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13 changed files with 545 additions and 485 deletions

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@ -3,34 +3,25 @@
#include "server.h"
#include "servo.h"
#include "message.h"
#include "storage.h"
#include "fresh.h"
#include <ESPAsyncWebServer.h>
struct EthernetConfiguration {
struct WifiConfiguration {
// The MAC address of the ethernet connection
uint8_t macAddress[6];
// The WiFi network to connect to
const char* ssid;
// The master-in slave-out pin of the SPI connection for the Ethernet module
int8_t spiPinMiso;
// The WiFi password to connect to the above network
const char* password;
// The master-out slave-in pin of the SPI connection for the Ethernet module
int8_t spiPinMosi;
// The name of the device on the network
const char* networkName;
// The slave clock pin of the SPI connection for the Ethernet module
int8_t spiPinSclk;
// The slave-select pin of the SPI connection for the Ethernet module
int8_t spiPinSS;
unsigned long dhcpLeaseTimeoutMs;
unsigned long dhcpLeaseResponseTimeoutMs;
// The static IP address to assign if DHCP fails
uint8_t manualIp[4];
// The IP address of the DNS server, if DHCP fails
uint8_t manualDnsAddress[4];
// The interval to reconnect to WiFi if the connection is broken
uint32_t reconnectInterval;
uint32_t periodicReconnectInterval;
};
struct KeyConfiguration {
@ -38,133 +29,55 @@ struct KeyConfiguration {
const uint8_t* remoteKey;
const uint8_t* localKey;
uint32_t challengeExpiryMs;
};
class SesameController: public ServerConnectionCallbacks {
public:
SesameController(uint16_t localWebServerPort);
SesameController(uint16_t localWebServerPort, uint8_t remoteDeviceCount);
void configure(ServoConfiguration servoConfig, ServerConfiguration serverConfig, EthernetConfiguration ethernetConfig, KeyConfiguration keyConfig);
void configure(ServoConfiguration servoConfig, ServerConfiguration serverConfig, TimeConfiguration timeConfig, WifiConfiguration wifiConfig, KeyConfiguration keyConfig);
void loop(uint32_t millis);
private:
uint32_t currentTime = 0;
ServerConnection server;
ServoController servo;
AsyncWebServer localWebServer;
TimeCheck timeCheck;
Storage storage;
EthernetConfiguration ethernetConfig;
bool ethernetIsConfigured = false;
WifiConfiguration wifiConfig;
KeyConfiguration keyConfig;
bool isReconnecting = false;
// Buffer to get local message
SignedMessage receivedLocalMessage;
// The buffer to hold a received message while it is read
uint8_t receivedMessageBuffer[AUTHENTICATED_MESSAGE_SIZE];
uint32_t currentClientChallenge;
uint32_t currentChallengeExpiry = 0;
uint32_t currentServerChallenge;
// 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;
SignedMessage outgoingMessage;
bool hasCurrentChallenge() {
return currentChallengeExpiry > currentTime;
}
void clearCurrentChallenge() {
currentClientChallenge = 0;
currentServerChallenge = 0;
currentChallengeExpiry = 0;
}
// MARK: Local client callbacks
void ensureWiFiConnection(uint32_t time);
void ensureWebSocketConnection();
void handleLocalMessage(AsyncWebServerRequest *request);
// MARK: Socket Callbacks
/**
* @brief Callback to send an error back to the server via the web socket.
*
* This function is called when the socket get's an error.
*
* @param event The error to report back
*/
void sendServerError(MessageResult event);
// 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);
// MARK: Message processing
void processMessage(AuthenticatedMessage* message);
SesameEvent verifyAndProcessReceivedMessage(AuthenticatedMessage* message);
/**
* @brief Process a received message (local or socket).
*
* @param message The message to process.
*
* Note: Prepares the response in the outgoing message buffer.
*/
void processMessage(SignedMessage* message);
/**
* @brief Checks that the message is valid and prepares a challenge.
*
* This function is also called when a challenge response arrives too late.
*
* @param message The message to respond to
*
* Note: Prepares the response in the outgoing message buffer.
*/
void checkAndPrepareChallenge(Message* message);
/**
* @brief Prepare a server challenge for a local or socket message.
*
* @param message The message to respond to
*
* Note: Prepares the response in the outgoing message buffer.
*/
void prepareChallenge(Message* message);
/**
* @brief Complete an unlock request for a local or socket message.
*
* @param message The message to respond to
*
* Note: Prepares the response in the outgoing message buffer.
*/
void completeUnlockRequest(Message* message);
// MARK: Responses
/**
* @brief Prepare the outgoing message buffer for both socket and local responses.
*
* @param event The resulting state to transmit
* @param message An optional message to echo
*/
void prepareResponseBuffer(MessageResult event, Message* message = NULL);
/**
* @brief Send the prepared outgoing message to a locally connected client
*
* @param request The original request of the client
*/
void prepareResponseBuffer(SesameEvent event, uint8_t deviceId = 0);
void sendPreparedLocalResponse(AsyncWebServerRequest *request);
void sendPreparedServerResponse();
/**
* @brief Send the prepared outgoing message to the server
*/
void sendPreparedResponseToServer();
// MARK: Helper
bool convertHexMessageToBinary(const char* str);
void periodicallyReconnectWifiAndSocket(uint32_t millis);
};

