SessionManager.php

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<?php
namespace MediaWiki\Session;

use MediaWiki\MediaWikiServices;
use MWException;
use Psr\Log\LoggerInterface;
use BagOStuff;
use CachedBagOStuff;
use Config;
use FauxRequest;
use User;
use WebRequest;
use Wikimedia\ObjectFactory;

final class SessionManager implements SessionManagerInterface {
    private static $instance = null;

    private static $globalSession = null;

    private static $globalSessionRequest = null;

    private $logger;

    private $config;

    private $store;

    private $sessionProviders = null;

    private $varyCookies = null;

    private $varyHeaders = null;

    private $allSessionBackends = [];

    private $allSessionIds = [];

    private $preventUsers = [];

    public static function singleton() {
        if ( self::$instance === null ) {
            self::$instance = new self();
        }
        return self::$instance;
    }

    public static function getGlobalSession() {
        if ( !PHPSessionHandler::isEnabled() ) {
            $id = '';
        } else {
            $id = session_id();
        }

        $request = \RequestContext::getMain()->getRequest();
        if (
            !self::$globalSession // No global session is set up yet
            || self::$globalSessionRequest !== $request // The global WebRequest changed
            || $id !== '' && self::$globalSession->getId() !== $id // Someone messed with session_id()
        ) {
            self::$globalSessionRequest = $request;
            if ( $id === '' ) {
                // session_id() wasn't used, so fetch the Session from the WebRequest.
                // We use $request->getSession() instead of $singleton->getSessionForRequest()
                // because doing the latter would require a public
                // "$request->getSessionId()" method that would confuse end
                // users by returning SessionId|null where they'd expect it to
                // be short for $request->getSession()->getId(), and would
                // wind up being a duplicate of the code in
                // $request->getSession() anyway.
                self::$globalSession = $request->getSession();
            } else {
                // Someone used session_id(), so we need to follow suit.
                // Note this overwrites whatever session might already be
                // associated with $request with the one for $id.
                self::$globalSession = self::singleton()->getSessionById( $id, true, $request )
                    ?: $request->getSession();
            }
        }
        return self::$globalSession;
    }

    public function __construct( $options = [] ) {
        if ( isset( $options['config'] ) ) {
            $this->config = $options['config'];
            if ( !$this->config instanceof Config ) {
                throw new \InvalidArgumentException(
                    '$options[\'config\'] must be an instance of Config'
                );
            }
        } else {
            $this->config = MediaWikiServices::getInstance()->getMainConfig();
        }

        if ( isset( $options['logger'] ) ) {
            if ( !$options['logger'] instanceof LoggerInterface ) {
                throw new \InvalidArgumentException(
                    '$options[\'logger\'] must be an instance of LoggerInterface'
                );
            }
            $this->setLogger( $options['logger'] );
        } else {
            $this->setLogger( \MediaWiki\Logger\LoggerFactory::getInstance( 'session' ) );
        }

        if ( isset( $options['store'] ) ) {
            if ( !$options['store'] instanceof BagOStuff ) {
                throw new \InvalidArgumentException(
                    '$options[\'store\'] must be an instance of BagOStuff'
                );
            }
            $store = $options['store'];
        } else {
            $store = \ObjectCache::getInstance( $this->config->get( 'SessionCacheType' ) );
        }
        $this->store = $store instanceof CachedBagOStuff ? $store : new CachedBagOStuff( $store );

        register_shutdown_function( [ $this, 'shutdown' ] );
    }

    public function setLogger( LoggerInterface $logger ) {
        $this->logger = $logger;
    }

    public function getSessionForRequest( WebRequest $request ) {
        $info = $this->getSessionInfoForRequest( $request );

        if ( !$info ) {
            $session = $this->getEmptySession( $request );
        } else {
            $session = $this->getSessionFromInfo( $info, $request );
        }
        return $session;
    }

    public function getSessionById( $id, $create = false, WebRequest $request = null ) {
        if ( !self::validateSessionId( $id ) ) {
            throw new \InvalidArgumentException( 'Invalid session ID' );
        }
        if ( !$request ) {
            $request = new FauxRequest;
        }

        $session = null;
        $info = new SessionInfo( SessionInfo::MIN_PRIORITY, [ 'id' => $id, 'idIsSafe' => true ] );

