[fix] fix left/right modifier key injection while preserving scan code metadata

src/device_controller/device_controller.h

@@ -7,9 +7,10 @@
 #ifndef _DEVICE_CONTROLLER_H_
 #define _DEVICE_CONTROLLER_H_
 
-#include <cstring>
 #include <stdio.h>
 
+#include <cstdint>
+#include <cstring>
 #include <nlohmann/json.hpp>
 #include <string>
 
@@ -49,6 +50,8 @@ typedef struct {
 
 typedef struct {
   size_t key_value;
+  uint32_t scan_code;
+  bool extended;
   KeyFlag flag;
 } Key;
 
@@ -103,7 +106,10 @@ struct RemoteAction {
             {"x", a.m.x}, {"y", a.m.y}, {"s", a.m.s}, {"flag", a.m.flag}};
         break;
       case ControlType::keyboard:
-        j["keyboard"] = {{"key_value", a.k.key_value}, {"flag", a.k.flag}};
+        j["keyboard"] = {{"key_value", a.k.key_value},
+                         {"scan_code", a.k.scan_code},
+                         {"extended", a.k.extended},
+                         {"flag", a.k.flag}};
         break;
       case ControlType::audio_capture:
         j["audio_capture"] = a.a;
@@ -113,8 +119,7 @@ struct RemoteAction {
         break;
       case ControlType::service_status:
         j["service_status"] = {{"available", a.ss.available},
-                               {"interactive_stage",
-                                a.ss.interactive_stage}};
+                               {"interactive_stage", a.ss.interactive_stage}};
         break;
       case ControlType::service_command:
         j["service_command"] = {{"flag", a.c.flag}};
@@ -152,6 +157,9 @@ struct RemoteAction {
           break;
         case ControlType::keyboard:
           out.k.key_value = j.at("keyboard").at("key_value").get<size_t>();
+          out.k.scan_code =
+              j.at("keyboard").value("scan_code", static_cast<uint32_t>(0));
+          out.k.extended = j.at("keyboard").value("extended", false);
           out.k.flag = (KeyFlag)j.at("keyboard").at("flag").get<int>();
           break;
         case ControlType::audio_capture:
@@ -164,16 +172,15 @@ struct RemoteAction {
           const auto& service_status_json = j.at("service_status");
           out.ss.available = service_status_json.value("available", false);
           std::string interactive_stage =
-            service_status_json.value("interactive_stage", std::string());
+              service_status_json.value("interactive_stage", std::string());
           std::strncpy(out.ss.interactive_stage, interactive_stage.c_str(),
-                 sizeof(out.ss.interactive_stage) - 1);
-          out.ss.interactive_stage[sizeof(out.ss.interactive_stage) - 1] =
-            '\0';
+                       sizeof(out.ss.interactive_stage) - 1);
+          out.ss.interactive_stage[sizeof(out.ss.interactive_stage) - 1] = '\0';
           break;
         }
         case ControlType::service_command:
           out.c.flag = static_cast<ServiceCommandFlag>(
-            j.at("service_command").at("flag").get<int>());
+              j.at("service_command").at("flag").get<int>());
           break;
         case ControlType::host_infomation: {
           std::string host_name =
@@ -212,8 +219,8 @@ struct RemoteAction {
   }
 };
 
-// int key_code, bool is_down
-typedef void (*OnKeyAction)(int, bool, void*);
+// int key_code, bool is_down, uint32_t scan_code, bool extended
+typedef void (*OnKeyAction)(int, bool, uint32_t, bool, void*);
 
 class DeviceController {
  public:

src/device_controller/keyboard/linux/keyboard_capturer.cpp

@@ -37,7 +37,7 @@ static int KeyboardEventHandler(Display* display, XEvent* event) {
     bool is_key_down = (event->xkey.type == KeyPress);
 
     if (g_on_key_action) {
-      g_on_key_action(key_code, is_key_down, g_user_ptr);
+      g_on_key_action(key_code, is_key_down, 0, false, g_user_ptr);
     }
   }
   return 0;
@@ -146,7 +146,10 @@ int KeyboardCapturer::Unhook() {
   return 0;
 }
 
