Improve configuration, refactoring

include/controller.h

@@ -0,0 +1,79 @@
+#pragma once
+
+#include "server.h"
+#include "servo.h"
+#include "message.h"
+#include "storage.h"
+#include "fresh.h"
+#include <ESPAsyncWebServer.h>
+
+struct WifiConfiguration {
+
+    // The WiFi network to connect to
+    const char* ssid;
+
+    // The WiFi password to connect to the above network
+    const char* password;
+
+    // The name of the device on the network
+    const char* networkName;
+
+    // The interval to reconnect to WiFi if the connection is broken
+    uint32_t reconnectInterval;
+};
+
+struct KeyConfiguration {
+
+    const uint8_t* remoteKey;
+
+    const uint8_t* localKey;
+};
+
+class SesameController: public ServerConnectionCallbacks {
+
+public:
+    SesameController(uint16_t localWebServerPort, uint8_t remoteDeviceCount);
+
+    void configure(ServoConfiguration servoConfig, ServerConfiguration serverConfig, TimeConfiguration timeConfig, WifiConfiguration wifiConfig, KeyConfiguration keyConfig);
+
+    void loop(uint32_t millis);
+
+private:
+
+    ServerConnection server;
+    ServoController servo;
+    AsyncWebServer localWebServer;
+    TimeCheck timeCheck;
+    Storage storage;
+
+    WifiConfiguration wifiConfig;
+    KeyConfiguration keyConfig;
+
+    bool isReconnecting = false;
+
+    // The buffer to hold a received message while it is read
+    uint8_t receivedMessageBuffer[AUTHENTICATED_MESSAGE_SIZE];
+
+    // The buffer to hold a response while it is sent
+    uint8_t responseBuffer[AUTHENTICATED_MESSAGE_SIZE+1];
+    SesameEvent* responseStatus;
+    AuthenticatedMessage* responseMessage;
+    uint16_t responseSize = 0;
+
+    void ensureWiFiConnection(uint32_t time);
+    void ensureWebSocketConnection();
+
+    void handleLocalMessage(AsyncWebServerRequest *request);
+    // Based on https://stackoverflow.com/a/23898449/266720
+    bool convertHexMessageToBinary(const char* str);
+
+    void handleServerMessage(uint8_t* payload, size_t length);
+    void sendServerError(SesameEvent event);
+
+    void processMessage(AuthenticatedMessage* message);
+    SesameEvent verifyAndProcessReceivedMessage(AuthenticatedMessage* message);
+
+    uint16_t prepareResponseBuffer(SesameEvent event, uint8_t deviceId = 0);
+    void sendPreparedLocalResponse(AsyncWebServerRequest *request);
+    void sendPreparedServerResponse();
+};

include/example_config.h

@@ -52,11 +52,7 @@ constexpr uint32_t wifiReconnectInterval = 10000;
 /* Local server */
 
 // The port for the local server to directly receive messages over WiFi
-constexpr uint16_t localPort = 80;
-
-// The url parameter to send the message to the local server
-constexpr char messageUrlParameter[] = "m";
-
+constexpr uint16_t localWebServerPort = 80;
 
 /* Server */ 
 

include/fresh.h

@@ -1,117 +1,80 @@
 #pragma once
 
 #include <stdint.h>
-#include "config.h"
 
-/**
- * @brief The size of the message counter in bytes (uint32_t)
- */
-#define MESSAGE_COUNTER_SIZE sizeof(uint32_t)
+struct TimeConfiguration {
 
-/**
- * @brief Configure an NTP server to get the current time
- * 
- * @param offsetToGMT The timezone offset in seconds
- * @param offsetDaylightSavings The daylight savings offset in seconds
- * @param serverUrl The url of the NTP server
- */
-void configureNTP(int32_t offsetToGMT, int32_t offsetDaylightSavings, const char* serverUrl);
+    /**
+     * @brief The timezone offset in seconds
+     */
+    int32_t offsetToGMT;
 
-/**
- * @brief Print the current time to the serial output
- * 
- * The time must be initialized by calling `configureNTP()` before use.
- */
-void printLocalTime();
+    /**
+     * @brief The daylight savings offset in seconds
+     */
+    int32_t offsetDaylightSavings;
 
-/** 
- * Gets the current epoch time
- */
-uint32_t getEpochTime();
+    /**
+     * @brief The url of the NTP server
+     */
+    const char* ntpServerUrl;
 
-/**
- * @brief The allowed time discrepancy (in seconds)
- * 
- * Specifies the allowed discrepancy between the time of a received message
- * and the device time (in seconds).
- * 
- * A stricter (lower) value better prevents against replay attacks,
- * but may lead to issues when dealing with slow networks and other
- * routing delays.
- * 
- * @param offset The offset in both directions (seconds)
- */
-void setMessageTimeAllowedOffset(uint32_t offset);
+    /**
+     * @brief The allowed discrepancy between the time of a received message
+     * and the device time (in seconds)
+     * 
+     * A stricter (lower) value better prevents against replay attacks,
+     * but may lead to issues when dealing with slow networks and other
+     * routing delays.
+     */
+    uint32_t allowedTimeOffset;
+};
 
-/**
- * @brief Check wether the time of a message is within the allowed bounds regarding freshness.
- * 
- * The timestamp is used to ensure 'freshness' of the messages,
- * i.e. that they are not unreasonably delayed or captured and
- * later replayed by an attacker.
- * 
- * @param messageTime The timestamp of the message (seconds since epoch) 
- * @return true The time is within the acceptable offset of the local time
- * @return false The message time is invalid
- */
-bool isMessageTimeAcceptable(uint32_t messageTime);
+class TimeCheck {
 
-/**
- * @brief Initialize the use of the message counter API
- * 
- * The message counter is stored in EEPROM, which must be initialized before use.
- * 
- * @note The ESP32 does not have a true EEPROM, 
- * which is emulated using a section of the flash memory.
- */
-void prepareMessageCounterUsage();
+public:
 
-/**
- * @brief Get the expected count for the next message.
- * 
- * The counter is stored in EEPROM to persist across restarts
- * 
- * @return The next counter to use by the remote 
- */
-uint32_t getNextMessageCounter(uint8_t deviceId);
+    /**
+     * @brief Create a time checker instance
+     */
+    TimeCheck();
 
