ExOauth2Provider

The no-brainer library to use for adding OAuth 2.0 provider capabilities to your Elixir app. You can use phoenix_oauth2_provider for easy integration with your Phoenix app.

Installation

Add ExOauth2Provider to your list of dependencies in mix.exs:

def deps do
  [
    # ...
    {:ex_oauth2_provider, "~> 0.4.3"}
    # ...
  ]
end

Run mix deps.get to install it, and then run the install script:

mix ex_oauth2_provider.install

This will add the necessary Ecto migrations to your app, and set sample configuration in config/config.exs.

You are required to use a resource owner struct that already exists. This could be your User struct. If you don't have any User struct, you can create a migration with this:

mix ecto.gen.migration create_users --change $'    create table(:users) do\n      add :email, :string\n    end'

And use the struct in test/support/dummy/models/user.ex.

If you're not using auto incremental integer (:id) for your primary key(s), please read the Using UUID or custom primary key type section.

Authorize code flow

Authorization request

You have to ensure that a resource_owner has been authenticated on the following endpoints, and pass the struct as the first argument in the following methods.

# GET /oauth/authorize?response_type=code&client_id=CLIENT_ID&redirect_uri=CALLBACK_URL&scope=read
case ExOauth2Provider.Authorization.preauthorize(resource_owner, params) do
  {:ok, client, scopes}             -> # render authorization page
  {:redirect, redirect_uri}         -> # redirect to external redirect_uri
  {:native_redirect, %{code: code}} -> # redirect to local :show endpoint
  {:error, error, http_status}      -> # render error page
end

# POST /oauth/authorize?response_type=code&client_id=CLIENT_ID&redirect_uri=CALLBACK_URL&scope=read
ExOauth2Provider.Authorization.authorize(resource_owner, params) do
  {:redirect, redirect_uri}         -> # redirect to external redirect_uri
  {:native_redirect, %{code: code}} -> # redirect to local :show endpoint
  {:error, error, http_status}      -> # render error page
end

# DELETE /oauth/authorize?response_type=code&client_id=CLIENT_ID&redirect_uri=CALLBACK_URL&scope=read
ExOauth2Provider.Authorization.deny(resource_owner, params) do
  {:redirect, redirect_uri}         -> # redirect to external redirect_uri
  {:error, error, http_status}      -> # render error page
end

Authorization code grant

# POST /oauth/token?client_id=CLIENT_ID&client_secret=CLIENT_SECRET&grant_type=authorization_code&code=AUTHORIZATION_CODE&redirect_uri=CALLBACK_URL
case ExOauth2Provider.Token.grant(params) do
  {:ok, access_token}               -> # JSON response
  {:error, error, http_status}      -> # JSON response
end

Revocation

# GET /oauth/revoke?client_id=CLIENT_ID&client_secret=CLIENT_SECRET&token=ACCESS_TOKEN
case ExOauth2Provider.Token.revoke(params) do
  {:ok, %{}}                        -> # JSON response
  {:error, error, http_status}      -> # JSON response
end

Revocation will return {:ok, %{}} status even if the token is invalid.

Authorization code flow in a Single Page Application

ExOauth2Provider doesn't support implicit grant flow. Instead you should set up an application with no client secret, and use the Authorize code grant flow. client_secret isn't required unless it has been set for the application.

Other supported token grants

Client credentials

# POST /oauth/token?client_id=CLIENT_ID&client_secret=CLIENT_SECRET&grant_type=client_credentials
case ExOauth2Provider.Token.grant(params) do
  {:ok, access_token}               -> # JSON response
  {:error, error, http_status}      -> # JSON response
end

Refresh token

Refresh tokens can be enabled in the configuration:

config :ex_oauth2_provider, ExOauth2Provider,
  repo: ExOauth2Provider.Test.Repo,
  resource_owner: Dummy.User,
  use_refresh_token: true

The refresh_token grant flow will then be enabled.

# POST /oauth/token?client_id=CLIENT_ID&client_secret=CLIENT_SECRET&grant_type=refresh_token&refresh_token=REFRESH_TOKEN
case ExOauth2Provider.Token.grant(params) do
  {:ok, access_token}               -> # JSON response
  {:error, error, http_status}      -> # JSON response
end

Username and password

You'll need to provide an authorization method that accepts username and password as arguments, and returns {:ok, resource_owner} or {:error, reason}. Here'a an example:

# Configuration in config/config.exs
config :ex_oauth2_provider, ExOauth2Provider,
  password_auth: {MyApp.MyModule, :authenticate}

# Module example
defmodule MyApp.MyModule
  def authenticate(username, password) do
    user = repo.get_by(User, email: username)
    cond do
      user == nil                       -> {:error, :no_user_found}
      check_pw(user.password, password) -> {:ok, user}
      true                              -> {:error, :invalid_password}
    end
  end
end

The password grant flow will then be enabled.