-int KeyboardCapturer::SendKeyboardCommand(int key_code, bool is_down) {
+int KeyboardCapturer::SendKeyboardCommand(int key_code, bool is_down,
+                                          uint32_t scan_code, bool extended) {
+  (void)scan_code;
+  (void)extended;
   if (IsWaylandSession()) {
     if (!use_wayland_portal_ && !wayland_init_attempted_) {
       wayland_init_attempted_ = true;
@@ -159,7 +162,7 @@ int KeyboardCapturer::SendKeyboardCommand(int key_code, bool is_down) {
     }
 
     if (use_wayland_portal_) {
-      return SendWaylandKeyboardCommand(key_code, is_down);
+      return SendWaylandKeyboardCommand(key_code, is_down, scan_code, extended);
     }
   }
 

src/device_controller/keyboard/linux/keyboard_capturer.h

@@ -32,12 +32,15 @@ class KeyboardCapturer : public DeviceController {
  public:
   virtual int Hook(OnKeyAction on_key_action, void* user_ptr);
   virtual int Unhook();
-  virtual int SendKeyboardCommand(int key_code, bool is_down);
+  virtual int SendKeyboardCommand(int key_code, bool is_down,
+                                  uint32_t scan_code = 0,
+                                  bool extended = false);
 
  private:
   bool InitWaylandPortal();
   void CleanupWaylandPortal();
-  int SendWaylandKeyboardCommand(int key_code, bool is_down);
+  int SendWaylandKeyboardCommand(int key_code, bool is_down, uint32_t scan_code,
+                                 bool extended);
   bool NotifyWaylandKeyboardKeysym(int keysym, uint32_t state);
   bool NotifyWaylandKeyboardKeycode(int keycode, uint32_t state);
   bool SendWaylandPortalVoidCall(const char* method_name,

src/device_controller/keyboard/linux/keyboard_capturer_wayland.cpp

@@ -575,8 +575,12 @@ void KeyboardCapturer::CleanupWaylandPortal() {
   wayland_session_handle_.clear();
 }
 
-int KeyboardCapturer::SendWaylandKeyboardCommand(int key_code, bool is_down) {
+int KeyboardCapturer::SendWaylandKeyboardCommand(int key_code, bool is_down,
+                                                 uint32_t scan_code,
+                                                 bool extended) {
 #if defined(CROSSDESK_HAS_WAYLAND_CAPTURER) && CROSSDESK_HAS_WAYLAND_CAPTURER
+  (void)scan_code;
+  (void)extended;
   if (!dbus_connection_ || wayland_session_handle_.empty()) {
     return -1;
   }
@@ -613,6 +617,8 @@ int KeyboardCapturer::SendWaylandKeyboardCommand(int key_code, bool is_down) {
 #else
   (void)key_code;
   (void)is_down;
+  (void)scan_code;
+  (void)extended;
   return -1;
 #endif
 }

src/device_controller/keyboard/mac/keyboard_capturer.cpp

@@ -119,7 +119,7 @@ CGEventRef eventCallback(CGEventTapProxy proxy, CGEventType type,
         CGEventGetIntegerValueField(event, kCGKeyboardEventKeycode));
     int vk_code = ResolveVkCodeFromMacEvent(event, key_code, is_key_down);
     if (vk_code >= 0) {
-      g_on_key_action(vk_code, is_key_down, g_user_ptr);
+      g_on_key_action(vk_code, is_key_down, 0, false, g_user_ptr);
     }
   } else if (type == kCGEventFlagsChanged) {
     CGEventFlags current_flags = CGEventGetFlags(event);
@@ -135,35 +135,40 @@ CGEventRef eventCallback(CGEventTapProxy proxy, CGEventType type,
     bool caps_lock_state = (current_flags & kCGEventFlagMaskAlphaShift) != 0;
     if (caps_lock_state != keyboard_capturer->caps_lock_flag_) {
       keyboard_capturer->caps_lock_flag_ = caps_lock_state;
-      g_on_key_action(vk_code, keyboard_capturer->caps_lock_flag_, g_user_ptr);
+      g_on_key_action(vk_code, keyboard_capturer->caps_lock_flag_, 0, false,
+                      g_user_ptr);
     }
 
     // shift
     bool shift_state = (current_flags & kCGEventFlagMaskShift) != 0;
     if (shift_state != keyboard_capturer->shift_flag_) {
       keyboard_capturer->shift_flag_ = shift_state;
-      g_on_key_action(vk_code, keyboard_capturer->shift_flag_, g_user_ptr);
+      g_on_key_action(vk_code, keyboard_capturer->shift_flag_, 0, false,
+                      g_user_ptr);
     }
 
     // control
     bool control_state = (current_flags & kCGEventFlagMaskControl) != 0;
     if (control_state != keyboard_capturer->control_flag_) {
       keyboard_capturer->control_flag_ = control_state;
-      g_on_key_action(vk_code, keyboard_capturer->control_flag_, g_user_ptr);
+      g_on_key_action(vk_code, keyboard_capturer->control_flag_, 0, false,
+                      g_user_ptr);
     }
 
