SessionManager: Change behavior of getSessionById()

[mediawiki.git] / includes / session / SessionManager.php

<?php
/**
 * MediaWiki\Session entry point
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 * http://www.gnu.org/copyleft/gpl.html
 *
 * @file
 * @ingroup Session
 */

namespace MediaWiki\Session;

use Psr\Log\LoggerInterface;
use BagOStuff;
use Config;
use FauxRequest;
use Language;
use Message;
use User;
use WebRequest;

/**
 * This serves as the entry point to the MediaWiki session handling system.
 *
 * @ingroup Session
 * @since 1.27
 */
final class SessionManager implements SessionManagerInterface {
        /** @var SessionManager|null */
        private static $instance = null;

        /** @var Session|null */
        private static $globalSession = null;

        /** @var WebRequest|null */
        private static $globalSessionRequest = null;

        /** @var LoggerInterface */
        private $logger;

        /** @var Config */
        private $config;

        /** @var BagOStuff|null */
        private $store;

        /** @var SessionProvider[] */
        private $sessionProviders = null;

        /** @var string[] */
        private $varyCookies = null;

        /** @var array */
        private $varyHeaders = null;

        /** @var SessionBackend[] */
        private $allSessionBackends = array();

        /** @var SessionId[] */
        private $allSessionIds = array();

        /** @var string[] */
        private $preventUsers = array();

        /**
         * Get the global SessionManager
         * @return SessionManagerInterface
         *  (really a SessionManager, but this is to make IDEs less confused)
         */
        public static function singleton() {
                if ( self::$instance === null ) {
                        self::$instance = new self();
                }
                return self::$instance;
        }

        /**
         * Get the "global" session
         *
         * If PHP's session_id() has been set, returns that session. Otherwise
         * returns the session for RequestContext::getMain()->getRequest().
         *
         * @return Session
         */
        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;
        }

        /**
         * @param array $options
         *  - config: Config to fetch configuration from. Defaults to the default 'main' config.
         *  - logger: LoggerInterface to use for logging. Defaults to the 'session' channel.
         *  - store: BagOStuff to store session data in.
         */
        public function __construct( $options = array() ) {
                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 = \ConfigFactory::getDefaultInstance()->makeConfig( 'main' );
                }

                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'
                                );
                        }
                        $this->store = $options['store'];
                } else {
                        $this->store = \ObjectCache::getInstance( $this->config->get( 'SessionCacheType' ) );
                        $this->store->setLogger( $this->logger );
                }

                register_shutdown_function( array( $this, 'shutdown' ) );
        }

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

        public function getPersistedSessionId( WebRequest $request ) {
                $info = $this->getSessionInfoForRequest( $request );
                if ( $info && $info->wasPersisted() ) {
                        return $info->getId();
                } else {
                        return null;
                }
        }

        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;

                // Test this here to provide a better log message for the common case
                // of "no such ID"
                $key = wfMemcKey( 'MWSession', $id );
                if ( is_array( $this->store->get( $key ) ) ) {
                        $info = new SessionInfo( SessionInfo::MIN_PRIORITY, array( 'id' => $id, 'idIsSafe' => true ) );
                        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( __METHOD__ . ': failed to create empty session: ' .
                                        $ex->getMessage() );
                                $session = null;
                        }
                }

                return $session;
        }

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

        /**
         * @see SessionManagerInterface::getEmptySession
         * @param WebRequest|null $request
         * @param string|null $id ID to force on the new session
         * @return Session
         */
        private function getEmptySessionInternal( WebRequest $request = null, $id = null ) {
                if ( $id !== null ) {
                        if ( !self::validateSessionId( $id ) ) {
                                throw new \InvalidArgumentException( 'Invalid session ID' );
                        }

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

                $infos = array();
                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 = array( $info );
                        }
                }

