建立一个模拟数据库来存储你的登录用户名、密码，密码通过salt加密，然后能统计错误登录次数、密码衰老期、防止密码猜测，同时根据你的uid权限来启动shell

-The establishment of a simulation of a database to store your login usernames, passwords, password encryption salt, and then log on to the number of statistical error, password aging period, to prevent password guessing and at the same time based on your uid privileges to start shell