Recently we started using IRC to communicate between colleagues. IRC was fine, except that the user experience isn’t so good compared to modern chat clients. You lack notifications, inline images and it is not specially user friendly. A nice alternative targeting entreprises was Campfire, but sadly it is a closed source product. I forgot about it for a while, then stumbled upon Let’s chat, which is described by its authors as

Let’s Chat is a persistent messaging application that runs on Node.js and MongoDB. It’s designed to be easily deployable and fits well with small, intimate teams.

It’s free (MIT licensed) and ships with killer features such as LDAP/Kerberos authentication, a REST-like API and XMPP support.

Let’s Chat is a side-project of the development team at Security Compass. (A real life 10% time project!)

Plus it is supported (well sort of) by Hubot, which is our toy of choice. So after toying with it using the Vagrant image available on the website, I decided to start a new VPS and install it for a real world test.

Installing dependencies

Node.js

Installing Node.js is really easy, as there is a PPA (Personal Package Archive) available. We will also need the build-essential package, since some NPM modules need to be compiled.

# Adds the Node.js PPA
curl -sL https://deb.nodesource.com/setup | sudo bash -
sudo apt-get install nodejs build-essential

MongoDB

There is a package available:

sudo apt-get install mongodb-org

Python

Python 2.7 is already installed with Ubuntu 12.04, there is no need to install anything.

Installing Let’s Chat

For security reason, we will run Let’s Chat as its own user, with restricted privileges. First create this user:

adduser node

Then as the node user, run the following commands to install Let’s Chat:

https://github.com/sdelements/lets-chat
cd lets-chat
npm install

Configuration

Let’s chat settings are stored in settings.yaml. There is a sample available and here is mine, slightly adapted from it:

# See defaults.yml for all available options

env: production

http:
  enable: true
  host: '0.0.0.0'
  port: 5000

# Allow any file upload
files:
  enable: true
  restrictTypes: true

auth:
  local:
    salt: SALTSARESECRET

secrets:
  cookie: ITISASALTTOO

You can now run npm start and point your browser on your server (port 5000 for now, we will fix it in the next step).

Serving the site on port 80

Since we are running the web application with a non priviledged user, as you should be, we cannot bind to port 80. Recent Linux kernels can change this using a per-program authorization Since our program is interpreted by the node executable, it would mean any Node.js application could bind to lower ports, which is not ideal.

The solution that I choose is to run the server on a non priviledged port and redirect traffic coming on port 80 to this port using Linux’s builtin iptables.

To do this, simply run the following commands as root:

iptables -A PREROUTING -t nat -p tcp --dport 80 -j REDIRECT --to-port 5000
iptables -t nat -I OUTPUT -p tcp -d 127.0.0.1 --dport 80 -j REDIRECT --to-ports 5000

Running the site on server boot

Running the site with npm start is great, but it would be better if it is started automatically at boot. To do that we can use Ubuntu’s Upstart init system. It allows us to write job descriptions and when they should be run. We can also specify a user and a directory to run the script from.

Put the following in /etc/init/lets-chat.conf:

description "Let's chat application server"
author "Antoine Albertelli"

# Taken from nginx job definition
start on (filesystem and net-device-up IFACE=lo)
stop on runlevel [!2345]

setuid node
setgid node

chdir /home/node/lets-chat

exec npm start

We also need to make our iptables rules persistent on every reboot. To do this put the iptables commands above in /etc/rc.local, before the last line.

Tadaa ! Now you can run sudo initctl start lets-chat and try to connect to your host on port 80. Your service will be started automatically on every boot.

TODO

Support for HTTPS (using self signed certificate).
Add automatic respawn.

Installing Let's chat on Ubuntu 12.04