Delegated Authentication - Auto Redirection/Selection

By default, the list of available identity providers are displayed in a selection menu and the user is allowed to choose the provider. In certain scenarios, the browser may be instructed to auto-redirect to a preselected identity provider.

Explicit Auto-Redirection

CAS can be instructed to explicitly redirect to an external identity provider via a dedicated link. For example, you may redirect to the identity provider that is identified as Twitter in the CAS configuration via:

https://sso.example.org/cas/clientredirect?client_name=Twitter

The example assumes that CAS is configured (by default) to recognize identity provider names as query parameters under the client_name parameter.

Preselected Identity Provider

An identity provider can be instructed via CAS configuration to always perform an auto-redirect, regardless of the application type and/or authentication requests. The selected identity provider is considered by CAS to be the primary strategy for handling authentication requests.

Identity Provider Exclusivity

Authentication requests from the following application will be auto-redirected to the identity provider that is identified as Twitter in the CAS configuration, since the delegated authentication policy only allows the single exclusive use of this provider, removing selection menu and the ability to choose other alternative authentication methods.

{
  "@class" : "org.apereo.cas.services.CasRegisteredService",
  "serviceId" : "sample",
  "name" : "sample",
  "id" : 100,
  "accessStrategy" : {
    "@class" : "org.apereo.cas.services.DefaultRegisteredServiceAccessStrategy",
    "delegatedAuthenticationPolicy" : {
      "@class" : "org.apereo.cas.services.DefaultRegisteredServiceDelegatedAuthenticationPolicy",
      "allowedProviders" : [ "java.util.ArrayList", [ "Twitter" ] ],
      "exclusive": true
    }
  }
}

A chosen identity provider from the selection menu can be optionally tracked and stored using a dedicated cookie, which will then be used on subsequent attempts to auto-redirect to the identity provider, skipping the selection menu.

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

cas.authn.pac4j.cookie.auto-configure-cookie-pathDecide if cookie paths should be automatically configured based on the application context path, when the cookie path is not configured.

true

Decide if cookie paths should be automatically configured based on the application context path, when the cookie path is not configured.

Type: Boolean
Default: true
Defined by: Pac4jDelegatedAuthenticationCookieProperties

cas.authn.pac4j.cookie.domainCookie domain.

no default

Cookie domain. Specifies the domain within which this cookie should be presented. The form of the domain name is specified by RFC 2965. A domain name begins with a dot (.foo.com) and means that the cookie is visible to servers in a specified Domain Name System (DNS) zone (for example, www.foo.com, but not a.b.foo.com). By default, cookies are only returned to the server that sent them.

Type: String
Default: none
Defined by: Pac4jDelegatedAuthenticationCookieProperties

cas.authn.pac4j.cookie.enabledDetermine whether cookie settings should be enabled to track delegated authentication choices and identity providers.

false

Determine whether cookie settings should be enabled to track delegated authentication choices and identity providers.

Type: Boolean
Default: false
Defined by: Pac4jDelegatedAuthenticationCookieProperties

cas.authn.pac4j.cookie.http-onlytrue if this cookie contains the HttpOnly attribute.

true

true if this cookie contains the HttpOnly attribute. This means that the cookie should not be accessible to scripting engines, like javascript.

Type: Boolean
Default: true
Defined by: Pac4jDelegatedAuthenticationCookieProperties

cas.authn.pac4j.cookie.max-ageThe maximum age of the cookie, specified in seconds.

-1

Duration

The maximum age of the cookie, specified in seconds. By default, -1 indicating the cookie will persist until browser shutdown. A positive value indicates that the cookie will expire after that many seconds have passed. Note that the value is the maximum age when the cookie will expire, not the cookie's current age. A negative value means that the cookie is not stored persistently and will be deleted when the Web browser exits. A zero value causes the cookie to be deleted.

Type: String
Default: -1
Defined by: Pac4jDelegatedAuthenticationCookieProperties

cas.authn.pac4j.cookie.nameCookie name.

no default

Cookie name. Constructs a cookie with a specified name and value. The name must conform to RFC 2965. That means it can contain only ASCII alphanumeric characters and cannot contain commas, semicolons, or white space or begin with a $ character. The cookie's name cannot be changed after creation. By default, cookies are created according to the RFC 2965 cookie specification. Cookie names are automatically calculated assigned by CAS at runtime, and there is usually no need to customize the name or assign it a different value unless a special use case warrants the change.

Type: String
Default: none
Defined by: Pac4jDelegatedAuthenticationCookieProperties

cas.authn.pac4j.cookie.pathCookie path.

no default

Cookie path. Specifies a path for the cookie to which the client should return the cookie. The cookie is visible to all the pages in the directory you specify, and all the pages in that directory's subdirectories. A cookie's path must include the servlet that set the cookie, for example, /catalog, which makes the cookie visible to all directories on the server under /catalog. Consult RFC 2965 (available on the Internet) for more information on setting path names for cookies.

Type: String
Default: none
Defined by: Pac4jDelegatedAuthenticationCookieProperties

cas.authn.pac4j.cookie.same-site-policyIf a cookie is only intended to be accessed in a first party context, the developer has the option to apply one of settings SameSite=Lax or SameSite=Strict or SameSite=None to prevent external access.

no default

If a cookie is only intended to be accessed in a first party context, the developer has the option to apply one of settings SameSite=Lax or SameSite=Strict or SameSite=None to prevent external access.

To safeguard more websites and their users, the new secure-by-default model assumes all cookies should be protected from external access unless otherwise specified. Developers must use a new cookie setting, SameSite=None, to designate cookies for cross-site access. When the SameSite=None attribute is present, an additional Secure attribute is used so cross-site cookies can only be accessed over HTTPS connections.

