Delegated Authentication

CAS can act as a client (i.e. service provider or proxy) using the Pac4j library and delegate the authentication to:

  • CAS servers
  • SAML2 identity providers
  • OAuth2 providers such as Facebook, Twitter, GitHub, Google, LinkedIn, etc
  • OpenID Connect identity providers such as Google, Apple
  • ADFS

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

implementation "org.apereo.cas:cas-server-support-pac4j-webflow:${project.'cas.version'}"
dependencyManagement {
  imports {
    mavenBom "org.apereo.cas:cas-server-support-bom:${project.'cas.version'}"

dependencies {  
  implementation "org.apereo.cas:cas-server-support-pac4j-webflow"

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.pac4j.core.groovy-redirection-strategy.location=
  • The location of the resource. Resources can be URLS, or files found either on the classpath or outside somewhere in the file system.


    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.pac4j.core.lazy-init=true
  • Whether initialization of delegated identity providers should be done eagerly typically during startup.

  • The name of the authentication handler in CAS used for delegation.

  • cas.authn.pac4j.core.order=
  • Order of the authentication handler in the chain.

  • cas.authn.pac4j.core.principal-attribute-id=
  • The attribute to use as the principal identifier built during and upon a successful authentication attempt.

  • cas.authn.pac4j.core.replicate-sessions=true
  • Indicates whether profiles and other session data, collected as part of pac4j flows and requests that are kept by the container session, should be replicated across the cluster using CAS and its own ticket registry. Without this option, profile data and other related pieces of information should be manually replicated via means and libraries outside of CAS.

  • cas.authn.pac4j.core.typed-id-used=false
  • When constructing the final user profile from the delegated provider, determines if the provider id should be combined with the principal id.

    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.


    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 ettings 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. 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 client issuing the authentication request can be of any type (SAML, OAuth2, OpenID Connect, etc) and is allowed to submit the authentication request using any protocol that the CAS server supports and is configured to understand. This means that you may have an OAuth2 client using CAS in delegation mode to authenticate at an external SAML2 identity provider, another CAS server or Facebook and in the end of that flow receiving an OAuth2 user profile. The CAS server is able to act as a proxy, doing the protocol translation in the middle.

    Register Providers

    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 OAuth provider, the CAS server is considered as an OAuth client and therefore should be declared as an OAuth client at the OAuth provider. After the declaration, a key and a secret is given by the OAuth provider which has to be defined in the CAS configuration as well.


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

    Apple See this guide.
    Azure AD See this guide.
    CAS See this guide.