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PdoSessionHandler.php
001 <?php
002
003 /*
004 * This file is part of the Symfony package.
005 *
006 * (c) Fabien Potencier <fabien@symfony.com>
007 *
008 * For the full copyright and license information, please view the LICENSE
009 * file that was distributed with this source code.
010 */
011
012 namespace Symfony\Component\HttpFoundation\Session\Storage\Handler;
013
014 /**
015 * Session handler using a PDO connection to read and write data.
016 *
017 * It works with MySQL, PostgreSQL, Oracle, SQL Server and SQLite and implements
018 * different locking strategies to handle concurrent access to the same session.
019 * Locking is necessary to prevent loss of data due to race conditions and to keep
020 * the session data consistent between read() and write(). With locking, requests
021 * for the same session will wait until the other one finished writing. For this
022 * reason it's best practice to close a session as early as possible to improve
023 * concurrency. PHPs internal files session handler also implements locking.
024 *
025 * Attention: Since SQLite does not support row level locks but locks the whole database,
026 * it means only one session can be accessed at a time. Even different sessions would wait
027 * for another to finish. So saving session in SQLite should only be considered for
028 * development or prototypes.
029 *
030 * Session data is a binary string that can contain non-printable characters like the null byte.
031 * For this reason it must be saved in a binary column in the database like BLOB in MySQL.
032 * Saving it in a character column could corrupt the data. You can use createTable()
033 * to initialize a correctly defined table.
034 *
035 * @see https://php.net/sessionhandlerinterface
036 *
037 * @author Fabien Potencier <fabien@symfony.com>
038 * @author Michael Williams <michael.williams@funsational.com>
039 * @author Tobias Schultze <http://tobion.de>
040 */
041 class PdoSessionHandler extends AbstractSessionHandler
042 {
043 /**
044 * No locking is done. This means sessions are prone to loss of data due to
045 * race conditions of concurrent requests to the same session. The last session
046 * write will win in this case. It might be useful when you implement your own
047 * logic to deal with this like an optimistic approach.
048 */
049 const LOCK_NONE = 0;
050
051 /**
052 * Creates an application-level lock on a session. The disadvantage is that the
053 * lock is not enforced by the database and thus other, unaware parts of the
054 * application could still concurrently modify the session. The advantage is it
055 * does not require a transaction.
056 * This mode is not available for SQLite and not yet implemented for oci and sqlsrv.
057 */
058 const LOCK_ADVISORY = 1;
059
060 /**
061 * Issues a real row lock. Since it uses a transaction between opening and
062 * closing a session, you have to be careful when you use same database connection
063 * that you also use for your application logic. This mode is the default because
064 * it's the only reliable solution across DBMSs.
065 */
066 const LOCK_TRANSACTIONAL = 2;
067
068 /**
069 * @var \PDO|null PDO instance or null when not connected yet
070 */
071 private $pdo;
072
073 /**
074 * @var string|false|null DSN string or null for session.save_path or false when lazy connection disabled
075 */
076 private $dsn = false;
077
078 /**
079 * @var string Database driver
080 */
081 private $driver;
082
083 /**
084 * @var string Table name
085 */
086 private $table = 'sessions';
087
088 /**
089 * @var string Column for session id
090 */
091 private $idCol = 'sess_id';
092
093 /**
094 * @var string Column for session data
095 */
096 private $dataCol = 'sess_data';
097
098 /**
099 * @var string Column for lifetime
100 */
101 private $lifetimeCol = 'sess_lifetime';
102
103 /**
104 * @var string Column for timestamp
105 */
106 private $timeCol = 'sess_time';
107
108 /**
109 * @var string Username when lazy-connect
110 */
111 private $username = '';
112
113 /**
114 * @var string Password when lazy-connect
115 */
116 private $password = '';
117
118 /**
119 * @var array Connection options when lazy-connect
120 */
121 private $connectionOptions = [];
122
123 /**
124 * @var int The strategy for locking, see constants
125 */
126 private $lockMode = self::LOCK_TRANSACTIONAL;
127
128 /**
129 * It's an array to support multiple reads before closing which is manual, non-standard usage.
130 *
131 * @var \PDOStatement[] An array of statements to release advisory locks
132 */
133 private $unlockStatements = [];
134
135 /**
136 * @var bool True when the current session exists but expired according to session.gc_maxlifetime
137 */
138 private $sessionExpired = false;
139
140 /**
141 * @var bool Whether a transaction is active
142 */
143 private $inTransaction = false;
144
145 /**
146 * @var bool Whether gc() has been called
147 */
148 private $gcCalled = false;
149
150 /**
151 * You can either pass an existing database connection as PDO instance or
152 * pass a DSN string that will be used to lazy-connect to the database
153 * when the session is actually used. Furthermore it's possible to pass null
154 * which will then use the session.save_path ini setting as PDO DSN parameter.
