Can' t close OSK.exe under Windows 10 - c++

Question

I use below code to open osk.exe
HINSTANCE Dlg::ExecuteOSK()
{
typedef BOOL (WINAPI * LPFN_IsWow64Process)(HANDLE, PBOOL);
typedef BOOL (WINAPI * LPFN_Wow64DisableWow64FsRedirection)(PVOID *);
typedef BOOL (WINAPI * LPFN_Wow64RevertWow64FsRedirection)(PVOID);
LPFN_IsWow64Process fnIsWow64Process = NULL;
LPFN_Wow64DisableWow64FsRedirection fnWow64DisableWow64FsRedirection = NULL;
LPFN_Wow64RevertWow64FsRedirection fnWow64RevertWow64FsRedirection = NULL;
fnIsWow64Process = (LPFN_IsWow64Process) GetProcAddress(GetModuleHandle(TEXT("kernel32")), "IsWow64Process");
fnWow64DisableWow64FsRedirection = (LPFN_Wow64DisableWow64FsRedirection) GetProcAddress(GetModuleHandle(TEXT("kernel32")), "Wow64DisableWow64FsRedirection");
fnWow64RevertWow64FsRedirection = (LPFN_Wow64RevertWow64FsRedirection) GetProcAddress(GetModuleHandle(TEXT("kernel32")), "Wow64RevertWow64FsRedirection");
BOOL bIsWow64 = FALSE;
PVOID OldValue = NULL;
HINSTANCE handle;
if (NULL == fnIsWow64Process || NULL == fnWow64DisableWow64FsRedirection || NULL == fnWow64RevertWow64FsRedirection)
{
handle = ::ShellExecute(NULL, "open", "OSK", NULL, NULL, SW_SHOW);
}
else
{
fnIsWow64Process(GetCurrentProcess(), &bIsWow64);
if (TRUE == bIsWow64)
{
fnWow64DisableWow64FsRedirection(&OldValue);
handle = ::ShellExecute(NULL, "open", "OSK", NULL, NULL, SW_SHOW);
fnWow64RevertWow64FsRedirection(OldValue);
}
else
{
handle = ::ShellExecute(NULL, "open", "OSK", NULL, NULL, SW_SHOW);
}
}
return handle;
}
And then, I want to close the osk.exe when user press enter.
BOOL CALLBACK EnumWindowsProc(
_In_ HWND hwnd,
_In_ LPARAM lParam)
{
char name[256];
GetClassName( hwnd, name, sizeof(name) );
if(strcmp(name,"OSKMainClass") == 0)
SendMessage(hwnd, WM_CLOSE , NULL, NULL); //I have tried WM_DESTROY
return TRUE;
}
BOOL Dlg::PreTranslateMessage(MSG* pMsg)
{
if (pMsg->message == WM_KEYDOWN)
{
int nKey = (int)pMsg->wParam;
switch(nKey)
{
case VK_RETURN:
EnumWindows(EnumWindowsProc, NULL);
}
}
return CBitmapDialog::PreTranslateMessage(pMsg);
}
However, this part of code cannot be used to close osk.exe successful.
I have tried to catch another window, it can be closed successfully.
Does it is an issue on Windows 10?

Answer 1

if you looking to manifest of osk.exe you can view here next - uiAccess="true" this is User Interface Privilege Isolation (UIPI) , also read about similar problem UIAccess in Manifest Files
because osk.exe have uiAccess="true" in manifest it have Mandatory Label\High Mandatory Level in token. but your app, if running under UAC not elevated, usual have Medium Mandatory Level. as result:
A lower-privilege process cannot:
Use SendMessage or PostMessage to application windows running with higher rights. These APIs return success but silently drop the window
message.
but if your application get High Mandatory Level in token - you can close osk.exe by next code:
if (HWND hwnd = FindWindow(L"OSKMainClass", 0))
{
PostMessage(hwnd, WM_CLOSE, 0, 0);
}
so you need have <requestedExecutionLevel level='requireAdministrator' uiAccess='false'/> in manifest or somehow run your application as elevated