GUACAMOLE-518: Automatically release any automatically-pressed keys after user has released all keys on the client side.

src/protocols/rdp/decompose.c

@@ -162,12 +162,12 @@ int guac_rdp_decompose_keysym(guac_rdp_keyboard* keyboard, int keysym) {
         return 1;
 
     /* Press dead key */
-    guac_rdp_keyboard_update_keysym(keyboard, key->dead_keysym, 1);
+    guac_rdp_keyboard_update_keysym(keyboard, key->dead_keysym, 1, GUAC_RDP_KEY_SOURCE_SYNTHETIC);
-    guac_rdp_keyboard_update_keysym(keyboard, key->dead_keysym, 0);
+    guac_rdp_keyboard_update_keysym(keyboard, key->dead_keysym, 0, GUAC_RDP_KEY_SOURCE_SYNTHETIC);
 
     /* Press base key */
-    guac_rdp_keyboard_update_keysym(keyboard, key->base_keysym, 1);
+    guac_rdp_keyboard_update_keysym(keyboard, key->base_keysym, 1, GUAC_RDP_KEY_SOURCE_SYNTHETIC);
-    guac_rdp_keyboard_update_keysym(keyboard, key->base_keysym, 0);
+    guac_rdp_keyboard_update_keysym(keyboard, key->base_keysym, 0, GUAC_RDP_KEY_SOURCE_SYNTHETIC);
 
     /* Decomposed key successfully typed */
     return 0;

src/protocols/rdp/input.c

@@ -141,7 +141,7 @@ int guac_rdp_user_key_handler(guac_user* user, int keysym, int pressed) {
 
     /* Update keysym state */
     retval = guac_rdp_keyboard_update_keysym(rdp_client->keyboard,
-                keysym, pressed);
+                keysym, pressed, GUAC_RDP_KEY_SOURCE_CLIENT);
 
 complete:
     pthread_rwlock_unlock(&(rdp_client->lock));

src/protocols/rdp/keyboard.c

@@ -607,25 +607,25 @@ void guac_rdp_keyboard_update_modifiers(guac_rdp_keyboard* keyboard,
 
     /* Press/release Shift as needed */
     if (set_flags & GUAC_RDP_KEYMAP_MODIFIER_SHIFT) {
-        guac_rdp_keyboard_update_keysym(keyboard, 0xFFE1, 1);
+        guac_rdp_keyboard_update_keysym(keyboard, 0xFFE1, 1, GUAC_RDP_KEY_SOURCE_SYNTHETIC);
     }
     else if (clear_flags & GUAC_RDP_KEYMAP_MODIFIER_SHIFT) {
-        guac_rdp_keyboard_update_keysym(keyboard, 0xFFE1, 0);
+        guac_rdp_keyboard_update_keysym(keyboard, 0xFFE1, 0, GUAC_RDP_KEY_SOURCE_SYNTHETIC);
-        guac_rdp_keyboard_update_keysym(keyboard, 0xFFE2, 0);
+        guac_rdp_keyboard_update_keysym(keyboard, 0xFFE2, 0, GUAC_RDP_KEY_SOURCE_SYNTHETIC);
     }
 
     /* Press/release AltGr as needed */
     if (set_flags & GUAC_RDP_KEYMAP_MODIFIER_ALTGR) {
-        guac_rdp_keyboard_update_keysym(keyboard, 0xFE03, 1);
+        guac_rdp_keyboard_update_keysym(keyboard, 0xFE03, 1, GUAC_RDP_KEY_SOURCE_SYNTHETIC);
     }
     else if (clear_flags & GUAC_RDP_KEYMAP_MODIFIER_ALTGR) {
-        guac_rdp_keyboard_update_keysym(keyboard, 0xFE03, 0);
+        guac_rdp_keyboard_update_keysym(keyboard, 0xFE03, 0, GUAC_RDP_KEY_SOURCE_SYNTHETIC);
     }
 
