<?php

/**
 * Pure-PHP implementation of SFTP.
 *
 * PHP version 5
 *
 * Supports SFTPv2/3/4/5/6. Defaults to v3.
 *
 * The API for this library is modeled after the API from PHP's {@link http://php.net/book.ftp FTP extension}.
 *
 * Here's a short example of how to use this library:
 * <code>
 * <?php
 *    include 'vendor/autoload.php';
 *
 *    $sftp = new \phpseclib3\Net\SFTP('www.domain.tld');
 *    if (!$sftp->login('username', 'password')) {
 *        exit('Login Failed');
 *    }
 *
 *    echo $sftp->pwd() . "\r\n";
 *    $sftp->put('filename.ext', 'hello, world!');
 *    print_r($sftp->nlist());
 * ?>
 * </code>
 *
 * @category  Net
 * @package   SFTP
 * @author    Jim Wigginton <terrafrost@php.net>
 * @copyright 2009 Jim Wigginton
 * @license   http://www.opensource.org/licenses/mit-license.html  MIT License
 * @link      http://phpseclib.sourceforge.net
 */

namespace phpseclib3\Net;

use phpseclib3\Exception\FileNotFoundException;
use phpseclib3\Common\Functions\Strings;
use phpseclib3\Crypt\Common\AsymmetricKey;
use phpseclib3\System\SSH\Agent;

/**
 * Pure-PHP implementations of SFTP.
 *
 * @package SFTP
 * @author  Jim Wigginton <terrafrost@php.net>
 * @access  public
 */
class SFTP extends SSH2
{
    /**
     * SFTP channel constant
     *
     * \phpseclib3\Net\SSH2::exec() uses 0 and \phpseclib3\Net\SSH2::read() / \phpseclib3\Net\SSH2::write() use 1.
     *
     * @see \phpseclib3\Net\SSH2::send_channel_packet()
     * @see \phpseclib3\Net\SSH2::get_channel_packet()
     * @access private
     */
    const CHANNEL = 0x100;

    /**
     * Reads data from a local file.
     *
     * @access public
     * @see \phpseclib3\Net\SFTP::put()
     */
    const SOURCE_LOCAL_FILE = 1;
    /**
     * Reads data from a string.
     *
     * @access public
     * @see \phpseclib3\Net\SFTP::put()
     */
    // this value isn't really used anymore but i'm keeping it reserved for historical reasons
    const SOURCE_STRING = 2;
    /**
     * Reads data from callback:
     * function callback($length) returns string to proceed, null for EOF
     *
     * @access public
     * @see \phpseclib3\Net\SFTP::put()
     */
    const SOURCE_CALLBACK = 16;
    /**
     * Resumes an upload
     *
     * @access public
     * @see \phpseclib3\Net\SFTP::put()
     */
    const RESUME = 4;
    /**
     * Append a local file to an already existing remote file
     *
     * @access public
     * @see \phpseclib3\Net\SFTP::put()
     */
    const RESUME_START = 8;

    /**
     * Packet Types
     *
     * @see self::__construct()
     * @var array
     * @access private
     */
    private $packet_types = [];

    /**
     * Status Codes
     *
     * @see self::__construct()
     * @var array
     * @access private
     */
    private $status_codes = [];

    /**
     * The Request ID
     *
     * The request ID exists in the off chance that a packet is sent out-of-order.  Of course, this library doesn't support
     * concurrent actions, so it's somewhat academic, here.
     *
     * @var boolean
     * @see self::_send_sftp_packet()
     * @access private
     */
    private $use_request_id = false;

    /**
     * The Packet Type
     *
     * The request ID exists in the off chance that a packet is sent out-of-order.  Of course, this library doesn't support
     * concurrent actions, so it's somewhat academic, here.
     *
     * @var int
     * @see self::_get_sftp_packet()
     * @access private
     */
    private $packet_type = -1;

    /**
     * Packet Buffer
     *
     * @var string
     * @see self::_get_sftp_packet()
     * @access private
     */
    private $packet_buffer = '';

    /**
     * Extensions supported by the server
     *
     * @var array
     * @see self::_initChannel()
     * @access private
     */
    private $extensions = [];

    /**
     * Server SFTP version
     *
     * @var int
     * @see self::_initChannel()
     * @access private
     */
    private $version;

    /**
     * Default Server SFTP version
     *
     * @var int
     * @see self::_initChannel()
     * @access private
     */
    private $defaultVersion;

    /**
     * Preferred SFTP version
     *
     * @var int
     * @see self::_initChannel()
     * @access private
     */
    private $preferredVersion = 3;

    /**
     * Current working directory
     *
     * @var string
     * @see self::realpath()
     * @see self::chdir()
     * @access private
     */
    private $pwd = false;

    /**
     * Packet Type Log
     *
     * @see self::getLog()
     * @var array
     * @access private
     */
    private $packet_type_log = [];

    /**
     * Packet Log
     *
     * @see self::getLog()
     * @var array
     * @access private
     */
    private $packet_log = [];

    /**
     * Error information
     *
     * @see self::getSFTPErrors()
     * @see self::getLastSFTPError()
     * @var array
     * @access private
     */
    private $sftp_errors = [];

    /**
     * Stat Cache
     *
     * Rather than always having to open a directory and close it immediately there after to see if a file is a directory
     * we'll cache the results.
     *
     * @see self::_update_stat_cache()
     * @see self::_remove_from_stat_cache()
     * @see self::_query_stat_cache()
     * @var array
     * @access private
     */
    private $stat_cache = [];

    /**
     * Max SFTP Packet Size
     *
     * @see self::__construct()
     * @see self::get()
     * @var array
     * @access private
     */
    private $max_sftp_packet;

    /**
     * Stat Cache Flag
     *
     * @see self::disableStatCache()
     * @see self::enableStatCache()
     * @var bool
     * @access private
     */
    private $use_stat_cache = true;

    /**
     * Sort Options
     *
     * @see self::_comparator()
     * @see self::setListOrder()
     * @var array
     * @access private
     */
    protected $sortOptions = [];

