Autenticação usando somente Routes

Route::group(array('before' => 'auth'), function(){
    Route::controller(Controller::detect());
});


Route::get('login', function(){
    return View::make('dashboard.login');
});

Route::post('login', function(){
    $userinfo = array(
        'username' => Input::get('login'),
        'password' => Input::get('senha')
    );

    if(Auth::attempt($userinfo))
        return Redirect::to('/');
    else
        return Redirect::to('login')
            ->with('login_errors', true);
});

Route::get('logout', function(){
    Auth::logout();
    return Redirect::to('/');
});

Route::filter('auth', function()
{
    if (Auth::guest()) {
        return Redirect::to('login');
    }
});