Ah, Burp Suite - the Swiss Army knife of web security testing. But what happens when your favorite multi-tool needs a custom blade? You forge one yourself! In this guide, we’ll turn you from extension newbie to Python-powered Burp wizard faster than you can say “HTTP/2 Rapid Reset.”

The Bare Bones: Your First Extension

Let’s start with the “Hello World” of Burp extensions. Create buttify.py (you’ll get the joke soon):

from burp import IBurpExtender
class BurpExtender(IBurpExtender):
    def registerExtenderCallbacks(self, callbacks):
        callbacks.setExtensionName("Butt Maker 9000")
        print("Our quest to butt-ify the web begins!")

Load it in Burp via Extensions → Installed → Add (Python type). If you see our majestic message in the Output tab - congratulations! You’ve just created something 97% of security testers haven’t. Pat yourself on the back with one hand while clicking “Next” with the other.

Anatomy of a Burp Extension

graph TD A[Burp Suite] --> B[Python Interpreter] B --> C[Your Extension Code] C --> D[Burp API] D -->|Callbacks| A A -->|HTTP Traffic| C

This beautiful symbiotic relationship lets you meddle with web traffic like a digital puppeteer. The secret sauce? Burp’s API gives you hooks into:

  • HTTP requests/responses
  • Scanner functionality
  • Proxy history
  • Site maps
  • And more!

Making It Useful: Let’s Break the Internet

Remember that time your manager said “Can you make the cloud go away?” Let’s literally make it happen by replacing “cloud” with “butt” in all HTTP responses:

from burp import IBurpExtender, IHttpListener
class BurpExtender(IBurpExtender, IHttpListener):
    def registerExtenderCallbacks(self, callbacks):
        self._helpers = callbacks.getHelpers()
        callbacks.setExtensionName("Cloud-to-Butt Translator")
        callbacks.registerHttpListener(self)
    def processHttpMessage(self, tool, is_request, message):
        if not is_request:
            response = message.getResponse()
            modified_response = self._helpers.bytesToString(response).replace("cloud", "butt")
            message.setResponse(self._helpers.stringToBytes(modified_response))

Now visit any cloud-heavy site through Burp Proxy and behold - your private butt computing revolution! (Legal disclaimer: Please don’t actually use this in production. Or do. I’m not your mum.)

Pro Tips From the Trenches

1. The 3 AM Debugging Session Saver:

# Always include error handling unless you enjoy midnight support calls
try:
    your_risky_code()
except Exception as e:
    print(f"💥 Critical failure: {str(e)}")
    traceback.print_exc(file=sys.stdout)

2. Secret Sauce for API Testing:

from burp import IParameter
def analyze_parameters(parameters):
    for param in parameters:
        if param.getType() == IParameter.PARAM_JSON:
            print(f"Found JSON param: {param.getName()}")
            # Insert your JSON fuzzing logic here

3. The “Why Is This Not Built-In?” Feature:

from burp import IContextMenuFactory
class PwnMenu(IContextMenuFactory):
    def createMenuItems(self, invocation):
        menu = []
        if invocation.getInvocationContext() == 1:  # Message editor context
            menu.append(JMenuItem("Send to Hackulator", 
                lambda e: self.sendToHackulator(invocation)))
        return menu
    def sendToHackulator(self, invocation):
        # Your custom processing logic here
        print("Hackulating... because that's totally a word")

When Things Go Boom: Debugging 101

  1. Check the Errors tab - it’s like reading tea leaves, but for nerds
  2. Use print() statements liberally - the console is your confessional
  3. Remember: Python indentation errors have claimed more souls than Heartbleed
graph LR A[Extension Fails] --> B{Errors Tab} B -->|Yes| C[Fix Python Syntax] B -->|No| D{Print Debugging} D -->|Silent| E[Check Stdlib Imports] D -->|Noise| F[Follow Data Flow]

From Script Kiddie to Extension Jedi

Now that you’ve got the basics down, here’s how to level up:

  1. Hook into Scanner - Automate vulnerability detection
  2. Implement ISessionHandlingAction - Deal with those pesky auth tokens
  3. Create Custom Intruder Payloads - Because guessing is for amateurs
  4. Integrate with External Tools - Make OWASP ZAP cry in jealousy Remember: With great power comes great responsibility. Or in our case, great opportunities to accidentally DDoS yourself. Happy hacking!
# Final pro tip: Always include an easter egg
def registerExtenderCallbacks(self, callbacks):
    if datetime.now().month == 4:
        print("All your base are belong to us")