https://blog.wongcw.com/2018/10/25/ios-12-%e5%b0%81%e6%9d%80-graykey-%e7%a0%b4%e8%a7%a3%e9%bb%91%e7%9b%92%e5%ad%90-%e4%bd%86%e4%b8%8d%e7%9f%a5%e4%bc%9a%e5%9d%9a%e6%8c%81%e5%a4%9a%e4%b9%85/