155 *
156 * List of available options:
157 * * db_table: The name of the table [default: sessions]
158 * * db_id_col: The column where to store the session id [default: sess_id]
159 * * db_data_col: The column where to store the session data [default: sess_data]
160 * * db_lifetime_col: The column where to store the lifetime [default: sess_lifetime]
161 * * db_time_col: The column where to store the timestamp [default: sess_time]
162 * * db_username: The username when lazy-connect [default: '']
163 * * db_password: The password when lazy-connect [default: '']
164 * * db_connection_options: An array of driver-specific connection options [default: []]
165 * * lock_mode: The strategy for locking, see constants [default: LOCK_TRANSACTIONAL]
166 *
167 * @param \PDO|string|null $pdoOrDsn A \PDO instance or DSN string or URL string or null
168 * @param array $options An associative array of options
169 *
170 * @throws \InvalidArgumentException When PDO error mode is not PDO::ERRMODE_EXCEPTION
171 */
172 public function __construct($pdoOrDsn = null, array $options = [])
173 {
174 if ($pdoOrDsn instanceof \PDO) {
175 if (\PDO::ERRMODE_EXCEPTION !== $pdoOrDsn->getAttribute(\PDO::ATTR_ERRMODE)) {
176 throw new \InvalidArgumentException(sprintf('"%s" requires PDO error mode attribute be set to throw Exceptions (i.e. $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION)).', __CLASS__));
177 }
178
179 $this->pdo = $pdoOrDsn;
180 $this->driver = $this->pdo->getAttribute(\PDO::ATTR_DRIVER_NAME);
181 } elseif (\is_string($pdoOrDsn) && false !== strpos($pdoOrDsn, '://')) {
182 $this->dsn = $this->buildDsnFromUrl($pdoOrDsn);
183 } else {
184 $this->dsn = $pdoOrDsn;
185 }
186
187 $this->table = isset($options['db_table']) ? $options['db_table'] : $this->table;
188 $this->idCol = isset($options['db_id_col']) ? $options['db_id_col'] : $this->idCol;
189 $this->dataCol = isset($options['db_data_col']) ? $options['db_data_col'] : $this->dataCol;
190 $this->lifetimeCol = isset($options['db_lifetime_col']) ? $options['db_lifetime_col'] : $this->lifetimeCol;
191 $this->timeCol = isset($options['db_time_col']) ? $options['db_time_col'] : $this->timeCol;
192 $this->username = isset($options['db_username']) ? $options['db_username'] : $this->username;
193 $this->password = isset($options['db_password']) ? $options['db_password'] : $this->password;
194 $this->connectionOptions = isset($options['db_connection_options']) ? $options['db_connection_options'] : $this->connectionOptions;
195 $this->lockMode = isset($options['lock_mode']) ? $options['lock_mode'] : $this->lockMode;
196 }
197
198 /**
199 * Creates the table to store sessions which can be called once for setup.
200 *
201 * Session ID is saved in a column of maximum length 128 because that is enough even
202 * for a 512 bit configured session.hash_function like Whirlpool. Session data is
203 * saved in a BLOB. One could also use a shorter inlined varbinary column
204 * if one was sure the data fits into it.
205 *
206 * @throws \PDOException When the table already exists
207 * @throws \DomainException When an unsupported PDO driver is used
208 */
209 public function createTable()
210 {
211 // connect if we are not yet
212 $this->getConnection();
213
214 switch ($this->driver) {
215 case 'mysql':
216 // We use varbinary for the ID column because it prevents unwanted conversions:
217 // - character set conversions between server and client
218 // - trailing space removal
219 // - case-insensitivity
220 // - language processing like é == e
221 $sql = "CREATE TABLE $this->table ($this->idCol VARBINARY(128) NOT NULL PRIMARY KEY, $this->dataCol BLOB NOT NULL, $this->lifetimeCol INTEGER UNSIGNED NOT NULL, $this->timeCol INTEGER UNSIGNED NOT NULL) COLLATE utf8mb4_bin, ENGINE = InnoDB";
222 break;
223 case 'sqlite':
224 $sql = "CREATE TABLE $this->table ($this->idCol TEXT NOT NULL PRIMARY KEY, $this->dataCol BLOB NOT NULL, $this->lifetimeCol INTEGER NOT NULL, $this->timeCol INTEGER NOT NULL)";
225 break;
226 case 'pgsql':
227 $sql = "CREATE TABLE $this->table ($this->idCol VARCHAR(128) NOT NULL PRIMARY KEY, $this->dataCol BYTEA NOT NULL, $this->lifetimeCol INTEGER NOT NULL, $this->timeCol INTEGER NOT NULL)";
228 break;
229 case 'oci':
230 $sql = "CREATE TABLE $this->table ($this->idCol VARCHAR2(128) NOT NULL PRIMARY KEY, $this->dataCol BLOB NOT NULL, $this->lifetimeCol INTEGER NOT NULL, $this->timeCol INTEGER NOT NULL)";
231 break;
232 case 'sqlsrv':
233 $sql = "CREATE TABLE $this->table ($this->idCol VARCHAR(128) NOT NULL PRIMARY KEY, $this->dataCol VARBINARY(MAX) NOT NULL, $this->lifetimeCol INTEGER NOT NULL, $this->timeCol INTEGER NOT NULL)";
234 break;
235 default:
236 throw new \DomainException(sprintf('Creating the session table is currently not implemented for PDO driver "%s".', $this->driver));
237 }
238
239 try {
240 $this->pdo->exec($sql);
241 } catch (\PDOException $e) {
242 $this->rollback();
243
244 throw $e;
245 }
246 }
247
248 /**
249 * Returns true when the current session exists but expired according to session.gc_maxlifetime.
