        result = yaml.load(open(path, 'r').read())
         registers = [register for register in result['registers'] if 'pub_topic' in register]
         mqtt_interface._validate_registers(registers)
         return result
@@ -228,22 +250,41 @@ def loop_forever(self):
             self.poll()
             sleep(self.config['update_rate'])
 
+
 @click.command()
-@click.option('--hostname', default='localhost', help='The hostname or IP address of the MQTT server.', show_default=True)
-@click.option('--port', default=1883, help='The port of the MQTT server.', show_default=True)
-@click.option('--username', default='username', help='The username to authenticate to the MQTT server.', show_default=True)
-@click.option('--password', default='password', help='The password to authenticate to the MQTT server.', show_default=True)
-@click.option('--config', default='./Sungrow_SH5k_20.yaml', help='The YAML config file for your modbus device.', show_default=True)
-@click.option('--mqtt_topic_prefix', default='modbus4mqtt', help='A prefix for published MQTT topics.', show_default=True)
-def main(hostname, port, username, password, config, mqtt_topic_prefix):
+@click.option('--hostname', default='localhost',
+              help='The hostname or IP address of the MQTT server.', show_default=True)
+@click.option('--port', default=1883,
+              help='The port of the MQTT server.', show_default=True)
+@click.option('--username', default='username',
+              help='The username to authenticate to the MQTT server.', show_default=True)
+@click.option('--password', default='password',
+              help='The password to authenticate to the MQTT server.', show_default=True)
+@click.option('--mqtt_topic_prefix', default='modbus4mqtt',
+              help='A prefix for published MQTT topics.', show_default=True)
+@click.option('--config', default='./Sungrow_SH5k_20.yaml',
+              help='The YAML config file for your modbus device.', show_default=True)
+@click.option('--use_tls', default=False,
+              help='Configure network encryption and authentication options. Enables SSL/TLS.', show_default=True)
+@click.option('--insecure', default=True,
+              help='Do not check that the server certificate hostname matches the remote hostname.', show_default=True)
+@click.option('--cafile', default=None,
+              help='The path to a file containing trusted CA certificates to enable encryption.', show_default=True)
+@click.option('--cert', default=None,
+              help='Client certificate for authentication, if required by server.', show_default=True)
+@click.option('--key', default=None,
+              help='Client private key for authentication, if required by server.', show_default=True)
+def main(hostname, port, username, password, config, mqtt_topic_prefix, use_tls, insecure, cafile, cert, key):
     logging.basicConfig(
         format='%(asctime)s %(levelname)-8s %(message)s',
         level=logging.INFO,
         datefmt='%Y-%m-%d %H:%M:%S')
     logging.info("Starting modbus4mqtt v{}".format(version.version))
-    i = mqtt_interface(hostname, port, username, password, config, mqtt_topic_prefix)
+    i = mqtt_interface(hostname, port, username, password, config, mqtt_topic_prefix,
+                       use_tls, insecure, cafile, cert, key)
     i.connect()
     i.loop_forever()
 
+
 if __name__ == '__main__':
     main()