Require an uninstallation password

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Some Inno Setup users require that the user who wants to uninstall the software is asked for a password before this is possible. Anti virus software might be a candidate for this requirement, for instance.

The code below shows how to create a form, ask for a password, and uninstall the software only if the password is correct.

This method is very weak, it's easy to find out the password. So, someone who wants to use this strategy to protect his software from uninstallation needs to code something safer. If the user wants to uninstall and doesn't know the password files could be deleted anyway from the application's folder. In this sample the uninstall password is removeme.

[Setup]
AppName=UninsPassword
AppVerName=UninsPassword
DisableProgramGroupPage=true
DisableStartupPrompt=true
DefaultDirName={pf}\UninsPassword

[Code]
function AskPassword(): Boolean;
var
  Form: TSetupForm;
  OKButton, CancelButton: TButton;
  PwdEdit: TPasswordEdit;
begin

  Result := false;
  Form := CreateCustomForm();
  try
    Form.ClientWidth := ScaleX(256);
    Form.ClientHeight := ScaleY(100);
    Form.Caption := 'Uninstall Password';
    Form.BorderIcons := [biSystemMenu];
    Form.BorderStyle := bsDialog;
    Form.Center;

    OKButton := TButton.Create(Form);
    OKButton.Parent := Form;
    OKButton.Width := ScaleX(75);
    OKButton.Height := ScaleY(23);
    OKButton.Left := Form.ClientWidth - ScaleX(75 + 6 + 75 + 50);
    OKButton.Top := Form.ClientHeight - ScaleY(23 + 10);
    OKButton.Caption := 'OK';
    OKButton.ModalResult := mrOk;
    OKButton.Default := true;

    CancelButton := TButton.Create(Form);
    CancelButton.Parent := Form;
    CancelButton.Width := ScaleX(75);
    CancelButton.Height := ScaleY(23);
    CancelButton.Left := Form.ClientWidth - ScaleX(75 + 50);
    CancelButton.Top := Form.ClientHeight - ScaleY(23 + 10);
    CancelButton.Caption := 'Cancel';
    CancelButton.ModalResult := mrCancel;
    CancelButton.Cancel := True;

    PwdEdit := TPasswordEdit.Create(Form);
    PwdEdit.Parent := Form;
    PwdEdit.Width := ScaleX(210);
    PwdEdit.Height := ScaleY(23);
    PwdEdit.Left := ScaleX(23);
    PwdEdit.Top := ScaleY(23);

    Form.ActiveControl := PwdEdit;

    if Form.ShowModal() = mrOk then
    begin
      Result := PwdEdit.Text = 'removeme';
      if not Result then
            MsgBox('Password incorrect: Uninstallation prohibited.', mbInformation, MB_OK);
    end;
  finally
    Form.Free();
  end;
end;


function InitializeUninstall(): Boolean;
begin
  Result := AskPassword();
end;
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