    /**
     * Canonicalization Flag
     *
     * Determines whether or not paths should be canonicalized before being
     * passed on to the remote server.
     *
     * @see self::enablePathCanonicalization()
     * @see self::disablePathCanonicalization()
     * @see self::realpath()
     * @var bool
     * @access private
     */
    private $canonicalize_paths = true;

    /**
     * Request Buffers
     *
     * @see self::_get_sftp_packet()
     * @var array
     * @access private
     */
    private $requestBuffer = [];

    /**
     * Preserve timestamps on file downloads / uploads
     *
     * @see self::get()
     * @see self::put()
     * @var bool
     * @access private
     */
    private $preserveTime = false;

    /**
     * Arbitrary Length Packets Flag
     *
     * Determines whether or not packets of any length should be allowed,
     * in cases where the server chooses the packet length (such as
     * directory listings). By default, packets are only allowed to be
     * 256 * 1024 bytes (SFTP_MAX_MSG_LENGTH from OpenSSH's sftp-common.h)
     *
     * @see self::enableArbitraryLengthPackets()
     * @see self::_get_sftp_packet()
     * @var bool
     * @access private
     */
    private $allow_arbitrary_length_packets = false;

    /**
     * Was the last packet due to the channels being closed or not?
     *
     * @see self::get()
     * @see self::get_sftp_packet()
     * @var bool
     * @access private
     */
    private $channel_close = false;

    /**
     * Has the SFTP channel been partially negotiated?
     *
     * @var bool
     * @access private
     */
    private $partial_init = false;

    /**
     * Default Constructor.
     *
     * Connects to an SFTP server
     *
     * @param string $host
     * @param int $port
     * @param int $timeout
     * @return \phpseclib3\Net\SFTP
     * @access public
     */
    public function __construct($host, $port = 22, $timeout = 10)
    {
        parent::__construct($host, $port, $timeout);

        $this->max_sftp_packet = 1 << 15;

        $this->packet_types = [
            1  => 'NET_SFTP_INIT',
            2  => 'NET_SFTP_VERSION',
            3  => 'NET_SFTP_OPEN',
            4  => 'NET_SFTP_CLOSE',
            5  => 'NET_SFTP_READ',
            6  => 'NET_SFTP_WRITE',
            7  => 'NET_SFTP_LSTAT',
            9  => 'NET_SFTP_SETSTAT',
            10 => 'NET_SFTP_FSETSTAT',
            11 => 'NET_SFTP_OPENDIR',
            12 => 'NET_SFTP_READDIR',
            13 => 'NET_SFTP_REMOVE',
            14 => 'NET_SFTP_MKDIR',
            15 => 'NET_SFTP_RMDIR',
            16 => 'NET_SFTP_REALPATH',
            17 => 'NET_SFTP_STAT',
            18 => 'NET_SFTP_RENAME',
            19 => 'NET_SFTP_READLINK',
            20 => 'NET_SFTP_SYMLINK',
            21 => 'NET_SFTP_LINK',

            101=> 'NET_SFTP_STATUS',
            102=> 'NET_SFTP_HANDLE',
            103=> 'NET_SFTP_DATA',
            104=> 'NET_SFTP_NAME',
            105=> 'NET_SFTP_ATTRS',