 }
 
 int guac_rdp_keyboard_update_keysym(guac_rdp_keyboard* keyboard,
-        int keysym, int pressed) {
+        int keysym, int pressed, guac_rdp_key_source source) {
 
     /* Synchronize lock keys states, if this has not yet been done */
     if (!keyboard->synchronized) {
@@ -673,7 +673,39 @@ int guac_rdp_keyboard_update_keysym(guac_rdp_keyboard* keyboard,
         guac_rdp_keyboard_send_missing_key(keyboard, keysym);
     }
 
+    if (source == GUAC_RDP_KEY_SOURCE_CLIENT) {
+
+        /* Update tracking of client-side keyboard state but only for keys
+         * which are tracked server-side, as well (to ensure that the key count
+         * remains correct, even if a user sends extra unbalanced or excessive
+         * press and release events) */
+        if (key != NULL) {
+            if (pressed)
+                keyboard->user_pressed_keys++;
+            else
+                keyboard->user_pressed_keys--;
+        }
+
+        /* Reset RDP server keyboard state (releasing any automatically pressed
+         * keys) once all keys have been released on the client side */
+        if (keyboard->user_pressed_keys == 0)
+            guac_rdp_keyboard_reset(keyboard);
+
+    }
+
     return 0;
 
 }
 
+void guac_rdp_keyboard_reset(guac_rdp_keyboard* keyboard) {
+
+    /* Release all pressed keys */
+    for (int i = 0; i < keyboard->num_keys; i++) {
+        guac_rdp_key* key = &keyboard->keys[i];
+        if (key->pressed != NULL)
+            guac_rdp_keyboard_update_keysym(keyboard, key->pressed->keysym, 0,
+                    GUAC_RDP_KEY_SOURCE_SYNTHETIC);
+    }
+
+}
+

src/protocols/rdp/keyboard.h

@@ -37,6 +37,24 @@
  */
 #define GUAC_RDP_KEY_MAX_DEFINITIONS 4
 
+/**
+ * All possible sources of RDP key events tracked by guac_rdp_keyboard.
+ */
+typedef enum guac_rdp_key_source {
+
+    /**
+     * The key event was received directly from the Guacamole client via a
+     * "key" instruction.
+     */
+    GUAC_RDP_KEY_SOURCE_CLIENT = 0,
+
+    /**
+     * The key event is being synthesized internally within the RDP support.
+     */
+    GUAC_RDP_KEY_SOURCE_SYNTHETIC = 1
+
+} guac_rdp_key_source;
+
 /**
  * A representation of a single key within the overall local keyboard,
  * including the definition of that key within the RDP server's keymap and
@@ -130,6 +148,14 @@ typedef struct guac_rdp_keyboard {
      */
     guac_rdp_key* keys_by_keysym[0x20000];
 
+    /**
+     * The total number of keys that the user of the connection is currently
+     * holding down. This value indicates only the client-side keyboard state.
+     * It DOES NOT indicate the number of keys currently pressed within the RDP
+     * server.
+     */
+    int user_pressed_keys;
+
 } guac_rdp_keyboard;
 
 /**
@@ -234,11 +260,24 @@ void guac_rdp_keyboard_update_modifiers(guac_rdp_keyboard* keyboard,
  * @param pressed
  *     Zero if the keysym is being released, non-zero otherwise.
  *
+ * @param source
+ *     The source of the key event represented by this call to
+ *     guac_rdp_keyboard_update_keysym().
+ *
  * @return
  *     Zero if the keys were successfully sent, non-zero otherwise.
  */
 int guac_rdp_keyboard_update_keysym(guac_rdp_keyboard* keyboard,
-        int keysym, int pressed);
+        int keysym, int pressed, guac_rdp_key_source source);
+
+/**
+ * Releases all currently pressed keys, sending key release events to the RDP
+ * server as necessary. Lock states (Caps Lock, etc.) are not affected.
+ *
+ * @param keyboard
+ *     The guac_rdp_keyboard associated with the current RDP session.
+ */
+void guac_rdp_keyboard_reset(guac_rdp_keyboard* keyboard);
 
 #endif