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@ -3,15 +3,6 @@
#include "message.h"
#include <stddef.h>
void enableCrypto();
/**
* @brief Create a random server challenge.
*
* @return uint32_t
*/
uint32_t randomChallenge();
/**
* @brief Create a message authentication code (MAC) for some data.
*
@ -19,10 +10,11 @@ uint32_t randomChallenge();
* @param dataLength The number of bytes to authenticate
* @param mac The output to store the MAC (must be at least 32 bytes)
* @param key The secret key used for authentication
* @param keyLength The length of the secret key
* @return true The MAC was successfully written
* @return false The MAC could not be created
*/
bool authenticateData(const uint8_t* data, size_t dataLength, uint8_t* mac, const uint8_t* key);
bool authenticateData(const uint8_t* data, size_t dataLength, uint8_t* mac, const uint8_t* key, size_t keyLength);
/**
* @brief Calculate a MAC for message content.
@ -30,20 +22,22 @@ bool authenticateData(const uint8_t* data, size_t dataLength, uint8_t* mac, cons
* @param message The message for which to calculate the MAC.
* @param mac The output where the computed MAC is stored
* @param key The secret key used for authentication
* @param keyLength The length of the secret key
* @return true The MAC was successfully computed
* @return false The MAC could not be created
*/
bool authenticateMessage(Message* message, uint8_t* mac, const uint8_t* key);
bool authenticateMessage(Message* message, uint8_t* mac, const uint8_t* key, size_t keyLength);
/**
* @brief Create a message authentication code (MAC) for a message.
*
* @param message The message to authenticate
* @param key The secret key used for authentication
* @param keyLength The length of the secret key
* @return true The MAC was successfully added to the message
* @return false The MAC could not be created
*/
bool authenticateMessage(SignedMessage* message, const uint8_t* key);
bool authenticateMessage(AuthenticatedMessage* message, const uint8_t* key, size_t keyLength);
/**
* @brief Check if a received unlock message is authentic
@ -54,7 +48,8 @@ bool authenticateMessage(SignedMessage* message, const uint8_t* key);
*
* @param message The message to authenticate
* @param key The secret key used for authentication
* @param keyLength The length of the key in bytes
* @return true The message is authentic
* @return false The message is invalid, or the MAC could not be calculated
*/
bool isAuthenticMessage(SignedMessage* message, const uint8_t* key);
bool isAuthenticMessage(AuthenticatedMessage* message, const uint8_t* key, size_t keyLength);

80
include/fresh.h Normal file
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@ -0,0 +1,80 @@
#pragma once
#include <stdint.h>
struct TimeConfiguration {
/**
* @brief The timezone offset in seconds
*/
int32_t offsetToGMT;
/**
* @brief The daylight savings offset in seconds
*/
int32_t offsetDaylightSavings;
/**
* @brief The url of the NTP server
*/
const char* ntpServerUrl;
/**
* @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;
};
class TimeCheck {
public:
/**
* @brief Create a time checker instance
*/
TimeCheck();
/**
* @brief Set the configuration
*/
void configure(TimeConfiguration configuration);
/**
* @brief Configure the NTP server to get the current time
*/
void startNTP();
/**
* @brief Print the current time to the serial output
*
* The time must be initialized by calling `configureNTP()` before use.
*/
void printLocalTime();
/**
* Gets the current epoch time
*/
uint32_t getEpochTime();
/**
* @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;
};

