Assent.Strategy.OIDC (Assent v0.1.26) View Source

OpenID Connect strategy.

This is built upon the Assent.Strategy.OAuth2 strategy with added OpenID Connect capabilities.

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

See Assent.Strategy.OAuth2 for more configuration options.

Usage

config =  [
  client_id: "REPLACE_WITH_CLIENT_ID",
  site: "https://server.example.com",
  authorization_params: [scope: "user:read user:write"]
]

{:ok, {url: url, session_params: session_params}} =
  config
  |> Assent.Config.put(:redirect_uri, "http://localhost:4000/auth/callback")
  |> Assent.Strategy.OIDC.authorize_url()

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

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)

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

See Assent.Strategy.OIDC.authorize_url/1 for more.

Link to this section Summary

Functions

Generates an authorization URL for request phase.

Callback phase for generating access token and fetch user data.

Fetches user params and normalizes response.

Fetches claims from userinfo endpoint.

Validates the ID token.

Link to this section Functions

Specs

authorize_url(Assent.Config.t()) ::
  {:ok,
   %{
     session_params: %{state: binary()} | %{state: binary(), nonce: binary()},
     url: binary()
   }}
  | {:error, term()}

Generates an authorization URL for request phase.

The authorization url will be fetched from the OpenID configuration URI.

openid will automatically be added to the :scope in :authorization_params, unless :openid_default_scope has been set.

Add :nonce to the config to pass it with the authorization request. The nonce will be returned in :session_params. The nonce MUST be session based and unguessable. A cryptographic hash of a cryptographically random value could be stored in a httpOnly session cookie.

See Assent.Strategy.OAuth2.authorize_url/1 for more.

Link to this function

callback(config, params, strategy \\ __MODULE__)

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Specs

callback(Assent.Config.t(), map(), atom()) ::
  {:ok, %{user: map(), token: map()}} | {:error, term()}

Callback phase for generating access token and fetch user data.

The token url will be fetched from the OpenID configuration URI.

If the returned ID Token is signed with a symmetric key, :client_secret will be required and used to verify the ID Token. If it was signed with a private key, the appropriate public key will be fetched from the jwks_uri setting in the OpenID configuration to verify the ID Token.

The userinfo will be fetched from the userinfo_endpoint if it exists in the OpenID Configuration, otherwise the claims in the ID Token is used.

The ID Token will be validated per OpenID Connect Core 1.0 rules.

See Assent.Strategy.OAuth2.callback/3 for more.

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fetch_user(config, token)

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Specs

fetch_user(Assent.Config.t(), map()) :: {:ok, map()} | {:error, term()}

Fetches user params and normalizes response.

The ID Token is validated, and the claims is returned as the user params. Use fetch_userinfo/2 to fetch the claims from the userinfo endpoint.

Link to this function

fetch_userinfo(config, token)

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Specs

fetch_userinfo(Assent.Config.t(), map()) :: {:ok, map()} | {:error, term()}

Fetches claims from userinfo endpoint.

The userinfo will be fetched from the userinfo_endpoint OpenID configuration.

The returned claims will be validated against the id_token verifying that sub is equal.

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validate_id_token(config, id_token)

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Specs

validate_id_token(Assent.Config.t(), binary()) ::
  {:ok, map()} | {:error, term()}

Validates the ID token.

The OpenID configuration will be dynamically fetched if not set in the config.

The ID Token will be validated per OpenID Connect Core 1.0 rules.