CAS supports the standardized SAML 1.1 protocol primarily to support attribute release to clients and single sign-out.
Since SAML 1.1 is well-documented elsewhere, this document deals with CAS-specific concerns.

Requesting SAML

A SAML 1.1 ticket validation response is obtained by validating a ticket via POST at the /samlValidate URI. An example request/response follows for a successful ticket validation attempt.

Example Request

POST /cas/samlValidate?ticket=
Host: cas.example.com
Content-Length: 491
Content-Type: text/xml

<SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/">
  <SOAP-ENV:Header/>
  <SOAP-ENV:Body>
    <samlp:Request xmlns:samlp="urn:oasis:names:tc:SAML:1.0:protocol" MajorVersion="1"
      MinorVersion="1" RequestID="_192.168.16.51.1024506224022"
      IssueInstant="2002-06-19T17:03:44.022Z">
      <samlp:AssertionArtifact>
        ST-1-u4hrm3td92cLxpCvrjylcas.example.com
      </samlp:AssertionArtifact>
    </samlp:Request>
  </SOAP-ENV:Body>
</SOAP-ENV:Envelope>

Example Response

<SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/">
  <SOAP-ENV:Header />
  <SOAP-ENV:Body>
    <Response xmlns="urn:oasis:names:tc:SAML:1.0:protocol" xmlns:saml="urn:oasis:names:tc:SAML:1.0:assertion"
    xmlns:samlp="urn:oasis:names:tc:SAML:1.0:protocol" xmlns:xsd="http://www.w3.org/2001/XMLSchema"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" IssueInstant="2008-12-10T14:12:14.817Z"
    MajorVersion="1" MinorVersion="1" Recipient="https://eiger.iad.vt.edu/dat/home.do"
    ResponseID="_5c94b5431c540365e5a70b2874b75996">
      <Status>
        <StatusCode Value="samlp:Success">
        </StatusCode>
      </Status>
      <Assertion xmlns="urn:oasis:names:tc:SAML:1.0:assertion" AssertionID="_e5c23ff7a3889e12fa01802a47331653"
      IssueInstant="2008-12-10T14:12:14.817Z" Issuer="localhost" MajorVersion="1"
      MinorVersion="1">
        <Conditions NotBefore="2008-12-10T14:12:14.817Z" NotOnOrAfter="2008-12-10T14:12:44.817Z">
          <AudienceRestrictionCondition>
            <Audience>
              https://some-service.example.com/app/
            </Audience>
          </AudienceRestrictionCondition>
        </Conditions>
        <AttributeStatement>
          <Subject>
            <NameIdentifier>johnq</NameIdentifier>
            <SubjectConfirmation>
              <ConfirmationMethod>
                urn:oasis:names:tc:SAML:1.0:cm:artifact
              </ConfirmationMethod>
            </SubjectConfirmation>
          </Subject>
          <Attribute AttributeName="uid" AttributeNamespace="http://www.ja-sig.org/products/cas/">
            <AttributeValue>12345</AttributeValue>
          </Attribute>
          <Attribute AttributeName="groupMembership" AttributeNamespace="http://www.ja-sig.org/products/cas/">
            <AttributeValue>
              uugid=middleware.staff,ou=Groups,dc=vt,dc=edu
            </AttributeValue>
          </Attribute>
          <Attribute AttributeName="eduPersonAffiliation" AttributeNamespace="http://www.ja-sig.org/products/cas/">
            <AttributeValue>staff</AttributeValue>
          </Attribute>
          <Attribute AttributeName="accountState" AttributeNamespace="http://www.ja-sig.org/products/cas/">
            <AttributeValue>ACTIVE</AttributeValue>
          </Attribute>
        </AttributeStatement>
        <AuthenticationStatement AuthenticationInstant="2008-12-10T14:12:14.741Z"
        AuthenticationMethod="urn:oasis:names:tc:SAML:1.0:am:password">
          <Subject>
            <NameIdentifier>johnq</NameIdentifier>
            <SubjectConfirmation>
              <ConfirmationMethod>
                urn:oasis:names:tc:SAML:1.0:cm:artifact
              </ConfirmationMethod>
            </SubjectConfirmation>
          </Subject>
        </AuthenticationStatement>
      </Assertion>
    </Response>
  </SOAP-ENV:Body>
</SOAP-ENV:Envelope>

Client Support

The SAML 1.1 protocol is supported in the following clients as of this writing:

Jasig Java CAS Client 3.1.x, see Saml11TicketValidationFilter Example.
phpCAS 1.1.0, see phpCAS examples#phpCASexamples-SAMLProtocolwithAttributeRelease.
mod_auth_cas 1.0.9
.NET CAS Client

Customizing the SAML artifact used

In different versions of CAS, we've swapped the artifact type created by the SamlCompliantUniqueTicketIdGenerator. Unfortunately, not often for the better! As of CAS 3.4, the generator can handle both.

When constructing an instance of the SamlComplaintUniqueTicketIdGenerator, you may set the "saml2compliant" property to "true" in order to generate SAML2 artifacts. Otherwise SAML1 compliant artifacts are generated.

The example Spring configuration would look like the following (overriding the WEB-INF/spring-configuration/uniqueIdGenerators.xml):

<bean id="samlServiceTicketUniqueIdGenerator" class="org.jasig.cas.util.SamlCompliantUniqueTicketIdGenerator">
	<constructor-arg index="0" value="https://localhost:8443" />
	<property name="saml2compliant" value="true" />
</bean>