        // If we already have the backend loaded, use it directly
        if ( isset( $this->allSessionBackends[$id] ) ) {
            return $this->getSessionFromInfo( $info, $request );
        }

        // Test if the session is in storage, and if so try to load it.
        $key = $this->store->makeKey( 'MWSession', $id );
        if ( is_array( $this->store->get( $key ) ) ) {
            $create = false; // If loading fails, don't bother creating because it probably will fail too.
            if ( $this->loadSessionInfoFromStore( $info, $request ) ) {
                $session = $this->getSessionFromInfo( $info, $request );
            }
        }

        if ( $create && $session === null ) {
            $ex = null;
            try {
                $session = $this->getEmptySessionInternal( $request, $id );
            } catch ( \Exception $ex ) {
                $this->logger->error( 'Failed to create empty session: {exception}',
                    [
                        'method' => __METHOD__,
                        'exception' => $ex,
                ] );
                $session = null;
            }
        }

        return $session;
    }

    public function getEmptySession( WebRequest $request = null ) {
        return $this->getEmptySessionInternal( $request );
    }

    private function getEmptySessionInternal( WebRequest $request = null, $id = null ) {
        if ( $id !== null ) {
            if ( !self::validateSessionId( $id ) ) {
                throw new \InvalidArgumentException( 'Invalid session ID' );
            }

            $key = $this->store->makeKey( 'MWSession', $id );
            if ( is_array( $this->store->get( $key ) ) ) {
                throw new \InvalidArgumentException( 'Session ID already exists' );
            }
        }
        if ( !$request ) {
            $request = new FauxRequest;
        }

        $infos = [];
        foreach ( $this->getProviders() as $provider ) {
            $info = $provider->newSessionInfo( $id );
            if ( !$info ) {
                continue;
            }
            if ( $info->getProvider() !== $provider ) {
                throw new \UnexpectedValueException(
                    "$provider returned an empty session info for a different provider: $info"
                );
            }
            if ( $id !== null && $info->getId() !== $id ) {
                throw new \UnexpectedValueException(
                    "$provider returned empty session info with a wrong id: " .
                        $info->getId() . ' != ' . $id
                );
            }
            if ( !$info->isIdSafe() ) {
                throw new \UnexpectedValueException(
                    "$provider returned empty session info with id flagged unsafe"
                );
            }
            $compare = $infos ? SessionInfo::compare( $infos[0], $info ) : -1;
            if ( $compare > 0 ) {
                continue;
            }
            if ( $compare === 0 ) {
                $infos[] = $info;
            } else {
                $infos = [ $info ];
            }
        }

        // Make sure there's exactly one
        if ( count( $infos ) > 1 ) {
            throw new \UnexpectedValueException(
                'Multiple empty sessions tied for top priority: ' . implode( ', ', $infos )
            );
        } elseif ( count( $infos ) < 1 ) {
            throw new \UnexpectedValueException( 'No provider could provide an empty session!' );
        }

        return $this->getSessionFromInfo( $infos[0], $request );
    }

    public function invalidateSessionsForUser( User $user ) {
        $user->setToken();
        $user->saveSettings();

        foreach ( $this->getProviders() as $provider ) {
            $provider->invalidateSessionsForUser( $user );
        }
    }

    public function getVaryHeaders() {
        // @codeCoverageIgnoreStart
        if ( defined( 'MW_NO_SESSION' ) && MW_NO_SESSION !== 'warn' ) {
            return [];
        }
        // @codeCoverageIgnoreEnd
        if ( $this->varyHeaders === null ) {
            $headers = [];
            foreach ( $this->getProviders() as $provider ) {
                foreach ( $provider->getVaryHeaders() as $header => $options ) {
                    if ( !isset( $headers[$header] ) ) {
                        $headers[$header] = [];
                    }
                    if ( is_array( $options ) ) {
                        $headers[$header] = array_unique( array_merge( $headers[$header], $options ) );
                    }
                }
            }
            $this->varyHeaders = $headers;
        }
        return $this->varyHeaders;
    }

    public function getVaryCookies() {
        // @codeCoverageIgnoreStart
        if ( defined( 'MW_NO_SESSION' ) && MW_NO_SESSION !== 'warn' ) {
            return [];
        }
        // @codeCoverageIgnoreEnd
        if ( $this->varyCookies === null ) {
            $cookies = [];
            foreach ( $this->getProviders() as $provider ) {
                $cookies = array_merge( $cookies, $provider->getVaryCookies() );
            }
            $this->varyCookies = array_values( array_unique( $cookies ) );
        }
        return $this->varyCookies;
    }

    public static function validateSessionId( $id ) {
        return is_string( $id ) && preg_match( '/^[a-zA-Z0-9_-]{32,}$/', $id );
    }

    public function preventSessionsForUser( $username ) {
        $this->preventUsers[$username] = true;