Accepted values are:

Lax
Strict
None
Off: Disable the generation of the SameSite cookie attribute altogether.
Path to a Groovy script that is able to generate the SameSite cookie attribute dynamically.
Fully qualified name of a class that implements org.apereo.cas.web.cookie.CookieSameSitePolicy

Type: String
Default: none
Defined by: Pac4jDelegatedAuthenticationCookieProperties

cas.authn.pac4j.cookie.secureTrue if sending this cookie should be restricted to a secure protocol, or false if the it can be sent using any protocol.

true

True if sending this cookie should be restricted to a secure protocol, or false if the it can be sent using any protocol.

Type: Boolean
Default: true
Defined by: Pac4jDelegatedAuthenticationCookieProperties

Required settings may be needed to activate or affect the feature; review them even when they have a default. Optional settings only need to be set to change a default or to turn on the behavior they control. Third party settings belong to libraries such as Spring Boot that CAS builds on; their own documentation may have more detail.

Notes on configuration

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.

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, especially 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.

Identity Provider Groovy Selection

The auto-redirection strategy of a given identity provider may also be decided dynamically via a Groovy resource whose path is defined via CAS settings.

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

cas.authn.pac4j.core.groovy-redirection-strategy.locationThe location of the resource.

no default

Required

The location of the resource. Resources can be URLs, or files found either on the classpath or outside somewhere in the file system.

In the event the configured resource is a Groovy script, especially if the script is set to reload on changes, you may need to adjust the total number of inotify instances. On Linux, you may need to add the following line to /etc/sysctl.conf: fs.inotify.max_user_instances = 256.

You can check the current value via cat /proc/sys/fs/inotify/max_user_instances.

In situations and scenarios where CAS is able to automatically watch the underlying resource for changes and detect updates and modifications dynamically, you may be able to specify the following setting as either an environment variable or system property with a value of false to disable the resource watcher: org.apereo.cas.util.io.PathWatcherService.

Type: Resource
Default: none
Defined by: SpringResourceProperties

Groovy scripting

CAS takes advantage of Apache Groovy in forms of either embedded or external scripts that allow one to, by default, dynamically build constructs, attributes, access strategies and a lot more. To activate the functionality described here, you may need to prepare CAS to support and integrate with Apache Groovy.

Please review this guide to configure your build.

Notes on configuration

Configuration Metadata

Be Selective

YAGNI

Naming Convention

Note

Validation

Indexed Settings

The Groovy script would have the following outline:

import org.apereo.cas.web.*
import org.pac4j.core.context.*
import org.apereo.cas.pac4j.*
import org.apereo.cas.web.support.*
import java.util.stream.*
import java.util.*
import org.apereo.cas.configuration.model.support.delegation.*

def run(Object[] args) {
    def (requestContext,service,registeredService,providers,applicationContext,logger) = args
    providers.forEach(provider -> {
        logger.info("Checking ${provider.name}...")
        if (provider.name.equals("Twitter")) {
            provider.autoRedirectType = DelegationAutoRedirectTypes.CLIENT
            return provider
        }
    })
    return null
}

To prepare CAS to support and integrate with Apache Groovy, please review this guide.

The following parameters are passed to the script:

Parameter	Description
`requestContext`	Reference to the Spring Webflow request context, as `RequestContext`.
`service`	Reference to the application authentication request as `Service`, if any.
`registeredService`	Reference to registered service definition, if any.
`providers`	Reference to the set of identity provider configuration identified as `DelegatedClientIdentityProviderConfiguration`.
`applicationContext`	Reference to the application context as `ApplicationContext`.
`logger`	The object responsible for issuing log messages such as `logger.info(...)`.

Identity Provider Selection Per Service

The auto-redirection strategy of a given identity provider may also be decided dynamically via a Groovy resource whose path specified directly in the service definition as part of the authentication policy’s provider selection strategy:

{
  "@class" : "org.apereo.cas.services.CasRegisteredService",
  "serviceId" : "sample",
  "name" : "sample",
  "id" : 100,
  "accessStrategy" : {
    "@class" : "org.apereo.cas.services.DefaultRegisteredServiceAccessStrategy",
    "delegatedAuthenticationPolicy" : {
      "@class" : "org.apereo.cas.services.DefaultRegisteredServiceDelegatedAuthenticationPolicy",
      "selectionStrategy": "file:/path/to/script.groovy"
    }
  }
}

Usage

If you wish, you may also use a Groovy Inline syntax using the groovy {...} construct.

To prepare CAS to support and integrate with Apache Groovy, please review this guide. The collection of parameters and the script body are identical to the Identity Provider Groovy Selection option above.

Identity Provider Custom Selection

If you wish to create your own redirection strategy, you will need to design a component and register it with CAS as such:

@Bean
public DelegatedClientIdentityProviderRedirectionStrategy delegatedClientIdentityProviderRedirectionStrategy() {
    return new CustomDelegatedClientIdentityProviderRedirectionStrategy(); 
}

See this guide to learn more about how to register configurations into the CAS runtime.

Delegated Authentication - Auto Redirection/Selection

Explicit Auto-Redirection

Preselected Identity Provider

Identity Provider Exclusivity

Identity Provider Cookie Selection

Configuration Metadata

Be Selective

YAGNI

Naming Convention

Validation

Indexed Settings

Identity Provider Groovy Selection

Configuration Metadata

Be Selective

YAGNI

Naming Convention

Validation

Indexed Settings

Identity Provider Selection Per Service

Identity Provider Custom Selection