250 *
251 * Can be used to distinguish between a new session and one that expired due to inactivity.
252 *
253 * @return bool Whether current session expired
254 */
255 public function isSessionExpired()
256 {
257 return $this->sessionExpired;
258 }
259
260 /**
261 * {@inheritdoc}
262 */
263 public function open($savePath, $sessionName)
264 {
265 $this->sessionExpired = false;
266
267 if (null === $this->pdo) {
268 $this->connect($this->dsn ?: $savePath);
269 }
270
271 return parent::open($savePath, $sessionName);
272 }
273
274 /**
275 * {@inheritdoc}
276 */
277 public function read($sessionId)
278 {
279 try {
280 return parent::read($sessionId);
281 } catch (\PDOException $e) {
282 $this->rollback();
283
284 throw $e;
285 }
286 }
287
288 /**
289 * @return bool
290 */
291 public function gc($maxlifetime)
292 {
293 // We delay gc() to close() so that it is executed outside the transactional and blocking read-write process.
294 // This way, pruning expired sessions does not block them from being started while the current session is used.
295 $this->gcCalled = true;
296
297 return true;
298 }
299
300 /**
301 * {@inheritdoc}
302 */
303 protected function doDestroy($sessionId)
304 {
305 // delete the record associated with this id
306 $sql = "DELETE FROM $this->table WHERE $this->idCol = :id";
307
308 try {
309 $stmt = $this->pdo->prepare($sql);
310 $stmt->bindParam(':id', $sessionId, \PDO::PARAM_STR);
311 $stmt->execute();
312 } catch (\PDOException $e) {
313 $this->rollback();
314
315 throw $e;
316 }
317
318 return true;
319 }
320
321 /**
322 * {@inheritdoc}
323 */
324 protected function doWrite($sessionId, $data)
325 {
326 $maxlifetime = (int) ini_get('session.gc_maxlifetime');
327
328 try {
329 // We use a single MERGE SQL query when supported by the database.
330 $mergeStmt = $this->getMergeStatement($sessionId, $data, $maxlifetime);
331 if (null !== $mergeStmt) {
332 $mergeStmt->execute();
333
334 return true;
335 }
336
337 $updateStmt = $this->getUpdateStatement($sessionId, $data, $maxlifetime);
338 $updateStmt->execute();
339
340 // When MERGE is not supported, like in Postgres < 9.5, we have to use this approach that can result in
341 // duplicate key errors when the same session is written simultaneously (given the LOCK_NONE behavior).
342 // We can just catch such an error and re-execute the update. This is similar to a serializable
343 // transaction with retry logic on serialization failures but without the overhead and without possible
344 // false positives due to longer gap locking.