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@ -14,96 +14,58 @@
#pragma pack(push, 1)
typedef enum {
/// @brief The initial message from remote to device to request a challenge.
initial = 0,
/// @brief The second message in an unlock with the challenge from the device to the remote
challenge = 1,
/// @brief The third message with the signed challenge from the remote to the device
request = 2,
/// @brief The final message with the unlock result from the device to the remote
response = 3,
} MessageType;
enum class MessageResult: uint8_t {
/// @brief The message was accepted.
MessageAccepted = 0,
/// @brief The web socket received text while waiting for binary data.
TextReceived = 1,
/// @brief An unexpected socket event occured while performing the exchange.
UnexpectedSocketEvent = 2,
/// @brief The received message size is invalid.
InvalidMessageSize = 3,
/// @brief The message signature was incorrect.
MessageAuthenticationFailed = 4,
/// @brief The server challenge of the message did not match previous messages
ServerChallengeMismatch = 5,
/// @brief The client challenge of the message did not match previous messages
ClientChallengeInvalid = 6,
/// @brief An unexpected or unsupported message type was received
InvalidMessageType = 7,
/// @brief A message is already being processed
TooManyRequests = 8,
/// @brief The received message result was invalid
InvalidMessageResult = 9,
/// @brief An invalid Url parameter was set sending a message to the device over a local connection
InvalidUrlParameter = 10,
};
/**
* @brief A generic message to exchange during challenge-response authentication.
* @brief The content of an unlock message.
*
* The content is necessary to ensure freshness of the message
* by requiring a recent time and a monotonously increasing counter.
* This prevents messages from being delayed or being blocked and
* replayed later.
*/
typedef struct {
/// @brief The type of message being sent.
MessageType messageType;
/**
* The timestamp of message creation
*
* The timestamp is encoded as the epoch time, i.e. seconds since 1970 (GMT).
*
* 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.
*/
uint32_t time;
/**
* The counter of unlock messages
*
* This counter must always increase with each message from the remote
* in order for the messages to be deemed valid. Transfering the counters
* back and forth also gives information about lost messages and potential
* attacks. Both the remote and the device keep a record of at least the
* last used counter.
*/
uint32_t id;
/**
* @brief The random nonce created by the remote
*
* This nonce is a random number created by the remote, different for each unlock request.
* It is set for all message types.
* @brief The id of the device sending the message
*/
uint32_t clientChallenge;
/**
* @brief A random number to sign by the remote
*
* This nonce is set by the server after receiving an initial message.
* It is set for the message types `challenge`, `request`, and `response`.
*/
uint32_t serverChallenge;
/**
* @brief The response status for the previous message.
*
* It is set only for messages from the server, e.g. the `challenge` and `response` message types.
* Must be set to `MessageAccepted` for other messages.
*/
MessageResult result;
uint8_t device;
} Message;
constexpr size_t messageCounterSize = sizeof(uint32_t);
/**
* @brief The signed version of a message.
* @brief An authenticated message by the mobile device to command unlocking.
*
* The message is protected by a message authentication code (MAC) based on
* a symmetric key shared by the device and the remote. This code ensures
* that the contents of the request were not altered. The message further
* contains a timestamp to ensure that the message is recent, and not replayed
* by an attacker. An additional counter is also included for this purpose,
* which must continously increase for a message to be valid. This increases
* security a bit, since the timestamp validation must be tolerant to some
* inaccuracy due to mismatching clocks.
*/
typedef struct {
@ -115,18 +77,38 @@ typedef struct {
*/
uint8_t mac[SHA256_MAC_SIZE];
/// @brief The message
/**
* @brief The message content.
*
* The content is necessary to ensure freshness of the message
* by requiring a recent time and a monotonously increasing counter.
* This prevents messages from being delayed or being blocked and
* replayed later.
*/
Message message;
} SignedMessage;
constexpr size_t messageCounterSize = sizeof(uint32_t);
} AuthenticatedMessage;
#pragma pack(pop)
constexpr int MESSAGE_CONTENT_SIZE = sizeof(Message);
constexpr int SIGNED_MESSAGE_SIZE = sizeof(SignedMessage);
constexpr int AUTHENTICATED_MESSAGE_SIZE = sizeof(AuthenticatedMessage);
/**
* An event signaled from the device
*/
enum class SesameEvent {
TextReceived = 1,
UnexpectedSocketEvent = 2,
InvalidMessageSize = 3,
MessageAuthenticationFailed = 4,
MessageTimeMismatch = 5,
MessageCounterInvalid = 6,
MessageAccepted = 7,
MessageDeviceInvalid = 8,
InvalidUrlParameter = 20,
InvalidResponseAuthentication = 21,
};
/**
* @brief A callback for messages received over the socket
@ -139,5 +121,5 @@ typedef void (*MessageCallback)(uint8_t* payload, size_t length);
/**
* @brief A callback for socket errors
*/
typedef void (*ErrorCallback)(MessageResult event);
typedef void (*ErrorCallback)(SesameEvent event);

