Lab 7: Using Burp Suite to Intercept Client-Side Requests

Objective

Learn how to use Burp Suite, a powerful web application security testing tool, to intercept and analyze HTTP/S requests between a client (browser) and a server. This lab demonstrates how attackers and penetration testers can inspect and manipulate traffic.

Prerequisites

1. Kali Linux or Any Linux Distro with Burp Suite Installed:
   • Verify Burp Suite is installed:

     burpsuite --version
     

   • Install it if necessary:

     sudo apt update && sudo apt install burpsuite
     

2. Web Browser:
   • Install a browser extension or configure your browser to work with Burp Suite as a proxy (e.g., Firefox or Chrome).
3. Basic Understanding of HTTP Requests and Responses:
   • Familiarity with GET, POST, headers, and cookies is helpful.

Step 1: Launching Burp Suite

1. Open Burp Suite from your terminal or application menu:

   burpsuite
   

2. Select Temporary Project and click Next.
3. Choose the Use Burp Defaults option and click Start Burp.
4. Once Burp Suite is open, navigate to the Proxy tab and ensure the Intercept sub-tab is selected.

Step 2: Configuring Your Browser to Use Burp as a Proxy

1. Open your browser’s network settings.
2. Configure the proxy settings to match Burp Suite’s default settings:
   • HTTP Proxy: 127.0.0.1
   • Port: 8080

3. Disable proxy for localhost (if applicable).

4. Install Burp’s CA certificate:
   • Navigate to http://burp in your browser.

   • Download and install the Burp CA certificate to ensure HTTPS requests are intercepted properly.

   • Tip: Installing the certificate enables Burp to decrypt and inspect HTTPS traffic.

Step 3: Intercepting Requests

1. Open a website in your browser (e.g., http://example.com).
2. Check the Proxy > Intercept tab in Burp Suite:
   • The HTTP request will appear here, waiting for your action.
3. Modify or forward the request:
   • Click Forward to send the request to the server as is.

   • Click Drop to discard the request.

   • Insight: Modifying requests allows you to test how the server handles unexpected or malicious input.

Step 4: Using the HTTP History Tab

1. Navigate to the HTTP history tab under Proxy.
2. View all intercepted requests and responses:

   • Click on a request to inspect details like headers, parameters, and body.

   • Tip: Use this tab to analyze how data flows between the client and server.

Step 5: Repeating and Testing Requests

1. Right-click on a request in the HTTP history and select Send to Repeater.
2. Navigate to the Repeater tab.
3. Modify the request as needed and click Send.
4. Review the response:
   • Test how the server reacts to different inputs.
   • Insight: Repeater is invaluable for testing vulnerabilities like SQL injection and XSS.

Step 6: Automating Testing with Burp Scanner

1. Send a request to the Scanner by right-clicking on it in the HTTP history.
2. Navigate to the Scanner tab to view scan results.
3. Analyze potential vulnerabilities identified by Burp, such as:
   • SQL injection.
   • Cross-site scripting (XSS).

   • Insecure cookies.

   • Tip: The Scanner is part of Burp Suite Professional, so free users may have limited functionality.

Step 7: Cleaning Up

1. Disable the proxy in your browser settings when you’re done.
2. Close Burp Suite to terminate the proxy server.
3. Remove the Burp CA certificate if it was installed temporarily.

Additional Tips and Insights

1. Ethical Use:
   • Only intercept and test traffic for applications you own or have explicit permission to test.
   • Insight: Unauthorized interception of traffic is illegal and unethical.
2. Advanced Features:
   • Explore other tools in Burp Suite, such as the Intruder (for automated attacks) and Sequencer (for analyzing randomness).
3. HTTPS Troubleshooting:
   • If HTTPS traffic is not intercepted, double-check the proxy configuration and CA certificate installation.
4. Filter Traffic:
   • Use filters in the Proxy tab to focus on specific requests or exclude irrelevant traffic.

Key Takeaways

1. Burp Suite is a powerful tool for analyzing and manipulating HTTP/S traffic.
2. Interception allows you to understand and test how web applications handle client requests.
3. Responsible use and adherence to ethical guidelines are critical for using Burp Suite effectively.