OmniAuth LTI Example Application

This web application is a basic web application for demoing the use of the omniauth-lti gem.

There is a live example in http://omniauth-lti-example.herokuapp.com

Installation

Clone this repository and set up the database with rake db:migrate.

Set up a tool_provider in your LTI consumer with:

• /auth/lti/callback as the launch_url (f.i.: http://omniauth-lti-example.herokuapp.com/auth/lti/callback)
• test as the key
• secret as the secret

How to add Omniauth-LTI

The steps done in this application for authenticating using omniauth-lti are:

1. Add the gem

---

Add the omniauth-lti gem in you Gemfile:

gem 'omniauth-lti'

Run bundle install for downloading and installing the gem:

bundle install --without production

2. Set up

---

Edit (or create) an initializer config/initializers/omniauth.rb, adding the lti omniauth strategy:

Rails.application.config.middleware.use OmniAuth::Builder do
  provider :lti, :oauth_credentials => LTI_CREDENTIALS_HASH
end

Create config/initializers/lti.rb, enabling Oauth 1.0 support:

# You also need to explicitly enable OAuth 1 support in the environment.rb or an initializer:
OAUTH_10_SUPPORT = true

If the credentials of your tool consumers are static, add them here too:

# Tool consumer credentials
LTI_CREDENTIALS_HASH = {:test => 'secret'}

Set up the omniauth route, if not set up yet. Edit your config/routes.rb, adding the line:

# set the route for omniauth
post '/auth/:provider/callback', to: 'sessions#create'

Note that the HTTP method for the route is POST. Note that there is no request phase in this authentication mechanism. That is because LTI spec defines the authentication from the LTI consumer to the LTI provider (this webapp).

3. Include Module

---

Include Omniauth::Lti::Context in your application_controller.rb:

class ApplicationController < ActionController::Base
  ...

  # Include LTI context for accessing it in our views and actions
  include Omniauth::Lti::Context

  ...
end

4. Save and use the context

---

If you want to use the LTI context in your application, first you'll have to save it. Call save_lti_context when you are creating the sessions (typically in SessionsController\#create in a normal Omniauth application)

The context is saved for use anywhere in your application, just call

lti_tool_provider

for retriving it. For instance, in app/views/user/show.html.haml:

%p
	This application has been launched from 
	%code
		=lti_tool_provider.resource_link_title
		(
		=lti_tool_provider.resource_link_id
		)
%p
	The key used for the tool_provider is
	%code=lti_tool_provider.consumer_key
	and the secret is
	%code=lti_tool_provider.consumer_secret	

Get the secret In order to get the consumer_secret, needed for making outcome calls, you'll have to pass to the LTI context a hash of tool_consumer credentials, where the key is the consumer_key and the value is the consumer_secret.

To pass this hash you'll have to call lti_credentials= in your controller, as below:

class UserController < ApplicationController
  before_filter :set_lti_credentials

  ... 

  private 

  # set tool consumer credentials in LTI context
  def set_lti_credentials
    self.lti_credentials = LTI_CREDENTIALS_HASH
  end
end