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@ -2,6 +2,8 @@
#include "message.h"
#include "crypto.h"
#include <WiFiMulti.h>
#include <WiFiClientSecure.h>
#include <WebSocketsClient.h>
struct ServerConfiguration {
@ -28,17 +30,13 @@ struct ServerConfiguration {
uint32_t reconnectTime;
uint32_t socketHeartbeatIntervalMs;
uint32_t socketHeartbeatTimeoutMs;
uint8_t socketHeartbeatFailureReconnectCount;
};
class ServerConnectionCallbacks {
public:
virtual void sendServerError(MessageResult event) = 0;
virtual void sendServerError(SesameEvent event) = 0;
virtual void handleServerMessage(uint8_t* payload, size_t length) = 0;
};
@ -55,13 +53,11 @@ public:
*/
void configure(ServerConfiguration configuration, ServerConnectionCallbacks* callbacks);
/**
* @brief Call this function regularly to handle socket operations.
*
* Connecting and disconnecting is done automatically.
*
*/
void loop(uint32_t millis);
void connect();
void disconnect();
void loop();
/**
* @brief Send a response message over the socket
@ -71,26 +67,11 @@ public:
*/
void sendResponse(uint8_t* buffer, uint16_t length);
private:
uint32_t currentTime;
bool socketIsConnected() {
bool isSocketConnected() {
return webSocket.isConnected();
}
void connect();
void disconnect();
bool shouldReconnect = true;
bool isConnecting = false;
uint32_t connectionTimeout = 0;
uint32_t nextReconnectAttemptMs = 0;
void didDisconnect();
void didConnect();
private:
ServerConfiguration configuration;

83
include/storage.h Normal file
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@ -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);
};

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@ -13,11 +13,7 @@ platform = espressif32
board = az-delivery-devkit-v4
framework = arduino
lib_deps =
; links2004/WebSockets@^2.4.0
links2004/WebSockets@^2.3.7
madhephaestus/ESP32Servo@^1.1.0
ottowinter/ESPAsyncWebServer-esphome@^3.0.0
arduino-libraries/Ethernet@^2.0.2
https://github.com/christophhagen/arduinoWebSockets#master
monitor_speed = 115200
build_flags= -D WEBSOCKETS_NETWORK_TYPE=NETWORK_W5100