-/**
- * @brief Print info about the current message counter to the serial output
- * 
- */
-void printMessageCounters();
+    /**
+     * @brief Set the configuration
+     */
+    void configure(TimeConfiguration configuration);
 
-bool isDeviceIdValid(uint8_t deviceId);
+    /**
+     * @brief Configure the NTP server to get the current time
+     */
+    void startNTP();
 
-/**
- * @brief Check if a received counter is valid
- * 
- * The counter is valid if it is larger than the previous counter
- * (larger or equal to the next expected counter).
- * 
- * @param counter The counter to check
- * @return true The counter is valid
- * @return false The counter belongs to an old message
- */
-bool isMessageCounterValid(uint32_t counter, uint8_t deviceId);
+    /**
+     * @brief Print the current time to the serial output
+     * 
+     * The time must be initialized by calling `configureNTP()` before use.
+     */
+    void printLocalTime();
 
-/**
- * @brief Mark a counter of a message as used.
- * 
- * The counter value is stored in EEPROM to persist across restarts.
- * 
- * All messages with counters lower than the given one will become invalid.
- * 
- * @param counter The counter used in the last message.
- */
-void didUseMessageCounter(uint32_t counter, uint8_t deviceId);
+    /** 
+     * Gets the current epoch time
+     */
+    uint32_t getEpochTime();
 
-/**
- * @brief Reset the message counter.
- * 
- * @warning The counter should never be reset in production environments,
- * and only together with a new secret key. Otherwise old messages may be
- * used for replay attacks.
- * 
- */
-void resetMessageCounters();
+    /**
+     * @brief Check wether the time of a message is within the allowed bounds regarding freshness.
+     * 
+     * The timestamp is used to ensure 'freshness' of the messages,
+     * i.e. that they are not unreasonably delayed or captured and
+     * later replayed by an attacker.
+     * 
+     * @param messageTime The timestamp of the message (seconds since epoch) 
+     * @return true The time is within the acceptable offset of the local time
+     * @return false The message time is invalid
+     */
+    bool isMessageTimeAcceptable(uint32_t messageTime);
+
+private:
+
+    TimeConfiguration config;
+};

include/message.h

@@ -1,6 +1,7 @@
 #pragma once
 
-#include "stdint.h"
+#include <stdint.h>
+#include <stddef.h>
 
 /**
  * @brief The size of a message authentication code
@@ -52,6 +53,8 @@ typedef struct {
 
 } Message;
 
+constexpr size_t messageCounterSize = sizeof(uint32_t);
+
 /**
  * @brief An authenticated message by the mobile device to command unlocking.
  * 
@@ -87,9 +90,9 @@ typedef struct {
 } AuthenticatedMessage;
 #pragma pack(pop)
 
-#define MESSAGE_CONTENT_SIZE sizeof(Message)
+constexpr int MESSAGE_CONTENT_SIZE = sizeof(Message);
 
-#define AUTHENTICATED_MESSAGE_SIZE sizeof(AuthenticatedMessage)
+constexpr int AUTHENTICATED_MESSAGE_SIZE = sizeof(AuthenticatedMessage);
 
 /**
  * An event signaled from the device
@@ -97,19 +100,27 @@ typedef struct {
 enum class SesameEvent {
     TextReceived = 1,
     UnexpectedSocketEvent = 2,
-    InvalidMessageData = 3,
+    InvalidMessageSize = 3,
     MessageAuthenticationFailed = 4,
     MessageTimeMismatch = 5,
     MessageCounterInvalid = 6,
     MessageAccepted = 7,
     MessageDeviceInvalid = 8,
+    InvalidUrlParameter = 9, 
+    InvalidResponseAuthentication = 10,
+    DeviceSetupIncomplete = 11,
 };
 
 /**
  * @brief A callback for messages received over the socket
  * 
- * The first parameter is the received message.
- * The second parameter is the response to the remote.
- * The return value is the type of event to respond with.
+ * The first parameter is a pointer to the byte buffer.
+ * The second parameter indicates the number of received bytes.
  */
-typedef SesameEvent (*MessageCallback)(AuthenticatedMessage*, AuthenticatedMessage*);
+typedef void (*MessageCallback)(uint8_t* payload, size_t length);
+
+/**
+ * @brief A callback for socket errors
+ */
+typedef void (*ErrorCallback)(SesameEvent event);
+

include/server.h

@@ -6,42 +6,81 @@
 #include <WiFiClientSecure.h>
 #include <WebSocketsClient.h>
 
+struct ServerConfiguration {
+
+    /**
+     * @brief The url of the remote server to connect to
+     */
+    const char* url; 
+    
+    /**
+     * @brief The server port
+     */
+    int port;
+
+    /**
+     * @brief The path on the server
+     */
+    const char* path;
+
+    /**
+     * @brief The authentication key for the server
+     */
+    const char* key;
+    
+    uint32_t reconnectTime;
+
+};
+
+class ServerConnectionCallbacks {
+
+public:
+
+    virtual void sendServerError(SesameEvent event) = 0;
+    virtual void handleServerMessage(uint8_t* payload, size_t length) = 0;
+};
+
 class ServerConnection {
 
 public:
 
-    ServerConnection(const char* url, int port, const char* path);
+    ServerConnection();
 
-    void connect(const char* key, uint32_t reconnectTime = 5000);
+    /**
+     * @brief Set the configuration and the callback handler
+     * 
+     * @param callback The handler to handle messages and errors
+     */
+    void configure(ServerConfiguration configuration, ServerConnectionCallbacks* callbacks);
 
-    void connectSSL(const char* key, uint32_t reconnectTime = 5000);
+    void connect();
 
     void loop();
 
-    void onMessage(MessageCallback callback);
+    /**
+     * @brief Send a response message over the socket
+     * 
+     * @param buffer The data buffer
+     * @param length The number of bytes to send
+     */
+    void sendResponse(uint8_t* buffer, uint16_t length);
+
+    bool isSocketConnected() {
+        return socketIsConnected;
+    }
+
+private:
+
+    ServerConfiguration configuration;
 
