PHPSessionHandler: Implement SessionHandlerInterface

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

<?php
/**
 * Session storage in object cache.
 *
 * 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;

/**
 * Adapter for PHP's session handling
 * @ingroup Session
 * @since 1.27
 */
class PHPSessionHandler implements \SessionHandlerInterface {
        /** @var PHPSessionHandler */
        protected static $instance = null;

        /** @var bool Whether PHP session handling is enabled */
        protected $enable = false;
        protected $warn = true;

        /** @var SessionManager|null */
        protected $manager;

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

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

        /** @var array Track original session fields for later modification check */
        protected $sessionFieldCache = array();

        protected function __construct( SessionManager $manager ) {
                $this->setEnableFlags(
                        \RequestContext::getMain()->getConfig()->get( 'PHPSessionHandling' )
                );
                $manager->setupPHPSessionHandler( $this );
        }

        /**
         * Set $this->enable and $this->warn
         *
         * Separate just because there doesn't seem to be a good way to test it
         * otherwise.
         *
         * @param string $PHPSessionHandling See $wgPHPSessionHandling
         */
        private function setEnableFlags( $PHPSessionHandling ) {
                switch ( $PHPSessionHandling ) {
                        case 'enable':
                                $this->enable = true;
                                $this->warn = false;
                                break;

                        case 'warn':
                                $this->enable = true;
                                $this->warn = true;
                                break;

                        case 'disable':
                                $this->enable = false;
                                $this->warn = false;
                                break;
                }
        }

        /**
         * Test whether the handler is installed
         * @return bool
         */
        public static function isInstalled() {
                return (bool)self::$instance;
        }

        /**
         * Test whether the handler is installed and enabled
         * @return bool
         */
        public static function isEnabled() {
                return self::$instance && self::$instance->enable;
        }

        /**
         * Install a session handler for the current web request
         * @param SessionManager $manager
         */
        public static function install( SessionManager $manager ) {
                if ( self::$instance ) {
                        $manager->setupPHPSessionHandler( self::$instance );
                        return;
                }

                self::$instance = new self( $manager );

                // Close any auto-started session, before we replace it
                session_write_close();

                // Tell PHP not to mess with cookies itself
                ini_set( 'session.use_cookies', 0 );
                ini_set( 'session.use_trans_sid', 0 );

                // T124510: Disable automatic PHP session related cache headers.
                // MediaWiki adds it's own headers and the default PHP behavior may
                // set headers such as 'Pragma: no-cache' that cause problems with
                // some user agents.
                session_cache_limiter( '' );

                // Also set a sane serialization handler
                \Wikimedia\PhpSessionSerializer::setSerializeHandler();

                // Register this as the save handler, and register an appropriate
                // shutdown function.
                session_set_save_handler( self::$instance, true );
        }

        /**
         * Set the manager, store, and logger
         * @private Use self::install().
         * @param SessionManager $manager
         * @param BagOStuff $store
         * @param LoggerInterface $store
         */
        public function setManager(
                SessionManager $manager, BagOStuff $store, LoggerInterface $logger
        ) {
                if ( $this->manager !== $manager ) {
                        // Close any existing session before we change stores
                        if ( $this->manager ) {
                                session_write_close();
                        }
                        $this->manager = $manager;
                        $this->store = $store;
                        $this->logger = $logger;
                        \Wikimedia\PhpSessionSerializer::setLogger( $this->logger );
                }
        }

        /**
         * Initialize the session (handler)
         * @private For internal use only
         * @param string $save_path Path used to store session files (ignored)
         * @param string $session_name Session name (ignored)
         * @return bool Success
         */
        public function open( $save_path, $session_name ) {
                if ( self::$instance !== $this ) {
                        throw new \UnexpectedValueException( __METHOD__ . ': Wrong instance called!' );
                }
                if ( !$this->enable ) {
                        throw new \BadMethodCallException( 'Attempt to use PHP session management' );
                }
                return true;
        }

        /**
         * Close the session (handler)
         * @private For internal use only
         * @return bool Success
         */
        public function close() {
                if ( self::$instance !== $this ) {
                        throw new \UnexpectedValueException( __METHOD__ . ': Wrong instance called!' );
                }
                $this->sessionFieldCache = array();
                return true;
        }

        /**
         * Read session data
         * @private For internal use only
         * @param string $id Session id
         * @return string Session data
         */
        public function read( $id ) {
                if ( self::$instance !== $this ) {
                        throw new \UnexpectedValueException( __METHOD__ . ': Wrong instance called!' );
                }
                if ( !$this->enable ) {
                        throw new \BadMethodCallException( 'Attempt to use PHP session management' );
                }

                $session = $this->manager->getSessionById( $id, false );
                if ( !$session ) {
                        return '';
                }
                $session->persist();

                $data = iterator_to_array( $session );
                $this->sessionFieldCache[$id] = $data;
                return (string)\Wikimedia\PhpSessionSerializer::encode( $data );
        }