345 if (!$updateStmt->rowCount()) {
346 try {
347 $insertStmt = $this->getInsertStatement($sessionId, $data, $maxlifetime);
348 $insertStmt->execute();
349 } catch (\PDOException $e) {
350 // Handle integrity violation SQLSTATE 23000 (or a subclass like 23505 in Postgres) for duplicate keys
351 if (0 === strpos($e->getCode(), '23')) {
352 $updateStmt->execute();
353 } else {
354 throw $e;
355 }
356 }
357 }
358 } catch (\PDOException $e) {
359 $this->rollback();
360
361 throw $e;
362 }
363
364 return true;
365 }
366
367 /**
368 * {@inheritdoc}
369 */
370 public function updateTimestamp($sessionId, $data)
371 {
372 $maxlifetime = (int) ini_get('session.gc_maxlifetime');
373
374 try {
375 $updateStmt = $this->pdo->prepare(
376 "UPDATE $this->table SET $this->lifetimeCol = :lifetime, $this->timeCol = :time WHERE $this->idCol = :id"
377 );
378 $updateStmt->bindParam(':id', $sessionId, \PDO::PARAM_STR);
379 $updateStmt->bindParam(':lifetime', $maxlifetime, \PDO::PARAM_INT);
380 $updateStmt->bindValue(':time', time(), \PDO::PARAM_INT);
381 $updateStmt->execute();
382 } catch (\PDOException $e) {
383 $this->rollback();
384
385 throw $e;
386 }
387
388 return true;
389 }
390
391 /**
392 * {@inheritdoc}
393 */
394 public function close()
395 {
396 $this->commit();
397
398 while ($unlockStmt = array_shift($this->unlockStatements)) {
399 $unlockStmt->execute();
400 }
401
402 if ($this->gcCalled) {
403 $this->gcCalled = false;
404
405 // delete the session records that have expired
406 if ('mysql' === $this->driver) {
407 $sql = "DELETE FROM $this->table WHERE $this->lifetimeCol + $this->timeCol < :time";
408 } else {
409 $sql = "DELETE FROM $this->table WHERE $this->lifetimeCol < :time - $this->timeCol";
410 }
411
412 $stmt = $this->pdo->prepare($sql);
413 $stmt->bindValue(':time', time(), \PDO::PARAM_INT);
414 $stmt->execute();
415 }
416
417 if (false !== $this->dsn) {
418 $this->pdo = null; // only close lazy-connection
419 }
420
421 return true;
422 }
423
424 /**
425 * Lazy-connects to the database.
426 *
427 * @param string $dsn DSN string
428 */
429 private function connect($dsn)
430 {
431 $this->pdo = new \PDO($dsn, $this->username, $this->password, $this->connectionOptions);
432 $this->pdo->setAttribute(\PDO::ATTR_ERRMODE, \PDO::ERRMODE_EXCEPTION);
433 $this->driver = $this->pdo->getAttribute(\PDO::ATTR_DRIVER_NAME);
434 }
435
436 /**
437 * Builds a PDO DSN from a URL-like connection string.
438 *
439 * @param string $dsnOrUrl
440 *
441 * @return string
442 *
443 * @todo implement missing support for oci DSN (which look totally different from other PDO ones)
444 */
445 private function buildDsnFromUrl($dsnOrUrl)
446 {
447 // (pdo_)?sqlite3?:///... => (pdo_)?sqlite3?://localhost/... or else the URL will be invalid
448 $url = preg_replace('#^((?:pdo_)?sqlite3?):///#', '$1://localhost/', $dsnOrUrl);
449
450 $params = parse_url($url);
451
452 if (false === $params) {
453 return $dsnOrUrl; // If the URL is not valid, let's assume it might be a DSN already.
454 }
455
456 $params = array_map('rawurldecode', $params);
457
458 // Override the default username and password. Values passed through options will still win over these in the constructor.
459 if (isset($params['user'])) {
460 $this->username = $params['user'];
461 }
462
463 if (isset($params['pass'])) {
464 $this->password = $params['pass'];
465 }
466
467 if (!isset($params['scheme'])) {
468 throw new \InvalidArgumentException('URLs without scheme are not supported to configure the PdoSessionHandler.');
469 }
470
471 $driverAliasMap = [
472 'mssql' => 'sqlsrv',
473 'mysql2' => 'mysql', // Amazon RDS, for some weird reason
474 'postgres' => 'pgsql',
475 'postgresql' => 'pgsql',
476 'sqlite3' => 'sqlite',
477 ];
478
479 $driver = isset($driverAliasMap[$params['scheme']]) ? $driverAliasMap[$params['scheme']] : $params['scheme'];
480
481 // Doctrine DBAL supports passing its internal pdo_* driver names directly too (allowing both dashes and underscores). This allows supporting the same here.