     // Indicator that the socket is connected.
     bool socketIsConnected = false;
 
-private:
-
-    const char* url;
-
-    int port;
-
-    const char* path;
-
-    const char* key = NULL;
-
-    MessageCallback messageCallback = NULL;
+    ServerConnectionCallbacks* controller = NULL;
 
     // WebSocket to connect to the control server
     WebSocketsClient webSocket;
 
-    void reconnectAfter(uint32_t reconnectTime);
-
-    void registerEventCallback();
-
     /**
      * Callback for WebSocket events.
      *
@@ -51,35 +90,4 @@ private:
      * @param length The number of bytes received
      */
     void webSocketEventHandler(WStype_t type, uint8_t * payload, size_t length);
-
-    /**
-     * Process received binary data.
-     *
-     * Checks whether the received data is a valid and unused key,
-     * and then signals that the motor should move.
-     * Sends the event id to the server as a response to the request.
-     *
-     * If the key is valid, then `shouldStartOpening` is set to true.
-     *
-     * @param payload The pointer to the received data.
-     * @param length The number of bytes received.
-     */
-    void processReceivedBytes(uint8_t* payload, size_t length);
-
-    /**
-     * Send a response event to the server and include the next key index.
-     *
-     * Sends the event type as three byte.
-     * @param event The event type
-     */
-    void sendFailureResponse(SesameEvent event);
-
-    /**
-     * Send a response event to the server and include the next key index.
-     *
-     * Sends the event type as three byte.
-     * @param event The event type
-     */
-    void sendResponse(SesameEvent event, AuthenticatedMessage* message);
-
 };

include/servo.h

@@ -3,6 +3,40 @@
 #include <stdint.h>
 #include <ESP32Servo.h> // To control the servo
 
+struct ServoConfiguration {
+    /**
+     * @brief The timer to use for the servo control
+     * number 0-3 indicating which timer to allocate in this library
+     */
+    int pwmTimer;
+
+    /**
+     * @brief The servo frequency (depending on the model used)
+     */
+    int pwmFrequency;
+
+    /**
+     * @brief The pin where the servo PWM line is connected
+     */
+    int pin;
+
+    /**
+     * @brief The duration (in ms) for which the button should remain pressed
+     */
+    uint32_t openDuration;
+
+    /**
+     * @brief The servo value (in µs) that specifies the 'pressed' state
+     */
+    int pressedValue;
+
+    /**
+     * @brief The servo value (in µs) that specifies the 'released' state
+     */
+    int releasedValue;
+
+};
+
 /**
  * @brief A controller for the button control servo
  * 
@@ -17,22 +51,16 @@ class ServoController {
 public:
 
     /**
-     * @brief Construct a new Servo Controller object
-     * 
-     * @param timer The timer to use for the servo control
-     * @param frequency The servo frequency (depending on the model used)
-     * @param pin The pin where the servo PWM line is connected
+     * @brief Construct a new servo controller
      */
-    ServoController(int timer, int frequency, int pin);
+    ServoController();
 
     /**
-     * @brief Configure the button values
+     * @brief Configure the servo
      * 
-     * @param openDuration The duration (in ms) for which the button should remain pressed
-     * @param pressedValue The servo value (in µs) that specifies the 'pressed' state
-     * @param releasedValue The servo value (in µs) that specifies the 'released' state
+     * @param The configuration for the servo
      */
-    void configure(uint32_t openDuration, int pressedValue, int releasedValue);
+    void configure(ServoConfiguration configuration);
 
     /**
      * @brief Update the servo state periodically
@@ -43,7 +71,7 @@ public:
      * There is no required interval to call this function, but the accuracy of
      * the opening interval is dependent on the calling frequency.
      */
-    void loop();
+    void loop(uint32_t millis);
 
     /**
      * Push the door opener button down by moving the servo arm.
@@ -60,12 +88,6 @@ private:
     // Indicator that the door button is pushed
     bool buttonIsPressed = false;
 
-    int timer;
-    
-    int frequency;
-    
-    int pin;
-
     uint32_t openDuration = 0;
 
     int pressedValue = 0;

include/storage.h

@@ -0,0 +1,83 @@
+#pragma once
+
+#include <stdint.h>
+
+class Storage {
+
+public:
+
+    Storage(uint8_t remoteDeviceCount) : remoteDeviceCount(remoteDeviceCount) { };
+
+    /**
+     * @brief Initialize the use of the message counter API
+     * 
+     * The message counter is stored in EEPROM, which must be initialized before use.
+     * 
+     * @note The ESP32 does not have a true EEPROM, 
+     * which is emulated using a section of the flash memory.
+     */
+    void configure();
+
+    /**
+     * @brief Check if a device ID is allowed
+     * 
+     * @param deviceId The ID to check
+     * @return true The id is valid
+     * @return false The id is invalid
+     */
+    bool isDeviceIdValid(uint8_t deviceId);
+
+    /**
+     * @brief Check if a received counter is valid
+     * 
+     * The counter is valid if it is larger than the previous counter
+     * (larger or equal to the next expected counter).
+     * 
+     * @param counter The counter to check
+     * @return true The counter is valid
+     * @return false The counter belongs to an old message
+     */
+    bool isMessageCounterValid(uint32_t counter, uint8_t deviceId);
+
+    /**
+     * @brief Mark a counter of a message as used.
+     * 
+     * The counter value is stored in EEPROM to persist across restarts.
+     * 
+     * All messages with counters lower than the given one will become invalid.
+     * 
+     * @param counter The counter used in the last message.
+     */
+    void didUseMessageCounter(uint32_t counter, uint8_t deviceId);
+
+    /**
+     * @brief Get the expected count for the next message.
+     * 
+     * The counter is stored in EEPROM to persist across restarts
+     * 
+     * @return The next counter to use by the remote 
+     */
+    uint32_t getNextMessageCounter(uint8_t deviceId);
+
+    /**
+     * @brief Print info about the current message counter to the serial output
+     * 
+     */
+    void printMessageCounters();
+
+    /**
+     * @brief Reset the message counter.
+     * 
+     * @warning The counter should never be reset in production environments,
+     * and only together with a new secret key. Otherwise old messages may be
+     * used for replay attacks.
+     * 
+     */
+    void resetMessageCounters();
+
+private:
+
+    uint8_t remoteDeviceCount;
+
+    void setMessageCounter(uint32_t counter, uint8_t deviceId);
+};

