Delegated Authentication Post Processing

Configured identity providers can go through a post-processing phase before they are presented to the user interface. Post processing operations have the ability to update and adjust the markup and settings for a delegated identity provider to change the title, redirect URL, etc. A common example for a post processor would be execute a server-side auto-redirect to the external identity provider conditionally, without having to wait for the browser to make that redirect.

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

cas.authn.pac4j.core.groovy-provider-post-processor.locationThe location of the resource.

no default

Required

The location of the resource. Resources can be URLs, or files found either on the classpath or outside somewhere in the file system.

In the event the configured resource is a Groovy script, especially if the script is set to reload on changes, you may need to adjust the total number of inotify instances. On Linux, you may need to add the following line to /etc/sysctl.conf: fs.inotify.max_user_instances = 256.

You can check the current value via cat /proc/sys/fs/inotify/max_user_instances.

In situations and scenarios where CAS is able to automatically watch the underlying resource for changes and detect updates and modifications dynamically, you may be able to specify the following setting as either an environment variable or system property with a value of false to disable the resource watcher: org.apereo.cas.util.io.PathWatcherService.

Type: Resource
Default: none
Defined by: SpringResourceProperties

Required settings may be needed to activate or affect the feature; review them even when they have a default. Optional settings only need to be set to change a default or to turn on the behavior they control. Third party settings belong to libraries such as Spring Boot that CAS builds on; their own documentation may have more detail.

Groovy scripting

CAS takes advantage of Apache Groovy in forms of either embedded or external scripts that allow one to, by default, dynamically build constructs, attributes, access strategies and a lot more. To activate the functionality described here, you may need to prepare CAS to support and integrate with Apache Groovy.

Please review this guide to configure your build.

Notes on configuration

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.

Note

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, especially 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.

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 outline of the Groovy script would be as follows:

import org.apereo.cas.web.*
import org.apereo.cas.web.support.*
import org.springframework.webflow.execution.*

def run(Object[] args) {
    def (requestContext,providers,logger) = args
    def provider = providers[0]
    logger.info("Checking provider ${provider.name}...")
    def response = WebUtils.getHttpServletResponseFromExternalWebflowContext(requestContext)
    logger.debug("Redirecting to ${provider.redirectUrl}")
    response.sendRedirect(provider.redirectUrl);
}

The parameters passed are as follows:

Parameter	Description
`requestContext`	The object representing Spring Webflow’s `RequestContext`.
`providers`	The set of delegated identity provider configurations.
`logger`	The object responsible for issuing log messages such as `logger.info(...)`.

Preprocessing Authentication

You may also opt into preprocessing the delegated authentication event prior to the final step in the process and before an SSO session is created. Preprocessing the authentication here allows one to manipulate and update the final authenticated principal before it’s fully baked into the SSO session. This can be done using the following bean definition and by implementing DelegatedAuthenticationPreProcessor:

@Bean
public DelegatedAuthenticationPreProcessor myProcessor() {
    return new MyDelegatedAuthenticationPreProcessor();
}

See this guide to learn more about how to register configurations into the CAS runtime.