Internal Fake Discussion: Penetration Test Guide

I. Information Gathering: The Foundation of a Successful Pentest

1. Host Discovery and Port Scanning: Unveiling the Attack Surface

In the information gathering stage of a penetration test, the initial steps are crucial. We begin by identifying active hosts on the local network and then determining which services they offer. For this host discovery and port scanning process, we employ tools like arp-scan and nmap. These tools help us map the target's attack surface. Guys, let's dive into the nitty-gritty details.

Host Discovery with arp-scan:

The first tool in our arsenal is arp-scan. This utility broadcasts ARP (Address Resolution Protocol) requests across the network. It then listens for responses, allowing us to identify live hosts and their corresponding IP addresses. In our case, using arp-scan revealed the target host's IP address as 192.168.205.136. This is a critical first step, as it gives us a specific target to focus on.

┌──(kali㉿kali)-[~]
└─$ sudo arp-scan -l
...
192.168.205.136 08:00:27:f7:e4:36 PCS Systemtechnik GmbH
...

Port Scanning with nmap:

With the target IP in hand, we move on to the next phase: port scanning. Here, we utilize nmap, a powerful and versatile network scanning tool. nmap allows us to probe the target host for open ports and identify the services running on them. This provides valuable insights into potential vulnerabilities. We initiate a full port scan, checking all 65535 ports to ensure we don't miss anything. The results show that ports 22 (SSH) and 80 (HTTP) are open. This immediately suggests potential avenues for attack, such as attempting to exploit SSH vulnerabilities or exploring the web service running on port 80.

┌──(kali㉿kali)-[~]
└─$ nmap -p- 192.168.205.136
...
PORT STATE SERVICE
22/tcp open ssh
80/tcp open http
...

The discovery of open SSH and HTTP ports is significant. SSH (Secure Shell) is commonly used for remote administration, and misconfigurations or weak credentials can lead to unauthorized access. HTTP, on the other hand, indicates the presence of a web server, which opens up a whole new realm of potential vulnerabilities, such as web application flaws or misconfigured server settings. Remember, a thorough reconnaissance is the backbone of any successful penetration test, providing the necessary information to plan and execute the next steps effectively. Keep those scans running, guys!

2. Web Service Reconnaissance: Digging Deeper into Port 80

Having identified an open HTTP port (80), the next logical step in our penetration testing journey is to delve deeper into the web service. This web service reconnaissance involves analyzing the website's content, structure, and behavior to uncover potential vulnerabilities or valuable information. This phase is critical because web applications are often a prime target for attackers, given their complexity and the potential for various security flaws. So, let's get started, folks!

Initial Website Analysis:

Our initial approach involves simply browsing the website hosted on port 80. We observe that it appears to be a standard website template. While this might seem unremarkable at first glance, even basic templates can inadvertently expose sensitive information or contain hidden vulnerabilities. What's important is to leave no stone unturned, guys. This is just the beginning.

Source Code Review for Hidden Clues:

Next, we dive into the website's source code. This is a crucial step, as developers sometimes leave comments or other artifacts that can provide valuable clues. In this case, our diligence pays off. While examining the HTML source, we stumble upon a critical comment: <!-- Pay attention to listen 12345 -->. This comment is a goldmine, strongly suggesting that the target host might be using UDP port 12345 to transmit some kind of data or service. Such a hint can drastically alter our attack strategy, so let's hold onto that, guys!

<!-- Pay attention to listen 12345 -->

Implications of the UDP Port Hint:

The discovery of this comment is significant because it hints at a less common, and potentially less secure, communication channel. UDP (User Datagram Protocol) is a connectionless protocol, meaning that data is sent without establishing a persistent connection. This can make it faster but also less reliable than TCP (Transmission Control Protocol), which is used by HTTP. The fact that the comment explicitly mentions listening on UDP 12345 implies that there might be a service or application on the target host that we can interact with. It could be anything from a custom service broadcasting information to a misconfigured application leaking sensitive data.

This crucial piece of information now guides our next steps. We'll need to investigate UDP port 12345 further, likely using tools that can capture and analyze network traffic, such as tcpdump or Wireshark. This is how a seemingly innocuous comment can become a pivotal point in a penetration test. So, always keep those eyes peeled for hints, guys! They're often hidden in plain sight.

II. Initial Access: Exploiting the Weakest Link

1. Discovering and Capturing the SSH Private Key Leak: A Critical Vulnerability

The previous step's web service reconnaissance pointed us towards a potentially exposed UDP port 12345. Now, our focus shifts to exploiting this lead. The goal here in discovering and capturing the SSH private key leak is to intercept any traffic on this port, hoping to uncover sensitive information. This is a high-stakes game because an SSH private key provides direct access to the target system, bypassing traditional password authentication. So, let's get our hands dirty, guys!

Using tcpdump to Monitor UDP Traffic:

Based on the comment found in the web source code, we suspect that the target host might be broadcasting data on UDP port 12345. To confirm this, we employ tcpdump, a powerful command-line packet analyzer. tcpdump allows us to capture and inspect network traffic in real-time. We set it up to listen specifically for traffic originating from the target host (192.168.205.136) on UDP port 12345. The -A flag tells tcpdump to display the captured data in ASCII format, which is essential for identifying human-readable information like SSH keys.

┌──(kali㉿kali)-[~]
└─$ sudo tcpdump -A host 192.168.205.136 and port 12345
...
-----BEGIN OPENSSH PRIVATE KEY-----
b3BlbnNzaC1rZXktdjEAAAAACmFlczI1Ni1jdHIAAAAGYmNyeXB0AAAAGAAAABDli31tjr
...

The Revelation: An Encrypted SSH Private Key:

Our patience pays off! The tcpdump output reveals a treasure trove: the beginning of an OpenSSH private key. The -----BEGIN OPENSSH PRIVATE KEY----- marker clearly indicates that we've intercepted a critical piece of authentication material. However, the key appears to be encrypted (aes256-ctr), meaning it's protected by a passphrase. This is a setback, but not a defeat. We now know that we need to crack the passphrase to use the key. The key point here is the need to decrypt before using the key, guys!

Addressing tcpdump Limitations with Wireshark:

It's important to note a potential pitfall: tcpdump can sometimes struggle with fragmented UDP packets. If the private key is transmitted in multiple packets, tcpdump might not reassemble them correctly, leading to an incomplete capture. This is where Wireshark, a graphical network protocol analyzer, comes to the rescue. Wireshark offers a powerful feature called