Delphi: Prompt for UAC elevation when needed

Question

We need to change some settings to the HKEY_LOCAL_MACHINE at runtime.

Is it possible to prompt for uac elevation if needed at runtime, or do I have to launch a second elevated process to do 'the dirty work'?

Answer 1

i would relaunch yourself as elevated, passing command line parameters indicating what elevated thing you want to do. You can then jump right to the appropriate form, or just save your HKLM stuff.

function RunAsAdmin(hWnd: HWND; filename: string; Parameters: string): Boolean;
{
    See Step 3: Redesign for UAC Compatibility (UAC)
    http://msdn.microsoft.com/en-us/library/bb756922.aspx

    This code is released into the public domain. No attribution required.
}
var
    sei: TShellExecuteInfo;
begin
    ZeroMemory(@sei, SizeOf(sei));
    sei.cbSize := SizeOf(TShellExecuteInfo);
    sei.Wnd := hwnd;
    sei.fMask := SEE_MASK_FLAG_DDEWAIT or SEE_MASK_FLAG_NO_UI;
    sei.lpVerb := PChar('runas');
    sei.lpFile := PChar(Filename); // PAnsiChar;
    if parameters <> '' then
        sei.lpParameters := PChar(parameters); // PAnsiChar;
    sei.nShow := SW_SHOWNORMAL; //Integer;

    Result := ShellExecuteEx(@sei);
end;

The other Microsoft suggested solution is to create an COM object out of process (using the specially created CoCreateInstanceAsAdmin function). i don't like this idea because you have to write and register a COM object.

---

Note: There is no "CoCreateInstanceAsAdmin" API call. It's just some code floating around. Here's the Dephi version i stumbled around for. It is apparently based on the trick of prefixing a class guid string with the "Elevation:Administrator!new:" prefix when normally hidden code internally calls CoGetObject:

function CoGetObject(pszName: PWideChar; pBindOptions: PBindOpts3; 
      const iid: TIID; ppv: PPointer): HResult; stdcall; external 'ole32.dll';

procedure CoCreateInstanceAsAdmin(const Handle: HWND; 
      const ClassID, IID: TGuid; PInterface: PPointer);
var
   BindOpts: TBindOpts3;
   MonikerName: WideString;
   Res: HRESULT;
begin
   //This code is released into the public domain. No attribution required.
   ZeroMemory(@BindOpts, Sizeof(TBindOpts3));
   BindOpts.cbStruct := Sizeof(TBindOpts3);
   BindOpts.hwnd := Handle;
   BindOpts.dwClassContext := CLSCTX_LOCAL_SERVER;

   MonikerName := 'Elevation:Administrator!new:' + GUIDToString(ClassID);

   Res := CoGetObject(PWideChar(MonikerName), @BindOpts, IID, PInterface);
   if Failed(Res) then 
      raise Exception.Create(SysErrorMessage(Res));
end;

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One other question: How do you handle someone running as standard user in Windows XP?