How to set an IP whitelist on a NodeJS socket.io server?

Question

I'd like to restrict the connection to the socket server only to a list of IP, is there any simple way to do that? I couldn't find any so far.

Thanks

Answer 1

Following @proxim0 post, I used a middleware :

io.use((socket, next) => {
    fs.readFile(__dirname + '/config.json', function(err, file) {
        if(err) return next(new Error("Internal error : " + err.message));

        const config = JSON.parse(file.toString('utf8'));
        if(!config.restrictAccess) return next();
        
        var ip = socket.request.headers['x-forwarded-for'] || socket.request.socket.remoteAddress || null;

        if(ip == null || config.allowedAddresses.indexOf(ip) == -1) {
            console.log("Access denied from remote IP " + ip);
            return next(new Error("Your IP address is not allowed to access this resource."));
        }
        next();
    });
});

With a config.json file with the following format :

{
    "restrictAccess": true,
    "allowedAddresses": [
        "127.0.0.1",
        "123.456.789"
    ]
}

Any comment on improvment is welcome.