src/controller.cpp

@@ -0,0 +1,218 @@
+#include "controller.h"
+#include "crypto.h"
+#include "config.h"
+
+#include <WiFi.h>
+
+// The url parameter to send the message to the local server
+constexpr char messageUrlParameter[] = "m";
+
+SesameController::SesameController(uint16_t localWebServerPort, uint8_t remoteDeviceCount) : 
+    storage(remoteDeviceCount), localWebServer(localWebServerPort) {
+    
+    // Set up response buffer
+    responseStatus = (SesameEvent*) responseBuffer;
+    responseMessage = (AuthenticatedMessage*) (responseBuffer + 1);
+}
+
+void SesameController::configure(ServoConfiguration servoConfig, ServerConfiguration serverConfig, TimeConfiguration timeConfig, WifiConfiguration wifiConfig, KeyConfiguration keyConfig) {
+    this->wifiConfig = wifiConfig;
+    this->keyConfig = keyConfig;
+
+    // Prepare EEPROM for reading and writing
+    storage.configure();
+    Serial.println("[INFO] Storage configured");
+    
+    servo.configure(servoConfig);
+    Serial.println("[INFO] Servo configured");
+
+    // Direct messages and errors over the websocket to the controller
+    server.configure(serverConfig, this);
+    Serial.println("[INFO] Server connection configured");
+
+    timeCheck.configure(timeConfig);
+
+    
+    // Direct messages from the local web server to the controller
+    localWebServer.on("/message", HTTP_POST, [this] (AsyncWebServerRequest *request) { 
+        this->handleLocalMessage(request); 
+        this->sendPreparedLocalResponse(request);
+    });
+
+    Serial.println("[INFO] Local web server configured");
+
+    //storage.resetMessageCounters();
+    storage.printMessageCounters();
+}
+
+void SesameController::loop(uint32_t millis) {
+    server.loop();
+    servo.loop(millis);
+
+    ensureWiFiConnection(millis);
+    ensureWebSocketConnection();
+}
+
+// MARK: Local
+
+void 
+SesameController::handleLocalMessage(AsyncWebServerRequest *request) {
+    if (!request->hasParam(messageUrlParameter)) {
+        Serial.println("Missing url parameter");
+        prepareResponseBuffer(SesameEvent::InvalidUrlParameter);
+        return;
+    }
+    String encoded = request->getParam(messageUrlParameter)->value();
+    if (!convertHexMessageToBinary(encoded.c_str())) {
+        Serial.println("Invalid hex encoding");
+        prepareResponseBuffer(SesameEvent::InvalidMessageSize);
+        return;
+    }
+    processMessage((AuthenticatedMessage*) receivedMessageBuffer);
+}
+
+void SesameController::sendPreparedLocalResponse(AsyncWebServerRequest *request) {
+    request->send_P(200, "application/octet-stream", responseBuffer, responseSize);
+    Serial.printf("[INFO] Local response %u (%u bytes)\n", responseBuffer[0], responseSize);
+}
+
+// MARK: Server
+
+void SesameController::sendServerError(SesameEvent event) {
+    prepareResponseBuffer(event);
+    sendPreparedServerResponse();
+}
+
+void SesameController::handleServerMessage(uint8_t* payload, size_t length) {
+    if (length != AUTHENTICATED_MESSAGE_SIZE) {
+        prepareResponseBuffer(SesameEvent::InvalidMessageSize);
+        return;
+    }
+    
+    processMessage((AuthenticatedMessage*) payload);
+    sendPreparedServerResponse();
+}
+
+void SesameController::sendPreparedServerResponse() {
+    server.sendResponse(responseBuffer, responseSize);
+    Serial.printf("[INFO] Server response %u (%u bytes)\n", responseBuffer[0], responseSize);
+}
+
+// MARK: Message handling
+
+void SesameController::processMessage(AuthenticatedMessage* message) {
+    SesameEvent event = verifyAndProcessReceivedMessage(message);
+    prepareResponseBuffer(event, message->message.device);
+}
+
+/**
+ * Process a received message.
+ *
+ * Checks whether the received data is a valid,
+ * and then signals that the motor should move.
+ *
+ * @param message The message received from the remote
+ * @return The response to signal to the server.
+ */
+SesameEvent SesameController::verifyAndProcessReceivedMessage(AuthenticatedMessage* message) {
+    if (!isAuthenticMessage(message, keyConfig.remoteKey, keySize)) {
+        return SesameEvent::MessageAuthenticationFailed;
+    }
+    if (!storage.isDeviceIdValid(message->message.device)) {
+        return SesameEvent::MessageDeviceInvalid;
+    }
+    if (!storage.isMessageCounterValid(message->message.id, message->message.device)) {
+        return SesameEvent::MessageCounterInvalid;
+    }
+    if (!timeCheck.isMessageTimeAcceptable(message->message.time)) {
+        return SesameEvent::MessageTimeMismatch;
+    }
+
+    storage.didUseMessageCounter(message->message.id, message->message.device);
+    // Move servo
+    servo.pressButton();
+    Serial.printf("[Info] Accepted message %d\n", message->message.id);
+    return SesameEvent::MessageAccepted;
+}
+
+bool allowMessageResponse(SesameEvent event) {
+    switch (event) {
+    case SesameEvent::MessageTimeMismatch:
+    case SesameEvent::MessageCounterInvalid:
+    case SesameEvent::MessageAccepted:
+    case SesameEvent::MessageDeviceInvalid:
+        return true;
+    default:
+        return false;
+    }
+}
+
+uint16_t SesameController::prepareResponseBuffer(SesameEvent event, uint8_t deviceId) {
+    *responseStatus = event;
+    if (!allowMessageResponse(event)) {
+        return 1;
+    }
+    responseMessage->message.time = timeCheck.getEpochTime();
+    responseMessage->message.id = storage.getNextMessageCounter(deviceId);
+    responseMessage->message.device = deviceId;
+    if (!authenticateMessage(responseMessage, keyConfig.localKey, keySize)) {
+        *responseStatus = SesameEvent::InvalidResponseAuthentication;
+        return 1;
+    }
+    return 1 + AUTHENTICATED_MESSAGE_SIZE;
+}
+
+// MARK: Reconnecting
+
+void SesameController::ensureWiFiConnection(uint32_t millis) {
+    static uint32_t nextWifiReconnect = 0;
+    // Reconnect to WiFi
+    if(millis > nextWifiReconnect && WiFi.status() != WL_CONNECTED) {
+        Serial.println("[INFO] Reconnecting WiFi...");
+        WiFi.setHostname(wifiConfig.networkName);
+        WiFi.begin(wifiConfig.ssid, wifiConfig.password);
+        isReconnecting = true;
+        nextWifiReconnect = millis + wifiConfig.reconnectInterval;
+    }
+}
+
+void SesameController::ensureWebSocketConnection() {
+    if (isReconnecting && WiFi.status() == WL_CONNECTED) {
+        isReconnecting = false;
+        Serial.print("WiFi IP address: ");
+        Serial.println(WiFi.localIP());
+        server.connect();
+        timeCheck.startNTP();
+        timeCheck.printLocalTime();
+        localWebServer.begin();
+    }
+}
+
+// MARK: Helper
+
+// Based on https://stackoverflow.com/a/23898449/266720
+bool SesameController::convertHexMessageToBinary(const char* str) {
+    // TODO: Fail if invalid hex values are used
+    uint8_t  idx0, idx1;
+
+    // mapping of ASCII characters to hex values
+    const uint8_t hashmap[] = {
+        0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, // 01234567
+        0x08, 0x09, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // 89:;<=>?
+        0x00, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 0x00, // @ABCDEFG
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // HIJKLMNO
+    };
+
+    size_t len = strlen(str);
+    if (len != AUTHENTICATED_MESSAGE_SIZE * 2) {
+        // Require exact message size
+        return false;
+    }
+
+    for (size_t pos = 0; pos < len; pos += 2) {
+        idx0 = ((uint8_t)str[pos+0] & 0x1F) ^ 0x10;
+        idx1 = ((uint8_t)str[pos+1] & 0x1F) ^ 0x10;
+        receivedMessageBuffer[pos/2] = (uint8_t)(hashmap[idx0] << 4) | hashmap[idx1];
+    };
+    return true;
+}