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@ -2,48 +2,23 @@
#include "crypto.h"
#include "config.h"
#include <SPI.h>
#include <Ethernet.h>
SesameController::SesameController(uint16_t localWebServerPort) : localWebServer(localWebServerPort) {
#include <WiFi.h>
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, EthernetConfiguration ethernetConfig, KeyConfiguration keyConfig) {
this->ethernetConfig = ethernetConfig;
void SesameController::configure(ServoConfiguration servoConfig, ServerConfiguration serverConfig, TimeConfiguration timeConfig, WifiConfiguration wifiConfig, KeyConfiguration keyConfig) {
this->wifiConfig = wifiConfig;
this->keyConfig = keyConfig;
// Ensure source of random numbers without WiFi and Bluetooth
enableCrypto();
// Initialize SPI interface to Ethernet module
SPI.begin(ethernetConfig.spiPinSclk, ethernetConfig.spiPinMiso, ethernetConfig.spiPinMosi, ethernetConfig.spiPinSS); //SCLK, MISO, MOSI, SS
pinMode(ethernetConfig.spiPinSS, OUTPUT);
Ethernet.init(ethernetConfig.spiPinSS);
if (Ethernet.begin(ethernetConfig.macAddress, ethernetConfig.dhcpLeaseTimeoutMs, ethernetConfig.dhcpLeaseResponseTimeoutMs) == 1) {
Serial.print("[INFO] DHCP assigned IP ");
Serial.println(Ethernet.localIP());
ethernetIsConfigured = true;
} else {
// Check for Ethernet hardware present
if (Ethernet.hardwareStatus() == EthernetNoHardware) {
Serial.println("[ERROR] Ethernet shield not found.");
} else if (Ethernet.linkStatus() == LinkOFF) {
Serial.println("[ERROR] Ethernet cable is not connected.");
} else if (Ethernet.linkStatus() == Unknown) {
Serial.println("[ERROR] Ethernet cable status unknown.");
} else if (Ethernet.linkStatus() == LinkON) {
Serial.println("[INFO] Ethernet cable is connected.");
// Try to configure using IP address instead of DHCP
Ethernet.begin(ethernetConfig.macAddress, ethernetConfig.manualIp, ethernetConfig.manualDnsAddress);
Serial.print("[WARNING] DHCP failed, using self-assigned IP ");
Serial.println(Ethernet.localIP());
ethernetIsConfigured = true;
}
}
// Prepare EEPROM for reading and writing
storage.configure();
Serial.println("[INFO] Storage configured");
servo.configure(servoConfig);
Serial.println("[INFO] Servo configured");
@ -51,6 +26,9 @@ void SesameController::configure(ServoConfiguration servoConfig, ServerConfigura
// 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) {
@ -59,12 +37,18 @@ void SesameController::configure(ServoConfiguration servoConfig, ServerConfigura
});
Serial.println("[INFO] Local web server configured");
//storage.resetMessageCounters();
storage.printMessageCounters();
}
void SesameController::loop(uint32_t millis) {
currentTime = millis;
server.loop(millis);
server.loop();
servo.loop(millis);
periodicallyReconnectWifiAndSocket(millis);
ensureWiFiConnection(millis);
ensureWebSocketConnection();
}
// MARK: Local
@ -72,154 +56,141 @@ void SesameController::loop(uint32_t millis) {
void SesameController::handleLocalMessage(AsyncWebServerRequest *request) {
if (!request->hasParam(messageUrlParameter)) {
Serial.println("Missing url parameter");
prepareResponseBuffer(MessageResult::InvalidUrlParameter);
prepareResponseBuffer(SesameEvent::InvalidUrlParameter);
return;
}
String encoded = request->getParam(messageUrlParameter)->value();
if (!convertHexMessageToBinary(encoded.c_str())) {
Serial.println("Invalid hex encoding");
prepareResponseBuffer(MessageResult::InvalidMessageSize);
prepareResponseBuffer(SesameEvent::InvalidMessageSize);
return;
}
processMessage(&receivedLocalMessage);
processMessage((AuthenticatedMessage*) receivedMessageBuffer);
}
void SesameController::sendPreparedLocalResponse(AsyncWebServerRequest *request) {
request->send_P(200, "application/octet-stream", (uint8_t*) &outgoingMessage, SIGNED_MESSAGE_SIZE);
Serial.printf("[INFO] Local response %u\n", outgoingMessage.message.messageType);
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(MessageResult result) {
prepareResponseBuffer(result); // No message to echo
sendPreparedResponseToServer();
void SesameController::sendServerError(SesameEvent event) {
prepareResponseBuffer(event);
sendPreparedServerResponse();
}
void SesameController::handleServerMessage(uint8_t* payload, size_t length) {
if (length != SIGNED_MESSAGE_SIZE) {
// No message saved to discard, don't accidentally delete for other operation
sendServerError(MessageResult::InvalidMessageSize);
if (length != AUTHENTICATED_MESSAGE_SIZE) {
prepareResponseBuffer(SesameEvent::InvalidMessageSize);
return;
}
processMessage((SignedMessage*) payload);
sendPreparedResponseToServer();
processMessage((AuthenticatedMessage*) payload);
sendPreparedServerResponse();
}
void SesameController::sendPreparedResponseToServer() {
server.sendResponse((uint8_t*) &outgoingMessage, SIGNED_MESSAGE_SIZE);
Serial.printf("[INFO] Server response %u\n", outgoingMessage.message.messageType);
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(SignedMessage* message) {
// Result must be empty
if (message->message.result != MessageResult::MessageAccepted) {
prepareResponseBuffer(MessageResult::InvalidMessageResult);
return;
}
if (!isAuthenticMessage(message, keyConfig.remoteKey)) {
