SimpleGoogleAuth

Want an extremely easy integration of Google's authentication system in your Rails site?

This is a dead simple gem that allows you to require a Google login for parts of your site. You can allow any user with a Google account, or limit access to certain users based on their Google e-mail address.

Being simple, it's limited in what it can do. But if your goal is to put your site behind a Google login instead of a crusty basic auth box, it'll do the trick. If you're after more power, there are quite a few gems that'll do what you're looking for, such as OmniAuth's Google strategy.

Installation

Follow these five steps to integrate with your site.

Step 1: Make yourself a project at https://cloud.google.com/console, if you haven't already.

Step 2: In that project, go to the "APIs & auth" tab, then the "Credentials" tab. Create a new client ID of application type "Web application". Set the Authorized Redirect URI to http://yoursite.com/google-callback. You might want to put in http://localhost:3000/google-callback so you can test locally too.

Step 3: Add simple_google_auth to your Gemfile

gem 'simple_google_auth'

Step 4: In your application.rb, put down some code inside the Application class:

SimpleGoogleAuth.configure do |config|
  config.client_id = "the client ID as supplied by Google in step 2"
  config.client_secret = "the client secret as supplied by Google in step 2"
  config.redirect_uri = "http://localhost:3000/google-callback"
  config.authenticate = lambda do |data|
    data["email"] == "your.email@example.com"
  end
end

Step 5: In your application_controller.rb, add a before filter:

before_filter :redirect_if_not_google_authenticated

Done! Any request to your site will now redirect off to Google for authentication. A route that captures requests coming in to /google-callback is automatically created and handled for you.

If you log in with your.email@example.com, it'll let you in to the site and take you to the page you were initially trying to go to. Otherwise it'll redirect to / (by default) with params[:message] set to the authentication error.

Setting up multiple environments

You might want to put a different configure block in your development.rb and production.rb, each specifying a different redirect URI. Just pop them on the end of the file.

# development.rb
SimpleGoogleAuth.configure do |config|
  config.redirect_uri = "http://localhost:3000/google-callback"
end

# production.rb
SimpleGoogleAuth.configure do |config|
  config.redirect_uri = "https://mysite.com/google-callback"
end

How do I tell who is logged in?

Call #google_auth_data from your controller or view and you'll get the identification hash that Google sends back.

Welcome, <%= google_auth_data["email"] %>!

Take a look at https://developers.google.com/accounts/docs/OAuth2Login#obtainuserinfo to find out more about the fields in the hash.

Configuring

There are a few configuration options that can be set using SimpleGoogleAuth.configure as in the example above.

Option	Default	Description
client_id	(required)	Client ID as provided by Google.
client_secret	(required)	Client secret as provided by Google.
redirect_uri	(required)	Where Google should redirect to after authentication.
redirect_path	nil	A route is created at this path. If no path is specified, the path is taken from redirect_uri.
authenticate	(required)	A lambda that's run to determine whether the user should be accepted as valid or not. Takes one argument, a hash of identification data as provided by Google. Should return true on success, or false if the login should not proceed.
failed_login_path	"/"	Where to redirect to upon a failed login. params[:message] will be set with the error that occurred.
ca_path	"/etc/ssl/certs"	A path or file of SSL certificates, used to check that we're really talking to the Google servers.
google_auth_url	"https://accounts.google.com/o/oauth2/auth"	Google's authentication URL.
google_token_url	"https://accounts.google.com/o/oauth2/token"	Google's token URL.
state_session_key_name	"simple-google-auth.state"	The name of the session variable used to store a random string used to prevent CSRF attacks during authentication.
data_session_key_name	"simple-google-auth.data"	The name of the session variable used to store identification data from Google.
request_parameters	"openid email"	Parameters to use when requesting a login from Google

Licence

MIT.