WebRTC Leak

Understanding WebRTC Leak in Proxy Networks

WebRTC, or Web Real-Time Communication, is a powerful technology that enables peer-to-peer audio, video, and data sharing directly between browsers. While it fuels a plethora of applications—from video conferencing to file sharing—its implementation can inadvertently expose users’ real IP addresses, even when they are utilizing proxy networks or VPNs. This phenomenon is what we term a WebRTC Leak.

What is a WebRTC Leak?

At a technical level, a WebRTC Leak occurs when the WebRTC API retrieves the user's local and public IP addresses and makes them accessible to web applications. This can happen regardless of the user's active connection to a proxy or VPN, undermining the very privacy protections those networks are meant to provide. When a web application, such as a video conferencing platform, initiates a connection, it can use the ICE (Interactive Connectivity Establishment) framework to discover the best path for peer-to-peer communication. During this process, the browser may expose the user's actual IP address, revealing their identity and location.

Interaction with Proxies and Networking

In a typical proxy setup, a user routes their internet traffic through an intermediary server, masking their original IP address. However, WebRTC bypasses traditional routing methods used by proxies. When a WebRTC connection is established, the browser engages in a series of STUN (Session Traversal Utilities for NAT) requests to determine the public IP address and local network configuration. This process can expose sensitive IP information directly to the target application.

Key networking protocols involved in this process include:

• STUN (Session Traversal Utilities for NAT): Used to discover the public IP address and port mappings.
• TURN (Traversal Using Relays around NAT): Provides a fallback method for relaying media when direct peer-to-peer connections fail.
• ICE (Interactive Connectivity Establishment): The framework that combines STUN and TURN to establish peer-to-peer connections.

In a scenario where a user is connected to a VPN, WebRTC may still reveal their true IP address through these mechanisms, effectively leaking their identity.

Key Parameters and Formats

To understand how WebRTC leaks occur, one must familiarize themselves with the parameters involved in ICE candidates. Here are the primary components:

1. Candidate Types:
2. host: An IP address directly reachable by the browser.
3. srflx: A STUN-discovered public IP address.

4. relay: An IP address provided by a TURN server.

5. Candidate Structure:
   Each ICE candidate is formatted as follows:
   candidate:<foundation> <componentId> <transport> <priority> <ip> <port> typ <type> [raddr <raddr>] [rport <rport>]
   For example:
   candidate:842163049 1 udp 2113937151 192.168.1.2 54321 typ host
candidate:1234567890 1 udp 1686052607 203.0.113.1 3478 typ srflx raddr 192.168.1.2 rport 54321

In this example, the first candidate is a local IP address (192.168.1.2), while the second one (203.0.113.1) is a public IP address discovered via STUN. If the user is connected through a VPN, the presence of the srflx candidate can potentially reveal their actual IP, hence the leak.

A Basic Example of WebRTC Leak

Imagine a user connected to a VPN service while trying to initiate a video call using a WebRTC-based application. The user’s VPN assigns them the IP address 10.8.0.1, masking their true location. However, upon establishing the video call, the browser executes the following sequence:

1. STUN Request: The browser sends a packet to a STUN server to determine its public IP address.
2. STUN Response: The STUN server replies with the public IP address (e.g., 203.0.113.1).
3. ICE Candidates Formation: The browser generates ICE candidates, including both the local address (e.g., 192.168.1.2) and the STUN-discovered public address (203.0.113.1).

When the application processes these candidates, it might inadvertently expose the public IP (203.0.113.1) to the other party in the call, thus leaking the user's true identity despite their active VPN connection.

Conclusion

In the intricate tapestry of modern networking, a WebRTC leak serves as a poignant reminder of the challenges inherent in ensuring privacy amidst powerful technologies. The interaction between WebRTC and proxy networks reveals vulnerabilities that can compromise user anonymity. As we move towards a more interconnected digital landscape, understanding these nuances becomes essential—not just for users seeking privacy, but also for developers aiming to build robust applications that respect user confidentiality. The elegance of WebRTC lies not only in its capabilities but also in the vigilance required to safeguard the privacy it can inadvertently jeopardize.