482 if (0 === strpos($driver, 'pdo_') || 0 === strpos($driver, 'pdo-')) {
483 $driver = substr($driver, 4);
484 }
485
486 switch ($driver) {
487 case 'mysql':
488 case 'pgsql':
489 $dsn = $driver.':';
490
491 if (isset($params['host']) && '' !== $params['host']) {
492 $dsn .= 'host='.$params['host'].';';
493 }
494
495 if (isset($params['port']) && '' !== $params['port']) {
496 $dsn .= 'port='.$params['port'].';';
497 }
498
499 if (isset($params['path'])) {
500 $dbName = substr($params['path'], 1); // Remove the leading slash
501 $dsn .= 'dbname='.$dbName.';';
502 }
503
504 return $dsn;
505
506 case 'sqlite':
507 return 'sqlite:'.substr($params['path'], 1);
508
509 case 'sqlsrv':
510 $dsn = 'sqlsrv:server=';
511
512 if (isset($params['host'])) {
513 $dsn .= $params['host'];
514 }
515
516 if (isset($params['port']) && '' !== $params['port']) {
517 $dsn .= ','.$params['port'];
518 }
519
520 if (isset($params['path'])) {
521 $dbName = substr($params['path'], 1); // Remove the leading slash
522 $dsn .= ';Database='.$dbName;
523 }
524
525 return $dsn;
526
527 default:
528 throw new \InvalidArgumentException(sprintf('The scheme "%s" is not supported by the PdoSessionHandler URL configuration. Pass a PDO DSN directly.', $params['scheme']));
529 }
530 }
531
532 /**
533 * Helper method to begin a transaction.
534 *
535 * Since SQLite does not support row level locks, we have to acquire a reserved lock
536 * on the database immediately. Because of https://bugs.php.net/42766 we have to create
537 * such a transaction manually which also means we cannot use PDO::commit or
538 * PDO::rollback or PDO::inTransaction for SQLite.
539 *
540 * Also MySQLs default isolation, REPEATABLE READ, causes deadlock for different sessions
541 * due to https://percona.com/blog/2013/12/12/one-more-innodb-gap-lock-to-avoid/ .
542 * So we change it to READ COMMITTED.
543 */
544 private function beginTransaction()
545 {
546 if (!$this->inTransaction) {
547 if ('sqlite' === $this->driver) {
548 $this->pdo->exec('BEGIN IMMEDIATE TRANSACTION');
549 } else {
550 if ('mysql' === $this->driver) {
551 $this->pdo->exec('SET TRANSACTION ISOLATION LEVEL READ COMMITTED');
552 }
553 $this->pdo->beginTransaction();
554 }
555 $this->inTransaction = true;
556 }
557 }
558
559 /**
560 * Helper method to commit a transaction.
561 */
562 private function commit()
563 {
564 if ($this->inTransaction) {
565 try {
566 // commit read-write transaction which also releases the lock
567 if ('sqlite' === $this->driver) {
568 $this->pdo->exec('COMMIT');
569 } else {
570 $this->pdo->commit();
571 }
572 $this->inTransaction = false;
573 } catch (\PDOException $e) {
574 $this->rollback();
575
576 throw $e;
577 }
578 }
579 }
580
581 /**
582 * Helper method to rollback a transaction.
583 */
584 private function rollback()
585 {
586 // We only need to rollback if we are in a transaction. Otherwise the resulting
587 // error would hide the real problem why rollback was called. We might not be
588 // in a transaction when not using the transactional locking behavior or when
589 // two callbacks (e.g. destroy and write) are invoked that both fail.
590 if ($this->inTransaction) {
591 if ('sqlite' === $this->driver) {
592 $this->pdo->exec('ROLLBACK');
593 } else {
594 $this->pdo->rollBack();
595 }
596 $this->inTransaction = false;
597 }
598 }
599
600 /**
601 * Reads the session data in respect to the different locking strategies.
602 *
603 * We need to make sure we do not return session data that is already considered garbage according
604 * to the session.gc_maxlifetime setting because gc() is called after read() and only sometimes.
605 *
606 * @param string $sessionId Session ID
607 *
608 * @return string The session data
609 */
610 protected function doRead($sessionId)
611 {
612 if (self::LOCK_ADVISORY === $this->lockMode) {
613 $this->unlockStatements[] = $this->doAdvisoryLock($sessionId);
614 }
615
616 $selectSql = $this->getSelectSql();
617 $selectStmt = $this->pdo->prepare($selectSql);
618 $selectStmt->bindParam(':id', $sessionId, \PDO::PARAM_STR);
619 $insertStmt = null;
620
621 do {
622 $selectStmt->execute();
623 $sessionRows = $selectStmt->fetchAll(\PDO::FETCH_NUM);
624
625 if ($sessionRows) {
626 if ($sessionRows[0][1] + $sessionRows[0][2] < time()) {
627 $this->sessionExpired = true;
628
629 return '';
630 }
631
632 return \is_resource($sessionRows[0][0]) ? stream_get_contents($sessionRows[0][0]) : $sessionRows[0][0];
633 }
634
635 if (null !== $insertStmt) {
636 $this->rollback();
637 throw new \RuntimeException('Failed to read session: INSERT reported a duplicate id but next SELECT did not return any data.');
638 }
639
640 if (!filter_var(ini_get('session.use_strict_mode'), \FILTER_VALIDATE_BOOLEAN) && self::LOCK_TRANSACTIONAL === $this->lockMode && 'sqlite' !== $this->driver) {
641 // In strict mode, session fixation is not possible: new sessions always start with a unique
642 // random id, so that concurrency is not possible and this code path can be skipped.
