BUUCTF:https://buuoj.cn/challenges

题目描述：
得到的 flag 请包上 flag{} 提交。

密文：
下载附件，得到一个.png图片。

---

解题思路：
1、使用QR research扫一下，得到“swpuctf{flag_is_not_here}”的提示。

2、放到010 Editor中看一下，没找到什么明显的特征。使用Kali中的binwalk工具进行检测，发现四个rar压缩包。

使用binwalk加上“-e”参数，直接分离rar压缩包。

binwalk -e BitcoinPay.png
#如果出现报错，可以尝试在命令后加上“--run-as=root”参数
binwalk -e BitcoinPay.png --run-as=root

解压三个没有密码的压缩包，得到encode.txt、flag.doc、flag.jpg还有一个rar压缩包。有两个压缩包提示需要密码，暂时无法解压。

3、先看encode.txt文件，打开发现是经过Base64加密的密文，使用在线工具解密，得到明文。

BASE64加密解密

YXNkZmdoamtsMTIzNDU2Nzg5MA==

asdfghjkl1234567890

4、再看flag.doc文件，打开发现也是Base家族，不过这个要循环解密很多次。我是使用工具不断复制粘贴解出明文的，后面找到一个Python脚本可以更快的完成这个任务。

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

Python脚本如下：

import re
from base64 import b64decodedef process_data(data):try:# 删除包含'flag'或汉字字符的部分data = re.sub(r'flag|[一-龥]', '', data)# 进行Base64解码decoded_data = b64decode(data)return decoded_data.decode(), Trueexcept:# 如果无法解码，返回原始数据和False表示无法继续解码return data, False# 读取文本文件内容
with open('flag.txt', 'r', encoding='utf-8') as file:data = file.read()iterations = 0# 循环处理数据，直到无法继续解码
while True:data, can_decode = process_data(data)iterations += 1
# 如果无法继续解码，输出结果并结束循环if not can_decode:print("最终结果:", data)print("循环次数:", iterations)break

comEON_YOuAreSOSoS0great

5、分别用解出的两个明文去解压两个需要密码的rar压缩包，得到两个文件夹。good文件夹内有一个.mp3文件，另一个文件夹内有一张出现过的图片flag.jpg。

先看good.mp3文件，得到一个音频，放到Audacity看看。
放大后看到一串音频，有很多分组，分组内由粗的音块和细的音块组成，类似莫尔斯电码的“-”和“.”。

举例如下图。按照这样的对应将音轨上的分组全部转译为莫尔斯电码，分组之间用空格填充，转换为“-- — .-. … . … … …- . .-. -.-- …- . .-. -.-- . .- … -.–”

-- --- .-. ... . .. ... ...- . .-. -.-- ...- . .-. -.-- . .- ... -.--

使用在线网站，将莫尔斯电码转换为明文字符，将得到的明文转换为小写，作为flag值提交。
在线摩斯密码翻译器
字母大小写转换工具

6、至于那两张重复的图片，似乎和开始的那个二维码一样，是烟雾弹。（这道题真是一堆东西，睡觉去了！@_@）

flag：

flag{morseisveryveryeasy}