<?php

/**
 * CodeIgniter
 *
 * An open source application development framework for PHP
 *
 * This content is released under the MIT License (MIT)
 *
 * Copyright (c) 2019 - 2022, CodeIgniter Foundation
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 *
 * @package CodeIgniter
 * @author  EllisLab Dev Team
 * @copyright   Copyright (c) 2008 - 2014, EllisLab, Inc. (https://ellislab.com/)
 * @copyright   Copyright (c) 2014 - 2019, British Columbia Institute of Technology (https://bcit.ca/)
 * @copyright   Copyright (c) 2019 - 2022, CodeIgniter Foundation (https://codeigniter.com/)
 * @license https://opensource.org/licenses/MIT MIT License
 * @link    https://codeigniter.com
 * @since   Version 3.0.0
 * @filesource
 */

defined('BASEPATH') or exit('No direct script access allowed');

/**
 * CodeIgniter Session Redis Driver
 *
 * @package CodeIgniter
 * @subpackage  Libraries
 * @category    Sessions
 * @author  Andrey Andreev
 * @link    https://codeigniter.com/userguide3/libraries/sessions.html
 */
class CI_Session_redis_driver extends CI_Session_driver implements CI_Session_driver_interface
{
    /**
     * phpRedis instance
     *
     * @var Redis
     */
    protected $_redis;

    /**
     * Key prefix
     *
     * @var string
     */
    protected $_key_prefix = 'ci_session:';

    /**
     * Lock key
     *
     * @var string
     */
    protected $_lock_key;

    /**
     * Key exists flag
     *
     * @var bool
     */
    protected $_key_exists = false;

    /**
     * Name of setTimeout() method in phpRedis
     *
     * Due to some deprecated methods in phpRedis, we need to call the
     * specific methods depending on the version of phpRedis.
     *
     * @var string
     */
    protected $_setTimeout_name;

    /**
     * Name of delete() method in phpRedis
     *
     * Due to some deprecated methods in phpRedis, we need to call the
     * specific methods depending on the version of phpRedis.
     *
     * @var string
     */
    protected $_delete_name;

    /**
     * Success return value of ping() method in phpRedis
     *
     * @var mixed
     */
    protected $_ping_success;

    // ------------------------------------------------------------------------

    /**
     * Class constructor
     *
     * @param   array   $params Configuration parameters
     * @return  void
     */
    public function __construct(&$params)
    {
        parent::__construct($params);

        // Detect the names of some methods in phpRedis instance
        if (version_compare(phpversion('redis'), '5', '>=')) {
            $this->_setTimeout_name = 'expire';
            $this->_delete_name = 'del';
            $this->_ping_success = true;
        } else {
            $this->_setTimeout_name = 'setTimeout';
            $this->_delete_name = 'delete';
            $this->_ping_success = '+PONG';
        }

        if (empty($this->_config['save_path'])) {
            log_message('error', 'Session: No Redis save path configured.');
        } elseif (preg_match('#(?:tcp://)?([^:?]+)(?:\:(\d+))?(\?.+)?#', $this->_config['save_path'], $matches)) {
            isset($matches[3]) or $matches[3] = ''; // Just to avoid undefined index notices below
            $this->_config['save_path'] = array(
                'host' => $matches[1],
                'port' => empty($matches[2]) ? null : $matches[2],
                'password' => preg_match('#auth=([^\s&]+)#', $matches[3], $match) ? $match[1] : null,
                'database' => preg_match('#database=(\d+)#', $matches[3], $match) ? (int) $match[1] : null,
                'timeout' => preg_match('#timeout=(\d+\.\d+)#', $matches[3], $match) ? (float) $match[1] : null
            );

            preg_match('#prefix=([^\s&]+)#', $matches[3], $match) && $this->_key_prefix = $match[1];
        } else {
            log_message('error', 'Session: Invalid Redis save path format: ' . $this->_config['save_path']);
        }

        if ($this->_config['match_ip'] === true) {
            $this->_key_prefix .= $_SERVER['REMOTE_ADDR'] . ':';
        }
    }