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

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

        public function getVaryHeaders() {
                if ( $this->varyHeaders === null ) {
                        $headers = array();
                        foreach ( $this->getProviders() as $provider ) {
                                foreach ( $provider->getVaryHeaders() as $header => $options ) {
                                        if ( !isset( $headers[$header] ) ) {
                                                $headers[$header] = array();
                                        }
                                        if ( is_array( $options ) ) {
                                                $headers[$header] = array_unique( array_merge( $headers[$header], $options ) );
                                        }
                                }
                        }
                        $this->varyHeaders = $headers;
                }
                return $this->varyHeaders;
        }

        public function getVaryCookies() {
                if ( $this->varyCookies === null ) {
                        $cookies = array();
                        foreach ( $this->getProviders() as $provider ) {
                                $cookies = array_merge( $cookies, $provider->getVaryCookies() );
                        }
                        $this->varyCookies = array_values( array_unique( $cookies ) );
                }
                return $this->varyCookies;
        }

        /**
         * Validate a session ID
         * @param string $id
         * @return bool
         */
        public static function validateSessionId( $id ) {
                return is_string( $id ) && preg_match( '/^[a-zA-Z0-9_-]{32,}$/', $id );
        }

        /**
         * @name Internal methods
         * @{
         */

        /**
         * Auto-create the given user, if necessary
         * @private Don't call this yourself. Let Setup.php do it for you at the right time.
         * @note This more properly belongs in AuthManager, but we need it now.
         *  When AuthManager comes, this will be deprecated and will pass-through
         *  to the corresponding AuthManager method.
         * @param User $user User to auto-create
         * @return bool Success
         */
        public static function autoCreateUser( User $user ) {
                global $wgAuth;

                $logger = self::singleton()->logger;

                // Much of this code is based on that in CentralAuth

                // Try the local user from the slave DB
                $localId = User::idFromName( $user->getName() );

                // Fetch the user ID from the master, so that we don't try to create the user
                // when they already exist, due to replication lag
                // @codeCoverageIgnoreStart
                if ( !$localId && wfGetLB()->getReaderIndex() != 0 ) {
                        $localId = User::idFromName( $user->getName(), User::READ_LATEST );
                }
                // @codeCoverageIgnoreEnd

                if ( $localId ) {
                        // User exists after all.
                        $user->setId( $localId );
                        $user->loadFromId();
                        return false;
                }

                // Denied by AuthPlugin? But ignore AuthPlugin itself.
                if ( get_class( $wgAuth ) !== 'AuthPlugin' && !$wgAuth->autoCreate() ) {
                        $logger->debug( __METHOD__ . ': denied by AuthPlugin' );
                        $user->setId( 0 );
                        $user->loadFromId();
                        return false;
                }

                // Wiki is read-only?
                if ( wfReadOnly() ) {
                        $logger->debug( __METHOD__ . ': denied by wfReadOnly()' );
                        $user->setId( 0 );
                        $user->loadFromId();
                        return false;
                }

                $userName = $user->getName();

                // Check the session, if we tried to create this user already there's
                // no point in retrying.
                $session = self::getGlobalSession();
                $reason = $session->get( 'MWSession::AutoCreateBlacklist' );
                if ( $reason ) {
                        $logger->debug( __METHOD__ . ": blacklisted in session ($reason)" );
                        $user->setId( 0 );
                        $user->loadFromId();
                        return false;
                }

                // Is the IP user able to create accounts?
                $anon = new User;
                if ( !$anon->isAllowedAny( 'createaccount', 'autocreateaccount' )
                        || $anon->isBlockedFromCreateAccount()
                ) {
                        // Blacklist the user to avoid repeated DB queries subsequently
                        $logger->debug( __METHOD__ . ': user is blocked from this wiki, blacklisting' );
                        $session->set( 'MWSession::AutoCreateBlacklist', 'blocked', 600 );
                        $session->persist();
                        $user->setId( 0 );
                        $user->loadFromId();
                        return false;
                }

                // Check for validity of username
                if ( !User::isCreatableName( $userName ) ) {
                        $logger->debug( __METHOD__ . ': Invalid username, blacklisting' );
                        $session->set( 'MWSession::AutoCreateBlacklist', 'invalid username', 600 );
                        $session->persist();
                        $user->setId( 0 );
                        $user->loadFromId();
                        return false;
                }

                // Give other extensions a chance to stop auto creation.
                $user->loadDefaults( $userName );
                $abortMessage = '';
                if ( !\Hooks::run( 'AbortAutoAccount', array( $user, &$abortMessage ) ) ) {
                        // In this case we have no way to return the message to the user,
                        // but we can log it.
                        $logger->debug( __METHOD__ . ": denied by hook: $abortMessage" );
                        $session->set( 'MWSession::AutoCreateBlacklist', "hook aborted: $abortMessage", 600 );
                        $session->persist();
                        $user->setId( 0 );
                        $user->loadFromId();
                        return false;
                }