            200=> 'NET_SFTP_EXTENDED'
        ];
        $this->status_codes = [
            0 => 'NET_SFTP_STATUS_OK',
            1 => 'NET_SFTP_STATUS_EOF',
            2 => 'NET_SFTP_STATUS_NO_SUCH_FILE',
            3 => 'NET_SFTP_STATUS_PERMISSION_DENIED',
            4 => 'NET_SFTP_STATUS_FAILURE',
            5 => 'NET_SFTP_STATUS_BAD_MESSAGE',
            6 => 'NET_SFTP_STATUS_NO_CONNECTION',
            7 => 'NET_SFTP_STATUS_CONNECTION_LOST',
            8 => 'NET_SFTP_STATUS_OP_UNSUPPORTED',
            9 => 'NET_SFTP_STATUS_INVALID_HANDLE',
            10 => 'NET_SFTP_STATUS_NO_SUCH_PATH',
            11 => 'NET_SFTP_STATUS_FILE_ALREADY_EXISTS',
            12 => 'NET_SFTP_STATUS_WRITE_PROTECT',
            13 => 'NET_SFTP_STATUS_NO_MEDIA',
            14 => 'NET_SFTP_STATUS_NO_SPACE_ON_FILESYSTEM',
            15 => 'NET_SFTP_STATUS_QUOTA_EXCEEDED',
            16 => 'NET_SFTP_STATUS_UNKNOWN_PRINCIPAL',
            17 => 'NET_SFTP_STATUS_LOCK_CONFLICT',
            18 => 'NET_SFTP_STATUS_DIR_NOT_EMPTY',
            19 => 'NET_SFTP_STATUS_NOT_A_DIRECTORY',
            20 => 'NET_SFTP_STATUS_INVALID_FILENAME',
            21 => 'NET_SFTP_STATUS_LINK_LOOP',
            22 => 'NET_SFTP_STATUS_CANNOT_DELETE',
            23 => 'NET_SFTP_STATUS_INVALID_PARAMETER',
            24 => 'NET_SFTP_STATUS_FILE_IS_A_DIRECTORY',
            25 => 'NET_SFTP_STATUS_BYTE_RANGE_LOCK_CONFLICT',
            26 => 'NET_SFTP_STATUS_BYTE_RANGE_LOCK_REFUSED',
            27 => 'NET_SFTP_STATUS_DELETE_PENDING',
            28 => 'NET_SFTP_STATUS_FILE_CORRUPT',
            29 => 'NET_SFTP_STATUS_OWNER_INVALID',
            30 => 'NET_SFTP_STATUS_GROUP_INVALID',
            31 => 'NET_SFTP_STATUS_NO_MATCHING_BYTE_RANGE_LOCK'
        ];
        // http://tools.ietf.org/html/draft-ietf-secsh-filexfer-13#section-7.1
        // the order, in this case, matters quite a lot - see \phpseclib3\Net\SFTP::_parseAttributes() to understand why
        $this->attributes = [
            0x00000001 => 'NET_SFTP_ATTR_SIZE',
            0x00000002 => 'NET_SFTP_ATTR_UIDGID',          // defined in SFTPv3, removed in SFTPv4+
            0x00000080 => 'NET_SFTP_ATTR_OWNERGROUP',      // defined in SFTPv4+
            0x00000004 => 'NET_SFTP_ATTR_PERMISSIONS',
            0x00000008 => 'NET_SFTP_ATTR_ACCESSTIME',
            0x00000010 => 'NET_SFTP_ATTR_CREATETIME',      // SFTPv4+
            0x00000020 => 'NET_SFTP_ATTR_MODIFYTIME',
            0x00000040 => 'NET_SFTP_ATTR_ACL',
            0x00000100 => 'NET_SFTP_ATTR_SUBSECOND_TIMES',
            0x00000200 => 'NET_SFTP_ATTR_BITS',            // SFTPv5+
            0x00000400 => 'NET_SFTP_ATTR_ALLOCATION_SIZE', // SFTPv6+
            0x00000800 => 'NET_SFTP_ATTR_TEXT_HINT',
            0x00001000 => 'NET_SFTP_ATTR_MIME_TYPE',
            0x00002000 => 'NET_SFTP_ATTR_LINK_COUNT',
            0x00004000 => 'NET_SFTP_ATTR_UNTRANSLATED_NAME',
            0x00008000 => 'NET_SFTP_ATTR_CTIME',
            // 0x80000000 will yield a floating point on 32-bit systems and converting floating points to integers
            // yields inconsistent behavior depending on how php is compiled.  so we left shift -1 (which, in
            // two's compliment, consists of all 1 bits) by 31.  on 64-bit systems this'll yield 0xFFFFFFFF80000000.
            // that's not a problem, however, and 'anded' and a 32-bit number, as all the leading 1 bits are ignored.
            (-1 << 31) & 0xFFFFFFFF => 'NET_SFTP_ATTR_EXTENDED'
        ];
        // http://tools.ietf.org/html/draft-ietf-secsh-filexfer-04#section-6.3
        // the flag definitions change somewhat in SFTPv5+.  if SFTPv5+ support is added to this library, maybe name
        // the array for that $this->open5_flags and similarly alter the constant names.
        $this->open_flags = [
            0x00000001 => 'NET_SFTP_OPEN_READ',
            0x00000002 => 'NET_SFTP_OPEN_WRITE',
            0x00000004 => 'NET_SFTP_OPEN_APPEND',
            0x00000008 => 'NET_SFTP_OPEN_CREATE',
            0x00000010 => 'NET_SFTP_OPEN_TRUNCATE',
            0x00000020 => 'NET_SFTP_OPEN_EXCL',
            0x00000040 => 'NET_SFTP_OPEN_TEXT' // defined in SFTPv4
        ];
        // SFTPv5+ changed the flags up:
        // https://datatracker.ietf.org/doc/html/draft-ietf-secsh-filexfer-13#section-8.1.1.3
        $this->open_flags5 = [
            // when SSH_FXF_ACCESS_DISPOSITION is a 3 bit field that controls how the file is opened
            0x00000000 => 'NET_SFTP_OPEN_CREATE_NEW',
            0x00000001 => 'NET_SFTP_OPEN_CREATE_TRUNCATE',
            0x00000002 => 'NET_SFTP_OPEN_OPEN_EXISTING',
            0x00000003 => 'NET_SFTP_OPEN_OPEN_OR_CREATE',
            0x00000004 => 'NET_SFTP_OPEN_TRUNCATE_EXISTING',
            // the rest of the flags are not supported
            0x00000008 => 'NET_SFTP_OPEN_APPEND_DATA', // "the offset field of SS_FXP_WRITE requests is ignored"
            0x00000010 => 'NET_SFTP_OPEN_APPEND_DATA_ATOMIC',
            0x00000020 => 'NET_SFTP_OPEN_TEXT_MODE',
            0x00000040 => 'NET_SFTP_OPEN_BLOCK_READ',
            0x00000080 => 'NET_SFTP_OPEN_BLOCK_WRITE',
            0x00000100 => 'NET_SFTP_OPEN_BLOCK_DELETE',
            0x00000200 => 'NET_SFTP_OPEN_BLOCK_ADVISORY',
            0x00000400 => 'NET_SFTP_OPEN_NOFOLLOW',
            0x00000800 => 'NET_SFTP_OPEN_DELETE_ON_CLOSE',
            0x00001000 => 'NET_SFTP_OPEN_ACCESS_AUDIT_ALARM_INFO',
            0x00002000 => 'NET_SFTP_OPEN_ACCESS_BACKUP',
            0x00004000 => 'NET_SFTP_OPEN_BACKUP_STREAM',
            0x00008000 => 'NET_SFTP_OPEN_OVERRIDE_OWNER',
        ];
        // http://tools.ietf.org/html/draft-ietf-secsh-filexfer-04#section-5.2
        // see \phpseclib3\Net\SFTP::_parseLongname() for an explanation
        $this->file_types = [
            1 => 'NET_SFTP_TYPE_REGULAR',
            2 => 'NET_SFTP_TYPE_DIRECTORY',
            3 => 'NET_SFTP_TYPE_SYMLINK',
            4 => 'NET_SFTP_TYPE_SPECIAL',
            5 => 'NET_SFTP_TYPE_UNKNOWN',
            // the following types were first defined for use in SFTPv5+
            // http://tools.ietf.org/html/draft-ietf-secsh-filexfer-05#section-5.2
            6 => 'NET_SFTP_TYPE_SOCKET',
            7 => 'NET_SFTP_TYPE_CHAR_DEVICE',
            8 => 'NET_SFTP_TYPE_BLOCK_DEVICE',
            9 => 'NET_SFTP_TYPE_FIFO'
        ];
        $this->define_array(
            $this->packet_types,
            $this->status_codes,
            $this->attributes,
            $this->open_flags,
            $this->open_flags5,
            $this->file_types
        );

        if (!defined('NET_SFTP_QUEUE_SIZE')) {
            define('NET_SFTP_QUEUE_SIZE', 32);
        }
        if (!defined('NET_SFTP_UPLOAD_QUEUE_SIZE')) {
            define('NET_SFTP_UPLOAD_QUEUE_SIZE', 1024);
        }
    }