     // option
     bool option_state = (current_flags & kCGEventFlagMaskAlternate) != 0;
     if (option_state != keyboard_capturer->option_flag_) {
       keyboard_capturer->option_flag_ = option_state;
-      g_on_key_action(vk_code, keyboard_capturer->option_flag_, g_user_ptr);
+      g_on_key_action(vk_code, keyboard_capturer->option_flag_, 0, false,
+                      g_user_ptr);
     }
 
     // command
     bool command_state = (current_flags & kCGEventFlagMaskCommand) != 0;
     if (command_state != keyboard_capturer->command_flag_) {
       keyboard_capturer->command_flag_ = command_state;
-      g_on_key_action(vk_code, keyboard_capturer->command_flag_, g_user_ptr);
+      g_on_key_action(vk_code, keyboard_capturer->command_flag_, 0, false,
+                      g_user_ptr);
     }
   }
 
@@ -264,7 +269,10 @@ inline bool IsFunctionKey(int key_code) {
   }
 }
 
-int KeyboardCapturer::SendKeyboardCommand(int key_code, bool is_down) {
+int KeyboardCapturer::SendKeyboardCommand(int key_code, bool is_down,
+                                          uint32_t scan_code, bool extended) {
+  (void)scan_code;
+  (void)extended;
   if (vkCodeToCGKeyCode.find(key_code) != vkCodeToCGKeyCode.end()) {
     CGKeyCode cg_key_code = vkCodeToCGKeyCode[key_code];
     CGEventRef event = CGEventCreateKeyboardEvent(NULL, cg_key_code, is_down);

src/device_controller/keyboard/mac/keyboard_capturer.h

@@ -21,7 +21,9 @@ class KeyboardCapturer : public DeviceController {
  public:
   virtual int Hook(OnKeyAction on_key_action, void* user_ptr);
   virtual int Unhook();
-  virtual int SendKeyboardCommand(int key_code, bool is_down);
+  virtual int SendKeyboardCommand(int key_code, bool is_down,
+                                  uint32_t scan_code = 0,
+                                  bool extended = false);
 
  private:
   CFMachPortRef event_tap_ = nullptr;

src/device_controller/keyboard/windows/keyboard_capturer.cpp

@@ -7,14 +7,56 @@ namespace crossdesk {
 static OnKeyAction g_on_key_action = nullptr;
 static void* g_user_ptr = nullptr;
 
+static int NormalizeModifierVkCode(const KBDLLHOOKSTRUCT* kb_data) {
+  if (kb_data == nullptr) {
+    return -1;
+  }
+
+  if (kb_data->vkCode != VK_SHIFT && kb_data->vkCode != VK_CONTROL &&
+      kb_data->vkCode != VK_MENU) {
+    return static_cast<int>(kb_data->vkCode);
+  }
+
+  UINT scan_code = static_cast<UINT>(kb_data->scanCode & 0xFF);
+  if ((kb_data->flags & LLKHF_EXTENDED) != 0) {
+    scan_code |= 0xE000;
+  }
+
+  const UINT normalized_vk = MapVirtualKeyW(scan_code, MAPVK_VSC_TO_VK_EX);
+  if (normalized_vk != 0) {
+    return static_cast<int>(normalized_vk);
+  }
+
+  return static_cast<int>(kb_data->vkCode);
+}
+
+static bool PreferSideSpecificVkInjection(int key_code) {
+  switch (key_code) {
+    case VK_LSHIFT:
+    case VK_RSHIFT:
+    case VK_LCONTROL:
+    case VK_RCONTROL:
+    case VK_LMENU:
+    case VK_RMENU:
+    case VK_LWIN:
+    case VK_RWIN:
+      return true;
+    default:
+      return false;
+  }
+}
+
 LRESULT CALLBACK KeyboardProc(int nCode, WPARAM wParam, LPARAM lParam) {
   if (nCode == HC_ACTION && g_on_key_action) {
     KBDLLHOOKSTRUCT* kbData = reinterpret_cast<KBDLLHOOKSTRUCT*>(lParam);
+    const int key_code = NormalizeModifierVkCode(kbData);
 
     if (wParam == WM_KEYDOWN || wParam == WM_SYSKEYDOWN) {
-      g_on_key_action(kbData->vkCode, true, g_user_ptr);
+      g_on_key_action(key_code, true, kbData->scanCode,
+                      (kbData->flags & LLKHF_EXTENDED) != 0, g_user_ptr);
     } else if (wParam == WM_KEYUP || wParam == WM_SYSKEYUP) {
-      g_on_key_action(kbData->vkCode, false, g_user_ptr);
+      g_on_key_action(key_code, false, kbData->scanCode,
+                      (kbData->flags & LLKHF_EXTENDED) != 0, g_user_ptr);
     }
     return 1;
   }
@@ -49,20 +91,40 @@ int KeyboardCapturer::Unhook() {
 }
 
