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 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
phpCAS 1.1.0
.NET CAS Client