GoogleAuth package provide a simple google based authentication. It does not provide the request phase( ie. Authentication url), it just implements the callback phase. You just need to pass google access_token received from google using google client side authentication. Using Google api client library you can generate access token on client side and pass it to a server. You can pass access_token as a query params or in headers

Example:

http://some_url.com?access_token=abc

OR

authorization: Token token=abc

When no access_token is passed to server then ‘google_auth_failure’ key will be added with value “Please send access token with request” to private inside Plug.Conn struct.

GoogleAuth plug will verify whether the token is valid and is generated using the google client id mentioned in the config files. If it is valid it will add ‘google_auth_success’ key with value as a map containing user name, email and picture url to private map inside Plug.Conn struct

If token passed is not valid it will add ‘google_auth_failure’ key with value consisting of error message in private inside Plug.Conn.

You need to add following config in to make GoogleAuth plug work.

config :google_auth,
  google_client_id: "646252629386-aalvnktjfsql35e0cmb28qirhvj7t2p.apps.googleusercontent.com"

Above is the google client id that we get when we register the oauth client at google. Access token will only be valid if its generated using above clien id.

Usage with phoenix framework:

# Inside routes.ex

get "/google_auth/callback", GoogleAuthController, :callback


# Inside controller

defmodule GoogleAuthController do
  use MyApp.Web, :controller
  use GoogleAuth

  def callback(%Plug.Conn{private: %{google_auth_success: user_details}} = conn, _) do
    # user_details will be like %{name: "rohan", email: "rohan@gmail.com", picture: "http://a/b.jpg"}
  end

  def callback(%Plug.Conn{private: %{google_auth_failure: error_message}} = conn, _) do
    conn
      |> put_status(401)
      |> json %{error: error_message}
  end
end

Testing:

During testing run GoogleAuth module is not used and instead Mock.GooogleAuth module is used. This package comes with Mock.GooogleAuth which provide mocking. To test the controller that uses GoogleAuth plug, you simply need to add mock data inside config/test.exs. Mock data must be in following format.

Format:

config :google_auth, :mock_data,
  valid_token_data: %{
    first_token: %{name: "rohan", email: "rohan@gmail.com", picture: "http://a.com/pic.jpg"},
    second_token: %{name: "raj", email: "raj@gmail.com", picture: "http://a.com/pic1.jpg"}
  }
config :google_auth,
  google_client_id: "646252629386-aalvnktjfsql35e0cmb28qirhvj7t2p.apps.googleusercontent.com"

‘first_token’ and ‘second_token’ represent the valid access_token which will. Passing ‘first_token’ as access_token in test will add %{name: “rohan”, email: “rohan@gmail.com”, picture: “http://a.com/pic.jpg"} to ‘google_auth_success’ private key inside Plug.Conn struct.

While testing use ‘first_token’ or ‘second_token’ as a valid access_token.

Example test case:

test "creates a user record when auth sucessfull"do
  user_mock_data = Application.get_ev(:google_auth, :mock_date)[:valid_token_data].first_token
  get conn(), "/api/v1/google_auth/callback?access_token=first_token"
  user = Repo.one(User |> order_by(desc: :updated_at) |> limit(1))
  assert user.name == user_mock_data.name
  assert user.email == user_mock_data.email
  assert user.picture == user_mock_data.picture
end

Any other token which are not keys of valid_toke_data map will be treated as invalid token and will add ‘google_auth_failure’ with value “Invalid access token”. You can also create Mock.GoogleAuth in your project if default mocking provided by this package is not sufficient.