Overview

The integration between the CAS Server and ADFS delegates user authentication from CAS Server to ADFS, making CAS Server a WS-Federation client. Claims released from ADFS are made available as attributes to CAS Server, and by extension CAS Clients.

:information_source: Remember

The functionality described here allows CAS to use ADFS as an external identity provider. If you wish to do the opposite, allowing ADFS to become a CAS client and using CAS as an identity provider, you may take advantage of SAML2 support in CAS as one integration option.

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



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<dependency>
    <groupId>org.apereo.cas</groupId>
    <artifactId>cas-server-support-wsfederation-webflow</artifactId>
    <version>${cas.version}</version>
</dependency>





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implementation "org.apereo.cas:cas-server-support-wsfederation-webflow:${project.'cas.version'}"





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dependencyManagement {
    imports {
        mavenBom "org.apereo.cas:cas-server-support-bom:${project.'cas.version'}"
    }
}

dependencies {
    implementation "org.apereo.cas:cas-server-support-wsfederation-webflow"
}





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dependencies {
    /*
        The following platform references should be included automatically and are listed here for reference only.

        implementation enforcedPlatform("org.apereo.cas:cas-server-support-bom:${project.'cas.version'}")
        implementation platform(org.springframework.boot.gradle.plugin.SpringBootPlugin.BOM_COORDINATES)
        
    */
    implementation "org.apereo.cas:cas-server-support-wsfederation-webflow"
}

You may also need to declare the following repository in your CAS Overlay to be able to resolve dependencies:



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repositories {
    maven { 
        mavenContent { releasesOnly() }
        url "https://build.shibboleth.net/maven/releases/" 
    }
}
:information_source: JCE Requirement

It's safe to make sure you have the proper JCE bundle installed in your Java environment that is used by CAS, specially if you need to consume encrypted payloads issued by ADFS. Be sure to pick the right version of the JCE for your Java version. Java versions can be detected via the java -version command.

WsFed Configuration

Adjust and provide settings for the ADFS instance, and make sure you have obtained the ADFS signing certificate and made it available to CAS at a location that can be resolved at runtime.

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.

This CAS feature is able to accept signing and encryption crypto keys. In most scenarios if keys are not provided, CAS will auto-generate them. The following instructions apply if you wish to manually and beforehand create the signing and encryption keys.

Note that if you are asked to create a JWK of a certain size for the key, you are to use the following set of commands to generate the token:



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wget https://raw.githubusercontent.com/apereo/cas/master/etc/jwk-gen.jar
java -jar jwk-gen.jar -t oct -s [size]

The outcome would be similar to:



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{
  "kty": "oct",
  "kid": "...",
  "k": "..."
}

The generated value for k needs to be assigned to the relevant CAS settings. Note that keys generated via the above algorithm are processed by CAS using the Advanced Encryption Standard (AES) algorithm which is a specification for the encryption of electronic data established by the U.S. National Institute of Standards and Technology.

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.

Authentication handlers that generally deal with username-password credentials can be configured to transform the user id prior to executing the authentication sequence. Each authentication strategy in CAS provides settings to properly transform the principal. Refer to the relevant settings for the authentication strategy at hand to learn more.

Authentication handlers as part of principal transformation may also be provided a path to a Groovy script to transform the provided username. The outline of the script may take on the following form:



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String run(final Object... args) {
    def (providedUsername,logger) = args
    return providedUsername.concat("SomethingElse")
}

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

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.

Signed Assertions

CAS is able to ascertain the validity of assertion signatures using dedicated certificate files that are defined via CAS settings. Certificate files and resources may be defined statically as file-system resources that are available to CAS to load and use, or the signing resource may point to ADFS federation metadata (either as a URL or XML file). When using the federation metadata, the signing certificate is extracted from the IDPSSODescriptor key descriptor that is marked for signing.

Encrypted Assertions

CAS is able to automatically decrypt SAML assertions that are issued by ADFS. To do this, you will first need to generate a private/public keypair:



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openssl genrsa -out private.key 1024
openssl rsa -pubout -in private.key -out public.key -inform PEM -outform DER
openssl pkcs8 -topk8 -inform PEM -outform DER -nocrypt -in private.key -out private.p8
openssl req -new -x509 -key private.key -out x509.pem -days 365

# convert the X509 certificate to DER format
openssl x509 -outform der -in x509.pem -out certificate.crt

Configure CAS to reference the keypair, and configure the relying party trust settings in ADFS to use the certificate.crt file for encryption.

Modifying ADFS Claims

The WsFed configuration optionally may allow you to manipulate claims coming from ADFS but before they are inserted into the CAS user principal. The manipulation of the attributes is carried out using an attribute mutator where its logic may be implemented inside a Groovy script and whose path is taught to CAS via settings.

The script may take on the following form:



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import org.apereo.cas.*
import java.util.*
import org.apereo.cas.authentication.*

Map run(final Object... args) {
    def (attributes,logger) = args
    logger.warn("Mutating attributes {}", attributes)
    return [upn: ["CASUser"]]
}

The parameters passed to the script are as follows:

Parameter Description
attributes A current Map of attributes provided from ADFS.
logger The object responsible for issuing log messages such as logger.info(...).

Note that the execution result of the script MUST ensure that attributes are collected into a Map where the attribute name, the key, is a simple String and the attribute value is transformed into a collection.

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

Handling CAS Logout

An optional step, the casLogoutView.html can be modified to place a link to ADFS’s logout page.



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<a href="https://adfs.example.org/adfs/ls/?wa=wsignout1.0">Logout</a>

Alternatively, you may instruct CAS to redirect to the above endpoint after logout operations have executed.

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.

Per-Service Relying Party Id

In order to specify a relying party identifier per service definition, adjust your service registry to match the following:



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{
  "@class" : "org.apereo.cas.services.CasRegisteredService",
  "serviceId" : "^https://.+",
  "name" : "sample service",
  "id" : 100,
  "properties" : {
    "@class" : "java.util.HashMap",
    "wsfed.relyingPartyIdentifier" : {
      "@class" : "org.apereo.cas.services.DefaultRegisteredServiceProperty",
      "values" : [ "java.util.HashSet", [ "custom-identifier" ] ]
    }
  }
}

The following properties are available and recognized by CAS for various modules and features:

Troubleshooting

Be aware of clock drift issues between CAS and the ADFS server. Validation failures of the response do show up in the logs, and the request is routed back to ADFS again, causing redirect loops.

To enable additional logging, configure the log4j configuration file to add the following levels:



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...
<Logger name="org.apereo.cas.support.wsfederation" level="debug" additivity="false">
    <AppenderRef ref="casConsole"/>
    <AppenderRef ref="casFile"/>
</Logger>
...