    /**
     * Check a few things before SFTP functions are called
     *
     * @return bool
     * @access public
     */
    private function precheck()
    {
        if (!($this->bitmap & SSH2::MASK_LOGIN)) {
            return false;
        }

        if ($this->pwd === false) {
            return $this->init_sftp_connection();
        }

        return true;
    }

    /**
     * Partially initialize an SFTP connection
     *
     * @throws \UnexpectedValueException on receipt of unexpected packets
     * @return bool
     * @access public
     */
    private function partial_init_sftp_connection()
    {
        $this->window_size_server_to_client[self::CHANNEL] = $this->window_size;

        $packet = Strings::packSSH2(
            'CsN3',
            NET_SSH2_MSG_CHANNEL_OPEN,
            'session',
            self::CHANNEL,
            $this->window_size,
            0x4000
        );

        $this->send_binary_packet($packet);

        $this->channel_status[self::CHANNEL] = NET_SSH2_MSG_CHANNEL_OPEN;

        $response = $this->get_channel_packet(self::CHANNEL, true);
        if ($response === true && $this->isTimeout()) {
            return false;
        }

        $packet = Strings::packSSH2(
            'CNsbs',
            NET_SSH2_MSG_CHANNEL_REQUEST,
            $this->server_channels[self::CHANNEL],
            'subsystem',
            true,
            'sftp'
        );
        $this->send_binary_packet($packet);

        $this->channel_status[self::CHANNEL] = NET_SSH2_MSG_CHANNEL_REQUEST;

        $response = $this->get_channel_packet(self::CHANNEL, true);
        if ($response === false) {
            // from PuTTY's psftp.exe
            $command = "test -x /usr/lib/sftp-server && exec /usr/lib/sftp-server\n" .
                       "test -x /usr/local/lib/sftp-server && exec /usr/local/lib/sftp-server\n" .
                       "exec sftp-server";
            // we don't do $this->exec($command, false) because exec() operates on a different channel and plus the SSH_MSG_CHANNEL_OPEN that exec() does
            // is redundant
            $packet = Strings::packSSH2(
                'CNsCs',
                NET_SSH2_MSG_CHANNEL_REQUEST,
                $this->server_channels[self::CHANNEL],
                'exec',
                1,
                $command
            );
            $this->send_binary_packet($packet);

            $this->channel_status[self::CHANNEL] = NET_SSH2_MSG_CHANNEL_REQUEST;

            $response = $this->get_channel_packet(self::CHANNEL, true);
            if ($response === false) {
                return false;
            }
        } else if ($response === true && $this->isTimeout()) {
            return false;
        }

        $this->channel_status[self::CHANNEL] = NET_SSH2_MSG_CHANNEL_DATA;
        $this->send_sftp_packet(NET_SFTP_INIT, "\0\0\0\3");

        $response = $this->get_sftp_packet();
        if ($this->packet_type != NET_SFTP_VERSION) {
            throw new \UnexpectedValueException('Expected NET_SFTP_VERSION. '
                                              . 'Got packet type: ' . $this->packet_type);
        }

        $this->use_request_id = true;

        list($this->defaultVersion) = Strings::unpackSSH2('N', $response);
        while (!empty($response)) {
            list($key, $value) = Strings::unpackSSH2('ss', $response);
            $this->extensions[$key] = $value;
        }

        $this->partial_init = true;

        return true;
    }

    /**
     * (Re)initializes the SFTP channel
     *
     * @return bool
     * @access private
     */
    private function init_sftp_connection()
    {
        if (!$this->partial_init && !$this->partial_init_sftp_connection()) {
            return false;
        }

        /*
         A Note on SFTPv4/5/6 support:
         <http://tools.ietf.org/html/draft-ietf-secsh-filexfer-13#section-5.1> states the following:

         "If the client wishes to interoperate with servers that support noncontiguous version
          numbers it SHOULD send '3'"

         Given that the server only sends its version number after the client has already done so, the above
         seems to be suggesting that v3 should be the default version.  This makes sense given that v3 is the
         most popular.

         <http://tools.ietf.org/html/draft-ietf-secsh-filexfer-13#section-5.5> states the following;

         "If the server did not send the "versions" extension, or the version-from-list was not included, the
          server MAY send a status response describing the failure, but MUST then close the channel without
          processing any further requests."

         So what do you do if you have a client whose initial SSH_FXP_INIT packet says it implements v3 and
         a server whose initial SSH_FXP_VERSION reply says it implements v4 and only v4?  If it only implements
         v4, the "versions" extension is likely not going to have been sent so version re-negotiation as discussed
         in draft-ietf-secsh-filexfer-13 would be quite impossible.  As such, what \phpseclib3\Net\SFTP would do is close the
         channel and reopen it with a new and updated SSH_FXP_INIT packet.
        */
        $this->version = $this->defaultVersion;
        if (isset($this->extensions['versions']) && (!$this->preferredVersion || $this->preferredVersion != $this->version)) {
            $versions = explode(',', $this->extensions['versions']);
            $supported = [6, 5, 4];
            if ($this->preferredVersion) {
                $supported = array_diff($supported, [$this->preferredVersion]);
                array_unshift($supported, $this->preferredVersion);
            }
            foreach ($supported as $ver) {
                if (in_array($ver, $versions)) {
                    if ($ver === $this->version) {
                        break;
                    }
                    $this->version = (int) $ver;
                    $packet = Strings::packSSH2('ss', 'version-select', "$ver");
                    $this->send_sftp_packet(NET_SFTP_EXTENDED, $packet);
                    $response = $this->get_sftp_packet();
                    if ($this->packet_type != NET_SFTP_STATUS) {
                        throw new \UnexpectedValueException('Expected NET_SFTP_STATUS. '
                            . 'Got packet type: ' . $this->packet_type);
                    }
                    list($status) = Strings::unpackSSH2('N', $response);
                    if ($status != NET_SFTP_STATUS_OK) {
                        $this->logError($response, $status);
                        throw new \UnexpectedValueException('Expected NET_SFTP_STATUS_OK. '
                            . ' Got ' . $status);
                    }
                    break;
                }
            }
        }

