Fix wssshc SIGINT crashes and multiple tunnel closure issues

- Fix double-free corruption in cleanup_tunnel by removing SSL freeing
- Add global shutdown flag for proper thread synchronization
- Improve SIGINT handling with better thread cleanup timing
- Send tunnel_close acknowledgment when receiving tunnel_close from server
- Prevent threads from accessing freed tunnel structures
- Ensure proper resource management during shutdown

wssshtools/tunnel.c

@@ -41,6 +41,9 @@ int active_tunnels_count = 0;
 int active_tunnels_capacity = 0;
 pthread_mutex_t tunnel_mutex = PTHREAD_MUTEX_INITIALIZER;
 
+// Global shutdown flag for threads
+volatile int global_shutdown = 0;
+
 frame_buffer_t *frame_buffer_init() {
     frame_buffer_t *fb = malloc(sizeof(frame_buffer_t));
     if (!fb) return NULL;
@@ -257,6 +260,9 @@ void handle_tunnel_request(SSL *ssl, const char *request_id, int debug, const ch
 void cleanup_tunnel(int debug) {
     pthread_mutex_lock(&tunnel_mutex);
 
+    // Set global shutdown flag to signal all threads to stop
+    global_shutdown = 1;
+
     // First, mark all tunnels as inactive to signal threads to stop
     for (int i = 0; i < active_tunnels_count; i++) {
         if (active_tunnels[i]) {
@@ -264,12 +270,12 @@ void cleanup_tunnel(int debug) {
         }
     }
 
-    // Give threads a moment to stop using SSL connections
+    // Give threads a moment to stop using resources
     pthread_mutex_unlock(&tunnel_mutex);
-    usleep(100000); // 100ms
+    usleep(200000); // 200ms - increased timeout for better thread cleanup
     pthread_mutex_lock(&tunnel_mutex);
 
-    // Now safely clean up
+    // Now safely clean up - don't free SSL contexts as they're managed at connection level
     for (int i = 0; i < active_tunnels_count; i++) {
         if (active_tunnels[i]) {
             if (active_tunnels[i]->sock >= 0) {
@@ -284,10 +290,10 @@ void cleanup_tunnel(int debug) {
                 close(active_tunnels[i]->local_sock);
                 active_tunnels[i]->local_sock = -1;
             }
-            if (active_tunnels[i]->ssl) {
-                SSL_free(active_tunnels[i]->ssl);
-                active_tunnels[i]->ssl = NULL;
-            }
+            // Don't free SSL here - it's managed at the connection level
+            // Just set the pointer to NULL to prevent use-after-free
+            active_tunnels[i]->ssl = NULL;
+
             if (active_tunnels[i]->outgoing_buffer) {
                 frame_buffer_free(active_tunnels[i]->outgoing_buffer);
             }
@@ -787,7 +793,7 @@ void send_tunnel_close(SSL *ssl, const char *request_id, int debug) {
     }
 }
 
-void handle_tunnel_close(SSL *ssl __attribute__((unused)), const char *request_id, int debug) {
+void handle_tunnel_close(SSL *ssl, const char *request_id, int debug) {
     pthread_mutex_lock(&tunnel_mutex);
     tunnel_t *tunnel = find_tunnel_by_request_id(request_id);
     if (tunnel) {
@@ -797,6 +803,8 @@ void handle_tunnel_close(SSL *ssl __attribute__((unused)), const char *request_i
             printf("[DEBUG - Tunnel] Tunnel %s closed\n", request_id);
             fflush(stdout);
         }
+        // Send tunnel_close back to server to acknowledge
+        send_tunnel_close(ssl, request_id, debug);
     }
     pthread_mutex_unlock(&tunnel_mutex);
 }

wssshtools/tunnel.h

@@ -57,6 +57,7 @@ extern int active_tunnels_count;
 extern int active_tunnels_capacity;
 extern pthread_mutex_t tunnel_mutex;
 extern pthread_mutex_t ssl_mutex;  // For synchronizing SSL operations
+extern volatile int global_shutdown;  // Global flag to signal threads to stop
 
 // Function declarations
 frame_buffer_t *frame_buffer_init(void);

wssshtools/wssshc.c

@@ -253,6 +253,9 @@ int connect_to_server(const wssshc_config_t *config) {
     char buffer[BUFFER_SIZE];
     int bytes_read;
 
+    // Reset global shutdown flag for new connection
+    global_shutdown = 0;
+
     // Clean up any leftover tunnel state from previous connection
     cleanup_tunnel(config->debug);