includes/session/PHPSessionHandler.php

   1 <?php
   2 /**
   3  * Session storage in object cache.
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  * @ingroup Session
  22  */
  23
  24 namespace MediaWiki\Session;
  25
  26 use Psr\Log\LoggerInterface;
  27 use BagOStuff;
  28
  29 /**
  30  * Adapter for PHP's session handling
  31  * @todo Once we drop support for PHP < 5.4, use SessionHandlerInterface
  32  *  (should just be a matter of adding "implements SessionHandlerInterface" and
  33  *  changing the session_set_save_handler() call).
  34  * @ingroup Session
  35  * @since 1.27
  36  */
  37 class PHPSessionHandler {
  38         /** @var PHPSessionHandler */
  39         protected static $instance = null;
  40
  41         /** @var bool Whether PHP session handling is enabled */
  42         protected $enable = false;
  43         protected $warn = true;
  44
  45         /** @var SessionManager|null */
  46         protected $manager;
  47
  48         /** @var BagOStuff|null */
  49         protected $store;
  50
  51         /** @var LoggerInterface */
  52         protected $logger;
  53
  54         /** @var array Track original session fields for later modification check */
  55         protected $sessionFieldCache = array();
  56
  57         protected function __construct( SessionManager $manager ) {
  58                 $this->setEnableFlags(
  59                         \RequestContext::getMain()->getConfig()->get( 'PHPSessionHandling' )
  60                 );
  61                 $manager->setupPHPSessionHandler( $this );
  62         }
  63
  64         /**
  65          * Set $this->enable and $this->warn
  66          *
  67          * Separate just because there doesn't seem to be a good way to test it
  68          * otherwise.
  69          *
  70          * @param string $PHPSessionHandling See $wgPHPSessionHandling
  71          */
  72         private function setEnableFlags( $PHPSessionHandling ) {
  73                 switch ( $PHPSessionHandling ) {
  74                         case 'enable':
  75                                 $this->enable = true;
  76                                 $this->warn = false;
  77                                 break;
  78
  79                         case 'warn':
  80                                 $this->enable = true;
  81                                 $this->warn = true;
  82                                 break;
  83
  84                         case 'disable':
  85                                 $this->enable = false;
  86                                 $this->warn = false;
  87                                 break;
  88                 }
  89         }
  90
  91         /**
  92          * Test whether the handler is installed
  93          * @return bool
  94          */
  95         public static function isInstalled() {
  96                 return (bool)self::$instance;
  97         }
  98
  99         /**
 100          * Test whether the handler is installed and enabled
 101          * @return bool
 102          */
 103         public static function isEnabled() {
 104                 return self::$instance && self::$instance->enable;
 105         }
 106
 107         /**
 108          * Install a session handler for the current web request
 109          * @param SessionManager $manager
 110          */
 111         public static function install( SessionManager $manager ) {
 112                 if ( self::$instance ) {
 113                         $manager->setupPHPSessionHandler( self::$instance );
 114                         return;
 115                 }
 116
 117                 self::$instance = new self( $manager );
 118
 119                 // Close any auto-started session, before we replace it
 120                 session_write_close();
 121
 122                 // Tell PHP not to mess with cookies itself
 123                 ini_set( 'session.use_cookies', 0 );
 124                 ini_set( 'session.use_trans_sid', 0 );
 125
 126                 // T124510: Disable automatic PHP session related cache headers.
 127                 // MediaWiki adds it's own headers and the default PHP behavior may
 128                 // set headers such as 'Pragma: no-cache' that cause problems with
 129                 // some user agents.
 130                 session_cache_limiter( '' );
 131
 132                 // Also set a sane serialization handler
 133                 \Wikimedia\PhpSessionSerializer::setSerializeHandler();
 134
 135                 session_set_save_handler(
 136                         array( self::$instance, 'open' ),
 137                         array( self::$instance, 'close' ),
 138                         array( self::$instance, 'read' ),
 139                         array( self::$instance, 'write' ),
 140                         array( self::$instance, 'destroy' ),
 141                         array( self::$instance, 'gc' )
 142                 );
 143
 144                 // It's necessary to register a shutdown function to call session_write_close(),
 145                 // because by the time the request shutdown function for the session module is
 146                 // called, other needed objects may have already been destroyed. Shutdown functions
 147                 // registered this way are called before object destruction.
 148                 register_shutdown_function( array( self::$instance, 'handleShutdown' ) );
 149         }
 150
 151         /**
 152          * Set the manager, store, and logger
 153          * @private Use self::install().
