<?php

/*
 +-----------------------------------------------------------------------+
 | This file is part of the Roundcube Webmail client                     |
 | Copyright (C) 2005-2014, The Roundcube Dev Team                       |
 | Copyright (C) 2011, Kolab Systems AG                                  |
 |                                                                       |
 | Licensed under the GNU General Public License version 3 or            |
 | any later version with exceptions for skins & plugins.                |
 | See the README file for a full license statement.                     |
 |                                                                       |
 | PURPOSE:                                                              |
 |   Provide database supported session management                       |
 +-----------------------------------------------------------------------+
 | Author: Thomas Bruederli <roundcube@gmail.com>                        |
 | Author: Aleksander Machniak <alec@alec.pl>                            |
 +-----------------------------------------------------------------------+
*/

/**
 * Class to provide database supported session storage
 *
 * @package    Framework
 * @subpackage Core
 * @author     Thomas Bruederli <roundcube@gmail.com>
 * @author     Aleksander Machniak <alec@alec.pl>
 */
class rcube_session
{
    private $db;
    private $ip;
    private $start;
    private $changed;
    private $time_diff = 0;
    private $reloaded = false;
    private $appends = array();
    private $gc_handlers = array();
    private $cookiename = 'roundcube_sessauth';
    private $vars;
    private $key;
    private $now;
    private $secret = '';
    private $ip_check = false;
    private $logging = false;
    private $storage;
    private $memcache;

    /**
     * Blocks session data from being written to database.
     * Can be used if write-race conditions are to be expected
     * @var boolean
     */
    public $nowrite = false;


    /**
     * Default constructor
     */
    public function __construct($db, $config)
    {
        $this->db      = $db;
        $this->start   = microtime(true);
        $this->ip      = rcube_utils::remote_addr();
        $this->logging = $config->get('log_session', false);

        $lifetime = $config->get('session_lifetime', 1) * 60;
        $this->set_lifetime($lifetime);

        // use memcache backend
        $this->storage = $config->get('session_storage', 'db');
        if ($this->storage == 'memcache') {
            $this->memcache = rcube::get_instance()->get_memcache();

            // set custom functions for PHP session management if memcache is available
            if ($this->memcache) {
                ini_set('session.serialize_handler', 'php');

                session_set_save_handler(
                    array($this, 'open'),
                    array($this, 'close'),
                    array($this, 'mc_read'),
                    array($this, 'mc_write'),
                    array($this, 'mc_destroy'),
                    array($this, 'gc'));
            }
            else {
                rcube::raise_error(array('code' => 604, 'type' => 'db',
                    'line' => __LINE__, 'file' => __FILE__,
                    'message' => "Failed to connect to memcached. Please check configuration"),
                true, true);
            }
        }
        else if ($this->storage != 'php') {
            ini_set('session.serialize_handler', 'php');

            // set custom functions for PHP session management
            session_set_save_handler(
                array($this, 'open'),
                array($this, 'close'),
                array($this, 'db_read'),
                array($this, 'db_write'),
                array($this, 'db_destroy'),
                array($this, 'gc'));

            $this->table_name = $this->db->table_name('session', true);
        }
    }


    /**
     * Wrapper for session_start()
     */
    public function start()
    {
        session_start();

        // copy some session properties to object vars
        if ($this->storage == 'php') {
            $this->key     = session_id();
            $this->ip      = $_SESSION['__IP'];
            $this->changed = $_SESSION['__MTIME'];
        }
    }


    public function open($save_path, $session_name)
    {
        return true;
    }


    public function close()
    {
        return true;
    }


    /**
     * Delete session data for the given key
     *
     * @param string Session ID
     */
    public function destroy($key)
    {
        return $this->memcache ? $this->mc_destroy($key) : $this->db_destroy($key);
    }


    /**
     * Wrapper for session_write_close()
     */
    public function write_close()
    {
        if ($this->storage == 'php') {
            $_SESSION['__IP'] = $this->ip;
            $_SESSION['__MTIME'] = time();
        }

        session_write_close();

        // write_close() is called on script shutdown, see rcube::shutdown()
        // execute cleanup functionality if enabled by session gc handler
        // we do this after closing the session for better performance
        $this->gc_shutdown();
    }


