Amur

Simple OAuth for Plug apps. Amur gives you a small OAuth callback flow and provider normalization layer. It is Plug-based and does not require Phoenix.

Installation

Add amur to your dependencies in mix.exs:

def deps do
  [
    {:amur, "~> 0.2"}
  ]
end

Setup

1. Configure your OAuth providers

# config/runtime.exs
config :amur,
  base_url: "http://localhost:4000",
  providers: [
    github: [
      client_id: System.fetch_env!("GITHUB_CLIENT_ID"),
      client_secret: System.fetch_env!("GITHUB_CLIENT_SECRET")
    ]
  ],
  on_success: &MyAppWeb.AuthController.on_success/2,
  on_failure: &MyAppWeb.AuthController.on_failure/2

Key	Required	Description
`base_url`	no	Base URL used to build the `redirect_uri` (`#{base_url}/auth/:provider/callback`). Defaults to `""`.
`providers`	yes	Keyword list of provider configurations. Each key is a provider name, each value is either a keyword list of credentials or a custom provider module.
`on_success`	yes	A `{module, function, args}` MFA tuple or a function capture of arity 2, called with `(conn, normalized_user)`.
`on_failure`	no	Same format as `on_success`, called with `(conn, reason)`. Defaults to a redirect to `/`.

2. Mount the router

# Phoenix
scope "/auth", alias: false do
  pipe_through :browser
  forward "/", Amur.Router
end

The alias: false on the scope is required — without it Phoenix rewrites Amur.Router as YourAppWeb.Amur.Router.

Inside a browser pipeline, session and flash helpers are available for your callbacks.

Amur works with Plug.Router too:

# Plug
forward "/auth", to: Amur.Router

The router exposes three endpoints:

Endpoint	Description
`GET /auth/:provider`	Initiates the OAuth flow
`GET /auth/:provider/callback`	Handles the provider callback
`GET /auth/logout`	Clears Amur's stored session params

3. Add an auth controller

defmodule MyAppWeb.AuthController do
  import Plug.Conn
  import Phoenix.Controller

  def on_success(conn, user) do
    conn
    |> put_flash(:info, "Logged in as #{user.email}")
    |> redirect(to: "/")
    |> halt()
  end

  def on_failure(conn, reason) do
    conn
    |> put_flash(:error, "Authentication failed")
    |> redirect(to: "/")
    |> halt()
  end
end

The normalized user map has the following shape:

%{
  provider: "github",      # the provider atom as a string
  uid: "12345",            # provider-specific user ID
  email: "user@example.com",
  name: "username",
  avatar: "https://..."
}

Different providers may return different fields. See each provider module's normalize_user/1 for the exact shape.

4. (Optional) Clear the session on logout

# In your own logout handler
Amur.logout(conn)

This deletes the :amur_session_params key from the session. The GET /auth/logout endpoint calls this automatically and redirects to /.

Built-in providers

Amur ships with support for the following providers:

Apple, Auth0, Azure AD, Basecamp, Bitbucket, DigitalOcean, Discord, Facebook, GitHub, GitLab, Google, Hack Club, Instagram, LINE, LinkedIn, Slack, Spotify, Strava, Stripe, Telegram, Twitch, Twitter (X), VK, Zitadel

Each is a thin wrapper around the corresponding Assent strategy.

Custom providers

You can define your own provider module using the Amur.Provider behaviour:

defmodule MyApp.Auth.CustomProvider do
  use Amur.Provider

  def strategy, do: Assent.Strategy.OAuth2

  def base_config do
    [
      base_url: "https://api.example.com",
      authorization_endpoint: "/oauth/authorize",
      token_endpoint: "/oauth/token",
      user_endpoint: "/user"
    ]
  end

  def normalize_user(user) do
    %{uid: user["id"], email: user["email"], name: user["name"]}
  end
end

Then reference it in your config:

config :amur,
  providers: [
    my_provider: MyApp.Auth.CustomProvider
  ]

Scopes

To request specific OAuth scopes, pass them in your provider config:

config :amur,
  providers: [
    github: [
      client_id: "..",
      client_secret: "..",
      scopes: "user:email,read:org"
    ]
  ]

License

MIT