OAuth2 (Client)

An Elixir OAuth2 Client

Install

# mix.exs

def application do
  # Add the application to your list of applications.
  # This will ensure that it will be included in a release.
  [applications: [:logger, :oauth2]]
end

defp deps do
  # Add the dependency
  [{:oauth2, "~> 0.9"}]
end

Configure a serializer

This library can be configured to handle encoding and decoding requests and responses automatically.

If you're using Poison for JSON in your application, this library is already pre-configured to use it for "application/json" request and response bodies. You will still need to include it as a dependency though.

If you need to handle different MIME types, you can simply configure it like so:

# config/config.exs
config :oauth2,
  serializers: %{
    "application/vnd.api+json" => Poison,
    "application/xml" => MyApp.XmlParser,
  }

The serializers option is a map where the keys are MIME types and the values are modules.

The modules are expected to export encode!/1 and decode!/1.

defmodule MyApp.XmlParser do
  def encode!(data), do: # ...
  def decode!(binary), do: # ...
end

Debug mode

Some times its handy to see what's coming back from the response when getting a token. You can configure OAuth2 to output the response like so:

config :oauth2, debug: true

Usage

Current implemented strategies:

• Authorization Code
• Password
• Client Credentials

Authorization Code Flow (AuthCode Strategy)

# Initialize a client with client_id, client_secret, site, and redirect_uri.
# The strategy option is optional as it defaults to `OAuth2.Strategy.AuthCode`.

client = OAuth2.Client.new([
  strategy: OAuth2.Strategy.AuthCode, #default
  client_id: "client_id",
  client_secret: "abc123",
  site: "https://auth.example.com",
  redirect_uri: "https://example.com/auth/callback"
])

# Generate the authorization URL and redirect the user to the provider.
OAuth2.Client.authorize_url!(client)
# => "https://auth.example.com/oauth/authorize?client_id=client_id&redirect_uri=https%3A%2F%2Fexample.com%2Fauth%2Fcallback&response_type=code"

# Use the authorization code returned from the provider to obtain an access token.
client = OAuth2.Client.get_token!(client, code: "someauthcode")

# Use the access token to make a request for resources
resource = OAuth2.Client.get!(client, "/api/resource").body

Write Your Own Strategy

Here's an example strategy for GitHub:

defmodule GitHub do
  use OAuth2.Strategy

  # Public API

  def client do
    OAuth2.Client.new([
      strategy: __MODULE__,
      client_id: System.get_env("GITHUB_CLIENT_ID"),
      client_secret: System.get_env("GITHUB_CLIENT_SECRET"),
      redirect_uri: "http://myapp.com/auth/callback",
      site: "https://api.github.com",
      authorize_url: "https://github.com/login/oauth/authorize",
      token_url: "https://github.com/login/oauth/access_token"
    ])
  end

  def authorize_url! do
    OAuth2.Client.authorize_url!(client(), scope: "user,public_repo")
  end

  # you can pass options to the underlying http library via `opts` parameter
  def get_token!(params \\ [], headers \\ [], opts \\ []) do
    OAuth2.Client.get_token!(client(), params, headers, opts)
  end

  # Strategy Callbacks

  def authorize_url(client, params) do
    OAuth2.Strategy.AuthCode.authorize_url(client, params)
  end

  def get_token(client, params, headers) do
    client
    |> put_param(:client_secret, client.client_secret)
    |> put_header("accept", "application/json")
    |> OAuth2.Strategy.AuthCode.get_token(params, headers)
  end
end

Here's how you'd use the example GitHub strategy:

Generate the authorize URL and redirect the client for authorization.

GitHub.authorize_url!

Capture the code in your callback route on your server and use it to obtain an access token.

client = GitHub.get_token!(code: code)

Use the access token to access desired resources.

user = OAuth2.Client.get!(client, "/user").body

# Or
case OAuth2.Client.get(client, "/user") do
  {:ok, %OAuth2.Response{body: user}} ->
    user
  {:error, %OAuth2.Response{status_code: 401, body: body}} ->
    Logger.error("Unauthorized token")
  {:error, %OAuth2.Error{reason: reason}} ->
    Logger.error("Error: #{inspect reason}")
end

Examples

• Authenticate with Github (OAuth2/Phoenix)

License

The MIT License (MIT)

Copyright (c) 2015 Sonny Scroggin

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.