How to authenticate Django users in node.js

django_auth.js

/*
 * Authenticate Django users in node.js.
 *
 * Django is great for many projects, while node.js does some fantastic
 * jobs that Django couldn't. For example, you may have a Django app
 * managing your user accounts and another real-time service or application
 * running on Node, then you probably will need to read Django user session
 * to authenticate users in the Node project.
 *
 * This gist is not production ready yet, but it demonstrates how could it
 * be done and where to start.
 *
 * Note, your Django project has to be using redis as session backend, and
 * serializing user session objects in json.
 *
 * Tested on:
 * - Django 1.7.1
 * - Node.js 0.10.35
 */

var django_session = require('./django_session.js');

// TODO: Randomize it
var session_id = "z8dfbzthqwjru1rchan89owg5p3x8v39";

function anonymous(callback) {
    django_session.setSession(session_id, {}, function(err){
        callback(err, session_id);
    });
}

function login(user_id, callback) {
    django_session.setSession(
        session_id,
        {
            // TODO: Create a real hash
            "_auth_user_hash": "077ff3aaedd42e66642e2c7df037d1ced2ed6fbf",
            "_auth_user_backend": "django.contrib.auth.backends.ModelBackend",
            "_auth_user_id": user_id
        },
        function(err){
            callback(err, session_id);
        }
    );
}

function logout(session_id) {
    django_session.setSession(session_id, {}, function(err){
        callback(err, session_id);
    });
}

module.exports = {
    anonymous: anonymous,
    login: login,
    logout: logout
};

django_session.js

/**
 * Read and parse Django user session, so we can perform authentication &
 * authorization actions in node.js project.
 *
 * Currently we assume Django user session is stored in a redis server, but
 * this lib should be able to be extended for other session storage backend.
 *
 * A raw django session is encoded by utf-8 & base64. After decoding a typical
 * session looks like (no line breaks):
 *
 * 8dd6ffb4e993a6a3bbe3d986452f2746db737132:
 * {"_auth_user_hash":"077ff3aaedd42e66642e2c7df037d1ced2ed6fbf",
 * "_auth_user_backend":"django.contrib.auth.backends.ModelBackend",
 *"_auth_user_id":1, "test":123}
 *
 * Keys prefixed with "_auth" only exist for authenticated users.
 *
 *
 * Usage: getSession(session_id, callback) gets session data from django
 *        session store, wrap it in a session object, which is passed into
 *        callback function. The session object contains not only the original
 *        value of the session data, but also a set of helper attributes.
 *
 *        E.g.,
 *        getSession("t98h2r94r3934r53", function(err, session){
 *            console.log(session);
 *            console.log(session.user_id);
 *        });
 *
 *
 * Note, we haven't implemented django's session hashing function here.
 * So updateSession and setSession are not yet ready for use other than
 * testing until we can clone django's hashing algorithm here.
 * Refer django/contrib/sessions/backends/base.py for details.
 */

var redis  = require("redis"),
    _      = require("underscore"),
    config = require("../../config/config.js");


// Build connection
var client = redis.createClient(
    config.redis.django_session.port,
    config.redis.django_session.host,
    {}
);
client.on("error", function (err) {
    console.log("Error connecting redis: " + err);
});


function buildSessionKey(session_id) {
    /* Build redis key for a session id. */
    return "session:" + session_id;
}


function getSession(session_id, callback) {
    /*
     * session_id: A string contains django session id.
     * callback: After session retrieved, callback will be called with
     *           a session object contains following attributes:
     *           - value: A JSON object contains parsed session value.
     *           - raw_value: A raw B64 encoded string containing session.
     *           - user_id: A short-cut to user id.
     */

    // TODO: Validate the hash, make sure session is not corrupted.

    client.get(buildSessionKey(session_id), function(err, reply) {
        if (err) {
            callback(err, null);
        } else {
            var raw_value = new Buffer(reply, 'base64').toString('utf-8');
            var session_value = JSON.parse(
                raw_value.match(/^[a-z0-9]+:({.*})$/)[1]
            );
            var session = {
                value: session_value,
                raw_value: raw_value,
                user_id: session_value._auth_user_id || null
            };
            callback(err, session);
        }
    });
}


function updateSession(session_id, session_value, callback) {
    /*
     * If session_id already exists, update its value by merging session_value
     * into it.
     *
     * If session_id doesn't exist yet, which is NOT supposed to happen in a
     * normal working environment, we should return an error.
     *
     * session_id: A string contains django session id.
     * session_value: A JSON object contains the value to be added to session.
     * callback: After session set, callback will be called with err and reply.
     */

    getSession(session_id, function(err, session) {
        if (err) {
            callback(err, null);
        } else {
            session_value = _.extend(session.value, session_value);
            setSession(session_id, session_value, callback);
        }
    });
}


function setSession(session_id, session_value, callback) {
    /*
     * Set session value for a specific session_id.
     *
     * session_id: A string contains django session id.
     * session_value: A JSON object contains the value to be set as session.
     * callback: After session set, callback will be called with err and reply.
     */

    // TODO: Use a real hash, so django won't treat session as corrupted.

    var hash = new Buffer("An invalid node.js session hash").toString('hex');
    var encoded_session = new Buffer(hash + ":" + JSON.stringify(session_value)).toString('base64');

    client.set(buildSessionKey(session_id), encoded_session, function(err, reply) {
        callback(err, reply);
    });
}

module.exports = {
    getSession: getSession,
    updateSession: updateSession,
    setSession: setSession
};