prepareResponseBuffer(MessageResult::MessageAuthenticationFailed);
return;
}
switch (message->message.messageType) {
case MessageType::initial:
checkAndPrepareChallenge(&message->message);
return;
case MessageType::request:
completeUnlockRequest(&message->message);
return;
default:
prepareResponseBuffer(MessageResult::InvalidMessageType);
return;
}
void SesameController::processMessage(AuthenticatedMessage* message) {
SesameEvent event = verifyAndProcessReceivedMessage(message);
prepareResponseBuffer(event, message->message.device);
}
void SesameController::checkAndPrepareChallenge(Message* message) {
// Server challenge must be empty
if (message->serverChallenge != 0) {
prepareResponseBuffer(MessageResult::ClientChallengeInvalid);
return;
/**
* 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;
}
prepareChallenge(message);
}
void SesameController::prepareChallenge(Message* message) {
if (hasCurrentChallenge()) {
Serial.println("[INFO] Overwriting old challenge");
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;
}
// Set challenge and respond
currentClientChallenge = message->clientChallenge;
currentServerChallenge = randomChallenge();
currentChallengeExpiry = currentTime + keyConfig.challengeExpiryMs;
prepareResponseBuffer(MessageResult::MessageAccepted, message);
}
void SesameController::completeUnlockRequest(Message* message) {
// Client and server challenge must match
if (message->clientChallenge != currentClientChallenge) {
prepareResponseBuffer(MessageResult::ClientChallengeInvalid, message);
return;
}
if (message->serverChallenge != currentServerChallenge) {
prepareResponseBuffer(MessageResult::ServerChallengeMismatch, message);
return;
}
if (!hasCurrentChallenge()) {
// Directly send new challenge on expiry, since rest of message is valid
// This allows the remote to directly try again without requesting a new challenge.
// Security note: The client nonce is reused in this case, but an attacker would still
// not be able to create a valid unlock request due to the new server nonce.
prepareChallenge(message);
return;
}
clearCurrentChallenge();
storage.didUseMessageCounter(message->message.id, message->message.device);
// Move servo
servo.pressButton();
prepareResponseBuffer(MessageResult::MessageAccepted, message);
Serial.println("[INFO] Accepted message");
Serial.printf("[Info] Accepted message %d\n", message->message.id);
return SesameEvent::MessageAccepted;
}
void SesameController::prepareResponseBuffer(MessageResult result, Message* message) {
outgoingMessage.message.result = result;
if (message != NULL) {
outgoingMessage.message.clientChallenge = message->clientChallenge;
outgoingMessage.message.serverChallenge = message->serverChallenge;
// All outgoing messages are responses, except if an initial message is accepted
if (message->messageType == MessageType::initial && result == MessageResult::MessageAccepted) {
outgoingMessage.message.messageType = MessageType::challenge;
} else {
outgoingMessage.message.messageType = MessageType::response;
}
} else {
outgoingMessage.message.clientChallenge = message->clientChallenge;
outgoingMessage.message.serverChallenge = message->serverChallenge;
outgoingMessage.message.messageType = MessageType::response;
bool allowMessageResponse(SesameEvent event) {
switch (event) {
case SesameEvent::MessageTimeMismatch:
case SesameEvent::MessageCounterInvalid:
case SesameEvent::MessageAccepted:
case SesameEvent::MessageDeviceInvalid:
return true;
default:
return false;
}
}
if (!authenticateMessage(&outgoingMessage, keyConfig.localKey)) {
Serial.println("[ERROR] Failed to sign message");
void SesameController::prepareResponseBuffer(SesameEvent event, uint8_t deviceId) {
*responseStatus = event;
responseSize = 1;
if (!allowMessageResponse(event)) {
return;
}
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;
}
responseSize += 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
/**
* @brief
*
* Based on https://stackoverflow.com/a/23898449/266720
*
* @param str
* @return true
* @return false
*/
// Based on https://stackoverflow.com/a/23898449/266720
bool SesameController::convertHexMessageToBinary(const char* str) {
uint8_t* buffer = (uint8_t*) &receivedLocalMessage;
// TODO: Fail if invalid hex values are used
uint8_t idx0, idx1;
@ -232,7 +203,7 @@ bool SesameController::convertHexMessageToBinary(const char* str) {
};
size_t len = strlen(str);
if (len != SIGNED_MESSAGE_SIZE * 2) {
if (len != AUTHENTICATED_MESSAGE_SIZE * 2) {
// Require exact message size
return false;
}
@ -240,7 +211,17 @@ bool SesameController::convertHexMessageToBinary(const char* str) {
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;
buffer[pos/2] = (uint8_t)(hashmap[idx0] << 4) | hashmap[idx1];
receivedMessageBuffer[pos/2] = (uint8_t)(hashmap[idx0] << 4) | hashmap[idx1];
};
return true;
}
void SesameController::periodicallyReconnectWifiAndSocket(uint32_t millis) {
static uint32_t nextWifiReconnect = wifiConfig.periodicReconnectInterval;
if (millis > nextWifiReconnect) {
nextWifiReconnect += wifiConfig.periodicReconnectInterval;
server.disconnect();
WiFi.disconnect();
}
}

