Session.php

<?php
/**
 * The Session class holds information about a user session, and everything attached to it.
 *
 * The session will have a duration and validity, and also cache information about the different
 * federation protocols, as Shibboleth and SAML 2.0. On the IdP side the Session class holds
 * information about all the currently logged in SPs. This is used when the user initiates a
 * Single-Log-Out.
 *
 * Bear in mind that the session object implements the Serializable interface, and as such,
 * all its contents MUST be serializable. If you need to store something in the session object
 * that is not serializable, make sure to convert it first to a representation that can be
 * serialized.
 *
 * @author Andreas Åkre Solberg, UNINETT AS. <andreas.solberg@uninett.no>
 * @author Jaime Pérez Crespo, UNINETT AS <jaime.perez@uninett.no>
 * @package SimpleSAMLphp
 */
class SimpleSAML_Session implements Serializable
{

    /**
     * This is a timeout value for setData, which indicates that the data
     * should never be deleted, i.e. lasts the whole session lifetime.
     */
    const DATA_TIMEOUT_SESSION_END = 'sessionEndTimeout';


    /**
     * The list of loaded session objects.
     *
     * This is an associative array indexed with the session id.
     *
     * @var array
     */
    private static $sessions = array();


    /**
     * This variable holds the instance of the session - Singleton approach.
     *
     * Warning: do not set the instance manually, call SimpleSAML_Session::load() instead.
     */
    private static $instance = null;


    /**
     * The session ID of this session.
     *
     * @var string|null
     */
    private $sessionId;


    /**
     * Transient session flag.
     *
     * @var boolean|false
     */
    private $transient = false;


    /**
     * The track id is a new random unique identifier that is generated for each session.
     * This is used in the debug logs and error messages to easily track more information
     * about what went wrong.
     *
     * @var string|null
     */
    private $trackid = null;


    private $rememberMeExpire = null;


    /**
     * Marks a session as modified, and therefore needs to be saved before destroying
     * this object.
     *
     * @var bool
     */
    private $dirty = false;


    /**
     * Tells the session object that the save callback has been registered and there's no need to register it again.
     *
     * @var bool
     */
    private $callback_registered = false;


    /**
     * This is an array of objects which will expire automatically after a set time. It is used
     * where one needs to store some information - for example a logout request, but doesn't
     * want it to be stored forever.
     *
     * The data store contains three levels of nested associative arrays. The first is the data type, the
     * second is the identifier, and the third contains the expire time of the data and the data itself.
     *
     * @var array
     */
    private $dataStore = null;


    /**
     * The list of IdP-SP associations.
     *
     * This is an associative array with the IdP id as the key, and the list of
     * associations as the value.
     *
     * @var array
     */
    private $associations = array();


    /**
     * The authentication token.
     *
     * This token is used to prevent session fixation attacks.
     *
     * @var string|null
     */
    private $authToken;


    /**
     * Authentication data.
     *
     * This is an array with authentication data for the various authsources.
     *
     * @var array  Associative array of associative arrays.
     */
    private $authData = array();


    /**
     * Private constructor that restricts instantiation to either getSessionFromRequest() for the current session or
     * getSession() for a specific one.
     *
     * @param boolean $transient Whether to create a transient session or not.
     */
    private function __construct($transient = false)
    {
        if (php_sapi_name() === 'cli' || defined('STDIN')) {
            $this->trackid = 'CL'.bin2hex(openssl_random_pseudo_bytes(4));
            SimpleSAML\Logger::setTrackId($this->trackid);
            $this->transient = $transient;
            return;
        }

        if ($transient) { // transient session
            $sh = \SimpleSAML\SessionHandler::getSessionHandler();
            $this->trackid = 'TR'.bin2hex(openssl_random_pseudo_bytes(4));
            SimpleSAML\Logger::setTrackId($this->trackid);
            $this->transient = true;

