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 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:
cas.webflow.auto-configuration.enabled=true
Whether webflow auto-configuration should be enabled.
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cas.webflow.auto-configuration.order=0
The order in which the webflow is configured.
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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.
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:
Webflow Decorations
Learn how to fetch and display data dynamically from external data sources and endpoints and pass those along to the webflow by reviewing this guide.
Required Service for Authentication
By default, CAS will present a generic success page if the initial authentication request does not identify the target application. In some cases, the ability to login to CAS without logging in to a particular service may be considered a misfeature because in practice, too few users and institutions are prepared to understand, brand, and support what is at best a fringe use case of logging in to CAS for the sake of establishing an SSO session without logging in to any CAS-reliant service.
As such, CAS optionally allows adopters to not bother to prompt for credentials when no target application is presented and instead presents a message when users visit CAS directly without specifying a service.
The following settings and properties are available from the CAS configuration catalog:
cas.sso.allow-missing-service-parameter=true
Flag that indicates whether to allow SSO session with a missing target service.
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cas.sso.create-sso-cookie-on-renew-authn=true
Flag that indicates whether to create SSO session on re-newed authentication event.
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cas.sso.proxy-authn-enabled=true
Indicates whether CAS proxy authentication/tickets are supported by this server implementation.
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cas.sso.renew-authn-enabled=true
Indicates whether this server implementation should globally support CAS protocol authentication requests that are tagged with "renew=true".
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cas.sso.required-service-pattern=
A regular expression pattern that represents an application which must have established a session with CAS already before access to other applications can be allowed by CAS. This is the initial mandatory/required application with which the user must start before going anywhere else. Services that establish a session with CAS typically do so by receiving a service ticket from CAS.
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cas.sso.sso-enabled=true
Indicate whether single sign-on should be turned on and supported globally for the server.
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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.
Acceptable Usage Policy
CAS presents the ability to allow the user to accept the usage policy before moving on to the application. See this guide for more info.
Customizing Errors
See this guide for more info.
Custom Settings
All webflow components and CAS views have access to the entire bundle of CAS settings
defined from a variety of configuration sources. This allows one to extend and modify
any CAS view or webflow component using the variable casProperties to gain access to
a specific setting. Remember that this syntax only allowed access to settings
that are owned by CAS, noted by its very own prefix.
The following settings and properties are available from the CAS configuration catalog:
cas.custom.properties=
Collection of custom settings that can be utilized for a local deployment. The settings should be available to CAS views and webflows for altering UI and/or introducing custom behavior to any extended customized component without introducing a new property namespace. This is defined as a map, where the key should be the setting name and the value should be the setting value.
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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.
Troubleshooting
To enable additional logging, modify the logging configuration file to add the following:
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<Logger name="org.springframework.webflow" level="debug" additivity="false">
<AppenderRef ref="casConsole"/>
<AppenderRef ref="casFile"/>
</Logger>