Retrieving Public IP address of a client machine using webRTC

Question

We are unable get the public IP address of a client machine. It is showing the sdp is undefined while executing the code. Below is the code.

Get current IP in JS (no third party services)

https://github.com/diafygi/webrtc-ips

//get the IP addresses associated with an account
function getIPs(callback){
    var ip_dups = {};

    //compatibility for firefox and chrome
    var RTCPeerConnection = window.RTCPeerConnection
        || window.mozRTCPeerConnection
        || window.webkitRTCPeerConnection;
    var useWebKit = !!window.webkitRTCPeerConnection;

    //bypass naive webrtc blocking using an iframe
    if(!RTCPeerConnection){
        //NOTE: you need to have an iframe in the page right above the script tag
        //
        //<iframe id="iframe" sandbox="allow-same-origin" style="display: none"></iframe>
        //<script>...getIPs called in here...
        //
        var win = iframe.contentWindow;
        RTCPeerConnection = win.RTCPeerConnection
            || win.mozRTCPeerConnection
            || win.webkitRTCPeerConnection;
        useWebKit = !!win.webkitRTCPeerConnection;
    }

    //minimal requirements for data connection
    var mediaConstraints = {
        optional: [{RtpDataChannels: true}]
    };

    var servers = {iceServers: [{urls: "stun:stun.services.mozilla.com"}]};

    //construct a new RTCPeerConnection
    var pc = new RTCPeerConnection(servers, mediaConstraints);

    function handleCandidate(candidate){
        //match just the IP address
        var ip_regex = /([0-9]{1,3}(\.[0-9]{1,3}){3}|[a-f0-9]{1,4}(:[a-f0-9]{1,4}){7})/
        var ip_addr = ip_regex.exec(candidate)[1];

        //remove duplicates
        if(ip_dups[ip_addr] === undefined)
            callback(ip_addr);

        ip_dups[ip_addr] = true;
    }

    //listen for candidate events
    pc.onicecandidate = function(ice){

        //skip non-candidate events
        if(ice.candidate)
            handleCandidate(ice.candidate.candidate);
    };

    //create a bogus data channel
    pc.createDataChannel("");

    //create an offer sdp
    pc.createOffer(function(result){

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

    }, function(){});

    //wait for a while to let everything done
    setTimeout(function(){
        //read candidate info from local description
        var lines = pc.localDescription.sdp.split('\n');

        lines.forEach(function(line){
            if(line.indexOf('a=candidate:') === 0)
                handleCandidate(line);
        });
    }, 1000);
}

//Test: Print the IP addresses into the console
getIPs(function(ip){console.log(ip);});

While executing the code we are getting this error message:

'Cannot read property 'sdp' of null'

It says that `pc.localDescription` is null, why do you use that `setTimeout` instead of `pc.setLocalDescription`'s callback? Propably 1s is not enough (or there was some error, but your error callbacks do nothing, so you're not aware of it) — barbsan, Jul 26 '19 at 07:46

score 1 · Answer 1 · answered Jul 27 '19 at 22:17

1

The example code you are referencing is outdated and their demo page is no longer working either on recent Chrome versions:

https://diafygi.github.io/webrtc-ips/

Furthermore, it seems to use features that are not supported by some browsers.

I don't know your requirements but it is quite standard to send a request to a server in order to discover the public IP of a client. The server looks at headers (e.g. x-forwarded-for, this depends on the Web server used) and sends it back to the requester.

There also exist services such as Ipregistry (disclaimer: I run the service) that do it for you and return even more interesting information: client IP address, location, currency, threat data, etc.

answered Jul 27 '19 at 22:17

Laurent

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Hello Laurent, Actually I need to find the Public IP Address of a client machine (e.g If I am using X-forwarded-for in C# we are getting the Server IP address after hosting in the IIS server, If I am using X-forwarded-for in local environment I am getting IP address. But I need after hosted the project). But I need Client Public IP address. – Vinod Jul 29 '19 at 04:31
The X-Forwarded-For header identifies the originating IP address. If after hosting your app on your IIS server you are getting an IP address that is not your client IP it most probably because there is another server/load balancer/front end in the middle (between your client and your IIS server) that does not forward your client IP in the X-Forwarded-For header. – Laurent Jul 29 '19 at 08:54
Thanks for your response Laurent, Then how can I get the Public IP address of a client machine ? If you know about retrieving the public IP Address of the client after hosting the app please provide some sample code. – Vinod Jul 29 '19 at 09:17

divinelemon · Answer 2 · 2021-11-16T19:00:28.670

As of this writing, you cannot leak the private IP address of your users.

However, I found a github repo webrtc-ip which can leak a user's public IP address using WebRTC. This is powerful because you cannot trace it, as nothing is shown in the Networks tab.

Sadly, this leak does not work for private IPs, due to the gradual shift to mDNS (at least for WebRTC), which is completely in this great blog. Regardless, here's a working demo:

https://webrtc-ip.herokuapp.com/

I am not sure if this leaks your true IP address regardless of a proxy, but feel free to test it out.

If you look at the repo you referenced, the issues clearly state that the repo does not work and that the repository is not being maintained.

Retrieving Public IP address of a client machine using webRTC

2 Answers2