            /*
             * Initialize the session ID. It might be that we have a session cookie but we couldn't load the session.
             * If that's the case, use that ID. If not, create a new ID.
             */
            $this->sessionId = $sh->getCookieSessionId();
            if ($this->sessionId === null) {
                $this->sessionId = $sh->newSessionId();
            }
        } else { // regular session
            $sh = \SimpleSAML\SessionHandler::getSessionHandler();
            $this->sessionId = $sh->newSessionId();
            $sh->setCookie($sh->getSessionCookieName(), $this->sessionId, $sh->getCookieParams());


            $this->trackid = bin2hex(openssl_random_pseudo_bytes(5));
            SimpleSAML\Logger::setTrackId($this->trackid);

            $this->markDirty();

            // initialize data for session check function if defined
            $globalConfig = \SimpleSAML\Configuration::getInstance();
            $checkFunction = $globalConfig->getArray('session.check_function', null);
            if (isset($checkFunction)) {
                assert(is_callable($checkFunction));
                call_user_func($checkFunction, $this, true);
            }
        }
    }


    /**
     * Serialize this session object.
     *
     * This method will be invoked by any calls to serialize().
     *
     * @return string The serialized representation of this session object.
     */
    public function serialize()
    {
        $serialized = serialize(get_object_vars($this));
        return $serialized;
    }


    /**
     * Unserialize a session object and load it..
     *
     * This method will be invoked by any calls to unserialize(), allowing us to restore any data that might not
     * be serializable in its original form (e.g.: DOM objects).
     *
     * @param string $serialized The serialized representation of a session that we want to restore.
     */
    public function unserialize($serialized)
    {
        $session = unserialize($serialized);
        if (is_array($session)) {
            foreach ($session as $k => $v) {
                $this->$k = $v;
            }
        }

        // look for any raw attributes and load them in the 'Attributes' array
        foreach ($this->authData as $authority => $parameters) {
            if (!array_key_exists('RawAttributes', $parameters)) {
                continue;
            }

            foreach ($parameters['RawAttributes'] as $attribute => $values) {
                foreach ($values as $idx => $value) { // this should be originally a DOMNodeList
                    /* @var \SAML2\XML\saml\AttributeValue $value */
                    $this->authData[$authority]['Attributes'][$attribute][$idx] = $value->element->childNodes;
                }
            }
        }
    }


    /**
     * Retrieves the current session. Creates a new session if there's not one.
     *
     * @return SimpleSAML_Session The current session.
     * @throws Exception When session couldn't be initialized and the session fallback is disabled by configuration.
     */
    public static function getSessionFromRequest()
    {
        // check if we already have initialized the session
        if (isset(self::$instance)) {
            return self::$instance;
        }

        // check if we have stored a session stored with the session handler
        $session = null;
        try {
            $session = self::getSession();
        } catch (Exception $e) {
            /*
             * For some reason, we were unable to initialize this session. Note that this error might be temporary, and
             * it's possible that we can recover from it in subsequent requests, so we should not try to create a new
             * session here. Therefore, use just a transient session and throw the exception for someone else to handle
             * it.
             */
            SimpleSAML\Logger::error('Error loading session: '.$e->getMessage());
            self::useTransientSession();
            if ($e instanceof SimpleSAML_Error_Exception) {
                $cause = $e->getCause();
                if ($cause instanceof Exception) {
                    throw $cause;
                }
            }
            throw $e;
        }

        // if getSession() found it, use it
        if ($session instanceof SimpleSAML_Session) {
            return self::load($session);
        }

        /*
         * We didn't have a session loaded when we started, but we have it now. At this point, getSession() failed but
         * it must have triggered the creation of a session at some point during the process (e.g. while logging an
         * error message). This means we don't need to create a new session again, we can use the one that's loaded now
         * instead.
         */
        if (self::$instance !== null) {
            return self::$instance;
        }

