ACTF2020新生赛-BackupFile

 · 2020-7-10  ·次阅读


题目地址:buuctf

1

让我们尝试找源文件,在index.php.bak得到源文件

<?php
include_once "flag.php";

if(isset($_GET['key'])) {
    $key = $_GET['key'];
    if(!is_numeric($key)) {
        exit("Just num!");
    }
    $key = intval($key);
    $str = "123ffwsfwefwf24r2f32ir23jrw923rskfjwtsw54w3";
    if($key == $str) {
        echo $flag;
    }
}
else {
    echo "Try to find out source file!";
}

要求我们传入key值,key值只能是数字,并且key值等于123ffwsfwefwf24r2f32ir23jrw923rskfjwtsw54w3才能得到flag

PHP作为弱类型语言,当字符串与整型值比较时,字符串先转换成整型,然后再比较,也就是说只要key=123就能满足。

index.php?key=123得到flag