Strategy for authentication using an OpenID Connect compatible server as the source of truth.

This strategy builds on-top of AshAuthentication.Strategy.OAuth2 and assent.

In order to use OIDC you need to provide the following minimum configuration:

• client_id - The client id, required
• site - The OIDC issuer, required
• openid_configuration_uri - The URI for OpenID Provider, optional, defaults to /.well-known/openid-configuration
• client_authentication_method - The Client Authentication method to use, optional, defaults to client_secret_basic
• client_secret - The client secret, required if :client_authentication_method is :client_secret_basic, :client_secret_post, or :client_secret_jwt
• openid_configuration - The OpenID configuration, optional, the configuration will be fetched from :openid_configuration_uri if this is not defined
• id_token_signed_response_alg - The id_token_signed_response_alg parameter sent by the Client during Registration, defaults to RS256
• id_token_ttl_seconds - The number of seconds from iat that an ID Token will be considered valid, optional, defaults to nil
• nonce - The nonce to use for authorization request, optional, MUST be session based and unguessable.

Nonce

nonce can be set in the provider config. The nonce will be returned in the session_params along with state. You can use this to store the value in the current session e.g. a httpOnly session cookie.

A random value generator can look like this:

16
|> :crypto.strong_rand_bytes()
|> Base.encode64(padding: false)

AshAuthentication will dynamically generate one for the session if nonce is set to true.

DSL Documentation

Provides an OpenID Connect authentication strategy.

This strategy is built using the :oauth2 strategy, and thus provides all the same configuration options should you need them.

Schema:

• :name (atom/0) - Required. Uniquely identifies the strategy.

• :client_id - Required. The OAuth2 client ID.
  Takes either a module which implements the AshAuthentication.Secret behaviour, a 2 arity anonymous function or a string.
  See the module documentation for AshAuthentication.Secret for more information.

  Example:

  client_id fn _, resource ->
    :my_app
    |> Application.get_env(resource, [])
    |> Keyword.fetch(:oauth_client_id)
  end

• :site - Required. The base URL of the OAuth2 server - including the leading protocol (ie https://).
  Takes either a module which implements the AshAuthentication.Secret behaviour, a 2 arity anonymous function or a string.
  See the module documentation for AshAuthentication.Secret for more information.

  Example:

  site fn _, resource ->
    :my_app
    |> Application.get_env(resource, [])
    |> Keyword.fetch(:oauth_site)
  end

• :auth_method - The authentication strategy used, optional. If not set, no authentication will be used during the access token request. The value may be one of the following:

  • :client_secret_basic
  • :client_secret_post
  • :client_secret_jwt
  • :private_key_jwt Valid values are nil, :client_secret_basic, :client_secret_post, :client_secret_jwt, :private_key_jwt The default value is :client_secret_post.

• :client_secret - The OAuth2 client secret.
  Required if :auth_method is :client_secret_basic, :client_secret_post or :client_secret_jwt.
  Takes either a module which implements the AshAuthentication.Secret behaviour, a 2 arity anonymous function or a string.
  See the module documentation for AshAuthentication.Secret for more information.

  Example:

  site fn _, resource ->
    :my_app
    |> Application.get_env(resource, [])
    |> Keyword.fetch(:oauth_site)
  end

• :authorize_url - Required. The API url to the OAuth2 authorize endpoint.
  Relative to the value of site.
  Takes either a module which implements the AshAuthentication.Secret behaviour, a 2 arity anonymous function or a string.
  See the module documentation for AshAuthentication.Secret for more information.

  Example:

  authorize_url fn _, _ -> {:ok, "https://exampe.com/authorize"} end

• :token_url - Required. The API url to access the token endpoint.
  Relative to the value of site.
  Takes either a module which implements the AshAuthentication.Secret behaviour, a 2 arity anonymous function or a string.
  See the module documentation for AshAuthentication.Secret for more information.

