The gem omniauth-google-oauth2

Introducción

The

gem omniauth-google-oauth2 provides a strategy to authenticate with Google via OAuth2 in OmniAuth.

Get your API key at:

https://code.google.com/apis/console/

Note the Client ID and the Client Secret.

For more details, read the Google docs:

https://developers.google.com/accounts/docs/OAuth2.

Configuration

You can configure several options, which you pass in to the provider method via a hash:

• scope A comma-separated list of permissions you want to request from the user. See the Google OAuth 2.0 Playground for a full list of available permissions.

  Caveats:

  • The userinfo.email and userinfo.profile scopes are used by default. By defining your own scope, you override these defaults. If you need these scopes, don't forget to add them yourself!
  • Scopes starting with https://www.googleapis.com/auth/ do not need that prefix specified.

    So while you can use the smaller scope books since that permission starts with the mentioned prefix, you should use the full scope URL https://docs.google.com/feeds/ to access a user's docs, for example.

• prompt A space-delimited list of string values that determines whether the user is re-prompted for authentication and/or consent. Possible values are:
  • none No authentication or consent pages will be displayed; it will return an error if the user is not already authenticated and has not pre-configured consent for the requested scopes.

    This can be used as a method to check for existing authentication and/or consent.

  • consent The user will always be prompted for consent, even if he has previously allowed access a given set of scopes.
  • select_account The user will always be prompted to select a user account. This allows a user who has multiple current account sessions to select one amongst them.
  • If no value is specified, the user only sees the authentication page if he is not logged in
  • and only sees the consent page the first time he authorizes a given set of scopes.

• image_aspect_ratio The shape of the user's profile picture. Possible values are:
  • original Picture maintains its original aspect ratio.
  • square Picture presents equal width and height. Defaults to original.

• image_size The size of the user's profile picture.

  The image returned will have width equal to the given value and variable height, according to the image_aspect_ratio chosen.

  Additionally, a picture with specific width and height can be requested by setting this option to a hash with width and height as keys.

  If only width or height is specified, a picture whose width or height is closest to the requested size and requested aspect ratio will be returned.

  Defaults to the original width and height of the picture.

• name The name of the strategy. The default name is google_oauth2 but it can be changed to any value, for example google. The OmniAuth URL will thus change to /auth/google and the provider key in the auth hash will then return google.

• access_type Defaults to offline, so a refresh token is sent to be used when the user is not present at the browser. Can be set to online.

  Note that if you need a refresh token, google requires you to also to specify the option prompt: 'consent', which is not a default.

• login_hint When your app knows which user it is trying to authenticate, it can provide this parameter as a hint to the authentication server. Passing this hint suppresses the account chooser and either pre-fill the email box on the sign-in form, or select the proper session (if the user is using multiple sign-in), which can help you avoid problems that occur if your app logs in the wrong user account. The value can be either an email address or the sub string, which is equivalent to the user's Google+ ID.

• include_granted_scopes If this is provided with the value true, and the authorization request is granted, the authorization will include any previous authorizations granted to this user/application combination for other scopes. See Google's Incremental Autorization for additional details.

Here's an example of a possible configuration where

• the strategy name is changed,
• the user is asked for extra permissions,
• the user is always prompted to select his account when logging in and
• the user's profile picture is returned as a thumbnail:

Rails.application.config.middleware.use OmniAuth::Builder do
  provider :google_oauth2, ENV["GOOGLE_CLIENT_ID"], ENV["GOOGLE_CLIENT_SECRET"],
    {
      :name => "google",
      :scope => "userinfo.email, userinfo.profile, plus.me, http://gdata.youtube.com",
      :prompt => "select_account",
      :image_aspect_ratio => "square",
      :image_size => 50
    }
end

Auth Hash

Here's an example of an authentication hash available in the callback by accessing request.env["omniauth.auth"]:

{
    :provider => "google_oauth2",
    :uid => "123456789",
    :info => {
        :name => "John Doe",
        :email => "john@company_name.com",
        :first_name => "John",
        :last_name => "Doe",
        :image => "https://lh3.googleusercontent.com/url/photo.jpg"
    },
    :credentials => {
        :token => "token",
        :refresh_token => "another_token",
        :expires_at => 1354920555,
        :expires => true
    },
    :extra => {
        :raw_info => {
            :id => "123456789",
            :email => "user@domain.example.com",
            :verified_email => true,
            :name => "John Doe",
            :given_name => "John",
            :family_name => "Doe",
            :link => "https://plus.google.com/123456789",
            :picture => "https://lh3.googleusercontent.com/url/photo.jpg",
            :gender => "male",
            :birthday => "0000-06-25",
            :locale => "en",
            :hd => "company_name.com"
        }
    }
}