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Multi-provider framework in Elixir
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README.md

Assent

Build Status hex.pm

Multi-provider authentication framework.

Features

  • Includes the following base strategies:
    • OAuth 1.0 - Assent.Strategy.OAuth
    • OAuth 2.0 - Assent.Strategy.OAuth2
    • OpenID Connect - Assent.Strategy.OIDC
  • Includes the following provider strategies:
    • Apple Sign In - Assent.Strategy.Apple
    • Auth0 - Assent.Strategy.Auth0
    • Azure AD - Assent.Strategy.AzureAD
    • Basecamp - Assent.Strategy.Basecamp
    • Discord - Assent.Strategy.Discord
    • Facebook - Assent.Strategy.Facebook
    • Github - Assent.Strategy.Github
    • Gitlab - Assent.Strategy.Gitlab
    • Google - Assent.Strategy.Google
    • Instagram - Assent.Strategy.Instagram
    • Slack - Assent.Strategy.Slack
    • Twitter - Assent.Strategy.Twitter
    • VK - Assent.Strategy.VK

Installation

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

defp deps do
  [
    # ...
    {:assent, "~> 0.1.4"},

    # Optional, but recommended for SSL validation with :httpc adapter
    {:certifi, "~> 2.4"},
    {:ssl_verify_fun, "~> 1.1"}
  ]
end

Run mix deps.get to install it.

Getting started

A strategy consists of two phases; request and callback. In the request phase the user would normally be redirected to the provider for authentication. After authentication, the provider will be redirect the user back to the callback phase.

Single provider example

config = [
  client_id: "REPLACE_WITH_CLIENT_ID",
  client_secret: "REPLACE_WITH_CLIENT_SECRET",
  redirect_uri: "http://localhost:4000/oauth/callback"
]

# Redirect user to provider
{:ok, %{url: url, session_params: session_params}} = Assent.Strategy.Github.authorize_url(config)

# Handle callback
{:ok, %{user: user, token: token}} =
  config
  |> Assent.Config.put(:session_params, session_params)
  |> Assent.Strategy.Github.callback(params)

Multi-provider example

This is a generalized flow that's similar to what's used in PowAssent.

config :my_app, :strategies,
  github: [
    client_id: "REPLACE_WITH_CLIENT_ID",
    client_secret: "REPLACE_WITH_CLIENT_SECRET",
    strategy: Assent.Strategy.Github
  ],
  # ...
defmodule MultiProvider do
  @spec request(atom()) :: {:ok, map()} | {:error, term()}
  def request(provider) do
    config = config!(provider)

    config[:strategy].authorize_url(config)
  end

  @spec callback(atom(), map(), map()) :: {:ok, map()} | {:error, term()}
  def callback(provider, params, session_params \\ %{}) do
    config =
      provider
      |> config!()
      |> Assent.Config.put(:session_params, session_params)

    config[:strategy].callback(config, params)
  end

  defp config!(provider) do
    Application.get_env(:my_app, :strategies)[provider] || raise "No provider configuration for #{provider}"
  end
end

Custom provider

You can add your own custom strategy.

Here's an example of an OAuth 2.0 implementation using Assent.Strategy.OAuth2.Base:

defmodule TestProvider do
  use Assent.Strategy.OAuth2.Base

  @impl true
  def default_config(_config) do
    [
      site: "http://localhost:4000/",
      authorize_url: "http://localhost:4000/oauth/authorize",
      token_url: "http://localhost:4000/oauth/access_token",
      user_url: "/user",
      authorization_params: [scope: "email profile"],
      auth_method: :client_secret_post
    ]
  end

  @impl true
  def normalize(_config, user) do
    {:ok, %{
      "sub"   => user["sub"],
      "name"  => user["name"],
      "email" => user["email"]
    },
    %{
      "test_provider_bio" => user["bio"]
    }}
  end
end

The normalized user map should conform to the OpenID Connect Core 1.0 Standard Claims spec, and should return either {:ok, userinfo_claims} or {:ok, userinfo_claims, additional}.

You can also use Assent.Strategy:

defmodule TestProvider do
  @behaviour Assent.Strategy

  @spec authorize_url(Keyword.t()) :: {:ok, %{url: binary()}} | {:error, term()}
  def authorize_url(config) do
    # Generate authorization url
  end

  @spec callback(Keyword.t(), map()) :: {:ok, %{user: map()}} | {:error, term()}
  def callback(config, params) do
    # Handle callback response
  end
end

HTTP Adapter

By default Erlangs built-in :httpc is used for requests. SSL verification is automatically enabled when :certifi and :ssl_verify_fun packages are available. :httpc only supports HTTP/1.1.

If you would like HTTP/2 support, you should consider adding Mint to your project.

Update mix.exs:

defp deps do
  [
    # ...
    {:mint, "~> 0.4.0"},
    {:castore, "~> 0.1.0"} # Required for SSL validation
  ]
end

Pass the :http_adapter with your provider configuration:

config = [
  client_id: "REPLACE_WITH_CLIENT_ID",
  client_secret: "REPLACE_WITH_CLIENT_SECRET",
  http_adapter: Assent.HTTPAdapter.Mint
]

JWT Adapter

By default the built-in Assent.JWTAdapter.AssentJWT is used for JWT parsing, but you can change it to any third-party library with a custom Assent.JWTAdapter. A JOSE adapter Assent.JWTAdapter.JOSE is included.

To use JOSE, update mix.exs:

defp deps do
  [
    # ...
    {:jose, "~> 1.8"}
  ]
end

And pass the :jwt_adapter with your provider configuration:

config = [
  client_id: "REPLACE_WITH_CLIENT_ID",
  client_secret: "REPLACE_WITH_CLIENT_SECRET",
  jwt_adapter: Assent.JWTAdapter.JOSE
]

LICENSE

(The MIT License)

Copyright (c) 2019 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.

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