src/fresh.cpp

@@ -1,28 +1,19 @@
 #include "fresh.h"
 
-#include <Arduino.h>
+#include <Arduino.h> // configTime()
 #include <time.h>
-#include <EEPROM.h>
 
-/**
- * @brief The allowed discrepancy between the time of a received message
- * and the device time (in seconds)
- * 
- * A stricter (lower) value better prevents against replay attacks,
- * but may lead to issues when dealing with slow networks and other
- * routing delays.
- */
-uint32_t allowedOffset = 60;
+TimeCheck::TimeCheck() { }
 
-void setMessageTimeAllowedOffset(uint32_t offset) {
-    allowedOffset = offset;
+void TimeCheck::configure(TimeConfiguration configuration) {
+    config = configuration;
 }
 
-void configureNTP(int32_t offsetToGMT, int32_t offsetDaylightSavings, const char* serverUrl) {
-    configTime(offsetToGMT, offsetDaylightSavings, serverUrl);
+void TimeCheck::startNTP() {
+    configTime(config.offsetToGMT, config.offsetDaylightSavings, config.ntpServerUrl);
 }
 
-void printLocalTime() {
+void TimeCheck::printLocalTime() {
     struct tm timeinfo;
     if (getLocalTime(&timeinfo)) {
         Serial.println(&timeinfo, "[INFO] Time is %A, %d. %B %Y %H:%M:%S");
@@ -31,7 +22,7 @@ void printLocalTime() {
     }
 }
 
-uint32_t getEpochTime() {
+uint32_t TimeCheck::getEpochTime() {
     time_t now;
     struct tm timeinfo;
     if (!getLocalTime(&timeinfo)) {
@@ -42,67 +33,17 @@ uint32_t getEpochTime() {
     return now;
 }
 
-bool isMessageTimeAcceptable(uint32_t t) {
+bool TimeCheck::isMessageTimeAcceptable(uint32_t t) {
     uint32_t localTime = getEpochTime();
     if (localTime == 0) {
         Serial.println("No epoch time available");
         return false;
     }
-    if (t > localTime + allowedOffset) {
+    if (t > localTime + config.allowedTimeOffset) {
         return false;
     }
-    if (t < localTime - allowedOffset) {
+    if (t < localTime - config.allowedTimeOffset) {
         return false;
     }
     return true;
-}
-
-void prepareMessageCounterUsage() {
-    EEPROM.begin(MESSAGE_COUNTER_SIZE * remoteDeviceCount);
-}
-
-uint32_t getNextMessageCounter(uint8_t deviceId) {
-    int offset = deviceId * MESSAGE_COUNTER_SIZE;
-    uint32_t counter = (uint32_t) EEPROM.read(offset + 0) << 24;
-    counter         += (uint32_t) EEPROM.read(offset + 1) << 16;
-    counter         += (uint32_t) EEPROM.read(offset + 2) << 8;
-    counter         += (uint32_t) EEPROM.read(offset + 3);
-    return counter;
-}
-
-void printMessageCounters() {
-    Serial.print("[INFO] Next message numbers:");
-    for (uint8_t i = 0; i < remoteDeviceCount; i += 1) {
-        Serial.printf(" %u", getNextMessageCounter(i));
-    }
-    Serial.println("");
-}
-
-bool isDeviceIdValid(uint8_t deviceId) {
-    return deviceId < remoteDeviceCount;
-}
-
-bool isMessageCounterValid(uint32_t counter, uint8_t deviceId) {
-    return counter >= getNextMessageCounter(deviceId);
-}
-
-void setMessageCounter(uint32_t counter, uint8_t deviceId) {
-    int offset = deviceId * MESSAGE_COUNTER_SIZE;
-    EEPROM.write(offset + 0, (counter >> 24) & 0xFF);
-    EEPROM.write(offset + 1, (counter >> 16) & 0xFF);
-    EEPROM.write(offset + 2, (counter >>  8) & 0xFF);
-    EEPROM.write(offset + 3,  counter        & 0xFF);
-    EEPROM.commit();
-}
-
-void didUseMessageCounter(uint32_t counter, uint8_t deviceId) {
-    // Store the next counter, so that resetting starts at 0
-    setMessageCounter(counter+1, deviceId);
-}
-
-void resetMessageCounters() {
-    for (uint8_t i = 0; i < remoteDeviceCount; i += 1) {
-        setMessageCounter(0, i);
-    }
-    Serial.println("[WARN] Message counters reset");
-}
+}