643 // Exclusive-reading of non-existent rows does not block, so we need to do an insert to block
644 // until other connections to the session are committed.
645 try {
646 $insertStmt = $this->getInsertStatement($sessionId, '', 0);
647 $insertStmt->execute();
648 } catch (\PDOException $e) {
649 // Catch duplicate key error because other connection created the session already.
650 // It would only not be the case when the other connection destroyed the session.
651 if (0 === strpos($e->getCode(), '23')) {
652 // Retrieve finished session data written by concurrent connection by restarting the loop.
653 // We have to start a new transaction as a failed query will mark the current transaction as
654 // aborted in PostgreSQL and disallow further queries within it.
655 $this->rollback();
656 $this->beginTransaction();
657 continue;
658 }
659
660 throw $e;
661 }
662 }
663
664 return '';
665 } while (true);
666 }
667
668 /**
669 * Executes an application-level lock on the database.
670 *
671 * @param string $sessionId Session ID
672 *
673 * @return \PDOStatement The statement that needs to be executed later to release the lock
674 *
675 * @throws \DomainException When an unsupported PDO driver is used
676 *
677 * @todo implement missing advisory locks
678 * - for oci using DBMS_LOCK.REQUEST
679 * - for sqlsrv using sp_getapplock with LockOwner = Session
680 */
681 private function doAdvisoryLock($sessionId)
682 {
683 switch ($this->driver) {
684 case 'mysql':
685 // MySQL 5.7.5 and later enforces a maximum length on lock names of 64 characters. Previously, no limit was enforced.
686 $lockId = substr($sessionId, 0, 64);
687 // should we handle the return value? 0 on timeout, null on error
688 // we use a timeout of 50 seconds which is also the default for innodb_lock_wait_timeout
689 $stmt = $this->pdo->prepare('SELECT GET_LOCK(:key, 50)');
690 $stmt->bindValue(':key', $lockId, \PDO::PARAM_STR);
691 $stmt->execute();
692
693 $releaseStmt = $this->pdo->prepare('DO RELEASE_LOCK(:key)');
694 $releaseStmt->bindValue(':key', $lockId, \PDO::PARAM_STR);
695
696 return $releaseStmt;
697 case 'pgsql':
698 // Obtaining an exclusive session level advisory lock requires an integer key.
699 // When session.sid_bits_per_character > 4, the session id can contain non-hex-characters.
700 // So we cannot just use hexdec().
701 if (4 === \PHP_INT_SIZE) {
702 $sessionInt1 = $this->convertStringToInt($sessionId);
703 $sessionInt2 = $this->convertStringToInt(substr($sessionId, 4, 4));
704
705 $stmt = $this->pdo->prepare('SELECT pg_advisory_lock(:key1, :key2)');
706 $stmt->bindValue(':key1', $sessionInt1, \PDO::PARAM_INT);
707 $stmt->bindValue(':key2', $sessionInt2, \PDO::PARAM_INT);
708 $stmt->execute();
709
710 $releaseStmt = $this->pdo->prepare('SELECT pg_advisory_unlock(:key1, :key2)');
711 $releaseStmt->bindValue(':key1', $sessionInt1, \PDO::PARAM_INT);
712 $releaseStmt->bindValue(':key2', $sessionInt2, \PDO::PARAM_INT);
713 } else {
714 $sessionBigInt = $this->convertStringToInt($sessionId);
715
716 $stmt = $this->pdo->prepare('SELECT pg_advisory_lock(:key)');
717 $stmt->bindValue(':key', $sessionBigInt, \PDO::PARAM_INT);
718 $stmt->execute();
719
720 $releaseStmt = $this->pdo->prepare('SELECT pg_advisory_unlock(:key)');
721 $releaseStmt->bindValue(':key', $sessionBigInt, \PDO::PARAM_INT);
722 }
723
724 return $releaseStmt;
725 case 'sqlite':
726 throw new \DomainException('SQLite does not support advisory locks.');
727 default:
728 throw new \DomainException(sprintf('Advisory locks are currently not implemented for PDO driver "%s".', $this->driver));
729 }
730 }
731
732 /**
733 * Encodes the first 4 (when PHP_INT_SIZE == 4) or 8 characters of the string as an integer.
734 *
735 * Keep in mind, PHP integers are signed.
