OpenID Connect Authentication

Allow CAS to act as an OpenId Connect Provider (OP).

Remember

OpenId Connect is a continuation of the OAuth protocol with some additional variations. If you enable OpenId Connect, you will have automatically enabled OAuth as well. Options and behaviors that are documented for the OAuth protocol support may apply here just the same.

Support is enabled by including the following dependency in the WAR overlay:

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<dependency>
  <groupId>org.apereo.cas</groupId>
  <artifactId>cas-server-support-oidc</artifactId>
  <version>${cas.version}</version>
</dependency>

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implementation "org.apereo.cas:cas-server-support-oidc:${project.'cas.version'}"

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dependencyManagement {
  imports {
    mavenBom "org.apereo.cas:cas-server-support-bom:${project.'cas.version'}"
  }
}

dependencies {  
  implementation "org.apereo.cas:cas-server-support-oidc"
}

To learn more about OpenId Connect, please review this guide.

The current implementation provides support for:

Endpoints

Field Description
/oidc/.well-known The discovery endpoint used to query for CAS OIDC configuration information and metadata.
/oidc/.well-known/openid-configuration Same as .well-known discovery endpoint.
/oidc/.well-known/webfinger WebFinger discovery endpoint
/oidc/jwks Contains the server’s public keys, which clients may use to verify the digital signatures of access tokens and ID tokens issued by CAS. Accepts an optional state query parameter to narrow down keys by their current state (i.e. current, previous, future).
/oidc/authorize Authorization requests are handled here.
/oidc/profile User profile requests are handled here.
/oidc/logout Logout requests are handled here.
/oidc/introspect Query CAS to detect the status of a given access token via introspection. This endpoint expects HTTP basic authentication with OIDC service client_id and client_secret associated as username and password.
/oidc/accessToken, /oidc/token Produces authorized access tokens.
/oidc/revoke Revoke access or refresh tokens. This endpoint expects HTTP basic authentication with OIDC service client_id and client_secret associated as username and password.
/oidc/register Register clients via the dynamic client registration protocol.
Use Discovery

The above endpoints are not strictly defined in the OpenID Connect specification. The CAS software may choose to change URL endpoints at any point in time. Do NOT hardcode these endpoints in your application configuration. Instead, use the Dynamic Discovery endpoint and parse the discovery document to discover the endpoints.

Configuration

The following settings and properties are available from the CAS configuration catalog:

The configuration settings listed below are tagged as Required in the CAS configuration metadata. This flag indicates that the presence of the setting may be needed to activate or affect the behavior of the CAS feature and generally should be reviewed, possibly owned and adjusted. If the setting is assigned a default value, you do not need to strictly put the setting in your copy of the configuration, but should review it nonetheless to make sure it matches your deployment expectations.

  • cas.authn.oidc.core.issuer=http://localhost:8080/cas/oidc

    • OIDC issuer.

    org.apereo.cas.configuration.model.support.oidc.OidcCoreProperties.
    The configuration settings listed below are tagged as Optional in the CAS configuration metadata. This flag indicates that the presence of the setting is not immediately necessary in the end-user CAS configuration, because a default value is assigned or the activation of the feature is not conditionally controlled by the setting value.

  • cas.authn.oidc.core.accepted-issuers-pattern=a^

    • Defines the regular expression pattern that is matched against the calculated issuer from the request. If the issuer that is extracted from the request does not match the #issuer defined in the CAS configuration, this pattern acts as a secondary level rule to allow incoming requests to pass through if the match is successful. By default, the pattern is designed to never match anything.

    org.apereo.cas.configuration.model.support.oidc.OidcCoreProperties.
  • cas.authn.oidc.core.authentication-context-reference-mappings=

    • A mapping of authentication context refs (ACR) values. This is where specific authentication context classes are referenced and mapped to providers that CAS may support mainly for MFA purposes.

    Example might be acr-value->mfa-duo.

    org.apereo.cas.configuration.model.support.oidc.OidcCoreProperties.
  • cas.authn.oidc.core.claims-map=

    • Map fixed claims to CAS attributes. Key is the existing claim name for a scope and value is the new attribute that should take its place and value.

    org.apereo.cas.configuration.model.support.oidc.OidcCoreProperties.
  • cas.authn.oidc.core.dynamic-client-registration-mode=

    • Whether dynamic registration operates in OPEN or PROTECTED mode.

    org.apereo.cas.configuration.model.support.oidc.OidcCoreProperties.
  • cas.authn.oidc.core.include-id-token-claims=true

    • As per OpenID Connect Core section 5.4, "The Claims requested by the profile, email, address, and phone scope values are returned from the userinfo endpoint", except for response_type=id_token, where they are returned in the id_token (as there is no access token issued that could be used to access the userinfo endpoint). The Claims requested by the profile, email, address, and phone scope values are returned from the userinfo endpoint when a response_type value is used that results in an access token being issued. However, when no access token is issued (which is the case for the response_type value id_token), the resulting Claims are returned in the ID Token.

    Setting this flag to true will force CAS to include claims in the ID token regardless of the response type. Note that this setting MUST ONLY be used as a last resort, to stay compliant with the specification as much as possible. DO NOT use this setting without due consideration.

    Note that this setting is set to true by default mainly provided to preserve backward compatibility with previous CAS versions that included claims into the ID token without considering the response type. The behavior of this setting may change and it may be removed in future CAS releases.

    org.apereo.cas.configuration.model.support.oidc.OidcCoreProperties.
  • cas.authn.oidc.core.skew=PT5M

    • Skew value used to massage the authentication issue instance.

    This settings supports the java.time.Duration syntax [?].

    org.apereo.cas.configuration.model.support.oidc.OidcCoreProperties.
  • cas.authn.oidc.core.user-defined-scopes=

    • Mapping of user-defined scopes. Key is the new scope name and value is a comma-separated list of claims mapped to the scope.

    org.apereo.cas.configuration.model.support.oidc.OidcCoreProperties.