  Example:

  token_url fn _, _ -> {:ok, "https://example.com/oauth_token"} end

• :private_key - The private key to use if :auth_method is :private_key_jwt
  Takes either a module which implements the AshAuthentication.Secret behaviour, a 2 arity anonymous function or a string.
  See the module documentation for AshAuthentication.Secret for more information.

• :redirect_uri - Required. The callback URI base.
  Not the whole URI back to the callback endpoint, but the URI to your AuthPlug. We can generate the rest.
  Whilst not particularly secret, it seemed prudent to allow this to be configured dynamically so that you can use different URIs for different environments.
  Takes either a module which implements the AshAuthentication.Secret behaviour, a 2 arity anonymous function or a string.
  See the module documentation for AshAuthentication.Secret for more information.

• :authorization_params (keyword/0) - Any additional parameters to encode in the request phase.
  eg: authorization_params scope: "openid profile email" The default value is [].

• :registration_enabled? (boolean/0) - Is registration enabled for this provider?
  If this option is enabled, then new users will be able to register for your site when authenticating and not already present.
  If not, then only existing users will be able to authenticate. The default value is true.

• :register_action_name (atom/0) - The name of the action to use to register a user.
  Only needed if registration_enabled? is true.
  Because we we don't know the response format of the server, you must implement your own registration action of the same name.
  See the "Registration and Sign-in" section of the module documentation for more information.
  The default is computed from the strategy name eg: register_with_#{name}.

• :sign_in_action_name (atom/0) - The name of the action to use to sign in an existing user.
  Only needed if registration_enabled? is false.
  Because we don't know the response format of the server, you must implement your own sign-in action of the same name.
  See the "Registration and Sign-in" section of the module documentation for more information.
  The default is computed from the strategy name, eg: sign_in_with_#{name}.

• :identity_resource - The resource used to store user identities.
  Given that a user can be signed into multiple different authentication providers at once we use the AshAuthentication.UserIdentity resource to build a mapping between users, providers and that provider's uid.
  See the Identities section of the module documentation for more information.
  Set to false to disable. The default value is false.

• :identity_relationship_name (atom/0) - Name of the relationship to the provider identities resource The default value is :identities.

• :identity_relationship_user_id_attribute (atom/0) - The name of the destination (user_id) attribute on your provider identity resource.
  The only reason to change this would be if you changed the user_id_attribute_name option of the provider identity. The default value is :user_id.

• :icon (atom/0) - The name of an icon to use in any potential UI.
  This is a hint for UI generators to use, and not in any way canonical. The default value is :oauth2.

• :openid_configuration_uri (String.t/0) - The URI for the OpenID provider The default value is "/.well-known/openid-configuration".

• :client_authentication_method - The client authentication method to use. Valid values are :client_secret_basic, :client_secret_post, :client_secret_jwt, :private_key_jwt The default value is :client_secret_basic.

• :openid_configuration (map/0) - The OpenID configuration.
  If not set, the configuration will be retrieved from openid_configuration_uri. The default value is %{}.

• :id_token_signed_response_alg - The id_token_signed_response_alg parameter sent by the Client during Registration. Valid values are "HS256", "HS384", "HS512", "RS256", "RS384", "RS512", "ES256", "ES384", "ES512", "PS256", "PS384", "PS512", "Ed25519", "Ed25519ph", "Ed448", "Ed448ph", "EdDSA" The default value is "RS256".

• :id_token_ttl_seconds - The number of seconds from iat that an ID Token will be considered valid. The default value is nil.

• :nonce - A function for generating the session nonce.
  When set to true the nonce will be automatically generated using AshAuthentication.Strategy.Oidc.NonceGenerator. Set to false to explicitly disable.
  Takes either a module which implements the AshAuthentication.Secret behaviour, a 2 arity anonymous function or a string.
  See the module documentation for AshAuthentication.Secret for more information.

  Example:

  nonce fn _, _ ->
    16
    |> :crypto.strong_rand_bytes()
    |> Base.encode64(padding: false)
  end

  The default value is true.

• :trusted_audiences - A list of audiences which are trusted. The default value is nil.