Windows: Modified implementation for Secure Desktop handling to overcome Windows 11 issues

We use only alphanumeric characters for the name in addition to the '_' character
We ensure the random desktop name doesn't already exist
We create the random desktop on the Secure Desktop thread and we look over SwitchDesktop until it works.
We call SetThreadDesktop (hOriginalDesk) in main thread once we finish

src/Common/Dlgcode.c

@@ -13782,7 +13782,7 @@ static BOOL GenerateRandomString (HWND hwndDlg, LPTSTR szName, DWORD maxCharsCou
 		bRet = RandgetBytesFull (hwndDlg, indexes, maxCharsCount + 1, TRUE, TRUE); 
 		if (bRet)
 		{
-			static LPCTSTR chars = _T("0123456789@#$%^&_-*abcdefghijklmnopqrstuvwxyz");
+			static LPCTSTR chars = _T("0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_");
 			DWORD i, charsLen = (DWORD) _tcslen (chars);
 			DWORD effectiveLen = (indexes[0] % (64 - 16)) + 16; // random length between 16 to 64
 			effectiveLen = (effectiveLen > maxCharsCount)? maxCharsCount : effectiveLen;
@@ -13864,7 +13864,9 @@ static unsigned int __stdcall SecureDesktopMonitoringThread( LPVOID lpThreadPara
 					{
 						if (GetUserObjectInformation (currentDesk, UOI_NAME, szName, dwLen, &dwLen))
 						{
-							if (0 != _wcsicmp (szName, szVCDesktopName))
+							if (0 == _wcsicmp(szName, L"Default")) // default input desktop for the interactive window station
+								bPerformSwitch = TRUE;
+							else if (0 != _wcsicmp (szName, szVCDesktopName))
 								bPerformSwitch = TRUE;
 						}
 						free (szName);
@@ -13888,18 +13890,29 @@ static unsigned int __stdcall SecureDesktopThread( LPVOID lpThreadParameter )
 	SecureDesktopThreadParam* pParam = (SecureDesktopThreadParam*) lpThreadParameter;
 	SecureDesktopMonitoringThreadParam monitorParam;
 	BOOL bNewDesktopSet = FALSE;
+	HDESK hSecureDesk;
+	DWORD desktopAccess = DESKTOP_CREATEMENU | DESKTOP_CREATEWINDOW | DESKTOP_READOBJECTS | DESKTOP_SWITCHDESKTOP | DESKTOP_WRITEOBJECTS;
+
+	hSecureDesk = CreateDesktop (pParam->szDesktopName, NULL, NULL, 0, desktopAccess, NULL);
+	if (!hSecureDesk)
+	{
+		return 0;
+	}
+	
+	StringCbCopy(SecureDesktopName, sizeof (SecureDesktopName), pParam->szDesktopName);
+	pParam->hDesk = hSecureDesk;
 
 	// wait for SwitchDesktop to succeed before using it for current thread
 	while (true)
 	{
-		if (SwitchDesktop (pParam->hDesk))
+		if (SwitchDesktop (hSecureDesk))
 		{
 			break;
 		}
 		Sleep (SECUREDESKTOP_MONOTIR_PERIOD);
 	}
 
-	bNewDesktopSet = SetThreadDesktop (pParam->hDesk);
+	bNewDesktopSet = SetThreadDesktop (hSecureDesk);
 
 	if (bNewDesktopSet)
 	{
@@ -13909,7 +13922,7 @@ static unsigned int __stdcall SecureDesktopThread( LPVOID lpThreadParameter )
 		if (hStopEvent)
 		{
 			monitorParam.szVCDesktopName = pParam->szDesktopName;
-			monitorParam.hVcDesktop = pParam->hDesk;
+			monitorParam.hVcDesktop = hSecureDesk;
 			monitorParam.hStopEvent = hStopEvent;
 			hMonitoringThread = (HANDLE) _beginthreadex (NULL, 0, SecureDesktopMonitoringThread, (LPVOID) &monitorParam, 0, &monitoringThreadID);
 		}
@@ -13986,18 +13999,36 @@ INT_PTR SecureDesktopDialogBoxParam(
 
 	if (bEffectiveUseSecureDesktop && !IsThreadInSecureDesktop(GetCurrentThreadId()))
 	{
+		BOOL bRandomNameGenerated = FALSE;
+		HDESK existedDesk = NULL;
 		EnterCriticalSection (&csSecureDesktop);
 		bSecureDesktopOngoing = TRUE;
 		finally_do ({ bSecureDesktopOngoing = FALSE; LeaveCriticalSection (&csSecureDesktop); });
 
-		if (GenerateRandomString (hWndParent, szDesktopName, 64))
+		// ensure that the randomly generated name is not already used
+		do
+		{
+			if (existedDesk)
+			{
+				CloseDesktop (existedDesk);
+				existedDesk = NULL;
+			}
+			if (GenerateRandomString (hWndParent, szDesktopName, 64))
+			{
+				existedDesk = OpenDesktop (szDesktopName, 0, FALSE, GENERIC_READ);
+				if (!existedDesk)
+				{
+					bRandomNameGenerated = TRUE;
+				}
+			}
+		} while (existedDesk);
+
+		if (bRandomNameGenerated)
 		{
 			map<DWORD, BOOL> ctfmonBeforeList, ctfmonAfterList;
-			DWORD desktopAccess = DESKTOP_CREATEMENU | DESKTOP_CREATEWINDOW | DESKTOP_READOBJECTS | DESKTOP_SWITCHDESKTOP | DESKTOP_WRITEOBJECTS;
+			HDESK hOriginalDesk = NULL;
-			HDESK hSecureDesk;
+			SecureDesktopThreadParam param;
-			HDESK hOriginalDesk = GetThreadDesktop (GetCurrentThreadId());
 