736 *
737 * @param string $string
738 *
739 * @return int
740 */
741 private function convertStringToInt($string)
742 {
743 if (4 === \PHP_INT_SIZE) {
744 return (\ord($string[3]) << 24) + (\ord($string[2]) << 16) + (\ord($string[1]) << 8) + \ord($string[0]);
745 }
746
747 $int1 = (\ord($string[7]) << 24) + (\ord($string[6]) << 16) + (\ord($string[5]) << 8) + \ord($string[4]);
748 $int2 = (\ord($string[3]) << 24) + (\ord($string[2]) << 16) + (\ord($string[1]) << 8) + \ord($string[0]);
749
750 return $int2 + ($int1 << 32);
751 }
752
753 /**
754 * Return a locking or nonlocking SQL query to read session information.
755 *
756 * @return string The SQL string
757 *
758 * @throws \DomainException When an unsupported PDO driver is used
759 */
760 private function getSelectSql()
761 {
762 if (self::LOCK_TRANSACTIONAL === $this->lockMode) {
763 $this->beginTransaction();
764
765 switch ($this->driver) {
766 case 'mysql':
767 case 'oci':
768 case 'pgsql':
769 return "SELECT $this->dataCol, $this->lifetimeCol, $this->timeCol FROM $this->table WHERE $this->idCol = :id FOR UPDATE";
770 case 'sqlsrv':
771 return "SELECT $this->dataCol, $this->lifetimeCol, $this->timeCol FROM $this->table WITH (UPDLOCK, ROWLOCK) WHERE $this->idCol = :id";
772 case 'sqlite':
773 // we already locked when starting transaction
774 break;
775 default:
776 throw new \DomainException(sprintf('Transactional locks are currently not implemented for PDO driver "%s".', $this->driver));
777 }
778 }
779
780 return "SELECT $this->dataCol, $this->lifetimeCol, $this->timeCol FROM $this->table WHERE $this->idCol = :id";
781 }
782
783 /**
784 * Returns an insert statement supported by the database for writing session data.
785 *
786 * @param string $sessionId Session ID
787 * @param string $sessionData Encoded session data
788 * @param int $maxlifetime session.gc_maxlifetime
789 *
790 * @return \PDOStatement The insert statement
791 */
792 private function getInsertStatement($sessionId, $sessionData, $maxlifetime)
793 {
794 switch ($this->driver) {
795 case 'oci':
796 $data = fopen('php://memory', 'r+');
797 fwrite($data, $sessionData);
798 rewind($data);
799 $sql = "INSERT INTO $this->table ($this->idCol, $this->dataCol, $this->lifetimeCol, $this->timeCol) VALUES (:id, EMPTY_BLOB(), :lifetime, :time) RETURNING $this->dataCol into :data";
800 break;
801 default:
802 $data = $sessionData;
803 $sql = "INSERT INTO $this->table ($this->idCol, $this->dataCol, $this->lifetimeCol, $this->timeCol) VALUES (:id, :data, :lifetime, :time)";
804 break;
805 }
806
807 $stmt = $this->pdo->prepare($sql);
808 $stmt->bindParam(':id', $sessionId, \PDO::PARAM_STR);
809 $stmt->bindParam(':data', $data, \PDO::PARAM_LOB);
810 $stmt->bindParam(':lifetime', $maxlifetime, \PDO::PARAM_INT);
811 $stmt->bindValue(':time', time(), \PDO::PARAM_INT);
812
813 return $stmt;
814 }
815
816 /**
817 * Returns an update statement supported by the database for writing session data.
818 *
819 * @param string $sessionId Session ID
820 * @param string $sessionData Encoded session data
821 * @param int $maxlifetime session.gc_maxlifetime
822 *
823 * @return \PDOStatement The update statement
824 */
825 private function getUpdateStatement($sessionId, $sessionData, $maxlifetime)
826 {
827 switch ($this->driver) {
828 case 'oci':
829 $data = fopen('php://memory', 'r+');
830 fwrite($data, $sessionData);
831 rewind($data);
832 $sql = "UPDATE $this->table SET $this->dataCol = EMPTY_BLOB(), $this->lifetimeCol = :lifetime, $this->timeCol = :time WHERE $this->idCol = :id RETURNING $this->dataCol into :data";
833 break;
834 default:
835 $data = $sessionData;
836 $sql = "UPDATE $this->table SET $this->dataCol = :data, $this->lifetimeCol = :lifetime, $this->timeCol = :time WHERE $this->idCol = :id";
837 break;
838 }
839
840 $stmt = $this->pdo->prepare($sql);
841 $stmt->bindParam(':id', $sessionId, \PDO::PARAM_STR);
842 $stmt->bindParam(':data', $data, \PDO::PARAM_LOB);
843 $stmt->bindParam(':lifetime', $maxlifetime, \PDO::PARAM_INT);
844 $stmt->bindValue(':time', time(), \PDO::PARAM_INT);
845
846 return $stmt;
847 }
848
849 /**
850 * Returns a merge/upsert (i.e. insert or update) statement when supported by the database for writing session data.