        // try to create a new session
        try {
            self::load(new SimpleSAML_Session());
        } catch (\SimpleSAML\Error\CannotSetCookie $e) {
            // can't create a regular session because we can't set cookies. Use transient.
            $c = \SimpleSAML\Configuration::getInstance();
            self::useTransientSession();

            if ($e->getCode() === \SimpleSAML\Error\CannotSetCookie::SECURE_COOKIE) {
                throw new \SimpleSAML\Error\CriticalConfigurationError(
                    $e->getMessage(),
                    null,
                    $c->toArray()
                );
            }
            SimpleSAML\Logger::error('Error creating session: '.$e->getMessage());
        }

        // we must have a session now, either regular or transient
        return self::$instance;
    }

    /**
     * Get a session from the session handler.
     *
     * @param string|null $sessionId The session we should get, or null to get the current session.
     *
     * @return SimpleSAML_Session|null The session that is stored in the session handler, or null if the session wasn't
     * found.
     */
    public static function getSession($sessionId = null)
    {
        assert(is_string($sessionId) || $sessionId === null);

        $sh = \SimpleSAML\SessionHandler::getSessionHandler();

        if ($sessionId === null) {
            $checkToken = true;
            $sessionId = $sh->getCookieSessionId();
            if ($sessionId === null) {
                return null;
            }
        } else {
            $checkToken = false;
        }

        if (array_key_exists($sessionId, self::$sessions)) {
            return self::$sessions[$sessionId];
        }

        $session = $sh->loadSession($sessionId);
        if ($session === null) {
            return null;
        }

        assert($session instanceof self);

        if ($checkToken) {
            $globalConfig = \SimpleSAML\Configuration::getInstance();

            if ($session->authToken !== null) {
                $authTokenCookieName = $globalConfig->getString(
                    'session.authtoken.cookiename',
                    'SimpleSAMLAuthToken'
                );
                if (!isset($_COOKIE[$authTokenCookieName])) {
                    SimpleSAML\Logger::warning('Missing AuthToken cookie.');
                    return null;
                }
                if (!SimpleSAML\Utils\Crypto::secureCompare($session->authToken, $_COOKIE[$authTokenCookieName])) {
                    SimpleSAML\Logger::warning('Invalid AuthToken cookie.');
                    return null;
                }
            }

            // run session check function if defined
            $checkFunction = $globalConfig->getArray('session.check_function', null);
            if (isset($checkFunction)) {
                assert(is_callable($checkFunction));
                $check = call_user_func($checkFunction, $session);
                if ($check !== true) {
                    SimpleSAML\Logger::warning('Session did not pass check function.');
                    return null;
                }
            }
        }

        self::$sessions[$sessionId] = $session;

        return $session;
    }


    /**
     * Load a given session as the current one.
     *
     * This method will also set the track ID in the logger to the one in the given session.
     *
     * Warning: never set self::$instance yourself, call this method instead.
     *
     * @param SimpleSAML_Session $session The session to load.
     * @return SimpleSAML_Session The session we just loaded, just for convenience.
     */
    private static function load(SimpleSAML_Session $session)
    {
        SimpleSAML\Logger::setTrackId($session->getTrackID());
        self::$instance = $session;
        return self::$instance;
    }

    /**
     * Use a transient session.
     *
     * Create a session that should not be saved at the end of the request.
     * Subsequent calls to getInstance() will return this transient session.
     */
    public static function useTransientSession()
    {
        if (isset(self::$instance)) {
            // we already have a session, don't bother with a transient session
            return;
        }

        self::load(new SimpleSAML_Session(true));
    }

    /**
     * Create a new session and cache it.
     *
     * @param string $sessionId The new session we should create.
     */
    public static function createSession($sessionId)
    {
        assert(is_string($sessionId));
        self::$sessions[$sessionId] = null;
    }