-			HDESK hInputDesk = NULL;
 
 			// wait for the input desktop to be available before switching to 
 			// secure desktop. Under Windows 10, the user session can be started
@@ -14005,65 +14036,62 @@ INT_PTR SecureDesktopDialogBoxParam(
 			// case, we wait for the user to be really authenticated before starting 
 			// secure desktop mechanism
 
-			while (!(hInputDesk = OpenInputDesktop (0, TRUE, GENERIC_READ)))
+			while (!(hOriginalDesk = OpenInputDesktop (0, TRUE, GENERIC_ALL)))
 			{
 				Sleep (SECUREDESKTOP_MONOTIR_PERIOD);
 			}
-
-			CloseDesktop (hInputDesk);
 		
 			// get the initial list of ctfmon.exe processes before creating new desktop
 			GetCtfMonProcessIdList (ctfmonBeforeList);
 
-			hSecureDesk = CreateDesktop (szDesktopName, NULL, NULL, 0, desktopAccess, NULL);
+			param.hDesk = NULL;
-			if (hSecureDesk)
+			param.szDesktopName = szDesktopName;
+			param.hInstance = hInstance;
+			param.lpTemplateName = lpTemplateName;
+			param.lpDialogFunc = lpDialogFunc;
+			param.dwInitParam = dwInitParam;
+			param.retValue = 0;
+			param.bDlgDisplayed = FALSE;
+
+			// use _beginthreadex instead of CreateThread because lpDialogFunc may be using the C runtime library
+			HANDLE hThread = (HANDLE) _beginthreadex (NULL, 0, SecureDesktopThread, (LPVOID) &param, 0, NULL);
+			if (hThread)
 			{
-				SecureDesktopThreadParam param;
+				WaitForSingleObject (hThread, INFINITE);
-	
+				CloseHandle (hThread);
-				param.hDesk = hSecureDesk;
-				param.szDesktopName = szDesktopName;
-				param.hInstance = hInstance;
-				param.lpTemplateName = lpTemplateName;
-				param.lpDialogFunc = lpDialogFunc;
-				param.dwInitParam = dwInitParam;
-				param.retValue = 0;
-				param.bDlgDisplayed = FALSE;
 
-				// use _beginthreadex instead of CreateThread because lpDialogFunc may be using the C runtime library
+				if (param.bDlgDisplayed)
-				HANDLE hThread = (HANDLE) _beginthreadex (NULL, 0, SecureDesktopThread, (LPVOID) &param, 0, NULL);
-				if (hThread)
 				{
-					StringCbCopy(SecureDesktopName, sizeof (SecureDesktopName), szDesktopName);
+					// dialog box was indeed displayed in Secure Desktop
+					retValue = param.retValue;
+					bSuccess = TRUE;
+				}
+			}
 
-					WaitForSingleObject (hThread, INFINITE);
+			if (param.hDesk)
-					CloseHandle (hThread);
+			{	
-
+				while (!SwitchDesktop (hOriginalDesk))
-					if (param.bDlgDisplayed)
+				{
-					{
+					Sleep (SECUREDESKTOP_MONOTIR_PERIOD);
-						// dialog box was indeed displayed in Secure Desktop
-						retValue = param.retValue;
-						bSuccess = TRUE;
-					}
-
-					// switch back to original desktop
-					SwitchDesktop (hOriginalDesk);
 				}
 
-				CloseDesktop (hSecureDesk);
+				SetThreadDesktop (hOriginalDesk);
 
-				// get the new list of ctfmon.exe processes in order to find the ID of the
+				CloseDesktop (param.hDesk);
-				// ctfmon.exe instance that corresponds to the desktop we create so that
+			}
-				// we can kill it, otherwise it would remain running
-				GetCtfMonProcessIdList (ctfmonAfterList);
 
-				for (map<DWORD, BOOL>::iterator It = ctfmonAfterList.begin(); 
+			// get the new list of ctfmon.exe processes in order to find the ID of the
-					It != ctfmonAfterList.end(); It++)
+			// ctfmon.exe instance that corresponds to the desktop we create so that
+			// we can kill it, otherwise it would remain running
+			GetCtfMonProcessIdList (ctfmonAfterList);
+
+			for (map<DWORD, BOOL>::iterator It = ctfmonAfterList.begin(); 
+				It != ctfmonAfterList.end(); It++)
+			{
+				if (ctfmonBeforeList[It->first] != TRUE)
 				{
-					if (ctfmonBeforeList[It->first] != TRUE)
+					// Kill process
-					{
+					KillProcess (It->first);
-						// Kill process
-						KillProcess (It->first);
-					}
 				}
 			}