851 *
852 * @param string $sessionId Session ID
853 * @param string $data Encoded session data
854 * @param int $maxlifetime session.gc_maxlifetime
855 *
856 * @return \PDOStatement|null The merge statement or null when not supported
857 */
858 private function getMergeStatement($sessionId, $data, $maxlifetime)
859 {
860 switch (true) {
861 case 'mysql' === $this->driver:
862 $mergeSql = "INSERT INTO $this->table ($this->idCol, $this->dataCol, $this->lifetimeCol, $this->timeCol) VALUES (:id, :data, :lifetime, :time) ".
863 "ON DUPLICATE KEY UPDATE $this->dataCol = VALUES($this->dataCol), $this->lifetimeCol = VALUES($this->lifetimeCol), $this->timeCol = VALUES($this->timeCol)";
864 break;
865 case 'sqlsrv' === $this->driver && version_compare($this->pdo->getAttribute(\PDO::ATTR_SERVER_VERSION), '10', '>='):
866 // MERGE is only available since SQL Server 2008 and must be terminated by semicolon
867 // It also requires HOLDLOCK according to https://weblogs.sqlteam.com/dang/2009/01/31/upsert-race-condition-with-merge/
868 $mergeSql = "MERGE INTO $this->table WITH (HOLDLOCK) USING (SELECT 1 AS dummy) AS src ON ($this->idCol = ?) ".
869 "WHEN NOT MATCHED THEN INSERT ($this->idCol, $this->dataCol, $this->lifetimeCol, $this->timeCol) VALUES (?, ?, ?, ?) ".
870 "WHEN MATCHED THEN UPDATE SET $this->dataCol = ?, $this->lifetimeCol = ?, $this->timeCol = ?;";
871 break;
872 case 'sqlite' === $this->driver:
873 $mergeSql = "INSERT OR REPLACE INTO $this->table ($this->idCol, $this->dataCol, $this->lifetimeCol, $this->timeCol) VALUES (:id, :data, :lifetime, :time)";
874 break;
875 case 'pgsql' === $this->driver && version_compare($this->pdo->getAttribute(\PDO::ATTR_SERVER_VERSION), '9.5', '>='):
876 $mergeSql = "INSERT INTO $this->table ($this->idCol, $this->dataCol, $this->lifetimeCol, $this->timeCol) VALUES (:id, :data, :lifetime, :time) ".
877 "ON CONFLICT ($this->idCol) DO UPDATE SET ($this->dataCol, $this->lifetimeCol, $this->timeCol) = (EXCLUDED.$this->dataCol, EXCLUDED.$this->lifetimeCol, EXCLUDED.$this->timeCol)";
878 break;
879 default:
880 // MERGE is not supported with LOBs: https://oracle.com/technetwork/articles/fuecks-lobs-095315.html
881 return null;
882 }
883
884 $mergeStmt = $this->pdo->prepare($mergeSql);
885
886 if ('sqlsrv' === $this->driver) {
887 $mergeStmt->bindParam(1, $sessionId, \PDO::PARAM_STR);
888 $mergeStmt->bindParam(2, $sessionId, \PDO::PARAM_STR);
889 $mergeStmt->bindParam(3, $data, \PDO::PARAM_LOB);
890 $mergeStmt->bindParam(4, $maxlifetime, \PDO::PARAM_INT);
891 $mergeStmt->bindValue(5, time(), \PDO::PARAM_INT);
892 $mergeStmt->bindParam(6, $data, \PDO::PARAM_LOB);
893 $mergeStmt->bindParam(7, $maxlifetime, \PDO::PARAM_INT);
894 $mergeStmt->bindValue(8, time(), \PDO::PARAM_INT);
895 } else {
896 $mergeStmt->bindParam(':id', $sessionId, \PDO::PARAM_STR);
897 $mergeStmt->bindParam(':data', $data, \PDO::PARAM_LOB);
898 $mergeStmt->bindParam(':lifetime', $maxlifetime, \PDO::PARAM_INT);
899 $mergeStmt->bindValue(':time', time(), \PDO::PARAM_INT);
900 }
901
902 return $mergeStmt;
903 }
904
905 /**
906 * Return a PDO instance.
907 *
908 * @return \PDO
909 */
910 protected function getConnection()
911 {
912 if (null === $this->pdo) {
913 $this->connect($this->dsn ?: ini_get('session.save_path'));
914 }
915
916 return $this->pdo;
917 }
918 }
919