src/main.cpp

@@ -6,196 +6,61 @@
  * physical button.
  */
 #include <Arduino.h>
-#include <WiFi.h>
-#include <ESPAsyncWebServer.h>
 
-#include "crypto.h"
-#include "fresh.h"
 #include "message.h"
 #include "server.h"
 #include "servo.h"
+#include "controller.h"
 #include "config.h"
 
-/* Global variables */
-
-ServerConnection server(serverUrl, serverPort, serverPath);
-
-ServoController servo(pwmTimer, servoFrequency, servoPin);
-
-AsyncWebServer local(localPort);
-
-// The buffer to hold a received message while it is read
-uint8_t receivedMessageBuffer[AUTHENTICATED_MESSAGE_SIZE];
-
-/* Event callbacks */
-
-SesameEvent handleReceivedMessage(AuthenticatedMessage* payload, AuthenticatedMessage* response);
-
-// Forward declare monitoring functions
-void ensureWiFiConnection(uint32_t time);
-void ensureWebSocketConnection(uint32_t time);
-
-void sendFailureResponse(AsyncWebServerRequest *request, SesameEvent event);
-void sendMessageResponse(AsyncWebServerRequest *request, SesameEvent event, AuthenticatedMessage* message);
-void sendResponse(AsyncWebServerRequest *request, uint8_t* buffer, uint8_t size);
-void hexToBin(const char * str, uint8_t * bytes, size_t blen);
-
-/* Logic */
+SesameController controller(localWebServerPort, remoteDeviceCount);
 
 void setup() {
     Serial.begin(serialBaudRate);
     Serial.setDebugOutput(true);
     Serial.println("[INFO] Device started");
 
-    servo.configure(lockOpeningDuration, servoPressedState, servoReleasedState);
-    Serial.println("[INFO] Servo configured");
+    ServoConfiguration servoConfig {
+        .pwmTimer = pwmTimer,
+        .pwmFrequency = servoFrequency,
+        .pin = servoPin,
+        .openDuration = lockOpeningDuration,
+        .pressedValue = servoPressedState,
+        .releasedValue = servoReleasedState,
+    };
 
-    prepareMessageCounterUsage();
-    //resetMessageCounters();
-    printMessageCounters();
+    ServerConfiguration serverConfig {
+        .url = serverUrl,
+        .port = serverPort,
+        .path = serverPath,
+        .key = serverAccessKey,
+        .reconnectTime = 5000,
+    };
 
-    server.onMessage(handleReceivedMessage);
+    TimeConfiguration timeConfig {
+        .offsetToGMT = timeOffsetToGMT,
+        .offsetDaylightSavings = timeOffsetDaylightSavings,
+        .ntpServerUrl = ntpServerUrl,
+        .allowedTimeOffset = 60,
+    };
 
-    local.on("/message", HTTP_POST, [] (AsyncWebServerRequest *request) {
-        if (!request->hasParam(messageUrlParameter)) {
-            Serial.println("Missing url parameter");
-            sendFailureResponse(request, SesameEvent::InvalidMessageData);
-            return;
-        }
-        String encoded = request->getParam(messageUrlParameter)->value();
-        hexToBin(encoded.c_str(), receivedMessageBuffer, AUTHENTICATED_MESSAGE_SIZE);
-        // Process received message
-        AuthenticatedMessage* message = (AuthenticatedMessage*) receivedMessageBuffer;
-        AuthenticatedMessage responseMessage;
-        SesameEvent event = handleReceivedMessage(message, &responseMessage);
-        sendMessageResponse(request, event, &responseMessage);
-    });
+    WifiConfiguration wifiConfig {
+        .ssid = wifiSSID,
+        .password = wifiPassword,
+        .networkName = networkName,
+        .reconnectInterval = wifiReconnectInterval,
+    };
+
+    KeyConfiguration keyConfig {
+        .remoteKey = remoteKey,
+        .localKey = localKey,
+    };
+
+    controller.configure(servoConfig, serverConfig, timeConfig, wifiConfig, keyConfig);
 }
 
 void loop() {
     uint32_t time = millis();
 
