shib_logout.php

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<?php
require_once("../vendor/composer/vendor/autoload.php");
global $DIC;
$q = $DIC->http()->wrapper()->query();
if (
    $q->has('return')
    && $q->has('action')
    && $q->retrieve('action', $DIC->refinery()->to()->string()) === 'logout'
) {
    ilInitialisation::initILIAS();
    // Logout out user from application
    // Destroy application session/cookie etc
    $GLOBALS['DIC']['ilAuthSession']->logout();

    // Finally, send user to the return URL
    ilUtil::redirect($q->retrieve('action', $DIC->refinery()->kindlyTo()->string()));
}

// Back channel logout //

// Note: This is the preferred logout channel because it also allows
//       administrative logout. However, it requires your application to be
//       adapated in the sense that the user's Shibboleth session ID must be
//       stored in the application's session data.
//       See function LogoutNotification below

elseif (!empty($HTTP_RAW_POST_DATA)) {
    ilContext::init(ilContext::CONTEXT_SOAP);

    // Load ILIAS libraries and initialise ILIAS in non-web context
    ilInitialisation::initILIAS();

    // Set SOAP header
    $server = new SoapServer('https://' . $_SERVER['HTTP_HOST'] . $_SERVER['SCRIPT_NAME'] . '/LogoutNotification.wsdl');
    $server->addFunction("LogoutNotification");
    $server->handle();
}

// Return WSDL

// Note: This is needed for the PHP SoapServer class.
//       Since I'm not a web service guru it might be that the code below is not
//       absolutely correct but at least it seems to to its job properly when it
//       comes to Shibboleth logout

else {
    header('Content-Type: text/xml');

    $url = filter_var("https://{$_SERVER['HTTP_HOST']}/shib_logout.php", FILTER_SANITIZE_URL);

    echo <<<WSDL
<?xml version ="1.0" encoding ="UTF-8" ?>
<definitions name="LogoutNotification"
  targetNamespace="urn:mace:shibboleth:2.0:sp:notify"
  xmlns:notify="urn:mace:shibboleth:2.0:sp:notify"
  xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/"
  xmlns="http://schemas.xmlsoap.org/wsdl/">

        <types>
           <schema targetNamespace="urn:mace:shibboleth:2.0:sp:notify"
                   xmlns="http://www.w3.org/2000/10/XMLSchema"
                   xmlns:notify="urn:mace:shibboleth:2.0:sp:notify">

                        <simpleType name="string">
                                <restriction base="string">
                                        <minLength value="1"/>
                                </restriction>
                        </simpleType>

                        <element name="OK" type="notify:OKType"/>
                        <complexType name="OKType">
                                <sequence/>
                        </complexType>

                </schema>
        </types>

        <message name="getLogoutNotificationRequest">
                <part name="SessionID" type="notify:string" />
        </message>

        <message name="getLogoutNotificationResponse" >
                <part name="OK"/>
        </message>

        <portType name="LogoutNotificationPortType">
                <operation name="LogoutNotification">
                        <input message="getLogoutNotificationRequest"/>
                        <output message="getLogoutNotificationResponse"/>
                </operation>
        </portType>

        <binding name="LogoutNotificationBinding" type="notify:LogoutNotificationPortType">
                <soap:binding style="rpc" transport="http://schemas.xmlsoap.org/soap/http"/>
                <operation name="LogoutNotification">
                        <soap:operation soapAction="urn:xmethods-logout-notification#LogoutNotification"/>
                </operation>
        </binding>

        <service name="LogoutNotificationService">
                  <port name="LogoutNotificationPort" binding="notify:LogoutNotificationBinding">
                        <soap:address location="{$url}"/>
                  </port>
        </service>
</definitions>
WSDL;
    exit;
}

/******************************************************************************/
function LogoutNotification($SessionID): ?\SoapFault
{
    // Delete session of user using $SessionID to locate the user's session file
    // on the file system or in the database
    // Then delete this entry or record to clear the session
    // However, for that to work it is essential that the user's Shibboleth
    // SessionID is stored in the user session data!

    global $ilDB;

    $q = "SELECT session_id, data FROM usr_session WHERE expires > 'NOW()'";
    $r = $ilDB->query($q);

    while ($session_entry = $r->fetchRow(ilDBConstants::FETCHMODE_ASSOC)) {
        $user_session = unserializesession($session_entry['data']);

        // Look for session with matching Shibboleth session id
        // and then delete this ilias session
        foreach ($user_session as $user_session_entry) {
            // Delete this session entry
            if (is_array($user_session_entry) && array_key_exists('shibboleth_session_id', $user_session_entry) && $user_session_entry['shibboleth_session_id'] == $SessionID && !ilSession::_destroy($session_entry['session_id'])
            ) {
                return new SoapFault('LogoutError', 'Could not delete session entry in database.');
            }
        }
    }
    // If no SoapFault is returned, all is fine
    return null;
}

/******************************************************************************/
// Deserializes session data and returns it in a hash array of arrays
function unserializesession($serialized_string): array
{
    $variables = [];
    $a = preg_split("/(\w+)\|/", (string) $serialized_string, -1, PREG_SPLIT_NO_EMPTY | PREG_SPLIT_DELIM_CAPTURE);
    $counter = count($a);
    for ($i = 0; $i < $counter; $i += 2) {
        $variables[$a[$i]] = unserialize($a[$i + 1]);
    }

    return ($variables);
}