Webflow Errors Customization

By default CAS is configured to recognize and handle a number of exceptions for web flow during authentication. Each exception has the specific message bundle mapping in messages.properties. So that a specific message could be presented to end users on the login form. Any un-recognized or un-mapped exceptions results in the UNKNOWN mapping with a generic Invalid credentials. message.

To map custom exceptions in the webflow, one would need map the exception in CAS settings and then define the relevant error in messages.properties:

authenticationFailure.MyAuthenticationException=Authentication has failed, but it did it my way!

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.errors.groovy.location=

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, specially if the script 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.

org.apereo.cas.configuration.model.core.authentication.GroovyAuthenticationExceptionsProperties.

_{How can I configure this property?}

Configuration properties can be included and activated using the following strategies.

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.

CAS properties can be specified using the Java configuration property syntax in any and all .properties files:

cas.authn.errors.groovy.location=...

This is the most common form of property configuration that is recognized by CAS, regardless of the actual property source, which might in fact be managed separately outside the CAS environment, by another system or cloud framework.

CAS properties can be specified using the YAML syntax:

cas: 
  authn: 
    errors: 
      groovy: 
        location: "..."

Note that YAML is very specific about structure and indentation. Be sure to verify the correctness of the final result with your YAML validator of choice.

CAS properties can be passed to the CAS web application as system properties, when the application is launched:

java -Dcas.authn.errors.groovy.location="..." -jar build/libs/cas.war

The above example assumes that the CAS web application is packaged as cas.war with an embedded server container and can be found in the build/libs directory. Note the placement of the system property which must be specified before the CAS web application is launched.

CAS properties can specified as system environment variables before the CAS web application is launched:

export CAS_AUTHN_ERRORS_GROOVY_LOCATION="..."

java -jar build/libs/cas.war

The above example assumes that the CAS web application is packaged as cas.war with an embedded server container and can be found in the build/libs directory.

CAS properties can be passed to the CAS web application as command-line arguments, when the application is launched:

java -jar build/libs/cas.war --cas.authn.errors.groovy.location="..."

The above example assumes that the CAS web application is packaged as cas.war with an embedded server container and can be found in the build/libs directory.

_{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. In other words, you should only include this field in your
configuration if you need to modify the default value or if you need to turn on the feature controlled by the setting.}

cas.authn.errors.exceptions=

Define custom exceptions that can then be mapped to message bundles for custom error handling.

By default CAS is configured to recognize and handle a number of exceptions for during authentication. Each exception has the specific message bundle mapping so that a specific message could be presented to end users on the login form. Any un-recognized or un-mapped exceptions results in a generic message. To map custom exceptions, one would need map the exception, they can be defined here and then linked to custom messages.

org.apereo.cas.configuration.model.core.authentication.AuthenticationExceptionsProperties.

_{How can I configure this property?}

Configuration properties can be included and activated using the following strategies.

Note

CAS properties can be specified using the Java configuration property syntax in any and all .properties files:

cas.authn.errors.exceptions=...

CAS properties can be specified using the YAML syntax:

cas: 
  authn: 
    errors: 
      exceptions: "..."

Note that YAML is very specific about structure and indentation. Be sure to verify the correctness of the final result with your YAML validator of choice.

CAS properties can be passed to the CAS web application as system properties, when the application is launched:

java -Dcas.authn.errors.exceptions="..." -jar build/libs/cas.war

CAS properties can specified as system environment variables before the CAS web application is launched:

export CAS_AUTHN_ERRORS_EXCEPTIONS="..."

java -jar build/libs/cas.war

The above example assumes that the CAS web application is packaged as cas.war with an embedded server container and can be found in the build/libs directory.

CAS properties can be passed to the CAS web application as command-line arguments, when the application is launched:

java -jar build/libs/cas.war --cas.authn.errors.exceptions="..."

The above example assumes that the CAS web application is packaged as cas.war with an embedded server container and can be found in the build/libs directory.

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.

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

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. 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.

Groovy Error Handling

Exceptions and authentication errors that are reported back to the webflow may be caught and processed using an external Groovy script. If the script can support and handle the error, its outcome should be an event that the webflow should use as the final destination state:

The outline of the script should match the following:

import org.apereo.cas.*
import org.springframework.context.*
import org.springframework.webflow.*
import org.springframework.webflow.action.*
import org.springframework.webflow.execution.*

def run(Object[] args) {
    def (exception,requestContext,applicationContext,logger) = args
    logger.info("Handling {}", exception)
    new EventFactorySupport().event(this, "customEvent")
}

def supports(Object[] args) {
    def (exception,requestContext,applicationContext,logger) = args
    logger.info("Checking to support {}", exception)
    true
}

The parameters passed are as follows:

Parameter	Description
`exception`	The object representing the error.
`requestContext`	The object representing the Spring Webflow `RequestContext`.
`applicationContext`	The object representing the Spring `ApplicationContext`.
`logger`	The object responsible for issuing log messages such as `logger.info(...)`.

To prepare CAS to support and integrate with Apache Groovy, please review this guide.

Custom Error Handling

For more advanced scenarios, you can also design your webflow exception handler and register it with the CAS at runtime:

@Bean
public CasWebflowExceptionHandler customExceptionHandler(){
    return new CustomCasWebflowExceptionHandler();
}

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