    // ------------------------------------------------------------------------

    /**
     * Open
     *
     * Sanitizes save_path and initializes connection.
     *
     * @param   string  $save_path  Server path
     * @param   string  $name       Session cookie name, unused
     * @return  bool
     */
    public function open($save_path, $name)
    {
        if (empty($this->_config['save_path'])) {
            return $this->_failure;
        }

        $redis = new Redis();
        if (! $redis->connect($this->_config['save_path']['host'], $this->_config['save_path']['port'], $this->_config['save_path']['timeout'])) {
            log_message('error', 'Session: Unable to connect to Redis with the configured settings.');
        } elseif (isset($this->_config['save_path']['password']) && ! $redis->auth($this->_config['save_path']['password'])) {
            log_message('error', 'Session: Unable to authenticate to Redis instance.');
        } elseif (isset($this->_config['save_path']['database']) && ! $redis->select($this->_config['save_path']['database'])) {
            log_message('error', 'Session: Unable to select Redis database with index ' . $this->_config['save_path']['database']);
        } else {
            $this->_redis = $redis;
            $this->php5_validate_id();
            return $this->_success;
        }

        return $this->_failure;
    }

    // ------------------------------------------------------------------------

    /**
     * Read
     *
     * Reads session data and acquires a lock
     *
     * @param   string  $session_id Session ID
     * @return  string  Serialized session data
     */
    public function read($session_id)
    {
        if (isset($this->_redis) && $this->_get_lock($session_id)) {
            // Needed by write() to detect session_regenerate_id() calls
            $this->_session_id = $session_id;

            $session_data = $this->_redis->get($this->_key_prefix . $session_id);

            is_string($session_data)
                ? $this->_key_exists = true
                : $session_data = '';

            $this->_fingerprint = md5($session_data);
            return $session_data;
        }

        return $this->_failure;
    }

    // ------------------------------------------------------------------------

    /**
     * Write
     *
     * Writes (create / update) session data
     *
     * @param   string  $session_id Session ID
     * @param   string  $session_data   Serialized session data
     * @return  bool
     */
    public function write($session_id, $session_data)
    {
        if (! isset($this->_redis, $this->_lock_key)) {
            return $this->_failure;
        }
        // Was the ID regenerated?
        elseif ($session_id !== $this->_session_id) {
            if (! $this->_release_lock() or ! $this->_get_lock($session_id)) {
                return $this->_failure;
            }

            $this->_key_exists = false;
            $this->_session_id = $session_id;
        }

        $this->_redis->{$this->_setTimeout_name}($this->_lock_key, 300);
        if ($this->_fingerprint !== ($fingerprint = md5($session_data)) or $this->_key_exists === false) {
            if ($this->_redis->set($this->_key_prefix . $session_id, $session_data, $this->_config['expiration'])) {
                $this->_fingerprint = $fingerprint;
                $this->_key_exists = true;
                return $this->_success;
            }

            return $this->_failure;
        }

        return ($this->_redis->{$this->_setTimeout_name}($this->_key_prefix . $session_id, $this->_config['expiration']))
            ? $this->_success
            : $this->_failure;
    }

    // ------------------------------------------------------------------------

    /**
     * Close
     *
     * Releases locks and closes connection.
     *
     * @return  bool
     */
    public function close()
    {
        if (isset($this->_redis)) {
            try {
                if ($this->_redis->ping() === $this->_ping_success) {
                    $this->_release_lock();
                    if ($this->_redis->close() === false) {
                        return $this->_failure;
                    }
                }
            } catch (RedisException $e) {
                log_message('error', 'Session: Got RedisException on close(): ' . $e->getMessage());
            }

