OpenID Connect - Client-Initiated Backchannel Authentication (CIBA)

Client-Initiated Backchannel Authentication (CIBA) is a new authentication flow in which relying parties, that can obtain a valid identifier for the user they want to authenticate, will be able to initiate an interaction flow to authenticate their users without having end-user interaction from the consumption device. The flow involves direct communication from the Client to CAS without redirect through the user’s browser.

  • The Client shall make an “HTTP POST” request to the Backchannel Authentication Endpoint to ask for end-user authentication.
  • CAS will respond immediately with a unique identifier that identifies that authentication while it tries to authenticate the user in the background.
  • The Client will receive the ID Token, Access Token, and optionally Refresh Token through either the Poll, Ping, or Push modes.

Please study the specification to learn more.

Configuration

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. 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.

The following settings may also need to be defined to describe the mail server settings:

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.

Applications

Applications that wish to take advantage of CIBA can be registered with CAS:



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{
  "@class": "org.apereo.cas.services.OidcRegisteredService",
  "clientId": "client-id",
  "clientSecret": "secret",
  "serviceId": "^https://app.example.org/oidc",
  "name": "MyApplication",
  "id": 1,
  "supportedGrantTypes": [ "java.util.HashSet", [ "urn:openid:params:grant-type:ciba" ] ],
  "backchannelTokenDeliveryMode": "push",
  "backchannelClientNotificationEndpoint": "https://app.example.org/notify",
  "backchannelAuthenticationRequestSigningAlg": "",
  "backchannelUserCodeParameterSupported": false
}

Delivery Modes

The Client will receive the ID Token, Access Token, and optionally Refresh Token through either the poll, ping, or push modes. This choice MUST be established when the relying party is registered with CAS.

  • Poll Mode

When configured in Poll mode, the Client will poll the token endpoint to get a response with the tokens. That is, the authentication result is retrieved by the Client by polling the CAS token endpoint using the CIBA grant type.

  • Ping Mode

When configured in Ping mode, CAS will send a request to a callback URI previously registered by the Client with the unique identifier returned from the Backchannel Authentication Endpoint. Upon receipt of the notification, the Client makes a request to the token endpoint to obtain the tokens.

  • Push Mode

When configured in Push mode, CAS will send a POST request with the tokens to a callback URI previously registered by the Client.