New SSL implementation

Added support to secured connexion to mqtt server thanks to WiFiClientSecure class.

Please see comments in code. You can look for WiFiClientSecure, MY_GATEWAY_ESP8266_SECURE, MY_SSL_CERT, MY_SSL_FINGERPRINT and MY_SSL_CERT_CLIENT in the code below to see what has changed. No new method, no new class to be used by my_sensors. 

The following constants have to be defined from the gateway code:
MY_GATEWAY_ESP8266_SECURE    in place of MY_GATEWAY_ESP8266 to go to secure connections.
MY_SSL_CERT_AUTHx            Up to three root Certificates Authorities could be defined to validate the mqtt server' certificate. The most secure. Let's Encrypt requires at least two to validate all the certificates signed by them.
MY_SSL_FINGERPRINT           Alternatively, the mqtt server' certificate finger print could be used. Less secure and less convenient as you'll have to update the fingerprint each time the mqtt server' certificate is updated If neither MY_SSL_CERT_AUTH1 nor MY_SSL_FINGERPRINT are defined, insecure connexion will be established. The mqtt server' certificate will not be validated.
MY_SSL_CERT_CLIENT           The mqtt server may require client certificate for 
MY_SSL_KEY_CLIENT            authentication.

Author: Tico06

examples/GatewayESP8266SecureMQTTClient/GatewayESP8266SecureMQTTClient.ino

@@ -0,0 +1,226 @@
+/*
+ * The MySensors Arduino library handles the wireless radio link and protocol
+ * between your home built sensors/actuators and HA controller of choice.
+ * The sensors forms a self healing radio network with optional repeaters. Each
+ * repeater and gateway builds a routing tables in EEPROM which keeps track of the
+ * network topology allowing messages to be routed to nodes.
+ *
+ * Created by Henrik Ekblad <[email protected]>
+ * Copyright (C) 2013-2019 Sensnology AB
+ * Full contributor list: https://github.com/mysensors/MySensors/graphs/contributors
+ *
+ * Documentation: http://www.mysensors.org
+ * Support Forum: http://forum.mysensors.org
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * version 2 as published by the Free Software Foundation.
+ *
+ *******************************
+ *
+ * REVISION HISTORY
+ * Version 1.0 - Henrik Ekblad
+ *
+ * DESCRIPTION
+ * The ESP8266 MQTT gateway sends radio network (or locally attached sensors) data to your MQTT broker.
+ * The node also listens to MY_MQTT_TOPIC_PREFIX and sends out those messages to the radio network
+ *
+ * LED purposes:
+ * - To use the feature, uncomment any of the MY_DEFAULT_xx_LED_PINs in your sketch
+ * - RX (green) - blink fast on radio message received. In inclusion mode will blink fast only on presentation received
+ * - TX (yellow) - blink fast on radio message transmitted. In inclusion mode will blink slowly
+ * - ERR (red) - fast blink on error during transmission error or receive crc error
+ *
+ * See https://www.mysensors.org/build/connect_radio for wiring instructions.
+ *
+ * If you are using a "barebone" ESP8266, see
+ * https://www.mysensors.org/build/esp8266_gateway#wiring-for-barebone-esp8266
+ *
+ * Inclusion mode button:
+ * - Connect GPIO5 (=D1) via switch to GND ('inclusion switch')
+ *
+ * Hardware SHA204 signing is currently not supported!
+ *
+ * Make sure to fill in your ssid and WiFi password below for ssid & pass.
+ * 
+ ********************************
+ *
+ * SSL support by Eric Grammatico. You should have an updated version of MyGatewayTransportMQTTClient.cpp.
+ * Please see: https://forum.mysensors.org/topic/11941/esp8266-mqtt-gateway-ssl-connection
+ *
+ * The following constants have to be defined from the gateway code:
+ * MY_GATEWAY_ESP8266_SECURE    in place of MY_GATEWAY_ESP8266 to go to secure connexions.
+ * MY_SSL_CERT_AUTHx            Up to three root Certificates Authorities could be defined
+ *                              to validate the mqtt server' certificate. The most secure.
+ * MY_SSL_FINGERPRINT           Alternatively, the mqtt server' certificate finger print
+ *                              could be used. Less secure and less convenient as you'll 
+ *                              have to update the fingerprint each time the mqtt server'
+ *                              certificate is updated
+ *                              If neither MY_SSL_CERT_AUTH1 nor MY_SSL_FINGERPRINT are
+ *                              defined, insecure connexion will be established. The mqtt
+ *                              server' certificate will not be validated.
