SAML2 Authentication

CAS can act as a SAML2 identity provider accepting authentication requests and producing SAML assertions.

If you intend to allow CAS to delegate authentication to an external SAML2 identity provider, you need to review this guide.

Federation Interop Evaluation

The CAS project strives to conform to the SAML V2.0 Implementation Profile for Federation Interoperability. An evaluation of the requirements against the current CAS release is available here. It is recommended that you view, evaluate and comment on functionality that is currently either absent or marked questionable where verification is needed.

SAML Endpoints

The following CAS endpoints respond to supported SAML2 profiles:

• /idp/profile/SAML2/Redirect/SSO
• /idp/profile/SAML2/POST/SSO
• /idp/profile/SAML2/POST-SimpleSign/SSO
• /idp/profile/SAML2/POST/SLO
• /idp/profile/SAML2/Redirect/SLO
• /idp/profile/SAML2/Unsolicited/SSO
• /idp/profile/SAML2/SOAP/ECP
• /idp/profile/SAML2/SOAP/AttributeQuery
• /idp/profile/SAML1/SOAP/ArtifactResolution

IdP Metadata

The following CAS endpoints handle the generation of SAML2 metadata:

• /idp/metadata

This endpoint will display the CAS IdP SAML2 metadata upon receiving a GET request. If metadata is already available and generated, it will be displayed. If metadata is absent, one will be generated automatically. CAS configuration below dictates where metadata files/keys will be generated and stored.

Here is a generated metadata file as an example:

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<?xml version="1.0" encoding="UTF-8"?>
<EntityDescriptor xmlns="urn:oasis:names:tc:SAML:2.0:metadata" xmlns:ds="http://www.w3.org/2000/09/xmldsig#"
                xmlns:shibmd="urn:mace:shibboleth:metadata:1.0" xmlns:xml="http://www.w3.org/XML/1998/namespace"
                xmlns:mdui="urn:oasis:names:tc:SAML:metadata:ui" entityID="ENTITY_ID">
    <IDPSSODescriptor protocolSupportEnumeration="urn:oasis:names:tc:SAML:2.0:protocol">
        <Extensions>
            <shibmd:Scope regexp="false">SCOPE</shibmd:Scope>
        </Extensions>
        <KeyDescriptor use="signing">
            <ds:KeyInfo>
              <ds:X509Data>
                  <ds:X509Certificate>...</ds:X509Certificate>
              </ds:X509Data>
            </ds:KeyInfo>
        </KeyDescriptor>
        <KeyDescriptor use="encryption">
            <ds:KeyInfo>
              <ds:X509Data>
                  <ds:X509Certificate>...</ds:X509Certificate>
              </ds:X509Data>
            </ds:KeyInfo>
        </KeyDescriptor>

        <NameIDFormat>urn:mace:shibboleth:1.0:nameIdentifier</NameIDFormat>
        <NameIDFormat>urn:oasis:names:tc:SAML:2.0:nameid-format:transient</NameIDFormat>

        <SingleLogoutService Binding="urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST"
                             Location="https://HOST_NAME/cas/idp/profile/SAML2/POST/SLO"/>
        <SingleSignOnService Binding="urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST"
                             Location="https://HOST_NAME/cas/idp/profile/SAML2/POST/SSO"/>
        <SingleSignOnService Binding="urn:oasis:names:tc:SAML:2.0:bindings:HTTP-Redirect"
                             Location="https://HOST_NAME/cas/idp/profile/SAML2/Redirect/SSO"/>
    </IDPSSODescriptor>
</EntityDescriptor>

SAML2 identity provider metadata can be managed in dynamics ways as well. To learn more, please review this guide.

Service Provider Metadata

If the SP you wish to integrate with does not produce SAML metadata, you may be able to use this service to create the metadata, save it in an XML file and then reference and register it with CAS for the SP.

Configuration

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-saml-idp</artifactId>
  <version>${cas.version}</version>
</dependency>

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

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<repositories>
    ...
    <repository>
        <id>shibboleth-releases</id>
        <url>https://build.shibboleth.net/nexus/content/repositories/releases</url>
    </repository>
    ...
</repositories>

To see the relevant list of CAS properties, please review this guide.

