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   1  <?php
   2  
   3  /**
   4   * Pure-PHP ssh-agent client.
   5   *
   6   * PHP version 5
   7   *
   8   * Here are some examples of how to use this library:
   9   * <code>
  10   * <?php
  11   *    include 'vendor/autoload.php';
  12   *
  13   *    $agent = new \phpseclib\System\SSH\Agent();
  14   *
  15   *    $ssh = new \phpseclib\Net\SSH2('www.domain.tld');
  16   *    if (!$ssh->login('username', $agent)) {
  17   *        exit('Login Failed');
  18   *    }
  19   *
  20   *    echo $ssh->exec('pwd');
  21   *    echo $ssh->exec('ls -la');
  22   * ?>
  23   * </code>
  24   *
  25   * @category  System
  26   * @package   SSH\Agent
  27   * @author    Jim Wigginton <terrafrost@php.net>
  28   * @copyright 2014 Jim Wigginton
  29   * @license   http://www.opensource.org/licenses/mit-license.html  MIT License
  30   * @link      http://phpseclib.sourceforge.net
  31   * @internal  See http://api.libssh.org/rfc/PROTOCOL.agent
  32   */
  33  
  34  namespace phpseclib\System\SSH;
  35  
  36  use phpseclib\Crypt\RSA;
  37  use phpseclib\System\SSH\Agent\Identity;
  38  
  39  /**
  40   * Pure-PHP ssh-agent client identity factory
  41   *
  42   * requestIdentities() method pumps out \phpseclib\System\SSH\Agent\Identity objects
  43   *
  44   * @package SSH\Agent
  45   * @author  Jim Wigginton <terrafrost@php.net>
  46   * @access  public
  47   */
  48  class Agent
  49  {
  50      /**#@+
  51       * Message numbers
  52       *
  53       * @access private
  54       */
  55      // to request SSH1 keys you have to use SSH_AGENTC_REQUEST_RSA_IDENTITIES (1)
  56      const SSH_AGENTC_REQUEST_IDENTITIES = 11;
  57      // this is the SSH2 response; the SSH1 response is SSH_AGENT_RSA_IDENTITIES_ANSWER (2).
  58      const SSH_AGENT_IDENTITIES_ANSWER = 12;
  59      // the SSH1 request is SSH_AGENTC_RSA_CHALLENGE (3)
  60      const SSH_AGENTC_SIGN_REQUEST = 13;
  61      // the SSH1 response is SSH_AGENT_RSA_RESPONSE (4)
  62      const SSH_AGENT_SIGN_RESPONSE = 14;
  63      /**#@-*/
  64  
  65      /**@+
  66       * Agent forwarding status
  67       *
  68       * @access private
  69       */
  70      // no forwarding requested and not active
  71      const FORWARD_NONE = 0;
  72      // request agent forwarding when opportune
  73      const FORWARD_REQUEST = 1;
  74      // forwarding has been request and is active
  75      const FORWARD_ACTIVE = 2;
  76      /**#@-*/
  77  
  78      /**
  79       * Unused
  80       */
  81      const SSH_AGENT_FAILURE = 5;
  82  
  83      /**
  84       * Socket Resource
  85       *
  86       * @var resource
  87       * @access private
  88       */
  89      var $fsock;
  90  
  91      /**
  92       * Agent forwarding status
  93       *
  94       * @access private
  95       */
  96      var $forward_status = self::FORWARD_NONE;
  97  
  98      /**
  99       * Buffer for accumulating forwarded authentication
 100       * agent data arriving on SSH data channel destined
 101       * for agent unix socket
 102       *
 103       * @access private
 104       */
 105      var $socket_buffer = '';
 106  
 107      /**
 108       * Tracking the number of bytes we are expecting
 109       * to arrive for the agent socket on the SSH data
 110       * channel
 111       */
 112      var $expected_bytes = 0;
 113  
 114      /**
 115       * Default Constructor
 116       *
 117       * @return \phpseclib\System\SSH\Agent
 118       * @access public
 119       */
 120      function __construct($address = null)
 121      {
 122          if (!$address) {
 123              switch (true) {
 124                  case isset($_SERVER['SSH_AUTH_SOCK']):
 125                      $address = $_SERVER['SSH_AUTH_SOCK'];
 126                      break;
 127                  case isset($_ENV['SSH_AUTH_SOCK']):
 128                      $address = $_ENV['SSH_AUTH_SOCK'];
 129                      break;
 130                  default:
 131                      user_error('SSH_AUTH_SOCK not found');
 132                      return false;
 133              }
 134          }
 135  
 136          $this->fsock = fsockopen('unix://' . $address, 0, $errno, $errstr);
 137          if (!$this->fsock) {
 138              user_error("Unable to connect to ssh-agent (Error $errno: $errstr)");
 139          }
 140      }
 141  
 142      /**
 143       * Request Identities
 144       *
 145       * See "2.5.2 Requesting a list of protocol 2 keys"
 146       * Returns an array containing zero or more \phpseclib\System\SSH\Agent\Identity objects
 147       *
 148       * @return array
 149       * @access public
 150       */
 151      function requestIdentities()
 152      {
 153          if (!$this->fsock) {
 154              return array();
 155          }
 156  
 157          $packet = pack('NC', 1, self::SSH_AGENTC_REQUEST_IDENTITIES);
 158          if (strlen($packet) != fputs($this->fsock, $packet)) {
 159              user_error('Connection closed while requesting identities');
 160              return array();
 161          }
 162  
 163          $temp = fread($this->fsock, 4);
 164          if (strlen($temp) != 4) {
 165              user_error('Connection closed while requesting identities');
 166              return array();
 167          }
 168          $length = current(unpack('N', $temp));
 169          $type = ord(fread($this->fsock, 1));
 170          if ($type != self::SSH_AGENT_IDENTITIES_ANSWER) {
 171              user_error('Unable to request identities');
 172              return array();
 173          }
 174  
 175          $identities = array();
 176          $temp = fread($this->fsock, 4);