View File

@ -1,19 +1,8 @@
#include "crypto.h"
#include "config.h"
#include <string.h>
#include <mbedtls/md.h>
#include <esp_random.h>
#include <bootloader_random.h>
void enableCrypto() {
bootloader_random_enable();
}
uint32_t randomChallenge() {
return esp_random();
}
bool authenticateData(const uint8_t* data, size_t dataLength, uint8_t* mac, const uint8_t* key) {
bool authenticateData(const uint8_t* data, size_t dataLength, uint8_t* mac, const uint8_t* key, size_t keyLength) {
mbedtls_md_context_t ctx;
mbedtls_md_type_t md_type = MBEDTLS_MD_SHA256;
int result;
@ -23,7 +12,7 @@ bool authenticateData(const uint8_t* data, size_t dataLength, uint8_t* mac, cons
if (result) {
return false;
}
result = mbedtls_md_hmac_starts(&ctx, key, keySize);
result = mbedtls_md_hmac_starts(&ctx, key, keyLength);
if (result) {
return false;
}
@ -39,17 +28,17 @@ bool authenticateData(const uint8_t* data, size_t dataLength, uint8_t* mac, cons
return true;
}
bool authenticateMessage(Message* message, uint8_t* mac, const uint8_t* key) {
return authenticateData((const uint8_t*) message, MESSAGE_CONTENT_SIZE, mac, key);
bool authenticateMessage(Message* message, uint8_t* mac, const uint8_t* key, size_t keyLength) {
return authenticateData((const uint8_t*) message, MESSAGE_CONTENT_SIZE, mac, key, keyLength);
}
bool authenticateMessage(SignedMessage* message, const uint8_t* key) {
return authenticateMessage(&message->message, message->mac, key);
bool authenticateMessage(AuthenticatedMessage* message, const uint8_t* key, size_t keyLength) {
return authenticateMessage(&message->message, message->mac, key, keyLength);
}
bool isAuthenticMessage(SignedMessage* message, const uint8_t* key) {
bool isAuthenticMessage(AuthenticatedMessage* message, const uint8_t* key, size_t keyLength) {
uint8_t mac[SHA256_MAC_SIZE];
if (!authenticateMessage(&message->message, mac, key)) {
if (!authenticateMessage(&message->message, mac, key, keyLength)) {
return false;
}
return memcmp(mac, message->mac, SHA256_MAC_SIZE) == 0;

49
src/fresh.cpp Normal file
View File

@ -0,0 +1,49 @@
#include "fresh.h"
#include <Arduino.h> // configTime()
#include <time.h>
TimeCheck::TimeCheck() { }
void TimeCheck::configure(TimeConfiguration configuration) {
config = configuration;
}
void TimeCheck::startNTP() {
configTime(config.offsetToGMT, config.offsetDaylightSavings, config.ntpServerUrl);
}
void TimeCheck::printLocalTime() {
struct tm timeinfo;
if (getLocalTime(&timeinfo)) {
Serial.println(&timeinfo, "[INFO] Time is %A, %d. %B %Y %H:%M:%S");
} else {
Serial.println("[WARN] No local time available");
}
}
uint32_t TimeCheck::getEpochTime() {
time_t now;
struct tm timeinfo;
if (!getLocalTime(&timeinfo)) {
Serial.println("[WARN] Failed to obtain local time");
return(0);
}
time(&now);
return now;
}
bool TimeCheck::isMessageTimeAcceptable(uint32_t t) {
uint32_t localTime = getEpochTime();
if (localTime == 0) {
Serial.println("No epoch time available");
return false;
}
if (t > localTime + config.allowedTimeOffset) {
return false;
}
if (t < localTime - config.allowedTimeOffset) {
return false;
}
return true;
}

