Azure iothub direct method support (#21013)

* feature: azure iot hub direct method support

* null terminator

* Remove vulnerability

---------

Co-authored-by: s-hadinger <49731213+s-hadinger@users.noreply.github.com>

tasmota/tasmota_xdrv_driver/xdrv_02_9_mqtt.ino

@@ -476,6 +476,7 @@ void MqttSubscribeLib(const char *topic) {
   String realTopicString = "devices/" + String(SettingsText(SET_MQTT_CLIENT));
   realTopicString += "/messages/devicebound/#";
   MqttClient.subscribe(realTopicString.c_str());
+  MqttClient.subscribe("$iothub/methods/POST/#");
   SettingsUpdateText(SET_MQTT_FULLTOPIC, SettingsText(SET_MQTT_CLIENT));
   SettingsUpdateText(SET_MQTT_TOPIC, SettingsText(SET_MQTT_CLIENT));
 #else
@@ -577,6 +578,25 @@ void MqttDataHandler(char* mqtt_topic, uint8_t* mqtt_data, unsigned int data_len
 
   char topic[TOPSZ];
 #ifdef USE_MQTT_AZURE_IOT
+  #ifdef USE_AZURE_DIRECT_METHOD 
+      String fullTopicString = String(mqtt_topic);
+      int startOfMethod = fullTopicString.indexOf("methods/POST");
+      int endofMethod = fullTopicString.indexOf("/?$rid");
+      String req_id = fullTopicString.substring(endofMethod + 7);
+      if (startOfMethod == -1){
+        AddLog(LOG_LEVEL_ERROR, PSTR(D_LOG_MQTT "Azure IoT Hub message without a method."));
+        return;
+      }
+      String newMethod = fullTopicString.substring(startOfMethod + 12,endofMethod);
+      strlcpy(topic, newMethod.c_str(), sizeof(topic));
+      mqtt_data[data_len] = 0;
+      JsonParser mqtt_json_data((char*) mqtt_data);
+      JsonParserObject message_object = mqtt_json_data.getRootObject();
+      String mqtt_data_str= message_object.getStr("payload","");
+      strncpy(reinterpret_cast<char*>(mqtt_data),mqtt_data_str.c_str(),data_len);
+      mqtt_data[data_len] = 0;
+
+  #else
   // for Azure, we read the topic from the property of the message
   String fullTopicString = String(mqtt_topic);
   String toppicUpper = fullTopicString;
@@ -593,6 +613,7 @@ void MqttDataHandler(char* mqtt_topic, uint8_t* mqtt_data, unsigned int data_len
     return;
   }
   strlcpy(topic, newTopic.c_str(), sizeof(topic));
+  #endif
 #else
   strlcpy(topic, mqtt_topic, sizeof(topic));
 #endif  // USE_MQTT_AZURE_IOT
@@ -624,6 +645,11 @@ void MqttDataHandler(char* mqtt_topic, uint8_t* mqtt_data, unsigned int data_len
   if (Mqtt.disable_logging) {
     TasmotaGlobal.masterlog_level = LOG_LEVEL_NONE;  // Enable logging
   }
+  #ifdef USE_AZURE_DIRECT_METHOD // Send response for the direct method
+  String response_topic = "$iothub/methods/res/200/?$rid=" + req_id;
+  String payload = "{\"status\": \"success\"}";
+  MqttClient.publish(response_topic.c_str(),payload.c_str());
+  #endif
 }
 
 /*********************************************************************************************/