 154          * @param SessionManager $manager
 155          * @param BagOStuff $store
 156          * @param LoggerInterface $store
 157          */
 158         public function setManager(
 159                 SessionManager $manager, BagOStuff $store, LoggerInterface $logger
 160         ) {
 161                 if ( $this->manager !== $manager ) {
 162                         // Close any existing session before we change stores
 163                         if ( $this->manager ) {
 164                                 session_write_close();
 165                         }
 166                         $this->manager = $manager;
 167                         $this->store = $store;
 168                         $this->logger = $logger;
 169                         \Wikimedia\PhpSessionSerializer::setLogger( $this->logger );
 170                 }
 171         }
 172
 173         /**
 174          * Initialize the session (handler)
 175          * @private For internal use only
 176          * @param string $save_path Path used to store session files (ignored)
 177          * @param string $session_name Session name (ignored)
 178          * @return bool Success
 179          */
 180         public function open( $save_path, $session_name ) {
 181                 if ( self::$instance !== $this ) {
 182                         throw new \UnexpectedValueException( __METHOD__ . ': Wrong instance called!' );
 183                 }
 184                 if ( !$this->enable ) {
 185                         throw new \BadMethodCallException( 'Attempt to use PHP session management' );
 186                 }
 187                 return true;
 188         }
 189
 190         /**
 191          * Close the session (handler)
 192          * @private For internal use only
 193          * @return bool Success
 194          */
 195         public function close() {
 196                 if ( self::$instance !== $this ) {
 197                         throw new \UnexpectedValueException( __METHOD__ . ': Wrong instance called!' );
 198                 }
 199                 $this->sessionFieldCache = array();
 200                 return true;
 201         }
 202
 203         /**
 204          * Read session data
 205          * @private For internal use only
 206          * @param string $id Session id
 207          * @return string Session data
 208          */
 209         public function read( $id ) {
 210                 if ( self::$instance !== $this ) {
 211                         throw new \UnexpectedValueException( __METHOD__ . ': Wrong instance called!' );
 212                 }
 213                 if ( !$this->enable ) {
 214                         throw new \BadMethodCallException( 'Attempt to use PHP session management' );
 215                 }
 216
 217                 $session = $this->manager->getSessionById( $id, false );
 218                 if ( !$session ) {
 219                         return '';
 220                 }
 221                 $session->persist();
 222
 223                 $data = iterator_to_array( $session );
 224                 $this->sessionFieldCache[$id] = $data;
 225                 return (string)\Wikimedia\PhpSessionSerializer::encode( $data );
 226         }
 227
 228         /**
 229          * Write session data
 230          * @private For internal use only
 231          * @param string $id Session id
 232          * @param string $dataStr Session data. Not that you should ever call this
 233          *   directly, but note that this has the same issues with code injection
 234          *   via user-controlled data as does PHP's unserialize function.
 235          * @return bool Success
 236          */
 237         public function write( $id, $dataStr ) {
 238                 if ( self::$instance !== $this ) {
 239                         throw new \UnexpectedValueException( __METHOD__ . ': Wrong instance called!' );
 240                 }
 241                 if ( !$this->enable ) {
 242                         throw new \BadMethodCallException( 'Attempt to use PHP session management' );
 243                 }
 244
 245                 $session = $this->manager->getSessionById( $id, true );
 246                 if ( !$session ) {
 247                         // This can happen under normal circumstances, if the session exists but is
 248                         // invalid. Let's emit a log warning instead of a PHP warning.
 249                         $this->logger->warning(
 250                                 __METHOD__ . ': Session "{session}" cannot be loaded, skipping write.',
 251                                 array(
 252                                         'session' => $id,
 253                         ) );
 254                         return true;
 255                 }
 256
 257                 // First, decode the string PHP handed us
 258                 $data = \Wikimedia\PhpSessionSerializer::decode( $dataStr );
 259                 if ( $data === null ) {
 260                         // @codeCoverageIgnoreStart
 261                         return false;
 262                         // @codeCoverageIgnoreEnd
 263                 }
 264
 265                 // Now merge the data into the Session object.
 266                 $changed = false;
 267                 $cache = isset( $this->sessionFieldCache[$id] ) ? $this->sessionFieldCache[$id] : array();
 268                 foreach ( $data as $key => $value ) {
 269                         if ( !array_key_exists( $key, $cache ) ) {
 270                                 if ( $session->exists( $key ) ) {
 271                                         // New in both, so ignore and log
 272                                         $this->logger->warning(
 273                                                 __METHOD__ . ": Key \"$key\" added in both Session and \$_SESSION!"
