Simple Firebase Authentication for Ruby. The source of the idea is this article.

This gem receives the idToken issued by Firebase and sends a request to identitytoolkit.

And It will return the authenticated user's information.

Firebase idToken is a token for authentication, so you need to issue an authorization token in your application.

Add this line to your application's Gemfile:

gem 'fireauth'

And then execute:

$ bundle install

Or install it yourself as:

$ gem install fireauth

It's needed to set up your Firebase API Key.

If you are using Rails, this should go into config/initializers/fireauth.rb.

Fireauth.configure do |config|
  config.firebase_api_key = ENV['FIREBASE_API_KEY']
end

response = Fireauth::Authentication.call(id_token)
raise response['error']['message'] if response['error'].present?

authenticated_user = response['users'].first

# Ex.)
user = UserIdentity.find_by!(uid: authenticated_user['localId']).user
tokens = user.generate_tokens
render json: tokens # render (access_token, refresh_token) or jwt

A example of the payload structure from a Facebook login in JSON.

{
   "kind": "identitytoolkit#GetAccountInfoResponse",
   "users": [
      {
         "localId": "dummyLocalId",
         "displayName": "dummyDisplayName",
         "photoUrl": "https://example.com/picture",
         "providerUserInfo": [
            {
               "providerId": "facebook.com",
               "displayName": "dummyDisplayName",
               "photoUrl": "https://example.com/picture",
               "federatedId": "00000000",
               "email": "dummy@example.com",
               "rawId": "0000000000"
            }
         ],
         "validSince": "1611130616",
         "lastLoginAt": "1611375910133",
         "createdAt": "1611130616888",
         "lastRefreshAt": "2021-01-23T04:25:10.840Z"
      }
   ]
}

When a request is made with an invalid idToken.

{
   "error": {
      "code": 400,
      "message": "INVALID_ID_TOKEN",
      "errors": [
         {
            "domain": "global",
            "message": "INVALID_ID_TOKEN",
            "reason": "invalid"
         }
      ],
   }
}

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Bug reports and pull requests are welcome on GitHub at https://github.com/yuta17/fireauth.

The gem is available as open source under the terms of the MIT License.