    /**
     * Read session data from database
     *
     * @param string Session ID
     *
     * @return string Session vars
     */
    public function db_read($key)
    {
        $sql_result = $this->db->query(
            "SELECT `vars`, `ip`, `changed`, " . $this->db->now() . " AS ts"
            . " FROM {$this->table_name} WHERE `sess_id` = ?", $key);

        if ($sql_result && ($sql_arr = $this->db->fetch_assoc($sql_result))) {
            $this->time_diff = time() - strtotime($sql_arr['ts']);
            $this->changed   = strtotime($sql_arr['changed']);
            $this->ip        = $sql_arr['ip'];
            $this->vars      = $sql_arr['vars'];
            $this->key       = $key;

            return !empty($this->vars) ? (string) $this->vars : '';
        }

        return null;
    }


    /**
     * Save session data.
     * handler for session_read()
     *
     * @param string Session ID
     * @param string Serialized session vars
     *
     * @return boolean True on success
     */
    public function db_write($key, $vars)
    {
        $now = $this->db->now();
        $ts  = microtime(true);

        if ($this->nowrite)
            return true;

        // no session row in DB (db_read() returns false)
        if (!$this->key) {
            $oldvars = null;
        }
        // use internal data from read() for fast requests (up to 0.5 sec.)
        else if ($key == $this->key && (!$this->vars || $ts - $this->start < 0.5)) {
            $oldvars = $this->vars;
        }
        else { // else read data again from DB
            $oldvars = $this->db_read($key);
        }

        if ($oldvars !== null) {
            $newvars = $vars;

            if ($newvars !== $oldvars) {
                $this->db->query("UPDATE {$this->table_name} "
                    . "SET `changed` = $now, `vars` = ? WHERE `sess_id` = ?",
                    $newvars, $key);
            }
            else if ($ts - $this->changed + $this->time_diff > $this->lifetime / 2) {
                $this->db->query("UPDATE {$this->table_name} SET `changed` = $now"
                    . " WHERE `sess_id` = ?", $key);
            }
        }
        else {
            $this->db->query("INSERT INTO {$this->table_name}"
                . " (`sess_id`, `vars`, `ip`, `created`, `changed`)"
                . " VALUES (?, ?, ?, $now, $now)",
                $key, $vars, (string)$this->ip);
        }

        return true;
    }


    /**
     * Handler for session_destroy()
     *
     * @param string Session ID
     *
     * @return boolean True on success
     */
    public function db_destroy($key)
    {
        if ($key) {
            $this->db->query("DELETE FROM {$this->table_name} WHERE `sess_id` = ?", $key);
        }

        return true;
    }


    /**
     * Read session data from memcache
     *
     * @param string Session ID
     * @return string Session vars
     */
    public function mc_read($key)
    {
        if ($value = $this->memcache->get($key)) {
            $arr = unserialize($value);
            $this->changed = $arr['changed'];
            $this->ip      = $arr['ip'];
            $this->vars    = $arr['vars'];
            $this->key     = $key;

            return !empty($this->vars) ? (string) $this->vars : '';
        }

        return null;
    }


    /**
     * Save session data.
     * handler for session_read()
     *
     * @param string Session ID
     * @param string Serialized session vars
     *
     * @return boolean True on success
     */
    public function mc_write($key, $vars)
    {
        $ts = microtime(true);

        // no session data in cache (mc_read() returns false)
        if (!$this->key)
            $oldvars = null;
        // use internal data for fast requests (up to 0.5 sec.)
        else if ($key == $this->key && (!$this->vars || $ts - $this->start < 0.5))
            $oldvars = $this->vars;
        else // else read data again
            $oldvars = $this->mc_read($key);

        $newvars = $vars;

        if ($newvars !== $oldvars || $ts - $this->changed > $this->lifetime / 3) {
            return $this->memcache->set($key, serialize(array('changed' => time(), 'ip' => $this->ip, 'vars' => $newvars)),
                MEMCACHE_COMPRESSED, $this->lifetime + 60);
        }

        return true;
    }


    /**
     * Handler for session_destroy() with memcache backend
     *
     * @param string Session ID
     *
     * @return boolean True on success
     */
    public function mc_destroy($key)
    {
        if ($key) {
            // #1488592: use 2nd argument
            $this->memcache->delete($key, 0);
        }

        return true;
    }


    /**
     * Execute registered garbage collector routines
     */
    public function gc($maxlifetime)
    {
        // move gc execution to the script shutdown function
        // see rcube::shutdown() and rcube_session::write_close()
        return $this->gc_enabled = $maxlifetime;
    }


    /**
     * Register additional garbage collector functions
     *
     * @param mixed Callback function
     */
    public function register_gc_handler($func)
    {
        foreach ($this->gc_handlers as $handler) {
            if ($handler == $func) {
                return;
            }
        }

        $this->gc_handlers[] = $func;
    }


    /**
     * Garbage collector handler to run on script shutdown
     */
    protected function gc_shutdown()
    {
        if ($this->gc_enabled) {
            // just delete all expired sessions
            if ($this->storage == 'db') {
                $this->db->query("DELETE FROM {$this->table_name}"
                    . " WHERE `changed` < " . $this->db->now(-$this->gc_enabled));
            }

            foreach ($this->gc_handlers as $fct) {
                call_user_func($fct);
            }
        }
    }