    /**
     * Save the session to the store.
     *
     * This method saves the session to the session handler in case it has been marked as dirty.
     *
     * WARNING: please do not use this method directly unless you really need to and know what you are doing. Use
     * markDirty() instead.
     */
    public function save()
    {
        if (!$this->dirty) {
            // session hasn't changed, don't bother saving it
            return;
        }

        $this->dirty = false;
        $this->callback_registered = false;

        $sh = \SimpleSAML\SessionHandler::getSessionHandler();

        try {
            $sh->saveSession($this);
        } catch (Exception $e) {
            if (!($e instanceof SimpleSAML_Error_Exception)) {
                $e = new SimpleSAML_Error_UnserializableException($e);
            }
            SimpleSAML\Logger::error('Unable to save session.');
            $e->logError();
        }
    }


    /**
     * Save the current session and clean any left overs that could interfere with the normal application behaviour.
     *
     * Use this method if you are using PHP sessions in your application *and* in SimpleSAMLphp, *after* you are done
     * using SimpleSAMLphp and before trying to access your application's session again.
     */
    public function cleanup()
    {
        $this->save();
        $sh = \SimpleSAML\SessionHandler::getSessionHandler();
        if ($sh instanceof \SimpleSAML\SessionHandlerPHP) {
            $sh->restorePrevious();
        }
    }


    /**
     * Mark this session as dirty.
     *
     * This method will register a callback to save the session right before any output is sent to the browser.
     */
    public function markDirty()
    {
        if ($this->isTransient()) {
            return;
        }

        $this->dirty = true;

        if ($this->callback_registered) {
            // we already have a shutdown callback registered for this object, no need to add another one
            return;
        }
        $this->callback_registered = header_register_callback(array($this, 'save'));
    }


    /**
     * Destroy the session.
     *
     * Destructor for this class. It will save the session to the session handler
     * in case the session has been marked as dirty. Do nothing otherwise.
     */
    public function __destruct()
    {
        $this->save();
    }

    /**
     * Retrieve the session ID of this session.
     *
     * @return string|null  The session ID, or null if this is a transient session.
     */
    public function getSessionId()
    {
        return $this->sessionId;
    }

    /**
     * Retrieve if session is transient.
     *
     * @return boolean The session transient flag.
     */
    public function isTransient()
    {
        return $this->transient;
    }

    /**
     * Get a unique ID that will be permanent for this session.
     * Used for debugging and tracing log files related to a session.
     *
     * @return string|null The unique ID.
     */
    public function getTrackID()
    {
        return $this->trackid;
    }

    /**
     * Get remember me expire time.
     *
     * @return integer|null The remember me expire time.
     */
    public function getRememberMeExpire()
    {
        return $this->rememberMeExpire;
    }

    /**
     * Set remember me expire time.
     *
     * @param int $expire Unix timestamp when remember me session cookies expire.
     */
    public function setRememberMeExpire($expire = null)
    {
        assert(is_int($expire) || $expire === null);

        if ($expire === null) {
            $globalConfig = \SimpleSAML\Configuration::getInstance();
            $expire = time() + $globalConfig->getInteger('session.rememberme.lifetime', 14 * 86400);
        }
        $this->rememberMeExpire = $expire;

        $cookieParams = array('expire' => $this->rememberMeExpire);
        $this->updateSessionCookies($cookieParams);
    }

    /**
     * Marks the user as logged in with the specified authority.
     *
     * If the user already has logged in, the user will be logged out first.
     *
     * @param string     $authority The authority the user logged in with.
     * @param array|null $data The authentication data for this authority.
     *
     * @throws \SimpleSAML\Error\CannotSetCookie If the authentication token cannot be set for some reason.
     */
    public function doLogin($authority, array $data = null)
    {
        assert(is_string($authority));
        assert(is_array($data) || $data === null);

        SimpleSAML\Logger::debug('Session: doLogin("'.$authority.'")');

        $this->markDirty();

        if (isset($this->authData[$authority])) {
            // we are already logged in, log the user out first
            $this->doLogout($authority);
        }

        if ($data === null) {
            $data = array();
        }

        $data['Authority'] = $authority;