SAML Services

SAML relying parties and services must be registered within the CAS service registry similar to the following example:

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{
  "@class" : "org.apereo.cas.support.saml.services.SamlRegisteredService",
  "serviceId" : "the-entity-id-of-the-sp",
  "name" : "SAMLService",
  "id" : 10000003,
  "evaluationOrder" : 10,
  "metadataLocation" : "https://url/to/metadata.xml"
}

The following fields are available for SAML services:

Metadata Aggregates

CAS services are fundamentally recognized and loaded by service identifiers taught to CAS typically via regular expressions. This allows for common groupings of applications and services by url patterns (i.e. “Everything that belongs to example.org is registered with CAS). With aggregated metadata, CAS essentially does double authorization checks because it will first attempt to find the entity id in its collection of resolved metadata components and then it looks to see if that entity id is authorized via the pattern that is assigned to that service definition. This means you can do one of several things:

1. Open up the pattern to allow everything that is authorized in the metadata.
2. Restrict the pattern to only a select few entity ids found in the metadata. This is essentially the same thing as defining metadata criteria to filter down the list of resolved relying parties and entity ids except that its done after the fact once the metadata is fully loaded and parsed.
3. You can also instruct CAS to filter metadata entities by a defined criteria at resolution time when it reads the metadata itself. This is essentially the same thing as forcing the pattern to match entity ids, except that it’s done while CAS is reading the metadata and thus load times are improved.

Metadata Resolution

Service provider metadata is fetched and loaded on demand for every service and then cached in a global cache for a configurable duration. Subsequent requests for service metadata will always consult the cache first and if missed, will resort to actually resolving the metadata by loading or contacting the configured resource. Each service provider definition that is registered with CAS may optionally also specifically an expiration period of metadata resolution to override the default global value.

Dynamic Metadata Resolution

In addition to the more traditional means of managing service provider metadata such as direct XML files or URLs, CAS provides support for a number of other strategies to fetch metadata more dynamically with the likes of MDQ and more. To learn more, please review this guide.

Attribute Name Formats

Attribute name formats can be specified per relying party in the service registry.

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{
  "@class": "org.apereo.cas.support.saml.services.SamlRegisteredService",
  "serviceId" : "the-entity-id-of-the-sp",
  "name": "SAML Service",
  "metadataLocation" : "../../sp-metadata.xml",
  "id": 100001,
  "attributeNameFormats": {
    "@class": "java.util.HashMap",
    "attributeName": "basic|uri|unspecified|custom-format-etc"
  }
}

You may also have the option to define attributes and their relevant name format globally via CAS properties. To see the relevant list of CAS properties, please review this guide.

Attribute Friendly Names

Attribute friendly names can be specified per relying party in the service registry. If there is no friendly name defined for the attribute, the attribute name will be used instead in its place. Note that the name of the attribute is one that is designed to be released to the service provider, specially if the original attribute is mapped to a different name.

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{
  "@class": "org.apereo.cas.support.saml.services.SamlRegisteredService",
  "serviceId" : "the-entity-id-of-the-sp",
  "name": "SAML Service",
  "metadataLocation" : "../../sp-metadata.xml",
  "id": 100001,
  "attributeFriendlyNames": {
    "@class": "java.util.HashMap",
    "urn:oid:2.5.4.42": "friendly-name-to-use"
  }
}

Attribute Release

Attribute filtering and release policies are defined per SAML service. See this guide for more info.

Name ID Selection

Each service may specify a required Name ID format. If left undefined, the metadata will be consulted to find the right format. The Name ID value is always simply the authenticated user that is designed to be returned to this service. In other words, if you decide to configure CAS to return a particular attribute as the authenticated user name for this service, that value will then be used to construct the Name ID along with the right format.

Unsolicited SSO

SAML2 IdP Unsolicited/SSO profile supports the following parameters:

Attribute Queries

In order to allow CAS to support and respond to attribute queries, you need to make sure the generated metadata has the AttributeAuthorityDescriptor element enabled, with protocol support enabled for urn:oasis:names:tc:SAML:2.0:protocol and relevant binding that corresponds to the CAS endpoint(s). You also must ensure the AttributeAuthorityDescriptor tag lists all KeyDescriptor elements and certificates that are used for signing as well as authentication, specially if the SOAP client of the service provider needs to cross-compare the certificate behind the CAS endpoint with what is defined for the AttributeAuthorityDescriptor. CAS by default will always use its own signing certificate for signing of the responses generated as a result of an attribute query.

Also note that support for attribute queries need to be explicitly enabled and the behavior is off by default, given it imposes a burden on CAS and the underlying ticket registry to keep track of attributes and responses as tickets and have them be later used and looked up.

To see the relevant list of CAS properties, please review this guide.

Service Provider Integrations

A number of SAML2 service provider integrations are provided natively by CAS. To learn more, please review this guide.

Client Libraries

For Java-based applications, the following frameworks may be used to integrate your application with CAS acting as a SAML2 identity provider:

• Spring Security SAML
• Pac4j

Sample Client Applications

• Spring Security SAML Sample Webapp
• Okta

Troubleshooting

To enable additional logging, modify the logging configuration file to add the following:

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<AsyncLogger name="org.opensaml" level="debug" additivity="false">
    <AppenderRef ref="console"/>
    <AppenderRef ref="file"/>
</AsyncLogger>
<AsyncLogger name="PROTOCOL_MESSAGE" level="debug" additivity="false">
    <AppenderRef ref="console"/>
    <AppenderRef ref="file"/>
</AsyncLogger>