                // Make sure the name has not been changed
                if ( $user->getName() !== $userName ) {
                        $user->setId( 0 );
                        $user->loadFromId();
                        throw new \UnexpectedValueException(
                                'AbortAutoAccount hook tried to change the user name'
                        );
                }

                // Ignore warnings about master connections/writes...hard to avoid here
                \Profiler::instance()->getTransactionProfiler()->resetExpectations();

                $cache = \ObjectCache::getLocalClusterInstance();
                $backoffKey = wfMemcKey( 'MWSession', 'autocreate-failed', md5( $userName ) );
                if ( $cache->get( $backoffKey ) ) {
                        $logger->debug( __METHOD__ . ': denied by prior creation attempt failures' );
                        $user->setId( 0 );
                        $user->loadFromId();
                        return false;
                }

                // Checks passed, create the user...
                $from = isset( $_SERVER['REQUEST_URI'] ) ? $_SERVER['REQUEST_URI'] : 'CLI';
                $logger->info( __METHOD__ . ": creating new user ($userName) - from: $from" );

                try {
                        // Insert the user into the local DB master
                        $status = $user->addToDatabase();
                        if ( !$status->isOK() ) {
                                // @codeCoverageIgnoreStart
                                $logger->error( __METHOD__ . ': failed with message ' . $status->getWikiText() );
                                $user->setId( 0 );
                                $user->loadFromId();
                                return false;
                                // @codeCoverageIgnoreEnd
                        }
                } catch ( \Exception $ex ) {
                        // @codeCoverageIgnoreStart
                        $logger->error( __METHOD__ . ': failed with exception ' . $ex->getMessage() );
                        // Do not keep throwing errors for a while
                        $cache->set( $backoffKey, 1, 600 );
                        // Bubble up error; which should normally trigger DB rollbacks
                        throw $ex;
                        // @codeCoverageIgnoreEnd
                }

                # Notify hooks (e.g. Newuserlog)
                \Hooks::run( 'AuthPluginAutoCreate', array( $user ) );
                \Hooks::run( 'LocalUserCreated', array( $user, true ) );

                # Update user count
                \DeferredUpdates::addUpdate( new \SiteStatsUpdate( 0, 0, 0, 0, 1 ) );

                # Watch user's userpage and talk page
                $user->addWatch( $user->getUserPage(), \WatchedItem::IGNORE_USER_RIGHTS );

                return true;
        }

        /**
         * Prevent future sessions for the user
         *
         * The intention is that the named account will never again be usable for
         * normal login (i.e. there is no way to undo the prevention of access).
         *
         * @private For use from \\User::newSystemUser only
         * @param string $username
         */
        public function preventSessionsForUser( $username ) {
                $this->preventUsers[$username] = true;

                // Reset the user's token to kill existing sessions
                $user = User::newFromName( $username );
                if ( $user && $user->getToken() ) {
                        $user->setToken( true );
                        $user->saveSettings();
                }

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

        /**
         * Test if a user is prevented
         * @private For use from SessionBackend only
         * @param string $username
         * @return bool
         */
        public function isUserSessionPrevented( $username ) {
                return !empty( $this->preventUsers[$username] );
        }

        /**
         * Get the available SessionProviders
         * @return SessionProvider[]
         */
        protected function getProviders() {
                if ( $this->sessionProviders === null ) {
                        $this->sessionProviders = array();
                        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;
        }

        /**
         * Get a session provider by name
         *
         * Generally, this will only be used by internal implementation of some
         * special session-providing mechanism. General purpose code, if it needs
         * to access a SessionProvider at all, will use Session::getProvider().
         *
         * @param string $name
         * @return SessionProvider|null
         */
        public function getProvider( $name ) {
                $providers = $this->getProviders();
                return isset( $providers[$name] ) ? $providers[$name] : null;
        }

        /**
         * Save all active sessions on shutdown
         * @private For internal use with register_shutdown_function()
         */
        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->save( true );
                        }
                }
        }

