Shared Sessions between Node Apps?

I currently have two separate node apps running on two different ports but share the same backend data store. I need to share users sessions between the two apps so that when a user logs into through one app, their session is available and they appear to logged into the other app. In this case, its' a public facing website and an administrative backend.

Our setup is the following:

node with express
passport is being used to handle auth with Local Strategy
we're using connect-redis to allow us to share sessions via redis.
our domains look like this: www.mydomain.com and adm.mydomain.com

The config for for session stuff (and redis) is the same for both apps:

session: {
    options: {
        secret: "my secret",
        cookie: {
            domain: "mydomain.com",
            maxAge:1000*60*60*24
        }
    },
    redis: {
        host: 'my host',
        maxAge: 86400000,
        secret: "my secret"
    }
}

The config for session stuff in app.js looks like this:

if ( app.settings.env === "production" ) {
    session.options.store = new RedisStore(session.redis);
}
app.use(express.session(session.options));
app.use(passport.initialize());
app.use(passport.session({ secret: 'a different secret' }));

What I expect it to do: Allow us to see the same session id in the cookie between the two apps.

So my question is: How do I set up express, redis and passport so that you can have sessions shared across different subdomains?

Solution

Maybe a bit outdated, but at this time, Express-session can recognise domain option for cookie. According to source:

function session(options){
  var options = options || {}
  //  name - previously "options.key"
    , name = options.name || options.key || 'connect.sid'
    , store = options.store || new MemoryStore
    , cookie = options.cookie || {}
      ...

And this is for setting cookie:

var Cookie = module.exports = function Cookie(options) {
  this.path = '/';
  this.maxAge = null;
  this.httpOnly = true;
  if (options) merge(this, options);
  ...

So, something like this will work for current 1.10.1 master:

secret: "my secret",
    cookie: {
        domain: "mydomain.com",