-    server.loop();
-    servo.loop();
-
-    ensureWiFiConnection(time);
-    ensureWebSocketConnection(time);
-}
-
-uint32_t nextWifiReconnect = 0;
-bool isReconnecting = false;
-
-void ensureWiFiConnection(uint32_t time) {
-    // Reconnect to WiFi
-    if(time > nextWifiReconnect && WiFi.status() != WL_CONNECTED) {
-        Serial.println("[INFO] Reconnecting WiFi...");
-        WiFi.setHostname(networkName);
-        WiFi.begin(wifiSSID, wifiPassword);
-        isReconnecting = true;
-        nextWifiReconnect = time + wifiReconnectInterval;
-    }
-}
-
-void ensureWebSocketConnection(uint32_t time) {
-    if (isReconnecting && WiFi.status() == WL_CONNECTED) {
-        isReconnecting = false;
-        Serial.println("IP address: ");
-        Serial.println(WiFi.localIP());
-        Serial.println("[INFO] WiFi connected, opening socket");
-        server.connectSSL(serverAccessKey);
-        configureNTP(timeOffsetToGMT, timeOffsetDaylightSavings, ntpServerUrl);
-        printLocalTime();
-        local.begin();
-    }
-}
-
-SesameEvent processMessage(AuthenticatedMessage* message) {
-    if (!isDeviceIdValid(message->message.device)) {
-        return SesameEvent::MessageDeviceInvalid;
-    }
-    if (!isMessageCounterValid(message->message.id, message->message.device)) {
-        return SesameEvent::MessageCounterInvalid;
-    }
-    if (!isMessageTimeAcceptable(message->message.time)) {
-        return SesameEvent::MessageTimeMismatch;
-    }
-    if (!isAuthenticMessage(message, remoteKey, keySize)) {
-        return SesameEvent::MessageAuthenticationFailed;
-    }
-    return SesameEvent::MessageAccepted;
-}
-
-/**
- * Process received binary data.
- *
- * Checks whether the received data is a valid and unused key,
- * and then signals that the motor should move.
- *
- * @param payload The pointer to the received data.
- * @param length The number of bytes received.
- * @return The event to signal to the server.
- */
-SesameEvent handleReceivedMessage(AuthenticatedMessage* message, AuthenticatedMessage* response) {
-    SesameEvent event = processMessage(message);
-    
-    // Only open when message is valid
-    if (event == SesameEvent::MessageAccepted) {
-        didUseMessageCounter(message->message.id, message->message.device);
-        // Move servo
-        servo.pressButton();
-        Serial.printf("[Info] Accepted message %d\n", message->message.id);
-    }
-
-    // Create response for all cases
-    response->message.time = getEpochTime();
-    response->message.id = getNextMessageCounter(message->message.device);
-    if (!authenticateMessage(response, localKey, keySize)) {
-        return SesameEvent::MessageAuthenticationFailed;
-    }
-    return event;
-}
-
-void sendFailureResponse(AsyncWebServerRequest *request, SesameEvent event) {
-    uint8_t response = static_cast<uint8_t>(event);
-    sendResponse(request, &response, 1);
-}
-
-void sendMessageResponse(AsyncWebServerRequest *request, SesameEvent event, AuthenticatedMessage* message) {
-    uint8_t response[AUTHENTICATED_MESSAGE_SIZE+1];
-    response[0] = static_cast<uint8_t>(event);
-    memcpy(response+1, (uint8_t*) message, AUTHENTICATED_MESSAGE_SIZE);
-    sendResponse(request, response, AUTHENTICATED_MESSAGE_SIZE+1);
-}
-
-void sendResponse(AsyncWebServerRequest *request, uint8_t* buffer, uint8_t size) {
-    request->send_P(200, "application/octet-stream", buffer, size);
-    Serial.printf("[INFO] Local response %d\n", buffer[0]);
-}
-
-// Based on https://stackoverflow.com/a/23898449/266720
-void hexToBin(const char * str, uint8_t * bytes, size_t blen) {
-    uint8_t  idx0, idx1;
-
-    // mapping of ASCII characters to hex values
-    const uint8_t hashmap[] = {
-        0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, // 01234567
-        0x08, 0x09, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // 89:;<=>?
-        0x00, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 0x00, // @ABCDEFG
-        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // HIJKLMNO
-    };
-
-    memset(bytes, 0, blen);
-    
-    size_t len = strlen(str);
-    if (len % 2) {
-        // Require two chars per byte
-        return;
-    }
-    size_t end = min(blen*2, len);
-
-    for (size_t pos = 0; pos < end; pos += 2) {
-        idx0 = ((uint8_t)str[pos+0] & 0x1F) ^ 0x10;
-        idx1 = ((uint8_t)str[pos+1] & 0x1F) ^ 0x10;
-        bytes[pos/2] = (uint8_t)(hashmap[idx0] << 4) | hashmap[idx1];
-    };
+    controller.loop(time);
 }

src/server.cpp

@@ -4,44 +4,33 @@ constexpr int32_t pingInterval = 10000;
 constexpr uint32_t pongTimeout = 5000;
 uint8_t disconnectTimeoutCount = 3;
 
-ServerConnection::ServerConnection(const char* url, int port, const char* path) : 
-    url(url), port(port), path(path) {
+ServerConnection::ServerConnection() { }
 
+void ServerConnection::configure(ServerConfiguration configuration, ServerConnectionCallbacks *callbacks) {
+    controller = callbacks;
+    this->configuration = configuration;
 }
 
-void ServerConnection::connect(const char* key, uint32_t reconnectTime) {
-    webSocket.begin(url, port, path);
-    registerEventCallback();
-    reconnectAfter(reconnectTime);
-}
-
-void ServerConnection::connectSSL(const char* key, uint32_t reconnectTime) {
+void ServerConnection::connect() {
     if (socketIsConnected) {
         return;
     }
-    this->key = key;
-    webSocket.beginSSL(url, port, path);
-    registerEventCallback();
-    reconnectAfter(reconnectTime);
-}
+    if (controller == NULL) {
+        Serial.println("[ERROR] No callbacks set for server");
+        return;
+    }
 
-void ServerConnection::loop() {
-    webSocket.loop();
-}
+    webSocket.beginSSL(configuration.url, configuration.port, configuration.path);
 
-void ServerConnection::onMessage(MessageCallback callback) {
-    messageCallback = callback;
-}
-
-void ServerConnection::reconnectAfter(uint32_t reconnectTime) {
-    webSocket.setReconnectInterval(reconnectTime);
-}
-
-void ServerConnection::registerEventCallback() {
     std::function<void(WStype_t, uint8_t *, size_t)> f = [this](WStype_t type, uint8_t *payload, size_t length) {
         this->webSocketEventHandler(type, payload, length);
     };
     webSocket.onEvent(f);
+    webSocket.setReconnectInterval(configuration.reconnectTime);
+}
+
+void ServerConnection::loop() {
+    webSocket.loop();
 }
 
 void ServerConnection::webSocketEventHandler(WStype_t type, uint8_t * payload, size_t length) {
@@ -52,15 +41,15 @@ switch(type) {
         break;
     case WStype_CONNECTED:
         socketIsConnected = true;
-        webSocket.sendTXT(key);
+        webSocket.sendTXT(configuration.key);
         Serial.printf("[INFO] Socket connected to url: %s\n", payload);
         webSocket.enableHeartbeat(pingInterval, pongTimeout, disconnectTimeoutCount);
         break;
     case WStype_TEXT:
-        sendFailureResponse(SesameEvent::TextReceived);
+        controller->sendServerError(SesameEvent::TextReceived);
         break;
     case WStype_BIN:
-        processReceivedBytes(payload, length);
+        controller->handleServerMessage(payload, length);
         break;
     case WStype_PONG:
         break;
@@ -70,36 +59,11 @@ switch(type) {
     case WStype_FRAGMENT_BIN_START:
     case WStype_FRAGMENT:
     case WStype_FRAGMENT_FIN:
-        sendFailureResponse(SesameEvent::UnexpectedSocketEvent);
+        controller->sendServerError(SesameEvent::UnexpectedSocketEvent);
         break;
     }
 }
 