 // apply remote keyboard commands to the local machine
-int KeyboardCapturer::SendKeyboardCommand(int key_code, bool is_down) {
+int KeyboardCapturer::SendKeyboardCommand(int key_code, bool is_down,
+                                          uint32_t scan_code, bool extended) {
   INPUT input = {0};
   input.type = INPUT_KEYBOARD;
-  input.ki.wVk = (WORD)key_code;
 
-  const UINT scan_code =
-      MapVirtualKeyW(static_cast<UINT>(key_code), MAPVK_VK_TO_VSC_EX);
-  if (scan_code != 0) {
+  const bool prefer_vk = PreferSideSpecificVkInjection(key_code);
+  const UINT resolved_scan_code =
+      scan_code != 0
+          ? static_cast<UINT>(scan_code & 0xFF) | (extended ? 0xE000u : 0u)
+          : MapVirtualKeyW(static_cast<UINT>(key_code), MAPVK_VK_TO_VSC_EX);
+
+  if (scan_code != 0 && !prefer_vk) {
     input.ki.wVk = 0;
     input.ki.wScan = static_cast<WORD>(scan_code & 0xFF);
     input.ki.dwFlags |= KEYEVENTF_SCANCODE;
-    if ((scan_code & 0xFF00) != 0) {
+    if (extended) {
       input.ki.dwFlags |= KEYEVENTF_EXTENDEDKEY;
     }
+  } else {
+    input.ki.wVk = (WORD)key_code;
+
+    if (prefer_vk && resolved_scan_code != 0) {
+      input.ki.wScan = static_cast<WORD>(resolved_scan_code & 0xFF);
+      if ((resolved_scan_code & 0xFF00) != 0) {
+        input.ki.dwFlags |= KEYEVENTF_EXTENDEDKEY;
+      }
+    } else if (resolved_scan_code != 0) {
+      input.ki.wVk = 0;
+      input.ki.wScan = static_cast<WORD>(resolved_scan_code & 0xFF);
+      input.ki.dwFlags |= KEYEVENTF_SCANCODE;
+      if ((resolved_scan_code & 0xFF00) != 0) {
+        input.ki.dwFlags |= KEYEVENTF_EXTENDEDKEY;
+      }
+    }
   }
 
   if (!is_down) {

src/device_controller/keyboard/windows/keyboard_capturer.h

@@ -21,7 +21,9 @@ class KeyboardCapturer : public DeviceController {
  public:
   virtual int Hook(OnKeyAction on_key_action, void* user_ptr);
   virtual int Unhook();
-  virtual int SendKeyboardCommand(int key_code, bool is_down);
+  virtual int SendKeyboardCommand(int key_code, bool is_down,
+                                  uint32_t scan_code = 0,
+                                  bool extended = false);
 
  private:
   HHOOK keyboard_hook_ = nullptr;

src/gui/render.cpp

@@ -812,10 +812,11 @@ int Render::StartKeyboardCapturer() {
   }
 
   int keyboard_capturer_init_ret = keyboard_capturer_->Hook(
-      [](int key_code, bool is_down, void* user_ptr) {
+      [](int key_code, bool is_down, uint32_t scan_code, bool extended,
+         void* user_ptr) {
         if (user_ptr) {
           Render* render = (Render*)user_ptr;
-          render->SendKeyCommand(key_code, is_down);
+          render->SendKeyCommand(key_code, is_down, scan_code, extended);
         }
       },
       this);

src/gui/render.h

@@ -339,7 +339,8 @@ class Render {
   static void FreeRemoteAction(RemoteAction& action);
 
  private:
-  int SendKeyCommand(int key_code, bool is_down);
+  int SendKeyCommand(int key_code, bool is_down, uint32_t scan_code = 0,
+                     bool extended = false);
   static bool IsModifierVkKey(int key_code);
   void TrackPressedKeyState(int key_code, bool is_down);
   void ForceReleasePressedKeys();

src/gui/render_callback.cpp

@@ -200,6 +200,40 @@ int TranslateSdlKeyboardEventToVk(const SDL_KeyboardEvent& event) {
   }
 }
 