        // Instruct the session providers to kill any other sessions too.
        foreach ( $this->getProviders() as $provider ) {
            $provider->preventSessionsForUser( $username );
        }
    }

    public function isUserSessionPrevented( $username ) {
        return !empty( $this->preventUsers[$username] );
    }

    protected function getProviders() {
        if ( $this->sessionProviders === null ) {
            $this->sessionProviders = [];
            foreach ( $this->config->get( 'SessionProviders' ) as $spec ) {
                $provider = ObjectFactory::getObjectFromSpec( $spec );
                $provider->setLogger( $this->logger );
                $provider->setConfig( $this->config );
                $provider->setManager( $this );
                if ( isset( $this->sessionProviders[(string)$provider] ) ) {
                    throw new \UnexpectedValueException( "Duplicate provider name \"$provider\"" );
                }
                $this->sessionProviders[(string)$provider] = $provider;
            }
        }
        return $this->sessionProviders;
    }

    public function getProvider( $name ) {
        $providers = $this->getProviders();
        return $providers[$name] ?? null;
    }

    public function shutdown() {
        if ( $this->allSessionBackends ) {
            $this->logger->debug( 'Saving all sessions on shutdown' );
            if ( session_id() !== '' ) {
                // @codeCoverageIgnoreStart
                session_write_close();
            }
            // @codeCoverageIgnoreEnd
            foreach ( $this->allSessionBackends as $backend ) {
                $backend->shutdown();
            }
        }
    }

    private function getSessionInfoForRequest( WebRequest $request ) {
        // Call all providers to fetch "the" session
        $infos = [];
        foreach ( $this->getProviders() as $provider ) {
            $info = $provider->provideSessionInfo( $request );
            if ( !$info ) {
                continue;
            }
            if ( $info->getProvider() !== $provider ) {
                throw new \UnexpectedValueException(
                    "$provider returned session info for a different provider: $info"
                );
            }
            $infos[] = $info;
        }

        // Sort the SessionInfos. Then find the first one that can be
        // successfully loaded, and then all the ones after it with the same
        // priority.
        usort( $infos, 'MediaWiki\\Session\\SessionInfo::compare' );
        $retInfos = [];
        while ( $infos ) {
            $info = array_pop( $infos );
            if ( $this->loadSessionInfoFromStore( $info, $request ) ) {
                $retInfos[] = $info;
                while ( $infos ) {
                    $info = array_pop( $infos );
                    if ( SessionInfo::compare( $retInfos[0], $info ) ) {
                        // We hit a lower priority, stop checking.
                        break;
                    }
                    if ( $this->loadSessionInfoFromStore( $info, $request ) ) {
                        // This is going to error out below, but we want to
                        // provide a complete list.
                        $retInfos[] = $info;
                    } else {
                        // Session load failed, so unpersist it from this request
                        $info->getProvider()->unpersistSession( $request );
                    }
                }
            } else {
                // Session load failed, so unpersist it from this request
                $info->getProvider()->unpersistSession( $request );
            }
        }

        if ( count( $retInfos ) > 1 ) {
            $ex = new \OverflowException(
                'Multiple sessions for this request tied for top priority: ' . implode( ', ', $retInfos )
            );
            $ex->sessionInfos = $retInfos;
            throw $ex;
        }

        return $retInfos ? $retInfos[0] : null;
    }

    private function loadSessionInfoFromStore( SessionInfo &$info, WebRequest $request ) {
        $key = $this->store->makeKey( 'MWSession', $info->getId() );
        $blob = $this->store->get( $key );

        // If we got data from the store and the SessionInfo says to force use,
        // "fail" means to delete the data from the store and retry. Otherwise,
        // "fail" is just return false.
        if ( $info->forceUse() && $blob !== false ) {
            $failHandler = function () use ( $key, &$info, $request ) {
                $this->store->delete( $key );
                return $this->loadSessionInfoFromStore( $info, $request );
            };
        } else {
            $failHandler = function () {
                return false;
            };
        }