# POST /oauth/token?client_id=CLIENT_ID&grant_type=password&username=USERNAME&password=PASSWORD
case ExOauth2Provider.Token.grant(params) do
  {:ok, access_token}               -> # JSON response
  {:error, error, http_status}      -> # JSON response
end

Scopes

Server wide scopes can be defined in the configuration:

config :ex_oauth2_provider, ExOauth2Provider,
  repo: ExOauth2Provider.Test.Repo,
  resource_owner: Dummy.User,
  default_scopes: ~w(public),
  optional_scopes: ~w(read update)

Plug API

ExOauth2Provider.Plug.VerifyHeader

Looks for a token in the Authorization Header. If one is not found, this does nothing. This will always be necessary to run to load access token and resource owner.

ExOauth2Provider.Plug.EnsureAuthenticated

Looks for a verified token loaded by VerifyHeader. If one is not found it will call the :unauthenticated method in the :handler module.

You can use a custom :handler as part of a pipeline, or inside a Phoenix controller like so:

defmodule MyApp.MyController do
  use MyApp.Web, :controller

  plug ExOauth2Provider.Plug.EnsureAuthenticated, handler: MyApp.MyAuthErrorHandler
end

The :handler module always defaults to ExOauth2Provider.Plug.ErrorHandler.

ExOauth2Provider.Plug.EnsureScopes

Looks for a previously verified token. If one is found, confirms that all listed scopes are present in the token. If not, the :unauthorized function is called on your :handler.

defmodule MyApp.MyController do
  use MyApp.Web, :controller

  plug ExOauth2Provider.Plug.EnsureScopes, handler: MyApp.MyAuthErrorHandler, scopes: ~w(read write)
end

When scopes' sets are specified through a :one_of map, the token is searched for at least one matching scopes set to allow the request. The first set that matches will allow the request. If no set matches, the :unauthorized function is called.

defmodule MyApp.MyController do
  use MyApp.Web, :controller

  plug ExOauth2Provider.Plug.EnsureScopes, handler: MyApp.MyAuthErrorHandler,
    one_of: [~w(admin), ~w(read write)]
end

Current resource owner and access token

If the Authorization Header was verified, you'll be able to retrieve the current resource owner or access token.

ExOauth2Provider.Plug.current_access_token(conn) # access the token in the default location
ExOauth2Provider.Plug.current_access_token(conn, :secret) # access the token in the secret location

ExOauth2Provider.Plug.current_resource_owner(conn) # Access the loaded resource owner in the default location
ExOauth2Provider.Plug.current_resource_owner(conn, :secret) # Access the loaded resource owner in the secret location

Custom access token generator

You can add your own access token generator, as this example shows:

# config/config.exs
config :ex_oauth2_provider, ExOauth2Provider,
  access_token_generator: {MyModule, :my_method}

defmodule MyModule
  def my_method(access_token) do
    %JWT.token{
      resource_owner_id: access_token.resource_owner_id,
      application_id: access_token.application.id,
      scopes: access_token.scopes,
      expires_in: access_token.expires_in,
      created_at: access_token.created_at
    }
    |> with_signer(hs256("my_secret"))
  end
end

Remember to change the field type for the token column in the oauth_access_tokens table to accepts tokens larger than 255 characters.

Custom access token response body

You can add extra values to the response body.

# config/config.exs
config :ex_oauth2_provider, ExOauth2Provider,
  access_token_response_body_handler: {MyModule, :my_method}

defmodule MyModule
  def my_method(response_body, access_token) do
    response_body
    |> Map.merge(%{user_id: access_token.resource_owner.id})
  end
end

Remember to change the field type for the token column in the oauth_access_tokens table to accepts tokens larger than 255 characters.

Using UUID or custom primary key type

1. If only resource owner uses :uuid

You'll need to create the migration file with the argument --uuid resource_owners:

mix ex_oauth2_provider.install --uuid resource_owners

And set the config to use :binary_id for belongs_to fields:

config :ex_oauth2_provider, ExOauth2Provider,
  resource_owner: {Dummy.User, :binary_id}

2. If all structs should use :uuid

If you don't have auto-incrementing integers as primary keys in your database you can set up ExOauth2Provider to handle all primary keys as :uuid by doing the following.

Update the :ex_oauth2_provider config in config/config.exs to use the the UUID schema macro:

config :ex_oauth2_provider, ExOauth2Provider,
  resource_owner: {Dummy.User, :binary_id},
  app_schema: ExOauth2Provider.Schema.UUID

And generate a migration file that uses :uuid for all tables:

mix ex_oauth2_provider.install --uuid all

3. If you need something different than :uuid

It's also possible to use a completely different setup by adding a custom schema macro, however you'll need to ensure that the schema file is compiled before this library and that you've updated the migration file accordingly.

4. If you need custom belongs_to options for resource owner

You can provide a list of belongs_to options, by passing a keyword list instead. This is useful when you want to use a references value:

config :ex_oauth2_provider, ExOauth2Provider,
  resource_owner: {Dummy.User, [type: :binary_id, references: :uuid]}

Acknowledgement

This library was made thanks to doorkeeper, guardian and authable, that gave the conceptual building blocks.

Thanks to Benjamin Schultzer for helping to refactor the code.

LICENSE

(The MIT License)

Copyright (c) 2017 Dan Schultzer & the Contributors Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.