        $globalConfig = \SimpleSAML\Configuration::getInstance();
        if (!isset($data['AuthnInstant'])) {
            $data['AuthnInstant'] = time();
        }

        $maxSessionExpire = time() + $globalConfig->getInteger('session.duration', 8 * 60 * 60);
        if (!isset($data['Expire']) || $data['Expire'] > $maxSessionExpire) {
            // unset, or beyond our session lifetime. Clamp it to our maximum session lifetime
            $data['Expire'] = $maxSessionExpire;
        }

        // check if we have non-serializable attribute values
        foreach ($data['Attributes'] as $attribute => $values) {
            foreach ($values as $idx => $value) {
                if (is_string($value) || is_int($value)) {
                    continue;
                }

                // at this point, this should be a DOMNodeList object...
                if (!is_a($value, 'DOMNodeList')) {
                    continue;
                }

                /* @var \DOMNodeList $value */
                if ($value->length === 0) {
                    continue;
                }

                // create an AttributeValue object and save it to 'RawAttributes', using same attribute name and index
                $attrval = new \SAML2\XML\saml\AttributeValue($value->item(0)->parentNode);
                $data['RawAttributes'][$attribute][$idx] = $attrval;
            }
        }

        $this->authData[$authority] = $data;

        $this->authToken = SimpleSAML\Utils\Random::generateID();
        $sessionHandler = \SimpleSAML\SessionHandler::getSessionHandler();

        if (!$this->transient && (!empty($data['RememberMe']) || $this->rememberMeExpire) &&
            $globalConfig->getBoolean('session.rememberme.enable', false)
        ) {
            $this->setRememberMeExpire();
        } else {
            try {
                SimpleSAML\Utils\HTTP::setCookie(
                    $globalConfig->getString('session.authtoken.cookiename', 'SimpleSAMLAuthToken'),
                    $this->authToken,
                    $sessionHandler->getCookieParams()
                );
            } catch (SimpleSAML\Error\CannotSetCookie $e) {
                /*
                 * Something went wrong when setting the auth token. We cannot recover from this, so we better log a
                 * message and throw an exception. The user is not properly logged in anyway, so clear all login
                 * information from the session.
                 */
                unset($this->authToken);
                unset($this->authData[$authority]);
                \SimpleSAML\Logger::error('Cannot set authentication token cookie: '.$e->getMessage());
                throw $e;
            }
        }
    }

    /**
     * Marks the user as logged out.
     *
     * This function will call any registered logout handlers before marking the user as logged out.
     *
     * @param string $authority The authentication source we are logging out of.
     */
    public function doLogout($authority)
    {
        SimpleSAML\Logger::debug('Session: doLogout('.var_export($authority, true).')');

        if (!isset($this->authData[$authority])) {
            SimpleSAML\Logger::debug('Session: Already logged out of '.$authority.'.');
            return;
        }

        $this->markDirty();

        $this->callLogoutHandlers($authority);
        unset($this->authData[$authority]);

        if (!$this->isValid($authority) && $this->rememberMeExpire) {
            $this->rememberMeExpire = null;
            $this->updateSessionCookies();
        }
    }

    /**
     * This function calls all registered logout handlers.
     *
     * @param string $authority The authentication source we are logging out from.
     *
     * @throws Exception If the handler is not a valid function or method.
     */
    private function callLogoutHandlers($authority)
    {
        assert(is_string($authority));
        assert(isset($this->authData[$authority]));

        if (empty($this->authData[$authority]['LogoutHandlers'])) {
            return;
        }
        foreach ($this->authData[$authority]['LogoutHandlers'] as $handler) {
            // verify that the logout handler is a valid function
            if (!is_callable($handler)) {
                $classname = $handler[0];
                $functionname = $handler[1];

                throw new Exception(
                    'Logout handler is not a valid function: '.$classname.'::'.
                    $functionname
                );
            }