+#if _WIN32
+int NormalizeWindowsModifierVk(int key_code, uint32_t scan_code,
+                               bool extended) {
+  if (key_code != 0x10 && key_code != 0x11 && key_code != 0x12) {
+    return key_code;
+  }
+
+  UINT scan_code_with_prefix = static_cast<UINT>(scan_code & 0xFF);
+  if (extended) {
+    scan_code_with_prefix |= 0xE000;
+  }
+
+  const UINT normalized_vk =
+      MapVirtualKeyW(scan_code_with_prefix, MAPVK_VSC_TO_VK_EX);
+  return normalized_vk != 0 ? static_cast<int>(normalized_vk) : key_code;
+}
+
+void PopulateWindowsKeyMetadataFromVk(int key_code, uint32_t* scan_code_out,
+                                      bool* extended_out) {
+  if (scan_code_out == nullptr || extended_out == nullptr) {
+    return;
+  }
+
+  const UINT scan_code =
+      MapVirtualKeyW(static_cast<UINT>(key_code), MAPVK_VK_TO_VSC_EX);
+  if (scan_code == 0) {
+    return;
+  }
+
+  *scan_code_out = static_cast<uint32_t>(scan_code & 0xFF);
+  *extended_out = (scan_code & 0xFF00) != 0;
+}
+#endif
+
 #if _WIN32
 constexpr uint32_t kSecureDesktopInputLogIntervalMs = 2000;
 
@@ -353,15 +387,26 @@ void Render::ForceReleasePressedKeys() {
   }
 }
 
-int Render::SendKeyCommand(int key_code, bool is_down) {
-  RemoteAction remote_action;
+int Render::SendKeyCommand(int key_code, bool is_down, uint32_t scan_code,
+                           bool extended) {
+  RemoteAction remote_action{};
   remote_action.type = ControlType::keyboard;
   if (is_down) {
     remote_action.k.flag = KeyFlag::key_down;
   } else {
     remote_action.k.flag = KeyFlag::key_up;
   }
+
+#if _WIN32
+  if (scan_code == 0) {
+    PopulateWindowsKeyMetadataFromVk(key_code, &scan_code, &extended);
+  }
+  key_code = NormalizeWindowsModifierVk(key_code, scan_code, extended);
+#endif
+
   remote_action.k.key_value = key_code;
+  remote_action.k.scan_code = scan_code;
+  remote_action.k.extended = extended;
 
   std::string target_id = controlled_remote_id_.empty() ? focused_remote_id_
                                                         : controlled_remote_id_;
@@ -1048,8 +1093,9 @@ void Render::OnReceiveDataBufferCb(const char* data, size_t size,
       if (remote_action.type == ControlType::keyboard) {
         const int key_code = static_cast<int>(remote_action.k.key_value);
         const bool is_down = remote_action.k.flag == KeyFlag::key_down;
-        const std::string response =
-            SendCrossDeskSecureDesktopKeyInput(key_code, is_down, 1000);
+        const std::string response = SendCrossDeskSecureDesktopKeyInput(
+            key_code, is_down, remote_action.k.scan_code,
+            remote_action.k.extended, 1000);
         auto json = nlohmann::json::parse(response, nullptr, false);
         if (json.is_discarded() || !json.value("ok", false)) {
           LogSecureDesktopInputBlocked(
@@ -1076,7 +1122,8 @@ void Render::OnReceiveDataBufferCb(const char* data, size_t size,
                render->keyboard_capturer_) {
       render->keyboard_capturer_->SendKeyboardCommand(
           (int)remote_action.k.key_value,
-          remote_action.k.flag == KeyFlag::key_down);
+          remote_action.k.flag == KeyFlag::key_down, remote_action.k.scan_code,
+          remote_action.k.extended);
     } else if (remote_action.type == ControlType::display_id &&
                render->screen_capturer_) {
       render->selected_display_ = remote_action.d;

src/service/windows/service_host.cpp

@@ -313,10 +313,12 @@ std::string QueryNamedPipeMessage(const std::wstring& pipe_name,
   return std::string(buffer, buffer + bytes_read);
 }
 
-std::string BuildSecureDesktopKeyboardIpcCommand(int key_code, bool is_down) {
+std::string BuildSecureDesktopKeyboardIpcCommand(int key_code, bool is_down,
+                                                 uint32_t scan_code,
+                                                 bool extended) {
   std::ostringstream stream;
   stream << kSecureDesktopKeyboardIpcCommandPrefix << key_code << ":"
-         << (is_down ? 1 : 0);
+         << (is_down ? 1 : 0) << ":" << scan_code << ":" << (extended ? 1 : 0);
   return stream.str();
 }
 