        /*
         SFTPv4+ defines a 'newline' extension.  SFTPv3 seems to have unofficial support for it via 'newline@vandyke.com',
         however, I'm not sure what 'newline@vandyke.com' is supposed to do (the fact that it's unofficial means that it's
         not in the official SFTPv3 specs) and 'newline@vandyke.com' / 'newline' are likely not drop-in substitutes for
         one another due to the fact that 'newline' comes with a SSH_FXF_TEXT bitmask whereas it seems unlikely that
         'newline@vandyke.com' would.
        */
        /*
        if (isset($this->extensions['newline@vandyke.com'])) {
            $this->extensions['newline'] = $this->extensions['newline@vandyke.com'];
            unset($this->extensions['newline@vandyke.com']);
        }
        */
        if ($this->version < 2 || $this->version > 6) {
            return false;
        }

        $this->pwd = true;
        $this->pwd = $this->realpath('.');

        $this->update_stat_cache($this->pwd, []);

        return true;
    }

    /**
     * Disable the stat cache
     *
     * @access public
     */
    public function disableStatCache()
    {
        $this->use_stat_cache = false;
    }

    /**
     * Enable the stat cache
     *
     * @access public
     */
    public function enableStatCache()
    {
        $this->use_stat_cache = true;
    }

    /**
     * Clear the stat cache
     *
     * @access public
     */
    public function clearStatCache()
    {
        $this->stat_cache = [];
    }

    /**
     * Enable path canonicalization
     *
     * @access public
     */
    public function enablePathCanonicalization()
    {
        $this->canonicalize_paths = true;
    }

    /**
     * Enable path canonicalization
     *
     * @access public
     */
    public function disablePathCanonicalization()
    {
        $this->canonicalize_paths = false;
    }

    /**
     * Enable arbitrary length packets
     *
     * @access public
     */
    public function enableArbitraryLengthPackets()
    {
        $this->allow_arbitrary_length_packets = true;
    }

    /**
     * Disable arbitrary length packets
     *
     * @access public
     */
    public function disableArbitraryLengthPackets()
    {
        $this->allow_arbitrary_length_packets = false;
    }

    /**
     * Returns the current directory name
     *
     * @return mixed
     * @access public
     */
    public function pwd()
    {
        if (!$this->precheck()) {
            return false;
        }

        return $this->pwd;
    }

    /**
     * Logs errors
     *
     * @param string $response
     * @param int $status
     * @access private
     */
    private function logError($response, $status = -1)
    {
        if ($status == -1) {
            list($status) = Strings::unpackSSH2('N', $response);
        }

        $error = $this->status_codes[$status];

        if ($this->version > 2) {
            list($message) = Strings::unpackSSH2('s', $response);
            $this->sftp_errors[] = "$error: $message";
        } else {
            $this->sftp_errors[] = $error;
        }
    }

    /**
     * Canonicalize the Server-Side Path Name
     *
     * SFTP doesn't provide a mechanism by which the current working directory can be changed, so we'll emulate it.  Returns
     * the absolute (canonicalized) path.
     *
     * If canonicalize_paths has been disabled using disablePathCanonicalization(), $path is returned as-is.
     *
     * @see self::chdir()
     * @see self::disablePathCanonicalization()
     * @param string $path
     * @throws \UnexpectedValueException on receipt of unexpected packets
     * @return mixed
     * @access public
     */
    public function realpath($path)
    {
        if ($this->precheck() === false) {
            return false;
        }

        if (!$this->canonicalize_paths) {
            return $path;
        }

        if ($this->pwd === true) {
            // http://tools.ietf.org/html/draft-ietf-secsh-filexfer-13#section-8.9
            $this->send_sftp_packet(NET_SFTP_REALPATH, Strings::packSSH2('s', $path));

            $response = $this->get_sftp_packet();
            switch ($this->packet_type) {
                case NET_SFTP_NAME:
                    // although SSH_FXP_NAME is implemented differently in SFTPv3 than it is in SFTPv4+, the following
                    // should work on all SFTP versions since the only part of the SSH_FXP_NAME packet the following looks
                    // at is the first part and that part is defined the same in SFTP versions 3 through 6.
                    list(, $filename) = Strings::unpackSSH2('Ns', $response);
                    return $filename;
                case NET_SFTP_STATUS:
                    $this->logError($response);
                    return false;
                default:
                    throw new \UnexpectedValueException('Expected NET_SFTP_NAME or NET_SFTP_STATUS. '
                                                      . 'Got packet type: ' . $this->packet_type);
            }
        }

        if (!strlen($path) || $path[0] != '/') {
            $path = $this->pwd . '/' . $path;
        }

        $path = explode('/', $path);
        $new = [];
        foreach ($path as $dir) {
            if (!strlen($dir)) {
                continue;
            }
            switch ($dir) {
                case '..':
                    array_pop($new);
                case '.':
                    break;
                default:
                    $new[] = $dir;
            }
        }

        return '/' . implode('/', $new);
    }

    /**
     * Changes the current directory
     *
     * @param string $dir
     * @throws \UnexpectedValueException on receipt of unexpected packets
     * @return bool
     * @access public
     */
    public function chdir($dir)
    {
        if (!$this->precheck()) {
            return false;
        }

        // assume current dir if $dir is empty
        if ($dir === '') {
            $dir = './';
        // suffix a slash if needed
        } elseif ($dir[strlen($dir) - 1] != '/') {
            $dir.= '/';
        }

        $dir = $this->realpath($dir);

        // confirm that $dir is, in fact, a valid directory
        if ($this->use_stat_cache && is_array($this->query_stat_cache($dir))) {
            $this->pwd = $dir;
            return true;
        }

        // we could do a stat on the alleged $dir to see if it's a directory but that doesn't tell us
        // the currently logged in user has the appropriate permissions or not. maybe you could see if
        // the file's uid / gid match the currently logged in user's uid / gid but how there's no easy
        // way to get those with SFTP

        $this->send_sftp_packet(NET_SFTP_OPENDIR, Strings::packSSH2('s', $dir));

