Sesame-Device/src/controller.cpp

#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;
}