        $newParams = [];

        if ( $blob !== false ) {
            // Sanity check: blob must be an array, if it's saved at all
            if ( !is_array( $blob ) ) {
                $this->logger->warning( 'Session "{session}": Bad data', [
                    'session' => $info,
                ] );
                $this->store->delete( $key );
                return $failHandler();
            }

            // Sanity check: blob has data and metadata arrays
            if ( !isset( $blob['data'] ) || !is_array( $blob['data'] ) ||
                !isset( $blob['metadata'] ) || !is_array( $blob['metadata'] )
            ) {
                $this->logger->warning( 'Session "{session}": Bad data structure', [
                    'session' => $info,
                ] );
                $this->store->delete( $key );
                return $failHandler();
            }

            $data = $blob['data'];
            $metadata = $blob['metadata'];

            // Sanity check: metadata must be an array and must contain certain
            // keys, if it's saved at all
            if ( !array_key_exists( 'userId', $metadata ) ||
                !array_key_exists( 'userName', $metadata ) ||
                !array_key_exists( 'userToken', $metadata ) ||
                !array_key_exists( 'provider', $metadata )
            ) {
                $this->logger->warning( 'Session "{session}": Bad metadata', [
                    'session' => $info,
                ] );
                $this->store->delete( $key );
                return $failHandler();
            }

            // First, load the provider from metadata, or validate it against the metadata.
            $provider = $info->getProvider();
            if ( $provider === null ) {
                $newParams['provider'] = $provider = $this->getProvider( $metadata['provider'] );
                if ( !$provider ) {
                    $this->logger->warning(
                        'Session "{session}": Unknown provider ' . $metadata['provider'],
                        [
                            'session' => $info,
                        ]
                    );
                    $this->store->delete( $key );
                    return $failHandler();
                }
            } elseif ( $metadata['provider'] !== (string)$provider ) {
                $this->logger->warning( 'Session "{session}": Wrong provider ' .
                    $metadata['provider'] . ' !== ' . $provider,
                    [
                        'session' => $info,
                ] );
                return $failHandler();
            }

            // Load provider metadata from metadata, or validate it against the metadata
            $providerMetadata = $info->getProviderMetadata();
            if ( isset( $metadata['providerMetadata'] ) ) {
                if ( $providerMetadata === null ) {
                    $newParams['metadata'] = $metadata['providerMetadata'];
                } else {
                    try {
                        $newProviderMetadata = $provider->mergeMetadata(
                            $metadata['providerMetadata'], $providerMetadata
                        );
                        if ( $newProviderMetadata !== $providerMetadata ) {
                            $newParams['metadata'] = $newProviderMetadata;
                        }
                    } catch ( MetadataMergeException $ex ) {
                        $this->logger->warning(
                            'Session "{session}": Metadata merge failed: {exception}',
                            [
                                'session' => $info,
                                'exception' => $ex,
                            ] + $ex->getContext()
                        );
                        return $failHandler();
                    }
                }
            }

            // Next, load the user from metadata, or validate it against the metadata.
            $userInfo = $info->getUserInfo();
            if ( !$userInfo ) {
                // For loading, id is preferred to name.
                try {
                    if ( $metadata['userId'] ) {
                        $userInfo = UserInfo::newFromId( $metadata['userId'] );
                    } elseif ( $metadata['userName'] !== null ) { // Shouldn't happen, but just in case
                        $userInfo = UserInfo::newFromName( $metadata['userName'] );
                    } else {
                        $userInfo = UserInfo::newAnonymous();
                    }
                } catch ( \InvalidArgumentException $ex ) {
                    $this->logger->error( 'Session "{session}": {exception}', [
                        'session' => $info,
                        'exception' => $ex,
                    ] );
                    return $failHandler();
                }
                $newParams['userInfo'] = $userInfo;
            } else {
                // User validation passes if user ID matches, or if there
                // is no saved ID and the names match.
                if ( $metadata['userId'] ) {
                    if ( $metadata['userId'] !== $userInfo->getId() ) {
                        $this->logger->warning(
                            'Session "{session}": User ID mismatch, {uid_a} !== {uid_b}',
                            [
                                'session' => $info,
                                'uid_a' => $metadata['userId'],
                                'uid_b' => $userInfo->getId(),
                        ] );
                        return $failHandler();
                    }

