JWKS Rotation - OpenID Connect Authentication

Key rotation is when a key is retired and replaced by generating a new cryptographic key. Rotating keys on a regular basis is an industry standard and follows cryptographic best practices.

You can manually rotate keys periodically to change the JSON web key (JWK) key, or you can configure the appropriate schedule in CAS configuration so it would automatically rotate keys for you.

:information_source: Rotation Guidance

NIST guidelines seem to recommend a rotation schedule of at least once every two years. In practice, modest CAS deployments in size and scale tend to rotate keys once every six months, either manually or automatically on a schedule.

Keys that are generated by CAS and put into the keystore carry an extra state parameter that indicates the lifecycle status of the assigned key. The following values are accepted lifecycle states:

Value Description
0 The key is active and current, used for required operations.
1 The key will be the next key used during key rotation.
2 The key is no longer used and active, and will be removed after revocation operations.

CAS always signs with only one signing key at a time, typically the very first key listed and loaded from the keystore, that is deemed active and current judging by the state parameter. For backward compatibility, the absence of this parameter indicates that the key is active and current.

The dynamic discovery endpoint will always include both the current key and the next key, and it may also include the previous key(s) if the previous key has not yet been revoked. To provide a seamless experience in case of an emergency, client applications should be able to use any of the keys specified in the discovery document.

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

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.

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.

:information_source: 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, 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.

Custom

It is possible to design and inject your own key rotation and revocation strategy into CAS using the following @Bean that would be registered in a @AutoConfiguration class:



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@Bean
public OidcJsonWebKeystoreRotationService oidcJsonWebKeystoreRotationService() {
    return new MyJsonWebKeystoreRotationService();
}

Your configuration class needs to be registered with CAS. See this guide for better details.