Google Oauth2 Installed

Configure and authenticate to Google with OAuth2 as an installed application.

This is for when your application needs to authenticate to Google services, as opposed to your application's users.

Extracted from applications that use the DFP and Analytics APIs, google-oauth2-installed helps with configuration (from ENV). It also helps with setup by providing an easy command to generate your OAuth tokens.

For more information about Installed Apps: https://developers.google.com/accounts/docs/OAuth2InstalledApp

Why

Google provides three ways to authenticate with OAuth2:

1. Web application. This is what you use when your application needs access as the user of your application.
2. Service account. This is really what you want, but can only be used by applications authenticating with a google apps account. If you have a google apps account, do not use GoogleOAuth2Installed, use service accounts instead.
3. Installed application. This allows you to authenticate as an application, but still requires an access_token, which requires user interaction through a browser. google-oauth2-installed tries to make this process as simple as possible. The bad news is that access_tokens expire. The good news is that the access_token comes with a refresh_token that does not expire. So, once you've aquired your tokens, you can store them for later use and forget about it.

Installation

Add this line to your application's Gemfile:

gem 'google-oauth2-installed'

Or install it yourself as:

$ gem install google-oauth2-installed

Setup

Create an application in Google Cloud Console

First, you need to create an application identifier in Google Cloud Console. Please follow these instructions lovingly copied (and only slightly altered) from the google-api-ads-ruby library.

Visit Google Cloud Console and:

1. Click CREATE PROJECT to create a new project.
2. Enter the Project Name (and optionally, choose your own Project ID), and click Create.
3. The newly created project should automatically open. Click APIs & auth to expand the menu, and then click Credentials.
4. Click CREATE NEW CLIENT ID to create a new client identifier and client secret.
5. Choose Installed application, and *Other for the "Installed application type".
6. Click CREATE CLIENT ID to complete the registration. Client ID and client secret will be created and displayed.

The Client ID and secret values are the parameters you will need in the next step.

Then go to Concent screen and make sure *Email addresses and Product name are filled in or you will get a no application name error.

Set up your credentials in order to retrieve an access token

Define the following environment variables. I recommend using the dotenv gem (dotenv-rails in rails projects) and adding these variables to a .env file.

OAUTH2_CLIENT_ID="..."
OAUTH2_CLIENT_SECRET="..."
OAUTH2_SCOPE="..."

OAUTH2_SCOPE is a space delimited list of the scopes your application will need access to. For example, for readonly access to analytics, and write access to DFP, use:

OAUTH2_SCOPE="https://www.googleapis.com/auth/analytics.readonly https://www.google.com/apis/ads/publisher"

Get your access token

Once you have these environment variables defined, run this rake task and authenticate to google with the user you need access as.

rake googleoauth2installed:get_access_token

This rake task will give you a url to load up in the browser. You will need to log in to Google, allow access to the requested scopes, and copy the provided code. Paste this code back in to the rake task that is waiting for you. It will then output the rest of the environment variables you need to authenticate.

(If the URL shows an error, you may need to supply a Product Name under the Consent Screen section of your Google Developers Console.)

If you are using .env, it should now look something like:

OAUTH2_CLIENT_ID="..."
OAUTH2_CLIENT_SECRET="..."
OAUTH2_SCOPE="..."

OAUTH2_ACCESS_TOKEN="..."
OAUTH2_REFRESH_TOKEN="..."
OAUTH2_EXPIRES_AT="..."

Not in Rails?

You might need to reference our rake task from your Rakefile. Try something like this:

require 'rubygems'
require 'bundler/setup'
load 'tasks/get_access_token.rake'

Usage

Once you have all of your environment variables set up, just ask GoogleOauth2Installed for an access token. GoogleOauth2Installed will handle refreshing it if needed.

Example usage with Legato for Analytics:

Legato::User.new GoogleOauth2Installed.access_token

If you just need the details (and not a refreshed access token), use GoogleOauth2Installed.credentials.

Example usage with DfpApi:

dfp_authentication = GoogleOauth2Installed.credentials.merge(
  application_name: ENV['DFP_APPLICATION_NAME'],
  network_code: ENV['DFP_NETWORK_CODE'],
)

::DfpApi::Api.new({
  authentication: dfp_authentication,
  service: { environment: 'PRODUCTION' },
})

Contributing

1. Fork it (http://github.com/carnesmedia/google-oauth2-installed/fork)
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request