                    // If the user was renamed, probably best to fail here.
                    if ( $metadata['userName'] !== null &&
                        $userInfo->getName() !== $metadata['userName']
                    ) {
                        $this->logger->warning(
                            'Session "{session}": User ID matched but name didn\'t (rename?), {uname_a} !== {uname_b}',
                            [
                                'session' => $info,
                                'uname_a' => $metadata['userName'],
                                'uname_b' => $userInfo->getName(),
                        ] );
                        return $failHandler();
                    }

                } elseif ( $metadata['userName'] !== null ) { // Shouldn't happen, but just in case
                    if ( $metadata['userName'] !== $userInfo->getName() ) {
                        $this->logger->warning(
                            'Session "{session}": User name mismatch, {uname_a} !== {uname_b}',
                            [
                                'session' => $info,
                                'uname_a' => $metadata['userName'],
                                'uname_b' => $userInfo->getName(),
                        ] );
                        return $failHandler();
                    }
                } elseif ( !$userInfo->isAnon() ) {
                    // Metadata specifies an anonymous user, but the passed-in
                    // user isn't anonymous.
                    $this->logger->warning(
                        'Session "{session}": Metadata has an anonymous user, but a non-anon user was provided',
                        [
                            'session' => $info,
                    ] );
                    return $failHandler();
                }
            }

            // And if we have a token in the metadata, it must match the loaded/provided user.
            if ( $metadata['userToken'] !== null &&
                $userInfo->getToken() !== $metadata['userToken']
            ) {
                $this->logger->warning( 'Session "{session}": User token mismatch', [
                    'session' => $info,
                ] );
                return $failHandler();
            }
            if ( !$userInfo->isVerified() ) {
                $newParams['userInfo'] = $userInfo->verified();
            }

            if ( !empty( $metadata['remember'] ) && !$info->wasRemembered() ) {
                $newParams['remembered'] = true;
            }
            if ( !empty( $metadata['forceHTTPS'] ) && !$info->forceHTTPS() ) {
                $newParams['forceHTTPS'] = true;
            }
            if ( !empty( $metadata['persisted'] ) && !$info->wasPersisted() ) {
                $newParams['persisted'] = true;
            }

            if ( !$info->isIdSafe() ) {
                $newParams['idIsSafe'] = true;
            }
        } else {
            // No metadata, so we can't load the provider if one wasn't given.
            if ( $info->getProvider() === null ) {
                $this->logger->warning(
                    'Session "{session}": Null provider and no metadata',
                    [
                        'session' => $info,
                ] );
                return $failHandler();
            }

            // If no user was provided and no metadata, it must be anon.
            if ( !$info->getUserInfo() ) {
                if ( $info->getProvider()->canChangeUser() ) {
                    $newParams['userInfo'] = UserInfo::newAnonymous();
                } else {
                    $this->logger->info(
                        'Session "{session}": No user provided and provider cannot set user',
                        [
                            'session' => $info,
                    ] );
                    return $failHandler();
                }
            } elseif ( !$info->getUserInfo()->isVerified() ) {
                // probably just a session timeout
                $this->logger->info(
                    'Session "{session}": Unverified user provided and no metadata to auth it',
                    [
                        'session' => $info,
                ] );
                return $failHandler();
            }

            $data = false;
            $metadata = false;

            if ( !$info->getProvider()->persistsSessionId() && !$info->isIdSafe() ) {
                // The ID doesn't come from the user, so it should be safe
                // (and if not, nothing we can do about it anyway)
                $newParams['idIsSafe'] = true;
            }
        }

        // Construct the replacement SessionInfo, if necessary
        if ( $newParams ) {
            $newParams['copyFrom'] = $info;
            $info = new SessionInfo( $info->getPriority(), $newParams );
        }

        // Allow the provider to check the loaded SessionInfo
        $providerMetadata = $info->getProviderMetadata();
        if ( !$info->getProvider()->refreshSessionInfo( $info, $request, $providerMetadata ) ) {
            return $failHandler();
        }
        if ( $providerMetadata !== $info->getProviderMetadata() ) {
            $info = new SessionInfo( $info->getPriority(), [
                'metadata' => $providerMetadata,
                'copyFrom' => $info,
            ] );
        }

