superruzafa / goth

Elixir package for Oauth authentication via Google Cloud APIs

Goth

Google + Auth = Goth

A simple library to generate and retrieve OAuth2 tokens for use with Google Cloud Service accounts.

Installation

Note: below are instructions for using Goth v1.3+. For more information on earlier versions of Goth, see v1.2.0 documentation on hexdocs.pm.

1. Add :goth to your list of dependencies in mix.exs. To use the built-in, Hackney-based HTTP client adapter, add :hackney too:

   def deps do
     [
       {:goth, "~> 1.3-rc"},
       {:hackney, "~> 1.17"}
     ]
   end

2. Add Goth to your supervision tree:

   defmodule MyApp.Application do
     use Application
   
     def start(_type, _args) do
       credentials = "GOOGLE_APPLICATION_CREDENTIALS_JSON" |> System.fetch_env!() |> Jason.decode!()
       source = {:service_account, credentials, []}
   
       children = [
         {Goth, name: MyApp.Goth, source: source}
       ]
   
       Supervisor.start_link(children, strategy: :one_for_one)
     end
   end

3. Fetch the token:

   iex> {:ok, token} = Goth.fetch(MyApp.Goth)
   iex> token
   %Goth.Token{
     expires: 1453356568,
     token: "ya29.cALlJ4ICWRvMkYB-WsAR-CZnExE459PA7QPqKg5nei9y2T9-iqmbcgxq8XrTATNn_BPim",
     type: "Bearer",
     ...
   }

See Goth.start_link/1 for more information about possible configuration options.

Upgrading from Goth < 1.3

Earlier versions of Goth relied on global application environment configuration which is deprecated in favour of a more direct and explicit approach in Goth v1.3+. Previously, we were depending on the HTTPoison HTTP client, now we have an optional dependency on Hackney, so in order to use it, you need to explicitly include it in your dependencies too:

Change your mix.exs:

def deps do
 [
   {:goth, "~> 1.3-rc"},
   {:hackney, "~> 1.17"}
 ]
end

You might have code similar to this:

# config/config.exs
config :goth,
  json: {:system, "GCP_CREDENTIALS"}

# lib/myapp.ex
defmodule MyApp do
  def gcloud_authorization() do
    {:ok, token} = Goth.Token.for_scope("https://www.googleapis.com/auth/cloud-platform.read-only")
    "#{token.type} #{token.token}"
  end
end

Replace it with:

defmodule MyApp.Application do
  @moduledoc false
  use Application

  def start(_type, _args) do
    credentials = "GCP_CREDENTIALS" |> System.fetch_env!() |> Jason.decode!()
    scopes = ["https://www.googleapis.com/auth/cloud-platform.read-only"]
    source = {:service_account, credentials, scopes: scopes}

    children = [
      {Goth, name: MyApp.Goth, source: source}
    ]

    Supervisor.start_link(children, strategy: :one_for_one)
  end
end

# lib/myapp.ex
defmodule MyApp do
  def gcloud_authorization() do
    {:ok, token} = Goth.fetch(MyApp.Goth)
    "#{token.type} #{token.token}"
  end
end

For more information on earlier versions of Goth, see v1.2.0 documentation on hexdocs.pm.