Burp Suite: Firefox Portal Detection

TL;DR

This guide shows you how to configure Burp Suite to properly intercept traffic from Firefox when using a portal (like a web application login page). It addresses issues where Burp might not detect the browser or correctly proxy connections.

Configuring Burp Suite for Firefox Portal Detection

1. Install the Burp Suite CA Certificate in Firefox:
   • Open Firefox.
   • Type about:preferences#privacy into the address bar and press Enter.
   • Scroll down to ‘Certificates’ and click ‘View Certificates’.
   • Select the ‘Authorities’ tab.
   • Click ‘Import…’.
   • Browse to where you saved the Burp Suite CA certificate (usually in your Burp Suite installation directory under cacert.pem).
   • Check the box ‘Trust this CA for identifying websites’. Crucially, also check the box ‘Trust this CA for email’. This is often missed but important for some portal setups.
   • Click ‘OK’ and close the Certificate Manager.
2. Configure Firefox to use Burp Suite as a Proxy:
   • Type about:preferences#general into the address bar and press Enter.
   • Scroll down to ‘Network Settings’ and click ‘Settings…’.
   • Select ‘Manual proxy configuration’.
   • Enter the following:
     • HTTP Proxy: 127.0.0.1
     • Port: 8080 (or your Burp Suite port)
     • Check ‘Use this proxy server for all protocols’.
     • Add an exception for localhost/127.0.0.1 to bypass the proxy if needed.
   • Click ‘OK’ and close the Connection Settings window.
3. Verify Burp Suite is Intercepting Traffic:
   • Open Burp Suite.
   • Go to the ‘Proxy’ tab, then the ‘HTTP History’ sub-tab.
   • Browse to a website (e.g., http://example.com) in Firefox.
   • If you see traffic appearing in Burp Suite’s HTTP History, your proxy is working correctly.
4. Address Automatic Proxy Configuration Issues:
   • Some portals use automatic proxy configuration (PAC) files. If Burp isn’t intercepting traffic after steps 1 & 2, check if Firefox is using a PAC file.

     about:config

     Search for ‘network.proxy.pac_url’. If a URL is present, temporarily disable the PAC file by setting it to an empty string (double-click the preference and enter nothing).

5. Check Burp Suite’s Browser Settings:
   • In Burp Suite, go to ‘Proxy’ > ‘Options’.
   • Under ‘Browser Support’, ensure Firefox is listed and enabled.
   • If it isn’t automatically detected, try manually adding the Firefox executable path.
6. Restart Firefox:

   After making changes to proxy settings or Burp Suite configuration, restart Firefox completely (close all windows and processes) for the changes to take effect.