        // Give hooks a chance to abort. Combined with the SessionMetadata
        // hook, this can allow for tying a session to an IP address or the
        // like.
        $reason = 'Hook aborted';
        if ( !\Hooks::run(
            'SessionCheckInfo',
            [ &$reason, $info, $request, $metadata, $data ]
        ) ) {
            $this->logger->warning( 'Session "{session}": ' . $reason, [
                'session' => $info,
            ] );
            return $failHandler();
        }

        return true;
    }

    public function getSessionFromInfo( SessionInfo $info, WebRequest $request ) {
        // @codeCoverageIgnoreStart
        if ( defined( 'MW_NO_SESSION' ) ) {
            if ( MW_NO_SESSION === 'warn' ) {
                // Undocumented safety case for converting existing entry points
                $this->logger->error( 'Sessions are supposed to be disabled for this entry point', [
                    'exception' => new \BadMethodCallException( 'Sessions are disabled for this entry point' ),
                ] );
            } else {
                throw new \BadMethodCallException( 'Sessions are disabled for this entry point' );
            }
        }
        // @codeCoverageIgnoreEnd

        $id = $info->getId();

        if ( !isset( $this->allSessionBackends[$id] ) ) {
            if ( !isset( $this->allSessionIds[$id] ) ) {
                $this->allSessionIds[$id] = new SessionId( $id );
            }
            $backend = new SessionBackend(
                $this->allSessionIds[$id],
                $info,
                $this->store,
                $this->logger,
                $this->config->get( 'ObjectCacheSessionExpiry' )
            );
            $this->allSessionBackends[$id] = $backend;
            $delay = $backend->delaySave();
        } else {
            $backend = $this->allSessionBackends[$id];
            $delay = $backend->delaySave();
            if ( $info->wasPersisted() ) {
                $backend->persist();
            }
            if ( $info->wasRemembered() ) {
                $backend->setRememberUser( true );
            }
        }

        $request->setSessionId( $backend->getSessionId() );
        $session = $backend->getSession( $request );

        if ( !$info->isIdSafe() ) {
            $session->resetId();
        }

        \Wikimedia\ScopedCallback::consume( $delay );
        return $session;
    }

    public function deregisterSessionBackend( SessionBackend $backend ) {
        $id = $backend->getId();
        if ( !isset( $this->allSessionBackends[$id] ) || !isset( $this->allSessionIds[$id] ) ||
            $this->allSessionBackends[$id] !== $backend ||
            $this->allSessionIds[$id] !== $backend->getSessionId()
        ) {
            throw new \InvalidArgumentException( 'Backend was not registered with this SessionManager' );
        }

        unset( $this->allSessionBackends[$id] );
        // Explicitly do not unset $this->allSessionIds[$id]
    }

    public function changeBackendId( SessionBackend $backend ) {
        $sessionId = $backend->getSessionId();
        $oldId = (string)$sessionId;
        if ( !isset( $this->allSessionBackends[$oldId] ) || !isset( $this->allSessionIds[$oldId] ) ||
            $this->allSessionBackends[$oldId] !== $backend ||
            $this->allSessionIds[$oldId] !== $sessionId
        ) {
            throw new \InvalidArgumentException( 'Backend was not registered with this SessionManager' );
        }

        $newId = $this->generateSessionId();

        unset( $this->allSessionBackends[$oldId], $this->allSessionIds[$oldId] );
        $sessionId->setId( $newId );
        $this->allSessionBackends[$newId] = $backend;
        $this->allSessionIds[$newId] = $sessionId;
    }

    public function generateSessionId() {
        do {
            $id = \Wikimedia\base_convert( \MWCryptRand::generateHex( 40 ), 16, 32, 32 );
            $key = $this->store->makeKey( 'MWSession', $id );
        } while ( isset( $this->allSessionIds[$id] ) || is_array( $this->store->get( $key ) ) );
        return $id;
    }

    public function setupPHPSessionHandler( PHPSessionHandler $handler ) {
        $handler->setManager( $this, $this->store, $this->logger );
    }

    public static function resetCache() {
        if ( !defined( 'MW_PHPUNIT_TEST' ) ) {
            // @codeCoverageIgnoreStart
            throw new MWException( __METHOD__ . ' may only be called from unit tests!' );
            // @codeCoverageIgnoreEnd
        }

        self::$globalSession = null;
        self::$globalSessionRequest = null;
    }

}