        // see \phpseclib3\Net\SFTP::nlist() for a more thorough explanation of the following
        $response = $this->get_sftp_packet();
        switch ($this->packet_type) {
            case NET_SFTP_HANDLE:
                $handle = substr($response, 4);
                break;
            case NET_SFTP_STATUS:
                $this->logError($response);
                return false;
            default:
                throw new \UnexpectedValueException('Expected NET_SFTP_HANDLE or NET_SFTP_STATUS' .
                                                    'Got packet type: ' . $this->packet_type);
        }

        if (!$this->close_handle($handle)) {
            return false;
        }

        $this->update_stat_cache($dir, []);

        $this->pwd = $dir;
        return true;
    }

    /**
     * Returns a list of files in the given directory
     *
     * @param string $dir
     * @param bool $recursive
     * @return mixed
     * @access public
     */
    public function nlist($dir = '.', $recursive = false)
    {
        return $this->nlist_helper($dir, $recursive, '');
    }

    /**
     * Helper method for nlist
     *
     * @param string $dir
     * @param bool $recursive
     * @param string $relativeDir
     * @return mixed
     * @access private
     */
    private function nlist_helper($dir, $recursive, $relativeDir)
    {
        $files = $this->readlist($dir, false);

        if (!$recursive || $files === false) {
            return $files;
        }

        $result = [];
        foreach ($files as $value) {
            if ($value == '.' || $value == '..') {
                $result[] = $relativeDir . $value;
                continue;
            }
            if (is_array($this->query_stat_cache($this->realpath($dir . '/' . $value)))) {
                $temp = $this->nlist_helper($dir . '/' . $value, true, $relativeDir . $value . '/');
                $temp = is_array($temp) ? $temp : [];
                $result = array_merge($result, $temp);
            } else {
                $result[] = $relativeDir . $value;
            }
        }

        return $result;
    }

    /**
     * Returns a detailed list of files in the given directory
     *
     * @param string $dir
     * @param bool $recursive
     * @return mixed
     * @access public
     */
    public function rawlist($dir = '.', $recursive = false)
    {
        $files = $this->readlist($dir, true);
        if (!$recursive || $files === false) {
            return $files;
        }

        static $depth = 0;

        foreach ($files as $key => $value) {
            if ($depth != 0 && $key == '..') {
                unset($files[$key]);
                continue;
            }
            $is_directory = false;
            if ($key != '.' && $key != '..') {
                if ($this->use_stat_cache) {
                    $is_directory = is_array($this->query_stat_cache($this->realpath($dir . '/' . $key)));
                } else {
                    $stat = $this->lstat($dir . '/' . $key);
                    $is_directory = $stat && $stat['type'] === NET_SFTP_TYPE_DIRECTORY;
                }
            }

            if ($is_directory) {
                $depth++;
                $files[$key] = $this->rawlist($dir . '/' . $key, true);
                $depth--;
            } else {
                $files[$key] = (object) $value;
            }
        }

        return $files;
    }

    /**
     * Reads a list, be it detailed or not, of files in the given directory
     *
     * @param string $dir
     * @param bool $raw
     * @return mixed
     * @throws \UnexpectedValueException on receipt of unexpected packets
     * @access private
     */
    private function readlist($dir, $raw = true)
    {
        if (!$this->precheck()) {
            return false;
        }

        $dir = $this->realpath($dir . '/');
        if ($dir === false) {
            return false;
        }

        // http://tools.ietf.org/html/draft-ietf-secsh-filexfer-13#section-8.1.2
        $this->send_sftp_packet(NET_SFTP_OPENDIR, Strings::packSSH2('s', $dir));

        $response = $this->get_sftp_packet();
        switch ($this->packet_type) {
            case NET_SFTP_HANDLE:
                // http://tools.ietf.org/html/draft-ietf-secsh-filexfer-13#section-9.2
                // since 'handle' is the last field in the SSH_FXP_HANDLE packet, we'll just remove the first four bytes that
                // represent the length of the string and leave it at that
                $handle = substr($response, 4);
                break;
            case NET_SFTP_STATUS:
                // presumably SSH_FX_NO_SUCH_FILE or SSH_FX_PERMISSION_DENIED
                $this->logError($response);
                return false;
            default:
                throw new \UnexpectedValueException('Expected NET_SFTP_HANDLE or NET_SFTP_STATUS. '
                                                  . 'Got packet type: ' . $this->packet_type);
        }

        $this->update_stat_cache($dir, []);

        $contents = [];
        while (true) {
            // http://tools.ietf.org/html/draft-ietf-secsh-filexfer-13#section-8.2.2
            // why multiple SSH_FXP_READDIR packets would be sent when the response to a single one can span arbitrarily many
            // SSH_MSG_CHANNEL_DATA messages is not known to me.
            $this->send_sftp_packet(NET_SFTP_READDIR, Strings::packSSH2('s', $handle));

            $response = $this->get_sftp_packet();
            switch ($this->packet_type) {
                case NET_SFTP_NAME:
                    list($count) = Strings::unpackSSH2('N', $response);
                    for ($i = 0; $i < $count; $i++) {
                        list($shortname) = Strings::unpackSSH2('s', $response);
                        // SFTPv4 "removed the long filename from the names structure-- it can now be
                        //         built from information available in the attrs structure."
                        if ($this->version < 4) {
                            list($longname) = Strings::unpackSSH2('s', $response);
                        }
                        $attributes = $this->parseAttributes($response);
                        if (!isset($attributes['type']) && $this->version < 4) {
                            $fileType = $this->parseLongname($longname);
                            if ($fileType) {
                                $attributes['type'] = $fileType;
                            }
                        }
                        $contents[$shortname] = $attributes + ['filename' => $shortname];

