# Auth0 Quick Start Guide This is a _very quick_ tutorial on how to configure your application to use Auth0 for authentication. First, you need to configure an application in [the Auth0 dashboard](https://manage.auth0.com/) using the following steps: 1. Click "Create Application". 2. Set your application name to something that identifies it. You will likely need separate applications for development and production environments, so keep that in mind. 3. Select "Regular Web Application" and click "Create". 4. Switch to the "Settings" tab. 5. Copy the "Domain", "Client ID" and "Client Secret" somewhere safe - we'll need them soon. 6. In the "Allowed Callback URLs" section, add your callback URL. The callback URL is generated from the following information: - The base URL of the application - in development that would be `http://localhost:4000/` but in production will be your application's URL. - The mount point of the auth routes in your router - we'll assume `/auth`. - The "subject name" of the resource being authenticated - we'll assume `user`. - The name of the strategy in your configuration. By default this is `auth0`. This means that the callback URL should look something like `http://localhost:4000/auth/user/auth0/callback`. 7. Set "Allowed Web Origins" to your application's base URL. 8. Click "Save Changes". Next we can configure our resource (assuming you already have everything else set up): ```elixir defmodule MyApp.Accounts.User do use Ash.Resource, extensions: [AshAuthentication] authentication do strategies do auth0 do client_id MyApp.Secrets redirect_uri MyApp.Secrets client_secret MyApp.Secrets site MyApp.Secrets end end end end ``` Because all the configuration values should be kept secret (ie the `client_secret`) or are likely to be different for each environment we use the `AshAuthentication.Secret` behaviour to provide them. In this case we're delegating to the OTP application environment, however you may want to use a system environment variable or some other secret store (eg Vault). ```elixir defmodule MyApp.Secrets do use AshAuthentication.Secret def secret_for([:authentication, :strategies, :auth0, :client_id], MyApp.Accounts.User, _) do get_config(:client_id) end def secret_for([:authentication, :strategies, :auth0, :redirect_uri], MyApp.Accounts.User, _) do get_config(:redirect_uri) end def secret_for([:authentication, :strategies, :auth0, :client_secret], MyApp.Accounts.User, _) do get_config(:client_secret) end def secret_for([:authentication, :strategies, :auth0, :site], MyApp.Accounts.User, _) do get_config(:site) end defp get_config(key) do :my_app |> Application.get_env(:auth0, []) |> Keyword.fetch(key) end end ``` The values for this configuration should be: * `client_id` - the client ID copied from the Auth0 settings page. * `redirect_uri` - the URL to the generated auth routes in your application (eg `http://localhost:4000/auth`). * `client_secret` the client secret copied from the Auth0 settings page. * `site` - the "domain" value copied from the Auth0 settings page prefixed with `https://` (eg `https://dev-yu30yo5y4tg2hg0y.us.auth0.com`). Lastly, we need to add a register action to your user resource. This is defined as an upsert so that it can register new users, or update information for returning users. The default name of the action is `register_with_` followed by the strategy name. In our case that is `register_with_auth0`. The register action takes two arguments, `user_info` and the `oauth_tokens`. - `user_info` contains the [`GET /userinfo` response from Auth0](https://auth0.com/docs/api/authentication#get-user-info) which you can use to populate your user attributes as needed. - `oauth_tokens` contains the [`POST /oauth/token` response from Auth0](https://auth0.com/docs/api/authentication#get-token) - you may want to store these if you intend to call the Auth0 API on behalf of the user. ```elixir defmodule MyApp.Accounts.User do use Ash.Resource, extensions: [AshAuthentication] # ... actions do create :register_with_auth0 do argument :user_info, :map, allow_nil?: false argument :oauth_tokens, :map, allow_nil?: false upsert? true upsert_identity :email # Required if you have token generation enabled. change AshAuthentication.GenerateTokenChange # Required if you have the `identity_resource` configuration enabled. change AshAuthentication.Strategy.OAuth2.IdentityChange change fn changeset, _ -> user_info = Ash.Changeset.get_argument(changeset, :user_info) Ash.Changeset.change_attributes(changeset, Map.take(user_info, ["email"])) end end end # ... end ```