        /**
         * Fetch the SessionInfo(s) for a request
         * @param WebRequest $request
         * @return SessionInfo|null
         */
        private function getSessionInfoForRequest( WebRequest $request ) {
                // Call all providers to fetch "the" session
                $infos = array();
                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 = array();
                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;
                                        }
                                }
                        }
                }

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

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

        /**
         * Load and verify the session info against the store
         *
         * @param SessionInfo &$info Will likely be replaced with an updated SessionInfo instance
         * @param WebRequest $request
         * @return bool Whether the session info matches the stored data (if any)
         */
        private function loadSessionInfoFromStore( SessionInfo &$info, WebRequest $request ) {
                $key = wfMemcKey( 'MWSession', $info->getId() );
                $blob = $this->store->get( $key );

                $newParams = array();

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

                        // 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 $info: Bad data structure" );
                                $this->store->delete( $key );
                                return false;
                        }

                        $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 $info: Bad metadata" );
                                $this->store->delete( $key );
                                return false;
                        }

                        // 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 $info: Unknown provider, " . $metadata['provider'] );
                                        $this->store->delete( $key );
                                        return false;
                                }
                        } elseif ( $metadata['provider'] !== (string)$provider ) {
                                $this->logger->warning( "Session $info: Wrong provider, " .
                                        $metadata['provider'] . ' !== ' . $provider );
                                return false;
                        }

                        // 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 ( \UnexpectedValueException $ex ) {
                                                $this->logger->warning( "Session $info: Metadata merge failed: " . $ex->getMessage() );
                                                return false;
                                        }
                                }
                        }

                        // 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 $info: " . $ex->getMessage() );
                                        return false;
                                }
                                $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 $info: User ID mismatch, " .
                                                        $metadata['userId'] . ' !== ' . $userInfo->getId() );
                                                return false;
                                        }

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

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

                        // 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 $info: User token mismatch" );
                                return false;
                        }
                        if ( !$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 ( !$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 $info: Null provider and no metadata" );
                                return false;
                        }

                        // 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 $info: No user provided and provider cannot set user"
                                        );
                                        return false;
                                }
                        } elseif ( !$info->getUserInfo()->isVerified() ) {
                                $this->logger->warning(
                                        "Session $info: Unverified user provided and no metadata to auth it"
                                );
                                return false;
                        }

                        $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 false;
                }
                if ( $providerMetadata !== $info->getProviderMetadata() ) {
                        $info = new SessionInfo( $info->getPriority(), array(
                                '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.
                $reason = 'Hook aborted';
                if ( !\Hooks::run(
                        'SessionCheckInfo',
                        array( &$reason, $info, $request, $metadata, $data )
                ) ) {
                        $this->logger->warning( "Session $info: $reason" );
                        return false;
                }

                return true;
        }

        /**
         * Create a session corresponding to the passed SessionInfo
         * @private For use by a SessionProvider that needs to specially create its
         *  own session.
         * @param SessionInfo $info
         * @param WebRequest $request
         * @return Session
         */
        public function getSessionFromInfo( SessionInfo $info, WebRequest $request ) {
                $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();
                }

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

        /**
         * Deregister a SessionBackend
         * @private For use from \\MediaWiki\\Session\\SessionBackend only
         * @param SessionBackend $backend
         */
        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]
        }

        /**
         * Change a SessionBackend's ID
         * @private For use from \\MediaWiki\\Session\\SessionBackend only
         * @param SessionBackend $backend
         */
        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;
        }

        /**
         * Generate a new random session ID
         * @return string
         */
        public function generateSessionId() {
                do {
                        $id = wfBaseConvert( \MWCryptRand::generateHex( 40 ), 16, 32, 32 );
                        $key = wfMemcKey( 'MWSession', $id );
                } while ( isset( $this->allSessionIds[$id] ) || is_array( $this->store->get( $key ) ) );
                return $id;
        }

        /**
         * Call setters on a PHPSessionHandler
         * @private Use PhpSessionHandler::install()
         * @param PHPSessionHandler $handler
         */
        public function setupPHPSessionHandler( PHPSessionHandler $handler ) {
                $handler->setManager( $this, $this->store, $this->logger );
        }

        /**
         * Reset the internal caching for unit testing
         */
        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;
        }

        /**@}*/

}