            // call the logout handler
            call_user_func($handler);
        }

        // we require the logout handlers to register themselves again if they want to be called later
        unset($this->authData[$authority]['LogoutHandlers']);
    }

    /**
     * Is the session representing an authenticated user, and is the session still alive.
     * This function will return false after the user has timed out.
     *
     * @param string $authority The authentication source that the user should be authenticated with.
     *
     * @return true if the user has a valid session, false if not.
     */
    public function isValid($authority)
    {
        assert(is_string($authority));

        if (!isset($this->authData[$authority])) {
            SimpleSAML\Logger::debug(
                'Session: '.var_export($authority, true).
                ' not valid because we are not authenticated.'
            );
            return false;
        }

        if ($this->authData[$authority]['Expire'] <= time()) {
            SimpleSAML\Logger::debug('Session: '.var_export($authority, true).' not valid because it is expired.');
            return false;
        }

        SimpleSAML\Logger::debug('Session: Valid session found with '.var_export($authority, true).'.');

        return true;
    }

    /**
     * Update session cookies.
     *
     * @param array $params The parameters for the cookies.
     */
    public function updateSessionCookies($params = null)
    {
        assert(is_null($params) || is_array($params));

        $sessionHandler = \SimpleSAML\SessionHandler::getSessionHandler();

        if ($this->sessionId !== null) {
            $sessionHandler->setCookie($sessionHandler->getSessionCookieName(), $this->sessionId, $params);
        }

        $params = array_merge($sessionHandler->getCookieParams(), is_array($params) ? $params : array());

        if ($this->authToken !== null) {
            $globalConfig = \SimpleSAML\Configuration::getInstance();
            \SimpleSAML\Utils\HTTP::setCookie(
                $globalConfig->getString('session.authtoken.cookiename', 'SimpleSAMLAuthToken'),
                $this->authToken,
                $params
            );
        }
    }

    /**
     * Set the lifetime for authentication source.
     *
     * @param string $authority The authentication source we are setting expire time for.
     * @param int    $expire The number of seconds authentication source is valid.
     */
    public function setAuthorityExpire($authority, $expire = null)
    {
        assert(isset($this->authData[$authority]));
        assert(is_int($expire) || $expire === null);

        $this->markDirty();

        if ($expire === null) {
            $globalConfig = \SimpleSAML\Configuration::getInstance();
            $expire = time() + $globalConfig->getInteger('session.duration', 8 * 60 * 60);
        }

        $this->authData[$authority]['Expire'] = $expire;
    }

    /**
     * This function registers a logout handler.
     *
     * @param string $authority The authority for which register the handler.
     * @param string $classname The class which contains the logout handler.
     * @param string $functionname The logout handler function.
     *
     * @throws Exception If the handler is not a valid function or method.
     */
    public function registerLogoutHandler($authority, $classname, $functionname)
    {
        assert(isset($this->authData[$authority]));

        $logout_handler = array($classname, $functionname);

        if (!is_callable($logout_handler)) {
            throw new Exception(
                'Logout handler is not a vaild function: '.$classname.'::'.
                $functionname
            );
        }

        $this->authData[$authority]['LogoutHandlers'][] = $logout_handler;
        $this->markDirty();
    }

    /**
     * Delete data from the data store.
     *
     * This function immediately deletes the data with the given type and id from the data store.
     *
     * @param string $type The type of the data.
     * @param string $id The identifier of the data.
     */
    public function deleteData($type, $id)
    {
        assert(is_string($type));
        assert(is_string($id));