                        if (isset($attributes['type']) && $attributes['type'] == NET_SFTP_TYPE_DIRECTORY && ($shortname != '.' && $shortname != '..')) {
                            $this->update_stat_cache($dir . '/' . $shortname, []);
                        } else {
                            if ($shortname == '..') {
                                $temp = $this->realpath($dir . '/..') . '/.';
                            } else {
                                $temp = $dir . '/' . $shortname;
                            }
                            $this->update_stat_cache($temp, (object) ['lstat' => $attributes]);
                        }
                        // SFTPv6 has an optional boolean end-of-list field, but we'll ignore that, since the
                        // final SSH_FXP_STATUS packet should tell us that, already.
                    }
                    break;
                case NET_SFTP_STATUS:
                    list($status) = Strings::unpackSSH2('N', $response);
                    if ($status != NET_SFTP_STATUS_EOF) {
                        $this->logError($response, $status);
                        return false;
                    }
                    break 2;
                default:
                    throw new \UnexpectedValueException('Expected NET_SFTP_NAME or NET_SFTP_STATUS. '
                                                      . 'Got packet type: ' . $this->packet_type);
            }
        }

        if (!$this->close_handle($handle)) {
            return false;
        }

        if (count($this->sortOptions)) {
            uasort($contents, [&$this, 'comparator']);
        }

        return $raw ? $contents : array_map('strval', array_keys($contents));
    }

    /**
     * Compares two rawlist entries using parameters set by setListOrder()
     *
     * Intended for use with uasort()
     *
     * @param array $a
     * @param array $b
     * @return int
     * @access private
     */
    private function comparator($a, $b)
    {
        switch (true) {
            case $a['filename'] === '.' || $b['filename'] === '.':
                if ($a['filename'] === $b['filename']) {
                    return 0;
                }
                return $a['filename'] === '.' ? -1 : 1;
            case $a['filename'] === '..' || $b['filename'] === '..':
                if ($a['filename'] === $b['filename']) {
                    return 0;
                }
                return $a['filename'] === '..' ? -1 : 1;
            case isset($a['type']) && $a['type'] === NET_SFTP_TYPE_DIRECTORY:
                if (!isset($b['type'])) {
                    return 1;
                }
                if ($b['type'] !== $a['type']) {
                    return -1;
                }
                break;
            case isset($b['type']) && $b['type'] === NET_SFTP_TYPE_DIRECTORY:
                return 1;
        }
        foreach ($this->sortOptions as $sort => $order) {
            if (!isset($a[$sort]) || !isset($b[$sort])) {
                if (isset($a[$sort])) {
                    return -1;
                }
                if (isset($b[$sort])) {
                    return 1;
                }
                return 0;
            }
            switch ($sort) {
                case 'filename':
                    $result = strcasecmp($a['filename'], $b['filename']);
                    if ($result) {
                        return $order === SORT_DESC ? -$result : $result;
                    }
                    break;
                case 'mode':
                    $a[$sort]&= 07777;
                    $b[$sort]&= 07777;
                default:
                    if ($a[$sort] === $b[$sort]) {
                        break;
                    }
                    return $order === SORT_ASC ? $a[$sort] - $b[$sort] : $b[$sort] - $a[$sort];
            }
        }
    }

    /**
     * Defines how nlist() and rawlist() will be sorted - if at all.
     *
     * If sorting is enabled directories and files will be sorted independently with
     * directories appearing before files in the resultant array that is returned.
     *
     * Any parameter returned by stat is a valid sort parameter for this function.
     * Filename comparisons are case insensitive.
     *
     * Examples:
     *
     * $sftp->setListOrder('filename', SORT_ASC);
     * $sftp->setListOrder('size', SORT_DESC, 'filename', SORT_ASC);
     * $sftp->setListOrder(true);
     *    Separates directories from files but doesn't do any sorting beyond that
     * $sftp->setListOrder();
     *    Don't do any sort of sorting
     *
     * @param string[] ...$args
     * @access public
     */
    public function setListOrder(...$args)
    {
        $this->sortOptions = [];
        if (empty($args)) {
            return;
        }
        $len = count($args) & 0x7FFFFFFE;
        for ($i = 0; $i < $len; $i+=2) {
            $this->sortOptions[$args[$i]] = $args[$i + 1];
        }
        if (!count($this->sortOptions)) {
            $this->sortOptions = ['bogus' => true];
        }
    }

    /**
     * Save files / directories to cache
     *
     * @param string $path
     * @param mixed $value
     * @access private
     */
    private function update_stat_cache($path, $value)
    {
        if ($this->use_stat_cache === false) {
            return;
        }

        // preg_replace('#^/|/(?=/)|/$#', '', $dir) == str_replace('//', '/', trim($path, '/'))
        $dirs = explode('/', preg_replace('#^/|/(?=/)|/$#', '', $path));

        $temp = &$this->stat_cache;
        $max = count($dirs) - 1;
        foreach ($dirs as $i => $dir) {
            // if $temp is an object that means one of two things.
            //  1. a file was deleted and changed to a directory behind phpseclib's back
            //  2. it's a symlink. when lstat is done it's unclear what it's a symlink to
            if (is_object($temp)) {
                $temp = [];
            }
            if (!isset($temp[$dir])) {
                $temp[$dir] = [];
            }
            if ($i === $max) {
                if (is_object($temp[$dir]) && is_object($value)) {
                    if (!isset($value->stat) && isset($temp[$dir]->stat)) {
                        $value->stat = $temp[$dir]->stat;
                    }
                    if (!isset($value->lstat) && isset($temp[$dir]->lstat)) {
                        $value->lstat = $temp[$dir]->lstat;
                    }
                }
                $temp[$dir] = $value;
                break;
            }
            $temp = &$temp[$dir];
        }
    }

    /**
     * Remove files / directories from cache
     *
     * @param string $path
     * @return bool
     * @access private
     */
    private function remove_from_stat_cache($path)
    {
        $dirs = explode('/', preg_replace('#^/|/(?=/)|/$#', '', $path));

        $temp = &$this->stat_cache;
        $max = count($dirs) - 1;
        foreach ($dirs as $i => $dir) {
            if (!is_array($temp)) {
                return false;
            }
            if ($i === $max) {
                unset($temp[$dir]);
                return true;
            }
            if (!isset($temp[$dir])) {
                return false;
            }
            $temp = &$temp[$dir];
        }
    }

    /**
     * Checks cache for path
     *
     * Mainly used by file_exists
     *
     * @param string $path
     * @return mixed
     * @access private
     */
    private function query_stat_cache($path)
    {
        $dirs = explode('/', preg_replace('#^/|/(?=/)|/$#', '', $path));