    /**
     * Generate and set new session id
     *
     * @param boolean $destroy If enabled the current session will be destroyed
     */
    public function regenerate_id($destroy=true)
    {
        session_regenerate_id($destroy);

        $this->vars = null;
        $this->key  = session_id();

        return true;
    }


    /**
     * Append the given value to the certain node in the session data array
     *
     * @param string Path denoting the session variable where to append the value
     * @param string Key name under which to append the new value (use null for appending to an indexed list)
     * @param mixed  Value to append to the session data array
     */
    public function append($path, $key, $value)
    {
        // re-read session data from DB because it might be outdated
        if (!$this->reloaded && microtime(true) - $this->start > 0.5) {
            $this->reload();
            $this->reloaded = true;
            $this->start = microtime(true);
        }

        $node = &$this->get_node(explode('.', $path), $_SESSION);

        if ($key !== null) {
            $node[$key] = $value;
            $path .= '.' . $key;
        }
        else {
            $node[] = $value;
        }

        $this->appends[] = $path;

        // when overwriting a previously unset variable
        if ($this->unsets[$path])
            unset($this->unsets[$path]);
    }


    /**
     * Unset a session variable
     *
     * @param string Variable name (can be a path denoting a certain node in the session array, e.g. compose.attachments.5)
     * @return boolean True on success
     */
    public function remove($var=null)
    {
        if (empty($var)) {
            return $this->destroy(session_id());
        }

        if (isset($_SESSION[$var])) {
            unset($_SESSION[$var]);
        }
        else {
            $path = explode('.', $var);
            $key = array_pop($path);
            $node = &$this->get_node($path, $_SESSION);
            unset($node[$key]);
        }

        return true;
    }


    /**
     * Kill this session
     */
    public function kill()
    {
        $this->vars = null;
        $this->ip = rcube_utils::remote_addr(); // update IP (might have changed)
        $this->destroy(session_id());
        rcube_utils::setcookie($this->cookiename, '-del-', time() - 60);
    }


    /**
     * Re-read session data from storage backend
     */
    public function reload()
    {
        // collect updated data from previous appends
        $merge_data = array();
        foreach ((array)$this->appends as $var) {
            $path = explode('.', $var);
            $value = $this->get_node($path, $_SESSION);
            $k = array_pop($path);
            $node = &$this->get_node($path, $merge_data);
            $node[$k] = $value;
        }

        if ($this->key && $this->memcache)
            $data = $this->mc_read($this->key);
        else if ($this->key)
            $data = $this->db_read($this->key);

        if ($data) {
            session_decode($data);

            // apply appends and unsets to reloaded data
            $_SESSION = array_merge_recursive($_SESSION, $merge_data);

            foreach ((array)$this->unsets as $var) {
                if (isset($_SESSION[$var])) {
                    unset($_SESSION[$var]);
                }
                else {
                    $path = explode('.', $var);
                    $k = array_pop($path);
                    $node = &$this->get_node($path, $_SESSION);
                    unset($node[$k]);
                }
            }
        }

    }

    /**
     * Returns a reference to the node in data array referenced by the given path.
     * e.g. ['compose','attachments'] will return $_SESSION['compose']['attachments']
     */
    private function &get_node($path, &$data_arr)
    {
        $node = &$data_arr;
        if (!empty($path)) {
            foreach ((array)$path as $key) {
                if (!isset($node[$key]))
                    $node[$key] = array();
                $node = &$node[$key];
            }
        }

        return $node;
    }

    /**
     * Serialize session data
     */
    private function serialize($vars)
    {
        $data = '';
        if (is_array($vars)) {
            foreach ($vars as $var=>$value)
                $data .= $var.'|'.serialize($value);
        }
        else {
            $data = 'b:0;';
        }

        return $data;
    }


    /**
     * Unserialize session data
     * http://www.php.net/manual/en/function.session-decode.php#56106
     */
    private function unserialize($str)
    {
        $str    = (string)$str;
        $endptr = strlen($str);
        $p      = 0;

        $serialized = '';
        $items      = 0;
        $level      = 0;

        while ($p < $endptr) {
            $q = $p;
            while ($str[$q] != '|')
                if (++$q >= $endptr)
                    break 2;

            if ($str[$p] == '!') {
                $p++;
                $has_value = false;
            }
            else {
                $has_value = true;
            }

            $name = substr($str, $p, $q - $p);
            $q++;