        /**
         * Write session data
         * @private For internal use only
         * @param string $id Session id
         * @param string $dataStr Session data. Not that you should ever call this
         *   directly, but note that this has the same issues with code injection
         *   via user-controlled data as does PHP's unserialize function.
         * @return bool Success
         */
        public function write( $id, $dataStr ) {
                if ( self::$instance !== $this ) {
                        throw new \UnexpectedValueException( __METHOD__ . ': Wrong instance called!' );
                }
                if ( !$this->enable ) {
                        throw new \BadMethodCallException( 'Attempt to use PHP session management' );
                }

                $session = $this->manager->getSessionById( $id, true );
                if ( !$session ) {
                        // This can happen under normal circumstances, if the session exists but is
                        // invalid. Let's emit a log warning instead of a PHP warning.
                        $this->logger->warning(
                                __METHOD__ . ': Session "{session}" cannot be loaded, skipping write.',
                                array(
                                        'session' => $id,
                        ) );
                        return true;
                }

                // First, decode the string PHP handed us
                $data = \Wikimedia\PhpSessionSerializer::decode( $dataStr );
                if ( $data === null ) {
                        // @codeCoverageIgnoreStart
                        return false;
                        // @codeCoverageIgnoreEnd
                }

                // Now merge the data into the Session object.
                $changed = false;
                $cache = isset( $this->sessionFieldCache[$id] ) ? $this->sessionFieldCache[$id] : array();
                foreach ( $data as $key => $value ) {
                        if ( !array_key_exists( $key, $cache ) ) {
                                if ( $session->exists( $key ) ) {
                                        // New in both, so ignore and log
                                        $this->logger->warning(
                                                __METHOD__ . ": Key \"$key\" added in both Session and \$_SESSION!"
                                        );
                                } else {
                                        // New in $_SESSION, keep it
                                        $session->set( $key, $value );
                                        $changed = true;
                                }
                        } elseif ( $cache[$key] === $value ) {
                                // Unchanged in $_SESSION, so ignore it
                        } elseif ( !$session->exists( $key ) ) {
                                // Deleted in Session, keep but log
                                $this->logger->warning(
                                        __METHOD__ . ": Key \"$key\" deleted in Session and changed in \$_SESSION!"
                                );
                                $session->set( $key, $value );
                                $changed = true;
                        } elseif ( $cache[$key] === $session->get( $key ) ) {
                                // Unchanged in Session, so keep it
                                $session->set( $key, $value );
                                $changed = true;
                        } else {
                                // Changed in both, so ignore and log
                                $this->logger->warning(
                                        __METHOD__ . ": Key \"$key\" changed in both Session and \$_SESSION!"
                                );
                        }
                }
                // Anything deleted in $_SESSION and unchanged in Session should be deleted too
                // (but not if $_SESSION can't represent it at all)
                \Wikimedia\PhpSessionSerializer::setLogger( new \Psr\Log\NullLogger() );
                foreach ( $cache as $key => $value ) {
                        if ( !array_key_exists( $key, $data ) && $session->exists( $key ) &&
                                \Wikimedia\PhpSessionSerializer::encode( array( $key => true ) )
                        ) {
                                if ( $cache[$key] === $session->get( $key ) ) {
                                        // Unchanged in Session, delete it
                                        $session->remove( $key );
                                        $changed = true;
                                } else {
                                        // Changed in Session, ignore deletion and log
                                        $this->logger->warning(
                                                __METHOD__ . ": Key \"$key\" changed in Session and deleted in \$_SESSION!"
                                        );
                                }
                        }
                }
                \Wikimedia\PhpSessionSerializer::setLogger( $this->logger );

                // Save and update cache if anything changed
                if ( $changed ) {
                        if ( $this->warn ) {
                                wfDeprecated( '$_SESSION', '1.27' );
                                $this->logger->warning( 'Something wrote to $_SESSION!' );
                        }

                        $session->save();
                        $this->sessionFieldCache[$id] = iterator_to_array( $session );
                }

                $session->persist();

                return true;
        }

        /**
         * Destroy a session
         * @private For internal use only
         * @param string $id Session id
         * @return bool Success
         */
        public function destroy( $id ) {
                if ( self::$instance !== $this ) {
                        throw new \UnexpectedValueException( __METHOD__ . ': Wrong instance called!' );
                }
                if ( !$this->enable ) {
                        throw new \BadMethodCallException( 'Attempt to use PHP session management' );
                }
                $session = $this->manager->getSessionById( $id, false );
                if ( $session ) {
                        $session->clear();
                }
                return true;
        }

        /**
         * Execute garbage collection.
         * @private For internal use only
         * @param int $maxlifetime Maximum session life time (ignored)
         * @return bool Success
         */
        public function gc( $maxlifetime ) {
                if ( self::$instance !== $this ) {
                        throw new \UnexpectedValueException( __METHOD__ . ': Wrong instance called!' );
                }
                $before = date( 'YmdHis', time() );
                $this->store->deleteObjectsExpiringBefore( $before );
                return true;
        }
}