 274                                         );
 275                                 } else {
 276                                         // New in $_SESSION, keep it
 277                                         $session->set( $key, $value );
 278                                         $changed = true;
 279                                 }
 280                         } elseif ( $cache[$key] === $value ) {
 281                                 // Unchanged in $_SESSION, so ignore it
 282                         } elseif ( !$session->exists( $key ) ) {
 283                                 // Deleted in Session, keep but log
 284                                 $this->logger->warning(
 285                                         __METHOD__ . ": Key \"$key\" deleted in Session and changed in \$_SESSION!"
 286                                 );
 287                                 $session->set( $key, $value );
 288                                 $changed = true;
 289                         } elseif ( $cache[$key] === $session->get( $key ) ) {
 290                                 // Unchanged in Session, so keep it
 291                                 $session->set( $key, $value );
 292                                 $changed = true;
 293                         } else {
 294                                 // Changed in both, so ignore and log
 295                                 $this->logger->warning(
 296                                         __METHOD__ . ": Key \"$key\" changed in both Session and \$_SESSION!"
 297                                 );
 298                         }
 299                 }
 300                 // Anything deleted in $_SESSION and unchanged in Session should be deleted too
 301                 // (but not if $_SESSION can't represent it at all)
 302                 \Wikimedia\PhpSessionSerializer::setLogger( new \Psr\Log\NullLogger() );
 303                 foreach ( $cache as $key => $value ) {
 304                         if ( !array_key_exists( $key, $data ) && $session->exists( $key ) &&
 305                                 \Wikimedia\PhpSessionSerializer::encode( array( $key => true ) )
 306                         ) {
 307                                 if ( $cache[$key] === $session->get( $key ) ) {
 308                                         // Unchanged in Session, delete it
 309                                         $session->remove( $key );
 310                                         $changed = true;
 311                                 } else {
 312                                         // Changed in Session, ignore deletion and log
 313                                         $this->logger->warning(
 314                                                 __METHOD__ . ": Key \"$key\" changed in Session and deleted in \$_SESSION!"
 315                                         );
 316                                 }
 317                         }
 318                 }
 319                 \Wikimedia\PhpSessionSerializer::setLogger( $this->logger );
 320
 321                 // Save and update cache if anything changed
 322                 if ( $changed ) {
 323                         if ( $this->warn ) {
 324                                 wfDeprecated( '$_SESSION', '1.27' );
 325                                 $this->logger->warning( 'Something wrote to $_SESSION!' );
 326                         }
 327
 328                         $session->save();
 329                         $this->sessionFieldCache[$id] = iterator_to_array( $session );
 330                 }
 331
 332                 $session->persist();
 333
 334                 return true;
 335         }
 336
 337         /**
 338          * Destroy a session
 339          * @private For internal use only
 340          * @param string $id Session id
 341          * @return bool Success
 342          */
 343         public function destroy( $id ) {
 344                 if ( self::$instance !== $this ) {
 345                         throw new \UnexpectedValueException( __METHOD__ . ': Wrong instance called!' );
 346                 }
 347                 if ( !$this->enable ) {
 348                         throw new \BadMethodCallException( 'Attempt to use PHP session management' );
 349                 }
 350                 $session = $this->manager->getSessionById( $id, false );
 351                 if ( $session ) {
 352                         $session->clear();
 353                 }
 354                 return true;
 355         }
 356
 357         /**
 358          * Execute garbage collection.
 359          * @private For internal use only
 360          * @param int $maxlifetime Maximum session life time (ignored)
 361          * @return bool Success
 362          */
 363         public function gc( $maxlifetime ) {
 364                 if ( self::$instance !== $this ) {
 365                         throw new \UnexpectedValueException( __METHOD__ . ': Wrong instance called!' );
 366                 }
 367                 $before = date( 'YmdHis', time() );
 368                 $this->store->deleteObjectsExpiringBefore( $before );
 369                 return true;
 370         }
 371
 372         /**
 373          * Shutdown function.
 374          *
 375          * See the comment inside self::install for rationale.
 376          * @codeCoverageIgnore
 377          * @private For internal use only
 378          */
 379         public function handleShutdown() {
 380                 if ( $this->enable ) {
 381                         session_write_close();
 382                 }
 383         }
 384
 385 }