+ * MY_SSL_CERT_CLIENT           The mqtt server may require client certificate for 
+ * MY_SSL_KEY_CLIENT            authentication.
+ * 
+ * The certs.h file holds the mqtt server' fingerprint and root Certificate Authorities and
+ * client certificate and key. This a sample how to populate MY_SSL_CERT_AUTHx, MY_SSL_FINGERPRINT,
+ * MY_SSL_CERT_CLIENT and MY_SSL_KEY_CLIENT.
+ */
+
+// Imports certificates and client key 
+#include "certs.h"
+
+/**********************************
+ * MySensors node configuration
+ */
+
+// General settings
+#define SKETCH_NAME "MySensorsMQTTGW_Secure"
+#define SKETCH_VERSION "0.5"
+#define MY_DEBUG
+#define MY_NODE_ID 1
+
+// Use a bit lower baudrate for serial prints on ESP8266 than default in MyConfig.h
+#define MY_BAUD_RATE 9600
+
+// Enables and select radio type (if attached)
+//#define MY_RADIO_RF24
+//#define MY_RF24_PA_LEVEL RF24_PA_LOW
+
+//#define MY_RADIO_RFM69
+//#define MY_RADIO_RFM95
+
+/**************
+ * Secured connexion with ESP8266
+ */
+#define MY_GATEWAY_ESP8266_SECURE
+//** Set WIFI SSID and password
+#define MY_WIFI_SSID "ssid"
+#define MY_WIFI_PASSWORD "password"
+//** Set the hostname for the WiFi Client. This is the hostname
+//   passed to the DHCP server if not static.
+#define MY_HOSTNAME "esp8266-gw"
+//** Certificate Authorities. One or two should be enough
+#define MY_SSL_CERT_AUTH1 cert_isrgrootx1_Authority
+#define MY_SSL_CERT_AUTH2 cert_isrgrootx2_Authority
+//#define MY_SSL_CERT_AUTH3 cert_letsEncryptR3_Authority
+//** Server certificate validation with its fingerprint
+//   less secure and less convenient than with Certificate
+//   Authorities as server certificates are updated often.
+//   Will not be used if MY_SSL_CERT_AUTH1 defined.
+#define MY_SSL_FINGERPRINT mqtt_fingerprint
+//** The mqtt server may require client certificate for
+//   authentication.
+#define MY_SSL_CERT_CLIENT cert_client
+#define MY_SSL_KEY_CLIENT key_client
+
+
+/**************
+ * MQTT_CLIENT configuration
+ */
+#define MY_GATEWAY_MQTT_CLIENT
+//** MQTT broker if using URL instead of ip address.
+//   should correspond to the CN field in the mqtt server'
+//   certificate.
+#define MY_CONTROLLER_URL_ADDRESS mqtt_host
+//** The MQTT broker port to open
+#define MY_PORT mqtt_port
+//** Enable these if your MQTT broker requires username/password
+//#define MY_MQTT_USER "<mqtt-user>"
+//#define MY_MQTT_PASSWORD "<mqtt-passwd>"
+//** Set MQTT client id
+//#define MY_MQTT_CLIENT_ID "<mqtt-userID>"
+//** Set this node's subscribe and publish topic prefix
+#define MY_MQTT_PUBLISH_TOPIC_PREFIX "esp8266-gw/out"
+#define MY_MQTT_SUBSCRIBE_TOPIC_PREFIX "esp8266-gw/in"
+
+
+/***********************************
+ * NodeManager configuration
+ */
+
+#define NODEMANAGER_DEBUG ON
+#define NODEMANAGER_INTERRUPTS OFF
+#define NODEMANAGER_SLEEP OFF
+#define NODEMANAGER_RECEIVE ON
+#define NODEMANAGER_DEBUG_VERBOSE OFF
+#define NODEMANAGER_POWER_MANAGER OFF
+#define NODEMANAGER_CONDITIONAL_REPORT OFF
+#define NODEMANAGER_EEPROM OFF
+#define NODEMANAGER_TIME OFF
+#define NODEMANAGER_RTC OFF
+#define NODEMANAGER_SD OFF
+#define NODEMANAGER_HOOKING OFF
+#define NODEMANAGER_OTA_CONFIGURATION OFF
+#define NODEMANAGER_SERIAL_INPUT OFF
+
+
+// import NodeManager library (a nodeManager object will be then made available)
+#include <MySensors_NodeManager.h>
+
+/***********************************
+ * Add your sensors
+ */
+#include <sensors/SensorThermistor.h>
+SensorThermistor thermistor(A0);
+
+
+
+
+// before
+void before() {
+
+
+  
+  /***********************************
+   * Configure your sensors
+   */
+
+  // report measures of every attached sensors every 10 minutes
+  nodeManager.setReportIntervalMinutes(10);
+
+  // set an offset to -1 to a thermistor sensor
+  //thermistor.setOffset(-1);
+
+  // call NodeManager before routine
+  nodeManager.before();
+}
+
+void presentation()
+{
+  // call NodeManager presentation routine
+  nodeManager.presentation();
+}
+
+void setup()
+{
+
+  // SSL is cycles consuming for the ESP8266
+  system_update_cpu_freq(160);
+
+  // call NodeManager setup routine
+  nodeManager.setup();
+}
+
+
+void loop()
+{
+  // call NodeManager loop routine
+  nodeManager.loop();
+}
+
+#if NODEMANAGER_RECEIVE == ON
+// receive
+void receive(const MyMessage &message) {
+  // call NodeManager receive routine
+  nodeManager.receive(message);
+}
+#endif
+
+#if NODEMANAGER_TIME == ON
+// receiveTime
+void receiveTime(unsigned long ts) {
+  // call NodeManager receiveTime routine
+  nodeManager.receiveTime(ts);
+}
+#endif