        $temp = &$this->stat_cache;
        foreach ($dirs as $dir) {
            if (!is_array($temp)) {
                return null;
            }
            if (!isset($temp[$dir])) {
                return null;
            }
            $temp = &$temp[$dir];
        }
        return $temp;
    }

    /**
     * Returns general information about a file.
     *
     * Returns an array on success and false otherwise.
     *
     * @param string $filename
     * @return mixed
     * @access public
     */
    public function stat($filename)
    {
        if (!$this->precheck()) {
            return false;
        }

        $filename = $this->realpath($filename);
        if ($filename === false) {
            return false;
        }

        if ($this->use_stat_cache) {
            $result = $this->query_stat_cache($filename);
            if (is_array($result) && isset($result['.']) && isset($result['.']->stat)) {
                return $result['.']->stat;
            }
            if (is_object($result) && isset($result->stat)) {
                return $result->stat;
            }
        }

        $stat = $this->stat_helper($filename, NET_SFTP_STAT);
        if ($stat === false) {
            $this->remove_from_stat_cache($filename);
            return false;
        }
        if (isset($stat['type'])) {
            if ($stat['type'] == NET_SFTP_TYPE_DIRECTORY) {
                $filename.= '/.';
            }
            $this->update_stat_cache($filename, (object) ['stat' => $stat]);
            return $stat;
        }

        $pwd = $this->pwd;
        $stat['type'] = $this->chdir($filename) ?
            NET_SFTP_TYPE_DIRECTORY :
            NET_SFTP_TYPE_REGULAR;
        $this->pwd = $pwd;

        if ($stat['type'] == NET_SFTP_TYPE_DIRECTORY) {
            $filename.= '/.';
        }
        $this->update_stat_cache($filename, (object) ['stat' => $stat]);

        return $stat;
    }

    /**
     * Returns general information about a file or symbolic link.
     *
     * Returns an array on success and false otherwise.
     *
     * @param string $filename
     * @return mixed
     * @access public
     */
    public function lstat($filename)
    {
        if (!$this->precheck()) {
            return false;
        }

        $filename = $this->realpath($filename);
        if ($filename === false) {
            return false;
        }

        if ($this->use_stat_cache) {
            $result = $this->query_stat_cache($filename);
            if (is_array($result) && isset($result['.']) && isset($result['.']->lstat)) {
                return $result['.']->lstat;
            }
            if (is_object($result) && isset($result->lstat)) {
                return $result->lstat;
            }
        }

        $lstat = $this->stat_helper($filename, NET_SFTP_LSTAT);
        if ($lstat === false) {
            $this->remove_from_stat_cache($filename);
            return false;
        }
        if (isset($lstat['type'])) {
            if ($lstat['type'] == NET_SFTP_TYPE_DIRECTORY) {
                $filename.= '/.';
            }
            $this->update_stat_cache($filename, (object) ['lstat' => $lstat]);
            return $lstat;
        }

        $stat = $this->stat_helper($filename, NET_SFTP_STAT);

        if ($lstat != $stat) {
            $lstat = array_merge($lstat, ['type' => NET_SFTP_TYPE_SYMLINK]);
            $this->update_stat_cache($filename, (object) ['lstat' => $lstat]);
            return $stat;
        }

        $pwd = $this->pwd;
        $lstat['type'] = $this->chdir($filename) ?
            NET_SFTP_TYPE_DIRECTORY :
            NET_SFTP_TYPE_REGULAR;
        $this->pwd = $pwd;

        if ($lstat['type'] == NET_SFTP_TYPE_DIRECTORY) {
            $filename.= '/.';
        }
        $this->update_stat_cache($filename, (object) ['lstat' => $lstat]);

        return $lstat;
    }

    /**
     * Returns general information about a file or symbolic link
     *
     * Determines information without calling \phpseclib3\Net\SFTP::realpath().
     * The second parameter can be either NET_SFTP_STAT or NET_SFTP_LSTAT.
     *
     * @param string $filename
     * @param int $type
     * @throws \UnexpectedValueException on receipt of unexpected packets
     * @return mixed
     * @access private
     */
    private function stat_helper($filename, $type)
    {
        // SFTPv4+ adds an additional 32-bit integer field - flags - to the following:
        $packet = Strings::packSSH2('s', $filename);
        $this->send_sftp_packet($type, $packet);

        $response = $this->get_sftp_packet();
        switch ($this->packet_type) {
            case NET_SFTP_ATTRS:
                return $this->parseAttributes($response);
            case NET_SFTP_STATUS:
                $this->logError($response);
                return false;
        }

        throw new \UnexpectedValueException('Expected NET_SFTP_ATTRS or NET_SFTP_STATUS. '
                                          . 'Got packet type: ' . $this->packet_type);
    }

    /**
     * Truncates a file to a given length
     *
     * @param string $filename
     * @param int $new_size
     * @return bool
     * @access public
     */
    public function truncate($filename, $new_size)
    {
        $attr = Strings::packSSH2('NQ', NET_SFTP_ATTR_SIZE, $new_size);

        return $this->setstat($filename, $attr, false);
    }

    /**
     * Sets access and modification time of file.
     *
     * If the file does not exist, it will be created.
     *
     * @param string $filename
     * @param int $time
     * @param int $atime
     * @throws \UnexpectedValueException on receipt of unexpected packets
     * @return bool
     * @access public
     */
    public function touch($filename, $time = null, $atime = null)
    {
        if (!$this->precheck()) {
            return false;
        }

        $filename = $this->realpath($filename);
        if ($filename === false) {
            return false;
        }

        if (!isset($time)) {
            $time = time();
        }
        if (!isset($atime)) {
            $atime = $time;
        }

        $attr = $this->version < 4 ?
            pack('N3', NET_SFTP_ATTR_ACCESSTIME, $atime, $time) :
            Strings::packSSH2('NQ2', NET_SFTP_ATTR_ACCESSTIME | NET_SFTP_ATTR_MODIFYTIME, $atime, $time);

        $packet = Strings::packSSH2('s', $filename);
        $packet.= $this->version >= 5 ?
            pack('N2', 0,…