        if (!is_array($this->dataStore)) {
            return;
        }

        if (!array_key_exists($type, $this->dataStore)) {
            return;
        }

        unset($this->dataStore[$type][$id]);
        $this->markDirty();
    }

    /**
     * This function stores data in the data store.
     *
     * The timeout value can be SimpleSAML_Session::DATA_TIMEOUT_SESSION_END, which indicates
     * that the data should never be deleted.
     *
     * @param string   $type The type of the data. This is checked when retrieving data from the store.
     * @param string   $id The identifier of the data.
     * @param mixed    $data The data.
     * @param int|null $timeout The number of seconds this data should be stored after its last access.
     * This parameter is optional. The default value is set in 'session.datastore.timeout',
     * and the default is 4 hours.
     *
     * @throws Exception If the data couldn't be stored.
     *
     */
    public function setData($type, $id, $data, $timeout = null)
    {
        assert(is_string($type));
        assert(is_string($id));
        assert(is_int($timeout) || $timeout === null || $timeout === self::DATA_TIMEOUT_SESSION_END);

        // clean out old data
        $this->expireData();

        if ($timeout === null) {
            // use the default timeout
            $configuration = \SimpleSAML\Configuration::getInstance();

            $timeout = $configuration->getInteger('session.datastore.timeout', null);
            if ($timeout !== null) {
                if ($timeout <= 0) {
                    throw new Exception(
                        'The value of the session.datastore.timeout'.
                        ' configuration option should be a positive integer.'
                    );
                }
            }
        }

        if ($timeout === self::DATA_TIMEOUT_SESSION_END) {
            $expires = self::DATA_TIMEOUT_SESSION_END;
        } else {
            $expires = time() + $timeout;
        }

        $dataInfo = array(
            'expires' => $expires,
            'timeout' => $timeout,
            'data'    => $data
        );

        if (!is_array($this->dataStore)) {
            $this->dataStore = array();
        }

        if (!array_key_exists($type, $this->dataStore)) {
            $this->dataStore[$type] = array();
        }

        $this->dataStore[$type][$id] = $dataInfo;

        $this->markDirty();
    }

    /**
     * This function removes expired data from the data store.
     *
     * Note that this function doesn't mark the session object as dirty. This means that
     * if the only change to the session object is that some data has expired, it will not be
     * written back to the session store.
     */
    private function expireData()
    {
        if (!is_array($this->dataStore)) {
            return;
        }

        $ct = time();

        foreach ($this->dataStore as &$typedData) {
            foreach ($typedData as $id => $info) {
                if ($info['expires'] === self::DATA_TIMEOUT_SESSION_END) {
                    // this data never expires
                    continue;
                }

                if ($ct > $info['expires']) {
                    unset($typedData[$id]);
                }
            }
        }
    }

    /**
     * This function retrieves data from the data store.
     *
     * Note that this will not change when the data stored in the data store will expire. If that is required,
     * the data should be written back with setData.
     *
     * @param string      $type The type of the data. This must match the type used when adding the data.
     * @param string|null $id The identifier of the data. Can be null, in which case null will be returned.
     *
     * @return mixed The data of the given type with the given id or null if the data doesn't exist in the data store.
     */
    public function getData($type, $id)
    {
        assert(is_string($type));
        assert($id === null || is_string($id));

        if ($id === null) {
            return null;
        }

        $this->expireData();

        if (!is_array($this->dataStore)) {
            return null;
        }

        if (!array_key_exists($type, $this->dataStore)) {
            return null;
        }

        if (!array_key_exists($id, $this->dataStore[$type])) {
            return null;
        }

        return $this->dataStore[$type][$id]['data'];
    }

    /**
     * This function retrieves all data of the specified type from the data store.
     *
     * The data will be returned as an associative array with the id of the data as the key, and the data
     * as the value of each key. The value will be stored as a copy of the original data. setData must be
     * used to update the data.
     *
     * An empty array will be returned if no data of the given type is found.
     *
     * @param string $type The type of the data.
     *
     * @return array An associative array with all data of the given type.
     */
    public function getDataOfType($type)
    {
        assert(is_string($type));

        if (!is_array($this->dataStore)) {
            return array();
        }

        if (!array_key_exists($type, $this->dataStore)) {
            return array();