Webert S. Lima Webert S. Lima - 5 months ago 55
Node.js Question

NodeJS STARTTLS Use SNI

I'm building a simple, STARTTLS capable POP3 Proxy in Node.JS and I'm having quite a hard time.

The proxy serves as a front-end for many back-end servers, so it must load their certificates dynamically, depending on the Client's connection.

I'm trying to use the SNICallback, which brings me the servername the client uses, but I can't set the right certificate after this, because I need one certificate before I have this call, when I create the secure context.

The code is as bellow:

// Load libraries
var net = require('net');
var tls = require('tls');
var fs = require('fs');

// Load certificates (created with openssl)
var certs = [];
for (var i = 1; i <= 8; i++) {
var hostName = 'localhost' + i;
certs[hostName] = {
key : fs.readFileSync('./private-key.pem'),
cert : fs.readFileSync('./public-cert' + i + '.pem'),
}
}

var server = net.createServer(function(socket) {
socket.write('+OK localhost POP3 Proxy Ready\r\n');

socket.on('data', function(data) {
if (data == "STLS\r\n") {
socket.write("+OK begin TLS negotiation\r\n");
upgradeSocket(socket);
} else if (data == "QUIT\r\n") {
socket.write("+OK Logging out.\r\n");
socket.end();
} else {
socket.write("-ERR unknown command.\r\n");
}
});

}).listen(10110);


and upgradeSocket() is as follows:

function upgradeSocket(socket) {
// I need this 'details' or handshake will fail with a message:
// SSL routines:ssl3_get_client_hello:no shared cipher
var details = {
key : fs.readFileSync('./private-key.pem'),
cert : fs.readFileSync('./public-cert8.pem'),
}

var options = {
isServer : true,
server : server,
SNICallback : function(serverName) {
return tls.createSecureContext(certs[serverName]);
},
}

sslcontext = tls.createSecureContext(details);
pair = tls.createSecurePair(sslcontext, true, false, false, options);

pair.encrypted.pipe(socket);
socket.pipe(pair.encrypted);

pair.fd = socket.fd;
pair.on("secure", function() {
console.log("TLS connection secured");
});
}


It handshakes correctly but the certificate I use is the static one in 'details', not the one I get in the SNICallback.

To test it I'm running the server and using gnutls-cli as a Client:

~$ gnutls-cli -V -s -p 10110 --crlf --insecure -d 5 localhost3
STLS
^D (Control+D)


The above command is supposed to get me the 'localhost3' certificate but it's getting the 'localhost8' because it's defined in 'details' var;

There are just too many exaples throughout the internet with HTTPS or for TLS Clients, which it's a lot different from what I have here, and even for Servers as well but thei're not using SNI. Any help will be appreciated.

Thanks in advance.

Answer

The answer is quite simple using tls.TLSSocket, though there is gotcha with the listeners.

You have to remove all the listeners from the regular net.Socket you have, instantiate a new tls.TLSSocket using your net.Socket and put the listeners back on the tls.TLSSocket.

To achieve this easily, use a wrapper like Haraka's tls_socket pluggableStream over the regular net.Socket and replace the "upgrade" function to something like:

pluggableStream.prototype.upgrade = function(options) {
    var self = this;
    var socket = self;
    var netSocket = self.targetsocket;

    socket.clean();

    var secureContext = tls.createSecureContext(options)
    var tlsSocket = new tls.TLSSocket(netSocket, {
        secureContext : secureContext,
        //and other options you need
    });

    self.attach(tlsSocket);
}