Basic authentication using HMAC for federates joining a federation

core/federated/RTI/CMakeLists.txt

@@ -63,6 +63,11 @@ target_compile_definitions(RTI PUBLIC NUMBER_OF_WORKERS)
 find_package(Threads REQUIRED)
 target_link_libraries(RTI Threads::Threads)
 
+# Find OpenSSL and link to it
+find_package(OpenSSL REQUIRED)
+target_link_libraries(RTI OpenSSL::SSL)
+
+
 install(
     TARGETS RTI
     DESTINATION bin

core/federated/RTI/rti.c

@@ -58,6 +58,7 @@ THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #include <strings.h>    // Defines bzero().
 #include <assert.h>
 #include <sys/wait.h>   // Defines wait() for process to change state.
+#include <openssl/rand.h> // For secure random number generation.
 #include "platform.h"   // Platform-specific types and functions
 #include "utils/util.c" // Defines print functions (e.g., lf_print).
 #include "net_util.c"   // Defines network functions.
@@ -1790,6 +1791,18 @@ int receive_udp_message_and_set_up_clock_sync(int socket_id, uint16_t fed_id) {
     return 1;
 }
 
+/**
+ * Send RTI hello message for authenticated joining of federation.
+ * 
+ * @param socket Socket for the incoming federate tryting to authenticate.
+ */
+void send_rti_hello(int socket) {
+    size_t message_length = 1 + RTI_HELLO_LENGTH;
+    unsigned char buffer[message_length];
+    buffer[0] = MSG_TYPE_RTI_HELLO;
+    RAND_bytes(&(buffer[1]), RTI_HELLO_LENGTH);
+    ssize_t bytes_written = write_to_socket(socket, message_length, buffer);
+}
 
 /**
  * Wait for one incoming connection request from each federate,
@@ -1818,6 +1831,10 @@ void connect_to_federates(int socket_descriptor) {
             }
         }
 
+        // Send RTI hello including a nounce.
+        // If authenticated hello is required.
+        send_rti_hello(socket_id);
+
         // The first message from the federate should contain its ID and the federation ID.
         int32_t fed_id = receive_and_check_fed_id_message(socket_id, (struct sockaddr_in*)&client_fd);
         if (fed_id >= 0

core/federated/federate.c

@@ -856,6 +856,24 @@ void connect_to_federate(uint16_t remote_federate_id) {
     }
 }
 
+void perform_hmac_authentication(int rti_socket) {
+    LF_PRINT_LOG("Connected to an RTI. Performing HAMC-based authentication.");
+    unsigned char buffer[1 + RTI_HELLO_LENGTH];
+    read_from_socket_errexit(rti_socket, 1 + RTI_HELLO_LENGTH, buffer, "Failed to read RTI hello.");
+
+    if (buffer[0] != MSG_TYPE_RTI_HELLO) {
+        lf_print_error_and_exit("Received unexpected response %u from the RTI (see net_common.h).",
+                buffer[0]);
+    }
+
+    char hex_buffer[RTI_HELLO_LENGTH * 2 + 1];
+    for (int i = 0; i < RTI_HELLO_LENGTH; i++) {
+        sprintf(&hex_buffer[i * 2], "%x", buffer[1 + i]);
+    }
+    hex_buffer[RTI_HELLO_LENGTH * 2] = '\0';
+    LF_PRINT_LOG("Nonce received from RTI : %s", hex_buffer);
+}
+
 /**
  * Connect to the RTI at the specified host and port and return
  * the socket descriptor for the connection. If this fails, the
@@ -896,6 +914,9 @@ void connect_to_rti(const char* hostname, int port) {
     int result = -1;
     int count_retries = 0;
 
+    // See https://github.com/lf-lang/lingua-franca/issues/1146 for more information.
+    bool use_hmac_authentication = true;
+
     while (result < 0) {
         // Create an IPv4 socket for TCP (not UDP) communication over IP (0).
         _fed.socket_TCP_RTI = socket(AF_INET, SOCK_STREAM, 0);
@@ -964,6 +985,10 @@ void connect_to_rti(const char* hostname, int port) {
             // Notify the RTI of the ID of this federate and its federation.
             unsigned char buffer[4];
 
+            if (use_hmac_authentication) {
+                perform_hmac_authentication(_fed.socket_TCP_RTI);
+            }
+
             LF_PRINT_LOG("Connected to an RTI. Sending federation ID for authentication.");
 
             // Send the message type first.

core/federated/net_common.h

@@ -330,6 +330,17 @@ THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 #define MSG_TYPE_FED_IDS 1
 
+/**
+ * Byte identifying a message from an RTI to a federate containing
+ * a 8-byte nonce.
+ * The next eight bytes are a 8-byte random nonce.
+ */
+#define MSG_TYPE_RTI_HELLO 100
+#define RTI_HELLO_LENGTH 8
+
+#define MSG_TYPE_AUTHENTICATED_FED_IDS 101
+
+
 /**
  * Byte identifying a timestamp message, which is 64 bits long.
  * Each federate sends its starting physical time as a message of this