BUUCTF [ACTF2020 新生赛]BackupFile 1

BUUCTF [ACTF2020 新生赛]BackupFile 1

• 通过url后+index.php.bak 得到网站源码：

include_once "flag.php";
//get传参key 并判断key存在向下运行
if(isset($_GET['key'])) {

    $key = $_GET['key'];
   //如果不是数字 则退出
    if(!is_numeric($key)) {
        exit("Just num!");
    }
    //intval 获取整数值
    $key = intval($key);
    $str = "123ffwsfwefwf24r2f32ir23jrw923rskfjwtsw54w3";
    //即是$key==123
    if($key == $str) {
        echo $flag;
    }
}
else {
    echo "Try to find out source file!";
}

• url输出：?key=123
•