With OpenID Connect the trust is established out-of-band. This means that a network or channel separate from the primary network supplies the Service Provider with a username and a secret. All the necessary technical information such as endpoints, supported algorithms and supported claims can be found at the
.well-kown endpoint: https://connect.surfconext.nl/.well-known/openid-configuration.
SURFconext couples the SP and the IdP based on specific rules. Note that SURFconext itself does not authenticate users: this is done by the connected Identity Providers. This authentication flow in OpenID Connect is depicted below. Let's dive into this.
OpenID Connect authentication process in steps
The schematic is a representation of the login flow of the SURFconext OpenID Connect proxy.
A User accesses a Service Provider (Relying Party) and clicks "login via SURFconext"
The Relying Party (SP) generates an OpenID Connect Authorize request and
Redirects user to the OpenID Connect Authorization endpoint
OpenID Connect server receives request and prepares a SAML redirect to authenticate the user
In order to determine where to send the user for authentication, SURFconext shows the user a "Where Are You From?" (WAYF) page with all Identity Providers that have access to the service. The user chooses the institution that is his Identity Provider.
- The IdP authenticates the user, usually by asking to enter his credentials. After validating,
the IdP generates a SAML response and redirects the user back to SURFconext with a response message, saying that the user is authenticated. The message also contains the attributes from the user.
SURFconext validates the response message and if OK makes some alterations, e.g. rewriting the user's identifier and adding or modifying attributes and sends the SAML response to the OpenID Connect gateway. According to the attribute release policy applied, SURFconext determines the attributes that are allowed through to the Service Provider.
The OpenID connect gateway verifies the response, generates a code, and redirects the user to the Relying Party (SP) with the code
The Relying Party (SP) receives the authorization code
The Relying Party (SP) prepares a backchannel request to exchange the token for an access and ID token
The OpenID connect gateway receives the token and checks the validity
The OpenID connect gateway generates an access and ID token
- The access and ID token are posted to the redirect URL of the Client (SP)
The Relying Party (SP) now has 2 tokens; an ID token which contains a pseudonymous identifier and an access token that can be used to retrieve information from resource servers on behalf of the user. The picture above sketches this process.
- The Relying Party (SP) has received the access token in the authentication flow. It uses the token to retrieve information from a resource server. The OpenID Connect server itself has a special resource server, called the userinfo endpoint. This endpoint can supply user claims (attributes).
- The resource server receives the access token, and prepares a request to the introspect endpoint of the OpenID Connect server, where it checks the validity of the token
- The introspect endpoint verifies the validity of the access token, and returns some info about the user, allowing the resource server to identify the user
- The resource server receives the information on the user
- The resource server retrieves the requested user information and generates a response
- The Relying Party (SP) receives the information about the user (claims, group membership, other resources)
To get a feeling of how things work in reality, you can play around with our playground: https://oidc-playground.surfconext.nl/.