@@ -328,20 +330,27 @@ std::string BuildSecureDesktopMouseIpcCommand(int x, int y, int wheel,
   return stream.str();
 }
 
-std::string BuildSecureInputHelperKeyboardCommand(int key_code, bool is_down) {
+std::string BuildSecureInputHelperKeyboardCommand(int key_code, bool is_down,
+                                                  uint32_t scan_code,
+                                                  bool extended) {
   std::ostringstream stream;
   stream << kCrossDeskSecureInputKeyboardCommandPrefix << key_code << ":"
-         << (is_down ? 1 : 0);
+         << (is_down ? 1 : 0) << ":" << scan_code << ":" << (extended ? 1 : 0);
   return stream.str();
 }
 
 bool ParseSecureDesktopKeyboardIpcCommand(const std::string& command,
-                                          int* key_code_out,
-                                          bool* is_down_out) {
-  if (key_code_out == nullptr || is_down_out == nullptr) {
+                                          int* key_code_out, bool* is_down_out,
+                                          uint32_t* scan_code_out,
+                                          bool* extended_out) {
+  if (key_code_out == nullptr || is_down_out == nullptr ||
+      scan_code_out == nullptr || extended_out == nullptr) {
     return false;
   }
 
+  *scan_code_out = 0;
+  *extended_out = false;
+
   if (command.rfind(kSecureDesktopKeyboardIpcCommandPrefix, 0) != 0) {
     return false;
   }
@@ -358,13 +367,46 @@ bool ParseSecureDesktopKeyboardIpcCommand(const std::string& command,
     return false;
   }
 
-  const std::string state = command.substr(separator + 1);
+  const size_t scan_separator = command.find(':', separator + 1);
+  const std::string state =
+      scan_separator == std::string::npos
+          ? command.substr(separator + 1)
+          : command.substr(separator + 1, scan_separator - separator - 1);
   if (state == "1" || state == "down") {
     *is_down_out = true;
+  } else if (state == "0" || state == "up") {
+    *is_down_out = false;
+  } else {
+    return false;
+  }
+
+  if (scan_separator == std::string::npos) {
     return true;
   }
-  if (state == "0" || state == "up") {
-    *is_down_out = false;
+
+  const size_t extended_separator = command.find(':', scan_separator + 1);
+  const std::string scan_code_str =
+      extended_separator == std::string::npos
+          ? command.substr(scan_separator + 1)
+          : command.substr(scan_separator + 1,
+                           extended_separator - scan_separator - 1);
+  try {
+    *scan_code_out = static_cast<uint32_t>(std::stoul(scan_code_str));
+  } catch (...) {
+    return false;
+  }
+
+  if (extended_separator == std::string::npos) {
+    return true;
+  }
+
+  const std::string extended_str = command.substr(extended_separator + 1);
+  if (extended_str == "1" || extended_str == "true") {
+    *extended_out = true;
+    return true;
+  }
+  if (extended_str == "0" || extended_str == "false") {
+    *extended_out = false;
     return true;
   }
   return false;
@@ -1712,8 +1754,12 @@ std::string CrossDeskServiceHost::HandleIpcCommand(const std::string& command) {
   }
   int key_code = 0;
   bool is_down = false;
-  if (ParseSecureDesktopKeyboardIpcCommand(normalized, &key_code, &is_down)) {
-    return SendSecureDesktopKeyboardInput(key_code, is_down);
+  uint32_t scan_code = 0;
+  bool extended = false;
+  if (ParseSecureDesktopKeyboardIpcCommand(normalized, &key_code, &is_down,
+                                           &scan_code, &extended)) {
+    return SendSecureDesktopKeyboardInput(key_code, is_down, scan_code,
+                                          extended);
   }
   return BuildErrorJson("unknown_command");
 }
@@ -1928,8 +1974,8 @@ std::string CrossDeskServiceHost::SendSecureAttentionSequence() {
   return "{\"ok\":true,\"sent\":\"sas\"}";
 }
 
