How lock CTRL+ALT+DEL using SetWindowHookEx api? - delphi

Question

Good afternoon,
I need lock CTRL+ALT+DEL combination using SetWindowsHookEx and today i have done a code and don't is working until now.
This code is executing in a dll ( this dll is my software ) that is injected in other process.
So, how i can adapt this code below to work?
const
WH_KEYBOARD_LL = 13;
LLKHF_ALTDOWN = $20;
type
KBDLLHOOKSTRUCT = record
vkCode: DWORD;
scanCode: DWORD;
flags: DWORD;
time: DWORD;
dwExtraInfo: Longint ;
end;
var
hhkLowLevelKybd : HHOOK;
FoldProc : LongInt;
hSASWnd : HWND;
hThread : Cardinal;
{$R *.dfm}
Function LowLevelKeyboardProc(nCode : Integer; wParam : Longint; var LParam: KBDLLHOOKSTRUCT) : Longint; stdcall;
var
fEatKeystroke : Boolean;
dwThreadId : Cardinal;
begin
If (nCode = HC_ACTION) Then
begin
If (wParam = WM_KEYDOWN) Or
(wParam = WM_SYSKEYDOWN) Or
(wParam = WM_KEYUP) Or
(wParam = WM_SYSKEYUP) Then
begin
fEatKeystroke :=
(((GetKeyState(VK_CONTROL) And $8000) <> 0) And
((LParam.flags And LLKHF_ALTDOWN ) <> 0) And
(LParam.vkCode = VK_DELETE));
End;
If fEatKeystroke Then
Result := -1
Else
Result := CallNextHookEx(0, nCode, wParam, LongInt(#LParam));
End;
end;
////////// FormCreate event here ///////////
hhkLowLevelKybd := 0;
hhkLowLevelKybd := SetWindowsHookEx(WH_KEYBOARD_LL, #LowLevelKeyboardProc,
HInstance, 0);
end.

Answer 1

Windows does not allow you to intercept Ctrl+Alt+Del for security reasons. Earlier versions (pre-Vista?) used to allow it by replacing the GINA DLL, but it's not been allowed for years.
That key combination is known as a secure attention sequence which is guaranteed to be trustworthy as part of the login process.
If your goal is to only allow your application to be run, you can configure it to act in kiosk mode if you're running a suitable version of Windows, as shown in Set up a device for anyone to use (kiosk mode) at TechNet which #LURD kindly provided.

Answer 2

By design it's impossible to trap or block Ctrl+Alt+Del (The Secure Attention Sequence). There is however a commercial library available (disclaimer: I am the author), SasLibEx.
SasLibEx: a library that can simulate or block the Secure Attention
Sequence (Ctrl+Alt+Del) but it can even unlock a
workstation or session without entering or needing the user’s
credentials (and many more things)
See this screencast for a demo.

Answer 3

Impossible. The Ctl-Alt-Del gets trapped in the Kernel and never makes it to the user mode space where your app is running.
I have had to do this on kiosks systems (using Win XP and Vista) and I did it with a keyboard filter driver (which runs in the kernel) that swaps out the scan codes when the key are pressed.

Answer 4

Not is impossible, see the following code:
program Project1;
{$APPTYPE CONSOLE}
{$R *.res}
uses
SysUtils,
Windows,
Registry,
vcl.Dialogs;
procedure DisableCtrAltDel(boolState: Boolean);
var
SystemReg: TRegistry;
Data: Array [1 .. 48] of Byte;
i: Byte;
begin
try
for i := 1 to 48 do
Data[i] := $00;
Data[9] := $09;
Data[15] := $5B;
Data[16] := $E0;
Data[19] := $5C;
Data[20] := $E0;
Data[23] := $5D;
Data[24] := $E0;
Data[27] := $44;
Data[31] := $1D;
Data[35] := $38;
Data[39] := $1D;
Data[40] := $E0;
Data[43] := $38;
Data[44] := $E0;
try
SystemReg := TRegistry.Create;
with SystemReg do
begin
RootKey := HKEY_LOCAL_MACHINE;
OpenKey('\System\CurrentControlSet\Control\Keyboard Layout', True);
if boolState then
WriteBinaryData('Scancode Map', Data, SizeOf(Data))
else
DeleteValue('Scancode Map');
MessageDlg('Restart Windows in order the changes to take effect!',
mtInformation, [mbOK], 0);
CloseKey;
end;
finally
SystemReg.Free;
end;
except
MessageDlg
('Error occurred while trying to disable ctrl+alt+del and Task Manager',
mtWarning, [mbOK], 0);
end;
end;
begin
try
DisableCtrAltDel(True);
except
on E: Exception do
Writeln(E.ClassName, ': ', E.Message);
end;
end.
Reference