You are viewing the development documentation for the Apereo CAS server. The functionality presented here is not officially released yet. This is a work in progress and will be continually updated as development moves forward. You are most encouraged to test the changes presented.
OpenID Connect Authentication
Allow CAS to act as an OpenId Connect Provider (OP).
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:
The following platform references should be included automatically and are listed here for reference only.
To learn more about OpenId Connect, please review this guide.
The current implementation provides support for:
- Authorization Code Flow
- Implicit Flow
- Dynamic Discovery
- WebFinger Issuer Discovery
- Administration and registration of OIDC clients and relying parties.
- Administration and registration of OIDC clients and relying parties via Dynamic Client Registration protocol.
- Ability to resolve, map and release claims.
- Ability to configure expiration policies for various tokens.
|The discovery endpoint used to query for CAS OIDC configuration information and metadata.
.well-known discovery endpoint.
|WebFinger discovery endpoint
|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.
|Authorization requests are handled here.
|User profile requests are handled here.
|Logout requests are handled here.
|Query CAS to detect the status of a given access token via introspection. This endpoint expects HTTP basic authentication with OIDC service
client_secret associated as username and password.
|Produces authorized access tokens.
Revoke access or refresh tokens. This endpoint expects HTTP basic authentication with OIDC service
client_secret associated as username and password.
|Register clients via the dynamic client registration protocol.
|Obtain an initial master access token required for dynamic client registration when operating in
|Update or retrieve client application definitions, registered with the server.
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.
The following settings and properties are available from the CAS configuration catalog:
OIDC issuer. All OpenID Connect servers such as CAS are uniquely identified by a URL known as the issuer. This URL serves as the prefix of a service discovery endpoint as specified in the OpenID Connect Discovery standard.This URL must be using the https scheme with no query or fragment component that the identity provider (CAS) asserts as its Issuer Identifier. This also MUST be identical to the
iss claim value in ID Tokens issued from this issuer, unless overridden in very special circumstances as a last resort. CAS primarily supports a single issuer per deployment/host.
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
This settings supports regular expression patterns. [?].
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. Support for authentication context class references is implemented in form of
acr_values as part of the original authorization request, which is mostly taken into account by the multifactor authentication features of CAS. Once successful,
amr values are passed back to the relying party as part of the id token.
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. Claims associated with a scope (i.e. given_name for profile) are fixed in the OpenID specification. In the event that custom arbitrary attributes should be mapped to claims, mappings can be defined in CAS settings to link a CAS-defined attribute to a fixed given scope. For instance, CAS configuration may allow the value of the attribute
Skew value used to massage the authentication issue instance.
This settings supports the
Mapping of user-defined scopes. Key is the new scope name and value is a comma-separated list of claims mapped to the scope. Such user-defined scopes are also able to override the definition of system scopes. User-defined scopes as well as any and all custom claims that are mapped to the scope must also be defined as scopes and claims supported by CAS in OpenID Connect discovery.
The collection of configuration properties listed in this section are automatically generated from the CAS source and components that contain the actual field definitions, types, descriptions, modules, etc. This metadata may not always be 100% accurate, or could be lacking details and sufficient explanations.
This section is meant as a guide only. Do NOT copy/paste the entire collection of settings into your CAS configuration; rather pick only the properties that you need. Do NOT enable settings unless you are certain of their purpose and do NOT copy settings into your configuration only to keep them as reference. All these ideas lead to upgrade headaches, maintenance nightmares and premature aging.
Note that for nearly ALL use cases, declaring and configuring properties listed here is sufficient. You should NOT have to explicitly massage a CAS XML/Java/etc configuration file to design an authentication handler, create attribute release policies, etc. CAS at runtime will auto-configure all required changes for you. If you are unsure about the meaning of a given CAS setting, do NOT turn it on without hesitation. Review the codebase or better yet, ask questions to clarify the intended behavior.
Property names can be specified in very relaxed terms. For instance
cas.some_property are all valid names. While all
forms are accepted by CAS, there are certain components (in CAS and other frameworks used) whose activation at runtime is conditional on a property value, where
this property is required to have been specified in CAS configuration using kebab case. This is both true for properties that are owned by CAS as well as those
that might be presented to the system via an external library or framework such as Spring Boot, etc.
When possible, properties should be stored in lower-case kebab format, such as
The only possible exception to this rule is when naming actuator endpoints; The name of the
actuator endpoints (i.e.
ssoSessions) MUST remain in camelCase mode.
Settings and properties that are controlled by the CAS platform directly always begin with the prefix
cas. All other settings are controlled and provided
to CAS via other underlying frameworks and may have their own schemas and syntax. BE CAREFUL with
the distinction. Unrecognized properties are rejected by CAS and/or frameworks upon which CAS depends. This means if you somehow misspell a property definition
or fail to adhere to the dot-notation syntax and such, your setting is entirely refused by CAS and likely the feature it controls will never be activated in the
way you intend.
Configuration properties are automatically validated on CAS startup to report issues with configuration binding, specially if defined CAS settings cannot be recognized or validated by the configuration schema. Additional validation processes are also handled via Configuration Metadata and property migrations applied automatically on startup by Spring Boot and family.
CAS settings able to accept multiple values are typically documented with an index, such as
cas.some.setting=value. The index
 is meant to be
incremented by the adopter to allow for distinct multiple configuration blocks.
Sample Client Applications
To enable additional logging, configure the log4j configuration file to add the following levels:
<Logger name="org.apereo.cas.oidc" level="debug" additivity="false">
<Logger name="PROTOCOL_MESSAGE" level="debug" additivity="false">