            $serialized .= 's:' . strlen($name) . ':"' . $name . '";';

            if ($has_value) {
                for (;;) {
                    $p = $q;
                    switch (strtolower($str[$q])) {
                    case 'n': // null
                    case 'b': // boolean
                    case 'i': // integer
                    case 'd': // decimal
                        do $q++;
                        while ( ($q < $endptr) && ($str[$q] != ';') );
                        $q++;
                        $serialized .= substr($str, $p, $q - $p);
                        if ($level == 0)
                            break 2;
                        break;
                    case 'r': // reference
                        $q+= 2;
                        for ($id = ''; ($q < $endptr) && ($str[$q] != ';'); $q++)
                            $id .= $str[$q];
                        $q++;
                        // increment pointer because of outer array
                        $serialized .= 'R:' . ($id + 1) . ';';
                        if ($level == 0)
                            break 2;
                        break;
                    case 's': // string
                        $q+=2;
                        for ($length=''; ($q < $endptr) && ($str[$q] != ':'); $q++)
                            $length .= $str[$q];
                        $q+=2;
                        $q+= (int)$length + 2;
                        $serialized .= substr($str, $p, $q - $p);
                        if ($level == 0)
                            break 2;
                        break;
                    case 'a': // array
                    case 'o': // object
                        do $q++;
                        while ($q < $endptr && $str[$q] != '{');
                        $q++;
                        $level++;
                        $serialized .= substr($str, $p, $q - $p);
                        break;
                    case '}': // end of array|object
                        $q++;
                        $serialized .= substr($str, $p, $q - $p);
                        if (--$level == 0)
                            break 2;
                        break;
                    default:
                        return false;
                    }
                }
            }
            else {
                $serialized .= 'N;';
                $q += 2;
            }
            $items++;
            $p = $q;
        }

        return unserialize( 'a:' . $items . ':{' . $serialized . '}' );
    }


    /**
     * Setter for session lifetime
     */
    public function set_lifetime($lifetime)
    {
        $this->lifetime = max(120, $lifetime);

        // valid time range is now - 1/2 lifetime to now + 1/2 lifetime
        $now = time();
        $this->now = $now - ($now % ($this->lifetime / 2));
    }


    /**
     * Getter for remote IP saved with this session
     */
    public function get_ip()
    {
        return $this->ip;
    }


    /**
     * Setter for cookie encryption secret
     */
    function set_secret($secret)
    {
        $this->secret = $secret;
    }


    /**
     * Enable/disable IP check
     */
    function set_ip_check($check)
    {
        $this->ip_check = $check;
    }


    /**
     * Setter for the cookie name used for session cookie
     */
    function set_cookiename($cookiename)
    {
        if ($cookiename) {
            $this->cookiename = $cookiename;
        }
    }


    /**
     * Check session authentication cookie
     *
     * @return boolean True if valid, False if not
     */
    function check_auth()
    {
        $this->cookie = $_COOKIE[$this->cookiename];
        $result = $this->ip_check ? rcube_utils::remote_addr() == $this->ip : true;

        if (!$result) {
            $this->log("IP check failed for " . $this->key . "; expected " . $this->ip . "; got " . rcube_utils::remote_addr());
        }

        if ($result && $this->_mkcookie($this->now) != $this->cookie) {
            $this->log("Session auth check failed for " . $this->key . "; timeslot = " . date('Y-m-d H:i:s', $this->now));
            $result = false;

            // Check if using id from a previous time slot
            for ($i = 1; $i <= 2; $i++) {
                $prev = $this->now - ($this->lifetime / 2) * $i;
                if ($this->_mkcookie($prev) == $this->cookie) {
                    $this->log("Send new auth cookie for " . $this->key . ": " . $this->cookie);
                    $this->set_auth_cookie();
                    $result = true;
                }
            }
        }

        if (!$result) {
            $this->log("Session authentication failed for " . $this->key
                . "; invalid auth cookie sent; timeslot = " . date('Y-m-d H:i:s', $prev));
        }

        return $result;
    }


    /**
     * Set session authentication cookie
     */
    function set_auth_cookie()
    {
        $this->cookie = $this->_mkcookie($this->now);
        rcube_utils::setcookie($this->cookiename, $this->cookie, 0);
        $_COOKIE[$this->cookiename] = $this->cookie;
    }


    /**
     * Create session cookie from session data
     *
     * @param int Time slot to use
     */
    function _mkcookie($timeslot)
    {
        $auth_string = "$this->key,$this->secret,$timeslot";
        return "S" . (function_exists('sha1') ? sha1($auth_string) : md5($auth_string));
    }

    /**
     * Writes debug information to the log
     */
    function log($line)
    {
        if ($this->logging) {
            rcube::write_log('session', $line);
        }
    }
}