-void ServerConnection::processReceivedBytes(uint8_t* payload, size_t length) {
-    if (length != AUTHENTICATED_MESSAGE_SIZE) {
-        sendFailureResponse(SesameEvent::InvalidMessageData);
-        return;
-    }
-    AuthenticatedMessage* message = (AuthenticatedMessage*) payload;
-    if (messageCallback == NULL) {
-        sendFailureResponse(SesameEvent::MessageAuthenticationFailed);
-        return;
-    }
-    AuthenticatedMessage responseMessage;
-    SesameEvent event = messageCallback(message, &responseMessage);
-    sendResponse(event, &responseMessage);
-}
-
-void ServerConnection::sendFailureResponse(SesameEvent event) {
-    uint8_t response = static_cast<uint8_t>(event);
-    webSocket.sendBIN(&response, 1);
-    Serial.printf("[INFO] Socket failure %d\n", response);
-}
-
-void ServerConnection::sendResponse(SesameEvent event, AuthenticatedMessage* message) {
-    uint8_t response[AUTHENTICATED_MESSAGE_SIZE+1];
-    response[0] = static_cast<uint8_t>(event);
-    memcpy(response+1, (uint8_t*) message, AUTHENTICATED_MESSAGE_SIZE);
-    webSocket.sendBIN(response, AUTHENTICATED_MESSAGE_SIZE+1);
-    Serial.printf("[INFO] Socket response %d\n", response[0]);
+void ServerConnection::sendResponse(uint8_t* buffer, uint16_t length) {
+    webSocket.sendBIN(buffer, length);
 }

src/servo.cpp

@@ -2,18 +2,15 @@
 
 #include <esp32-hal.h> // For `millis()`
 
-ServoController::ServoController(int timer, int frequency, int pin) 
-    : timer(timer), frequency(frequency), pin(pin) {
-    
-}
+ServoController::ServoController() { }
 
-void ServoController::configure(uint32_t openDuration, int pressedValue, int releasedValue) {
-    this->openDuration = openDuration;
-    this->pressedValue = pressedValue;
-    this->releasedValue = releasedValue;
-    ESP32PWM::allocateTimer(timer);
-    servo.setPeriodHertz(frequency);
-    servo.attach(pin);
+void ServoController::configure(ServoConfiguration configuration) {
+    openDuration = configuration.openDuration;
+    pressedValue = configuration.pressedValue;
+    releasedValue = configuration.releasedValue;
+    ESP32PWM::allocateTimer(configuration.pwmTimer);
+    servo.setPeriodHertz(configuration.pwmFrequency);
+    servo.attach(configuration.pin);
     releaseButton();
 }
 
@@ -28,8 +25,8 @@ void ServoController::releaseButton() {
     buttonIsPressed = false;
 }
 
-void ServoController::loop() {
-    if (buttonIsPressed && millis() > openingEndTime) {
+void ServoController::loop(uint32_t millis) {
+    if (buttonIsPressed && millis > openingEndTime) {
         releaseButton();
     }
 }

src/storage.cpp

@@ -0,0 +1,53 @@
+#include "storage.h"
+#include "message.h"
+#include <EEPROM.h>
+
+void Storage::configure() {
+    EEPROM.begin(messageCounterSize * remoteDeviceCount);
+}
+
+bool Storage::isDeviceIdValid(uint8_t deviceId) {
+    return deviceId < remoteDeviceCount;
+}
+
+bool Storage::isMessageCounterValid(uint32_t counter, uint8_t deviceId) {
+    return counter >= getNextMessageCounter(deviceId);
+}
+
+void Storage::didUseMessageCounter(uint32_t counter, uint8_t deviceId) {
+    // Store the next counter, so that resetting starts at 0
+    setMessageCounter(counter+1, deviceId);
+}
+
+void Storage::setMessageCounter(uint32_t counter, uint8_t deviceId) {
+    int offset = deviceId * messageCounterSize;
+    EEPROM.write(offset + 0, (counter >> 24) & 0xFF);
+    EEPROM.write(offset + 1, (counter >> 16) & 0xFF);
+    EEPROM.write(offset + 2, (counter >>  8) & 0xFF);
+    EEPROM.write(offset + 3,  counter        & 0xFF);
+    EEPROM.commit();
+}
+
+uint32_t Storage::getNextMessageCounter(uint8_t deviceId) {
+    int offset = deviceId * messageCounterSize;
+    uint32_t counter = (uint32_t) EEPROM.read(offset + 0) << 24;
+    counter         += (uint32_t) EEPROM.read(offset + 1) << 16;
+    counter         += (uint32_t) EEPROM.read(offset + 2) << 8;
+    counter         += (uint32_t) EEPROM.read(offset + 3);
+    return counter;
+}
+
+void Storage::printMessageCounters() {
+    Serial.print("[INFO] Next message numbers:");
+    for (uint8_t i = 0; i < remoteDeviceCount; i += 1) {
+        Serial.printf(" %u", getNextMessageCounter(i));
+    }
+    Serial.println("");
+}
+
+void Storage::resetMessageCounters() {
+    for (uint8_t i = 0; i < remoteDeviceCount; i += 1) {
+        setMessageCounter(0, i);
+    }
+    Serial.println("[WARN] Message counters reset");
+}