-std::string CrossDeskServiceHost::SendSecureDesktopKeyboardInput(int key_code,
-                                                                 bool is_down) {
+std::string CrossDeskServiceHost::SendSecureDesktopKeyboardInput(
+    int key_code, bool is_down, uint32_t scan_code, bool extended) {
   RefreshSessionState();
   ReapSecureInputHelper();
   EnsureSessionHelper();
@@ -1963,7 +2009,9 @@ std::string CrossDeskServiceHost::SendSecureDesktopKeyboardInput(int key_code,
 
   return QueryNamedPipeMessage(
       GetCrossDeskSecureInputHelperPipeName(target_session_id),
-      BuildSecureInputHelperKeyboardCommand(key_code, is_down), 1000);
+      BuildSecureInputHelperKeyboardCommand(key_code, is_down, scan_code,
+                                            extended),
+      1000);
 }
 
 bool InstallCrossDeskService(const std::wstring& binary_path) {
@@ -2176,9 +2224,12 @@ std::string QueryCrossDeskService(const std::string& command,
 }
 
 std::string SendCrossDeskSecureDesktopKeyInput(int key_code, bool is_down,
+                                               uint32_t scan_code,
+                                               bool extended,
                                                DWORD timeout_ms) {
-  return QueryCrossDeskService(
-      BuildSecureDesktopKeyboardIpcCommand(key_code, is_down), timeout_ms);
+  return QueryCrossDeskService(BuildSecureDesktopKeyboardIpcCommand(
+                                   key_code, is_down, scan_code, extended),
+                               timeout_ms);
 }
 
 std::string SendCrossDeskSecureDesktopMouseInput(int x, int y, int wheel,

src/service/windows/service_host.h

@@ -9,6 +9,7 @@
 
 #include <Windows.h>
 
+#include <cstdint>
 #include <mutex>
 #include <string>
 #include <thread>
@@ -60,7 +61,9 @@ class CrossDeskServiceHost {
   std::string HandleIpcCommand(const std::string& command);
   std::string BuildStatusResponse();
   std::string SendSecureAttentionSequence();
-  std::string SendSecureDesktopKeyboardInput(int key_code, bool is_down);
+  std::string SendSecureDesktopKeyboardInput(int key_code, bool is_down,
+                                             uint32_t scan_code = 0,
+                                             bool extended = false);
 
   static void WINAPI ServiceMain(DWORD argc, LPWSTR* argv);
   static BOOL WINAPI ConsoleControlHandler(DWORD control_type);
@@ -138,6 +141,8 @@ bool StopCrossDeskService(DWORD timeout_ms = 5000);
 std::string QueryCrossDeskService(const std::string& command,
                                   DWORD timeout_ms = 1000);
 std::string SendCrossDeskSecureDesktopKeyInput(int key_code, bool is_down,
+                                               uint32_t scan_code = 0,
+                                               bool extended = false,
                                                DWORD timeout_ms = 1000);
 std::string SendCrossDeskSecureDesktopMouseInput(int x, int y, int wheel,
                                                  int flag,

src/service/windows/session_helper_main.cpp

@@ -485,20 +485,56 @@ bool EnsureThreadDesktop(const wchar_t* desktop_name,
   return true;
 }
 
-int InjectKeyboardInput(int key_code, bool is_down) {
+bool PreferSideSpecificVkInjection(int key_code) {
+  switch (key_code) {
+    case VK_LSHIFT:
+    case VK_RSHIFT:
+    case VK_LCONTROL:
+    case VK_RCONTROL:
+    case VK_LMENU:
+    case VK_RMENU:
+    case VK_LWIN:
+    case VK_RWIN:
+      return true;
+    default:
+      return false;
+  }
+}
+
+int InjectKeyboardInput(int key_code, bool is_down, uint32_t scan_code,
+                        bool extended) {
   INPUT input = {0};
   input.type = INPUT_KEYBOARD;
-  input.ki.wVk = static_cast<WORD>(key_code);
 
-  const UINT scan_code =
-      MapVirtualKeyW(static_cast<UINT>(key_code), MAPVK_VK_TO_VSC_EX);
-  if (scan_code != 0) {
+  const bool prefer_vk = PreferSideSpecificVkInjection(key_code);
+  const UINT resolved_scan_code =
+      scan_code != 0
+          ? static_cast<UINT>(scan_code & 0xFF) | (extended ? 0xE000u : 0u)
+          : MapVirtualKeyW(static_cast<UINT>(key_code), MAPVK_VK_TO_VSC_EX);
+
+  if (scan_code != 0 && !prefer_vk) {
     input.ki.wVk = 0;
     input.ki.wScan = static_cast<WORD>(scan_code & 0xFF);
     input.ki.dwFlags |= KEYEVENTF_SCANCODE;
-    if ((scan_code & 0xFF00) != 0) {
+    if (extended) {
       input.ki.dwFlags |= KEYEVENTF_EXTENDEDKEY;
     }
+  } else {
+    input.ki.wVk = static_cast<WORD>(key_code);
+
+    if (prefer_vk && resolved_scan_code != 0) {
+      input.ki.wScan = static_cast<WORD>(resolved_scan_code & 0xFF);
+      if ((resolved_scan_code & 0xFF00) != 0) {
+        input.ki.dwFlags |= KEYEVENTF_EXTENDEDKEY;
+      }
+    } else if (resolved_scan_code != 0) {
+      input.ki.wVk = 0;
+      input.ki.wScan = static_cast<WORD>(resolved_scan_code & 0xFF);
+      input.ki.dwFlags |= KEYEVENTF_SCANCODE;
+      if ((resolved_scan_code & 0xFF00) != 0) {
+        input.ki.dwFlags |= KEYEVENTF_EXTENDEDKEY;
+      }
+    }
   }
 
