Delegated Authentication - Identity Provider Registration

An identity provider is a server which can authenticate users (like Google, Yahoo…) instead of a CAS server. If you want to delegate the CAS authentication to Twitter for example, you have to add an OAuth client for the Twitter provider, which will be done automatically for you once provider settings are taught to CAS.

Notice that for each provider, the CAS server is considered as a client and therefore should be declared as an client at the external identity provider. After the declaration, a key and a secret may be given by the provider which has to be defined in the CAS configuration as well.

Actuator Endpoints

The following endpoints are provided by CAS:

Default

Identity providers for delegated authentication can be registered with CAS using settings.

Provider	Reference
Apple	See this guide.
Azure AD	See this guide.
CAS	See this guide.
DropBox	See this guide.
Facebook	See this guide.
FourSquare	See this guide.
Generic OpenID Connect	See this guide.
GitHub	See this guide.
Google	See this guide.
Google OpenID Connect	See this guide.
HiOrgServer	See this guide.
Keycloak	See this guide.
LinkedIn	See this guide.
OAuth20	See this guide.
PayPal	See this guide.
SAML	See this guide.
Twitter	See this guide.
WindowsLive	See this guide.
Wordpress	See this guide.
Yahoo	See this guide.

REST

Identity providers for delegated authentication can be provided to CAS using an external REST endpoint.

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.}

_{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. You should only include this field in your
configuration if you need to modify the default value.}

Configuration Metadata

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.

Be Selective

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.

YAGNI

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.

Naming Convention

Property names can be specified in very relaxed terms. For instance cas.someProperty, cas.some-property, 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 cas.property-name=value. 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.

Validation

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. The validation process is on by default and can be skipped on startup using a special system property SKIP_CONFIG_VALIDATION that should be set to true. Additional validation processes are also handled via Configuration Metadata and property migrations applied automatically on startup by Spring Boot and family.

Indexed Settings

CAS settings able to accept multiple values are typically documented with an index, such as cas.some.setting[0]=value. The index [0] is meant to be incremented by the adopter to allow for distinct multiple configuration blocks.

The expected payload type, that is controlled via CAS settings, can be understood and consumed in the following ways.

Pac4j Payload

This allows the CAS server to reach to a remote REST endpoint whose responsibility is to produce the following payload in the response body:

{
    "callbackUrl": "https://sso.example.org/cas/login",
    "properties": {
        "github.id": "...",
        "github.secret": "...",
        
        "cas.loginUrl.1": "...",
        "cas.protocol.1": "..."
    }
}

The syntax and collection of available properties in the above payload is controlled by the Pac4j library. The response that is returned must be accompanied by a 200 status code.

CAS Payload

This allows the CAS server to reach to a remote REST endpoint whose responsibility is to produce the following payload in the response body:

{
    "cas.authn.pac4j.github.client-name": "...",
    "cas.authn.pac4j.github.id": "...",
    "cas.authn.pac4j.github.secret": "...",
    
    "cas.authn.pac4j.cas[0].login-url": "...",
    "cas.authn.pac4j.cas[0].protocol": "..."
}

The payload is expected to contain CAS specific properties that would be used to construct external identity providers. The response that is returned must be accompanied by a 200 status code.

Caching

Note that once identity provider registration data is fetched, the results are cached by CAS using a configurable expiration policy and the endpoint is only contacted by CAS if the cache content is empty or has been invalidated. This cache is owned by each CAS server node, in case there is more than one in the same cluster and operations that interact with the cache must be able to apply task to the cache for all CAS server nodes.