            $this->_redis = null;
            return $this->_success;
        }

        return $this->_success;
    }

    // ------------------------------------------------------------------------

    /**
     * Destroy
     *
     * Destroys the current session.
     *
     * @param   string  $session_id Session ID
     * @return  bool
     */
    public function destroy($session_id)
    {
        if (isset($this->_redis, $this->_lock_key)) {
            if (($result = $this->_redis->{$this->_delete_name}($this->_key_prefix . $session_id)) !== 1) {
                log_message('debug', 'Session: Redis::' . $this->_delete_name . '() expected to return 1, got ' . var_export($result, true) . ' instead.');
            }

            $this->_cookie_destroy();
            return $this->_success;
        }

        return $this->_failure;
    }

    // ------------------------------------------------------------------------

    /**
     * Garbage Collector
     *
     * Deletes expired sessions
     *
     * @param   int     $maxlifetime    Maximum lifetime of sessions
     * @return  bool
     */
    public function gc($maxlifetime)
    {
        // Not necessary, Redis takes care of that.
        return $this->_success;
    }

    // --------------------------------------------------------------------

    /**
     * Update Timestamp
     *
     * Update session timestamp without modifying data
     *
     * @param   string  $id Session ID
     * @param   string  $data   Unknown & unused
     * @return  bool
     */
    public function updateTimestamp($id, $unknown)
    {
        return $this->_redis->{$this->_setTimeout_name}($this->_key_prefix . $id, $this->_config['expiration']);
    }

    // --------------------------------------------------------------------

    /**
     * Validate ID
     *
     * Checks whether a session ID record exists server-side,
     * to enforce session.use_strict_mode.
     *
     * @param   string  $id Session ID
     * @return  bool
     */
    public function validateId($id)
    {
        return (bool) $this->_redis->exists($this->_key_prefix . $id);
    }

    // ------------------------------------------------------------------------

    /**
     * Get lock
     *
     * Acquires an (emulated) lock.
     *
     * @param   string  $session_id Session ID
     * @return  bool
     */
    protected function _get_lock($session_id)
    {
        // PHP 7 reuses the SessionHandler object on regeneration,
        // so we need to check here if the lock key is for the
        // correct session ID.
        if ($this->_lock_key === $this->_key_prefix . $session_id . ':lock') {
            return $this->_redis->{$this->_setTimeout_name}($this->_lock_key, 300);
        }

        // 30 attempts to obtain a lock, in case another request already has it
        $lock_key = $this->_key_prefix . $session_id . ':lock';
        $attempt = 0;
        do {
            if (($ttl = $this->_redis->ttl($lock_key)) > 0) {
                sleep(1);
                continue;
            }

            if ($ttl === -2 && ! $this->_redis->set($lock_key, time(), array('nx', 'ex' => 300))) {
                // Sleep for 1s to wait for lock releases.
                sleep(1);
                continue;
            } elseif (! $this->_redis->setex($lock_key, 300, time())) {
                log_message('error', 'Session: Error while trying to obtain lock for ' . $this->_key_prefix . $session_id);
                return false;
            }

            $this->_lock_key = $lock_key;
            break;
        } while (++$attempt < 30);

        if ($attempt === 30) {
            log_message('error', 'Session: Unable to obtain lock for ' . $this->_key_prefix . $session_id . ' after 30 attempts, aborting.');
            return false;
        } elseif ($ttl === -1) {
            log_message('debug', 'Session: Lock for ' . $this->_key_prefix . $session_id . ' had no TTL, overriding.');
        }

        $this->_lock = true;
        return true;
    }

    // ------------------------------------------------------------------------

    /**
     * Release lock
     *
     * Releases a previously acquired lock
     *
     * @return  bool
     */
    protected function _release_lock()
    {
        if (isset($this->_redis, $this->_lock_key) && $this->_lock) {
            if (! $this->_redis->{$this->_delete_name}($this->_lock_key)) {
                log_message('error', 'Session: Error while trying to free lock for ' . $this->_lock_key);
                return false;
            }

            $this->_lock_key = null;
            $this->_lock = false;
        }

        return true;
    }
}