Webflow Customization

CAS uses Spring Webflow to do script processing of login and logout protocols. Spring Web Flow builds on Spring MVC and allows implementing the “flows” of a web application. A flow encapsulates a sequence of steps that guide a user through the execution of some business task. It spans multiple HTTP requests, has state, deals with transactional data, is reusable, and may be dynamic and long-running in nature. Each flow may contain among many other settings the following major elements:

  • Actions: components that describe an executable task and return back a result
  • Transitions: Routing the flow from one state to another; Transitions may be global to the entire flow.
  • Views: Components that describe the presentation layer displayed back to the client
  • Decisions: Components that conditionally route to other areas of flow and can make logical decisions

Spring Web Flow presents CAS with a pluggable architecture where custom actions, views and decisions may be injected into the flow to account for additional use cases and processes. Note that to customize the webflow, one must possess a reasonable level of understanding of the webflow’s internals and injection policies. The intention of this document is NOT to describe Spring Web Flow, but merely to demonstrate how the framework is used by CAS to carry out various aspects of the protocol and business logic execution.

Webflow Session

See this guide for more info.

Webflow Auto Configuration

Most CAS modules, when declared as a dependency, attempt to autoconfigure the CAS webflow to suit their needs. This practically means that the CAS adopter would no longer have to manually massage the CAS webflow configuration, and the module automatically takes care of all required changes. While this is the default behavior, it is possible that you may want to manually handle all such changes. For doing so, you will need to disable the CAS auto-configuration of the 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.

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.webflow.auto-configuration.enabled=true
  • Whether webflow auto-configuration should be enabled.

    org.apereo.cas.configuration.model.core.web.flow.WebflowAutoConfigurationProperties.

  • cas.webflow.auto-configuration.order=0
  • The order in which the webflow is configured.

    org.apereo.cas.configuration.model.core.web.flow.WebflowAutoConfigurationProperties.

    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.S 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.

    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.

    Note

    Only attempt to modify the Spring webflow configuration files by hand when/if absolutely necessary and the change is rather minimal or decorative. Extensive modifications of the webflow, if not done carefully may severely complicate your deployment and future upgrades. If reasonable, consider contributing or suggesting the change to the project and have it be maintained directly.

    CAS by default is configured to hot reload changes to the Spring webflow configuration.

    Extending Webflow

    If you want to learn how to modify and extend the CAS authentication flows, please see this guide.

    Actuator Endpoints

    The following endpoints are provided by CAS: