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<?php

/**

 * Pure-PHP ssh-agent client.

 *

 * PHP version 5

 *

 * Here are some examples of how to use this library:

 * <code>

 * <?php

 *    include 'vendor/autoload.php';

 *

 *    $agent = new \phpseclib\System\SSH\Agent();

 *

 *    $ssh = new \phpseclib\Net\SSH2('www.domain.tld');

 *    if (!$ssh->login('username', $agent)) {

 *        exit('Login Failed');

 *    }

 *

 *    echo $ssh->exec('pwd');

 *    echo $ssh->exec('ls -la');

 * ?>

 * </code>

 *

 * @category  System

 * @package   SSH\Agent

 * @author    Jim Wigginton <terrafrost@php.net>

 * @copyright 2014 Jim Wigginton

 * @license   http://www.opensource.org/licenses/mit-license.html  MIT License

 * @link      http://phpseclib.sourceforge.net

 * @internal  See http://api.libssh.org/rfc/PROTOCOL.agent

 */

namespace phpseclib\System\SSH;

use phpseclib\Crypt\RSA;

use phpseclib\System\SSH\Agent\Identity;

/**

 * Pure-PHP ssh-agent client identity factory

 *

 * requestIdentities() method pumps out \phpseclib\System\SSH\Agent\Identity objects

 *

 * @package SSH\Agent

 * @author  Jim Wigginton <terrafrost@php.net>

 * @access  internal

 */

class Agent

{

    /**#@+

     * Message numbers

     *

     * @access private

     */

    // to request SSH1 keys you have to use SSH_AGENTC_REQUEST_RSA_IDENTITIES (1)

    const SSH_AGENTC_REQUEST_IDENTITIES = 11;

    // this is the SSH2 response; the SSH1 response is SSH_AGENT_RSA_IDENTITIES_ANSWER (2).

    const SSH_AGENT_IDENTITIES_ANSWER = 12;

    // the SSH1 request is SSH_AGENTC_RSA_CHALLENGE (3)

    const SSH_AGENTC_SIGN_REQUEST = 13;

    // the SSH1 response is SSH_AGENT_RSA_RESPONSE (4)

    const SSH_AGENT_SIGN_RESPONSE = 14;

    /**#@-*/

    /**@+

     * Agent forwarding status

     *

     * @access private

     */

    // no forwarding requested and not active

    const FORWARD_NONE = 0;

    // request agent forwarding when opportune

    const FORWARD_REQUEST = 1;

    // forwarding has been request and is active

    const FORWARD_ACTIVE = 2;

    /**#@-*/

    /**

     * Unused

     */

    const SSH_AGENT_FAILURE = 5;

    /**

     * Socket Resource

     *

     * @var resource

     * @access private

     */

    var $fsock;

    /**

     * Agent forwarding status

     *

     * @access private

     */

    var $forward_status = self::FORWARD_NONE;

    /**

     * Buffer for accumulating forwarded authentication

     * agent data arriving on SSH data channel destined

     * for agent unix socket

     *

     * @access private

     */

    var $socket_buffer = '';

    /**

     * Tracking the number of bytes we are expecting

     * to arrive for the agent socket on the SSH data

     * channel

     */

    var $expected_bytes = 0;

    /**

     * Default Constructor

     *

     * @return \phpseclib\System\SSH\Agent

     * @access public

     */

    function __construct()

    {

        switch (true) {

            case isset($_SERVER['SSH_AUTH_SOCK']):

                $address = $_SERVER['SSH_AUTH_SOCK'];

                break;

            case isset($_ENV['SSH_AUTH_SOCK']):

                $address = $_ENV['SSH_AUTH_SOCK'];

                break;

            default:

                user_error('SSH_AUTH_SOCK not found');

                return false;

        }

        $this->fsock = fsockopen('unix://' . $address, 0, $errno, $errstr);

        if (!$this->fsock) {

            user_error("Unable to connect to ssh-agent (Error $errno: $errstr)");

        }

    }

    /**

     * Request Identities

     *

     * See "2.5.2 Requesting a list of protocol 2 keys"

     * Returns an array containing zero or more \phpseclib\System\SSH\Agent\Identity objects

     *

     * @return array

     * @access public

     */

    function requestIdentities()

    {

        if (!$this->fsock) {

            return array();

        }

        $packet = pack('NC', 1, self::SSH_AGENTC_REQUEST_IDENTITIES);

        if (strlen($packet) != fputs($this->fsock, $packet)) {

            user_error('Connection closed while requesting identities');

        }

        $length = current(unpack('N', fread($this->fsock, 4)));

        $type = ord(fread($this->fsock, 1));

        if ($type != self::SSH_AGENT_IDENTITIES_ANSWER) {

            user_error('Unable to request identities');

        }

        $identities = array();

        $keyCount = current(unpack('N', fread($this->fsock, 4)));

        for ($i = 0; $i < $keyCount; $i++) {

            $length = current(unpack('N', fread($this->fsock, 4)));

            $key_blob = fread($this->fsock, $length);

            $key_str = 'ssh-rsa ' . base64_encode($key_blob);

            $length = current(unpack('N', fread($this->fsock, 4)));

            if ($length) {

                $key_str.= ' ' . fread($this->fsock, $length);

            }

            $length = current(unpack('N', substr($key_blob, 0, 4)));

            $key_type = substr($key_blob, 4, $length);

            switch ($key_type) {

                case 'ssh-rsa':

                    $key = new RSA();

                    $key->loadKey($key_str);

                    break;

                case 'ssh-dss':

                    // not currently supported

                    break;

            }

            // resources are passed by reference by default

            if (isset($key)) {

                $identity = new Identity($this->fsock);

                $identity->setPublicKey($key);

                $identity->setPublicKeyBlob($key_blob);

                $identities[] = $identity;

                unset($key);

            }

        }

        return $identities;

    }

    /**

     * Signal that agent forwarding should

     * be requested when a channel is opened

     *

     * @param Net_SSH2 $ssh

     * @return bool

     * @access public

     */

    function startSSHForwarding($ssh)

    {

        if ($this->forward_status == self::FORWARD_NONE) {

            $this->forward_status = self::FORWARD_REQUEST;

        }

    }

    /**

     * Request agent forwarding of remote server

     *

     * @param Net_SSH2 $ssh

     * @return bool

     * @access private

     */

    function _request_forwarding($ssh)

    {

        $request_channel = $ssh->_get_open_channel();

        if ($request_channel === false) {

            return false;

        }

        $packet = pack(

            'CNNa*C',

            NET_SSH2_MSG_CHANNEL_REQUEST,

            $ssh->server_channels[$request_channel],

            strlen('auth-agent-req@openssh.com'),

            'auth-agent-req@openssh.com',

            1

        );

        $ssh->channel_status[$request_channel] = NET_SSH2_MSG_CHANNEL_REQUEST;

        if (!$ssh->_send_binary_packet($packet)) {

            return false;

        }

        $response = $ssh->_get_channel_packet($request_channel);

        if ($response === false) {

            return false;

        }

        $ssh->channel_status[$request_channel] = NET_SSH2_MSG_CHANNEL_OPEN;

        $this->forward_status = self::FORWARD_ACTIVE;

        return true;

    }

    /**

     * On successful channel open

     *

     * This method is called upon successful channel

     * open to give the SSH Agent an opportunity

     * to take further action. i.e. request agent forwarding

     *

     * @param Net_SSH2 $ssh

     * @access private

     */

    function _on_channel_open($ssh)

    {

        if ($this->forward_status == self::FORWARD_REQUEST) {

            $this->_request_forwarding($ssh);

        }

    }

    /**

     * Forward data to SSH Agent and return data reply

     *

     * @param string $data

     * @return data from SSH Agent

     * @access private

     */

    function _forward_data($data)

    {

        if ($this->expected_bytes > 0) {

            $this->socket_buffer.= $data;

            $this->expected_bytes -= strlen($data);

        } else {

            $agent_data_bytes = current(unpack('N', $data));

            $current_data_bytes = strlen($data);

            $this->socket_buffer = $data;

            if ($current_data_bytes != $agent_data_bytes + 4) {

                $this->expected_bytes = ($agent_data_bytes + 4) - $current_data_bytes;

                return false;

            }

        }

        if (strlen($this->socket_buffer) != fwrite($this->fsock, $this->socket_buffer)) {

            user_error('Connection closed attempting to forward data to SSH agent');

        }

        $this->socket_buffer = '';

        $this->expected_bytes = 0;

        $agent_reply_bytes = current(unpack('N', fread($this->fsock, 4)));

        $agent_reply_data = fread($this->fsock, $agent_reply_bytes);

        $agent_reply_data = current(unpack('a*', $agent_reply_data));

        return pack('Na*', $agent_reply_bytes, $agent_reply_data);

    }

}