Overview

Principal resolution converts information in the authentication credential into a security principal that commonly contains additional metadata attributes (i.e. user details such as affiliations, group membership, email, display name).

A CAS principal contains a unique identifier by which the authenticated user will be known to all requesting services. A principal also contains optional attributes that may be released to services to support authorization and personalization. Principal resolution is a requisite part of the authentication process that happens after credential authentication.

CAS AuthenticationHandler components provide basic principal resolution machinery by default. For example, the LdapAuthenticationHandler component supports fetching attributes and setting the principal ID attribute from an LDAP query. In all cases principals are resolved from the same store as that which provides authentication.

In many cases it is necessary to perform authentication by one means and resolve principals by another. The PrincipalResolver component provides this functionality. A common use case for this this mix-and-match strategy arises with X.509 authentication. It is common to store certificates in an LDAP directory and query the directory to resolve the principal ID and attributes from directory attributes. The X509CertificateAuthenticationHandler may be be combined with an LDAP-based principal resolver to accommodate this case.

Configuration

CAS uses the Person Directory library to provide a flexible principal resolution services against a number of data sources. The key to configuring PersonDirectoryPrincipalResolver is the definition of an IPersonAttributeDao object.

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. You should only include this field in your configuration if you need to modify the default value.

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.

PrincipalResolver vs. AuthenticationHandler

The principal resolution machinery provided by AuthenticationHandler components should be used in preference to PrincipalResolver in any situation where the former provides adequate functionality. If the principal that is resolved by the authentication handler suffices, then a null value may be passed in place of the resolver bean id in the final map.