View File

@ -4,15 +4,6 @@
*
* The code for a simple door unlock mechanism where a servo pushes on an existing
* physical button.
*
* On compile error:
*
* In <Server.h>
*
* change:
* virtual void begin(uint16_t port=0) =0;
* to:
* virtual void begin() =0;
*/
#include <Arduino.h>
@ -22,7 +13,7 @@
#include "controller.h"
#include "config.h"
SesameController controller(localPort);
SesameController controller(localPort, remoteDeviceCount);
void setup() {
Serial.begin(serialBaudRate);
@ -44,30 +35,29 @@ void setup() {
.path = serverPath,
.key = serverAccessKey,
.reconnectTime = 5000,
.socketHeartbeatIntervalMs = socketHeartbeatIntervalMs,
.socketHeartbeatTimeoutMs = socketHeartbeatTimeoutMs,
.socketHeartbeatFailureReconnectCount = socketHeartbeatFailureReconnectCount,
};
EthernetConfiguration ethernetConfig {
.macAddress = ethernetMacAddress,
.spiPinMiso = spiPinMiso,
.spiPinMosi = spiPinMosi,
.spiPinSclk = spiPinSclk,
.spiPinSS = spiPinSS,
.dhcpLeaseTimeoutMs = dhcpLeaseTimeoutMs,
.dhcpLeaseResponseTimeoutMs = dhcpLeaseResponseTimeoutMs,
.manualIp = manualIpAddress,
.manualDnsAddress = manualDnsServerAddress,
TimeConfiguration timeConfig {
.offsetToGMT = timeOffsetToGMT,
.offsetDaylightSavings = timeOffsetDaylightSavings,
.ntpServerUrl = ntpServerUrl,
.allowedTimeOffset = 60,
};
WifiConfiguration wifiConfig {
.ssid = wifiSSID,
.password = wifiPassword,
.networkName = networkName,
.reconnectInterval = wifiReconnectInterval,
.periodicReconnectInterval = wifiPeriodicReconnectInterval,
};
KeyConfiguration keyConfig {
.remoteKey = remoteKey,
.localKey = localKey,
.challengeExpiryMs = challengeExpiryMs,
};
controller.configure(servoConfig, serverConfig, ethernetConfig, keyConfig);
controller.configure(servoConfig, serverConfig, timeConfig, wifiConfig, keyConfig);
}
void loop() {

View File

@ -20,11 +20,7 @@ void ServerConnection::connect() {
return;
}
isConnecting = true;
Serial.printf("[INFO] Connecting to %s:%d%s\n", configuration.url, configuration.port, configuration.path);
connectionTimeout = currentTime + configuration.socketHeartbeatIntervalMs;
webSocket.begin(configuration.url, configuration.port, configuration.path);
webSocket.setAuthorization(configuration.key);
webSocket.beginSSL(configuration.url, configuration.port, configuration.path);
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);
@ -33,50 +29,26 @@ void ServerConnection::connect() {
webSocket.setReconnectInterval(configuration.reconnectTime);
}
void ServerConnection::didDisconnect() {
if (shouldReconnect || isConnecting) {
return; // Disconnect already registered.
}
Serial.println("[INFO] Socket disconnected");
nextReconnectAttemptMs = currentTime + configuration.socketHeartbeatIntervalMs;
shouldReconnect = true;
}
void ServerConnection::didConnect() {
isConnecting = false;
Serial.println("[INFO] Socket connected");
webSocket.enableHeartbeat(configuration.socketHeartbeatIntervalMs, configuration.socketHeartbeatTimeoutMs, configuration.socketHeartbeatFailureReconnectCount);
}
void ServerConnection::disconnect() {
webSocket.disconnect();
}
void ServerConnection::loop(uint32_t millis) {
currentTime = millis;
void ServerConnection::loop() {
webSocket.loop();
if (shouldReconnect && !isConnecting) {
shouldReconnect = false;
connect();
}
if (isConnecting && millis > connectionTimeout) {
Serial.println("[INFO] Failed to connect");
disconnect();
shouldReconnect = true;
isConnecting = false;
}
}
void ServerConnection::webSocketEventHandler(WStype_t type, uint8_t * payload, size_t length) {
switch(type) {
case WStype_DISCONNECTED:
didDisconnect();
Serial.println("[INFO] Socket disconnected.");
break;
case WStype_CONNECTED:
didConnect();
webSocket.sendTXT(configuration.key);
Serial.printf("[INFO] Socket connected to url: %s\n", payload);
webSocket.enableHeartbeat(pingInterval, pongTimeout, disconnectTimeoutCount);
break;
case WStype_TEXT:
controller->sendServerError(MessageResult::TextReceived);
controller->sendServerError(SesameEvent::TextReceived);
break;
case WStype_BIN:
controller->handleServerMessage(payload, length);
@ -84,20 +56,16 @@ switch(type) {
case WStype_PONG:
break;
case WStype_PING:
break;
case WStype_ERROR:
case WStype_FRAGMENT_TEXT_START:
case WStype_FRAGMENT_BIN_START:
case WStype_FRAGMENT:
case WStype_FRAGMENT_FIN:
Serial.printf("[WARN] Unexpected socket event %d\n", type);
controller->sendServerError(MessageResult::UnexpectedSocketEvent);
controller->sendServerError(SesameEvent::UnexpectedSocketEvent);
break;
}
}
void ServerConnection::sendResponse(uint8_t* buffer, uint16_t length) {
if (socketIsConnected()) {
webSocket.sendBIN(buffer, length);
}
webSocket.sendBIN(buffer, length);
}

53
src/storage.cpp Normal file
View File

@ -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");
}