OpenID Protocol

OpenID is an open, decentralized, free framework for user-centric digital identity. Users represent themselves using URIs. For more information see the http://www.openid.net.

Usage

This feature is deprecated and is scheduled to be removed in the future. If you can, consider using a more mainstream and recent authentication protocol.

CAS supports both the “dumb” and “smart” modes of the OpenID protocol. Dumb mode acts in a similar fashion to the existing CAS protocol. The smart mode differs in that it establishes an association between the client and the openId provider (OP) at the beginning. Thanks to that association and the key exchange done during association, information exchanged between the client and the provider are signed and verified using this key. There is no need for the final request (which is equivalent in CAS protocol to the ticket validation).

OpenID identifiers are URIs. The default mechanism in CAS support is an uri ending with the actual user login (ie. http://my.cas.server/openid/myusername where the actual user login id is myusername). This is not recommended and you should think of a more elaborated way of providing URIs to your users.

Pay Attention!

OpenID protocol is NOT the same thing as the OpenId Connect protocol whose details are documented here.

Configuration

Support is enabled by including the following dependency in the WAR overlay:

1
2
3
4
5
<dependency>
  <groupId>org.apereo.cas</groupId>
  <artifactId>cas-server-support-openid-webflow</artifactId>
  <version>${cas.version}</version>
</dependency>
1
implementation "org.apereo.cas:cas-server-support-openid-webflow:${project.'cas.version'}"
1
2
3
4
5
6
7
8
9
dependencyManagement {
  imports {
    mavenBom "org.apereo.cas:cas-server-support-bom:${project.'cas.version'}"
  }
}

dependencies {  
  implementation "org.apereo.cas:cas-server-support-openid-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.authn.openid.principal.active-attribute-repository-ids=
  • Activated attribute repository identifiers that should be used for fetching attributes if attribute resolution is enabled. The list here may include identifiers separated by comma.

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

  • cas.authn.openid.principal.attribute-resolution-enabled=
  • Whether attribute repositories should be contacted to fetch person attributes. Defaults to true if not set.

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

  • cas.authn.openid.principal.principal-attribute=
  • Attribute name to use to indicate the identifier of the principal constructed. If the attribute is blank or has no values, the default principal id will be used determined by the underlying authentication engine. The principal id attribute usually is removed from the collection of attributes collected, though this behavior depends on the schematics of the underlying authentication strategy.

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

  • cas.authn.openid.principal.principal-resolution-conflict-strategy=last
  • In the event that the principal resolution engine resolves more than one principal, (specially if such principals in the chain have different identifiers), this setting determines strategy by which the principal id would be chosen from the chain. Accepted values are: last, first.

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

  • cas.authn.openid.principal.principal-resolution-failure-fatal=
  • When true, throws an error back indicating that principal resolution has failed and no principal can be found based on the authentication requirements. Otherwise, logs the condition as an error without raising a catastrophic error.

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

  • cas.authn.openid.principal.return-null=
  • Return a null principal object if no attributes can be found for the principal.

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

  • cas.authn.openid.principal.use-existing-principal-id=
  • Uses an existing principal id that may have already been established in order to run person directory queries. This is generally useful in situations where authentication is delegated to an external identity provider and a principal is first established to then query an attribute source.

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

  • cas.authn.openid.enforce-rp-id=false
  • Whether relying party identifies should be enforced. This is used during the realm verification process. Deprecation: Since 6.2

    org.apereo.cas.configuration.model.support.openid.OpenIdProperties.

    Deprecation status is ERROR without a replacement setting.

  • cas.authn.openid.name=
  • Name of the underlying authentication handler. Deprecation: Since 6.2

    org.apereo.cas.configuration.model.support.openid.OpenIdProperties.

    Deprecation status is ERROR without a replacement setting.

  • cas.authn.openid.order=
  • Order of the authentication handler in the chain. Deprecation: Since 6.2

    org.apereo.cas.configuration.model.support.openid.OpenIdProperties.

    Deprecation status is ERROR without a replacement setting.

    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.

    Register Clients

    Register clients in the CAS service registry:

    1
    2
    3
    4
    5
    6
    7
    
    {
      "@class" : "org.apereo.cas.services.RegexRegisteredService",
      "serviceId" : "https://openid.example.org/myapp",
      "name" : "openid",
      "description" : "OpenID Sample Application",
      "id" : 10
    }
    

    Sample Client Applications

    OpenID Provider Delegation

    Using the OpenID