   if (!is_down) {
@@ -514,11 +550,17 @@ int InjectKeyboardInput(int key_code, bool is_down) {
 }
 
 bool ParseSecureInputKeyboardCommand(const std::string& command,
-                                     int* key_code_out, bool* is_down_out) {
-  if (key_code_out == nullptr || is_down_out == nullptr) {
+                                     int* key_code_out, bool* is_down_out,
+                                     uint32_t* scan_code_out,
+                                     bool* extended_out) {
+  if (key_code_out == nullptr || is_down_out == nullptr ||
+      scan_code_out == nullptr || extended_out == nullptr) {
     return false;
   }
 
+  *scan_code_out = 0;
+  *extended_out = false;
+
   if (command.rfind(crossdesk::kCrossDeskSecureInputKeyboardCommandPrefix, 0) !=
       0) {
     return false;
@@ -537,13 +579,46 @@ bool ParseSecureInputKeyboardCommand(const std::string& command,
     return false;
   }
 
-  const std::string state = command.substr(separator + 1);
+  const size_t scan_separator = command.find(':', separator + 1);
+  const std::string state =
+      scan_separator == std::string::npos
+          ? command.substr(separator + 1)
+          : command.substr(separator + 1, scan_separator - separator - 1);
   if (state == "1" || state == "down") {
     *is_down_out = true;
+  } else if (state == "0" || state == "up") {
+    *is_down_out = false;
+  } else {
+    return false;
+  }
+
+  if (scan_separator == std::string::npos) {
     return true;
   }
-  if (state == "0" || state == "up") {
-    *is_down_out = false;
+
+  const size_t extended_separator = command.find(':', scan_separator + 1);
+  const std::string scan_code_str =
+      extended_separator == std::string::npos
+          ? command.substr(scan_separator + 1)
+          : command.substr(scan_separator + 1,
+                           extended_separator - scan_separator - 1);
+  try {
+    *scan_code_out = static_cast<uint32_t>(std::stoul(scan_code_str));
+  } catch (...) {
+    return false;
+  }
+
+  if (extended_separator == std::string::npos) {
+    return true;
+  }
+
+  const std::string extended_str = command.substr(extended_separator + 1);
+  if (extended_str == "1" || extended_str == "true") {
+    *extended_out = true;
+    return true;
+  }
+  if (extended_str == "0" || extended_str == "false") {
+    *extended_out = false;
     return true;
   }
   return false;
@@ -807,13 +882,17 @@ std::vector<uint8_t> HandleSecureInputHelperCommand(
 
   int key_code = 0;
   bool is_down = false;
-  if (ParseSecureInputKeyboardCommand(command, &key_code, &is_down)) {
-    const int inject_result = InjectKeyboardInput(key_code, is_down);
+  uint32_t scan_code = 0;
+  bool extended = false;
+  if (ParseSecureInputKeyboardCommand(command, &key_code, &is_down, &scan_code,
+                                      &extended)) {
+    const int inject_result =
+        InjectKeyboardInput(key_code, is_down, scan_code, extended);
     if (inject_result != 0) {
       LOG_WARN(
           "Secure input helper SendInput failed for key_code={}, is_down={}, "
-          "err={}",
-          key_code, is_down, inject_result);
+          "scan_code={}, extended={}, err={}",
+          key_code, is_down, scan_code, extended, inject_result);
       return BuildTextResponseBytes(BuildErrorJson(
           "send_input_failed", static_cast<DWORD>(inject_result)));
     }
@@ -823,6 +902,8 @@ std::vector<uint8_t> HandleSecureInputHelperCommand(
     json["injected"] = "keyboard";
     json["key_code"] = key_code;
     json["is_down"] = is_down;
+    json["scan_code"] = scan_code;
+    json["extended"] = extended;
     json["desktop"] = WideToUtf8(GetCurrentThreadDesktopNameW());
     return BuildTextResponseBytes(json.dump());
   }