 177          if (strlen($temp) != 4) {
 178              user_error('Connection closed while requesting identities');
 179              return array();
 180          }
 181          $keyCount = current(unpack('N', $temp));
 182          for ($i = 0; $i < $keyCount; $i++) {
 183              $temp = fread($this->fsock, 4);
 184              if (strlen($temp) != 4) {
 185                  user_error('Connection closed while requesting identities');
 186                  return array();
 187              }
 188              $length = current(unpack('N', $temp));
 189              $key_blob = fread($this->fsock, $length);
 190              if (strlen($key_blob) != $length) {
 191                  user_error('Connection closed while requesting identities');
 192                  return array();
 193              }
 194              $key_str = 'ssh-rsa ' . base64_encode($key_blob);
 195              $temp = fread($this->fsock, 4);
 196              if (strlen($temp) != 4) {
 197                  user_error('Connection closed while requesting identities');
 198                  return array();
 199              }
 200              $length = current(unpack('N', $temp));
 201              if ($length) {
 202                  $temp = fread($this->fsock, $length);
 203                  if (strlen($temp) != $length) {
 204                      user_error('Connection closed while requesting identities');
 205                      return array();
 206                  }
 207                  $key_str.= ' ' . $temp;
 208              }
 209              $length = current(unpack('N', substr($key_blob, 0, 4)));
 210              $key_type = substr($key_blob, 4, $length);
 211              switch ($key_type) {
 212                  case 'ssh-rsa':
 213                      $key = new RSA();
 214                      $key->loadKey($key_str);
 215                      break;
 216                  case 'ssh-dss':
 217                      // not currently supported
 218                      break;
 219              }
 220              // resources are passed by reference by default
 221              if (isset($key)) {
 222                  $identity = new Identity($this->fsock);
 223                  $identity->setPublicKey($key);
 224                  $identity->setPublicKeyBlob($key_blob);
 225                  $identities[] = $identity;
 226                  unset($key);
 227              }
 228          }
 229  
 230          return $identities;
 231      }
 232  
 233      /**
 234       * Signal that agent forwarding should
 235       * be requested when a channel is opened
 236       *
 237       * @param Net_SSH2 $ssh
 238       * @return bool
 239       * @access public
 240       */
 241      function startSSHForwarding($ssh)
 242      {
 243          if ($this->forward_status == self::FORWARD_NONE) {
 244              $this->forward_status = self::FORWARD_REQUEST;
 245          }
 246      }
 247  
 248      /**
 249       * Request agent forwarding of remote server
 250       *
 251       * @param Net_SSH2 $ssh
 252       * @return bool
 253       * @access private
 254       */
 255      function _request_forwarding($ssh)
 256      {
 257          $request_channel = $ssh->_get_open_channel();
 258          if ($request_channel === false) {
 259              return false;
 260          }
 261  
 262          $packet = pack(
 263              'CNNa*C',
 264              NET_SSH2_MSG_CHANNEL_REQUEST,
 265              $ssh->server_channels[$request_channel],
 266              strlen('auth-agent-req@openssh.com'),
 267              'auth-agent-req@openssh.com',
 268              1
 269          );
 270  
 271          $ssh->channel_status[$request_channel] = NET_SSH2_MSG_CHANNEL_REQUEST;
 272  
 273          if (!$ssh->_send_binary_packet($packet)) {
 274              return false;
 275          }
 276  
 277          $response = $ssh->_get_channel_packet($request_channel);
 278          if ($response === false) {
 279              return false;
 280          }
 281  
 282          $ssh->channel_status[$request_channel] = NET_SSH2_MSG_CHANNEL_OPEN;
 283          $this->forward_status = self::FORWARD_ACTIVE;
 284  
 285          return true;
 286      }
 287  
 288      /**
 289       * On successful channel open
 290       *
 291       * This method is called upon successful channel
 292       * open to give the SSH Agent an opportunity
 293       * to take further action. i.e. request agent forwarding
 294       *
 295       * @param Net_SSH2 $ssh
 296       * @access private
 297       */
 298      function _on_channel_open($ssh)
 299      {
 300          if ($this->forward_status == self::FORWARD_REQUEST) {
 301              $this->_request_forwarding($ssh);
 302          }
 303      }
 304  
 305      /**
 306       * Forward data to SSH Agent and return data reply
 307       *
 308       * @param string $data
 309       * @return data from SSH Agent
 310       * @access private
 311       */
 312      function _forward_data($data)
 313      {
 314          if ($this->expected_bytes > 0) {
 315              $this->socket_buffer.= $data;
 316              $this->expected_bytes -= strlen($data);
 317          } else {
 318              $agent_data_bytes = current(unpack('N', $data));
 319              $current_data_bytes = strlen($data);
 320              $this->socket_buffer = $data;
 321              if ($current_data_bytes != $agent_data_bytes + 4) {
 322                  $this->expected_bytes = ($agent_data_bytes + 4) - $current_data_bytes;
 323                  return false;
 324              }
 325          }
 326  
 327          if (strlen($this->socket_buffer) != fwrite($this->fsock, $this->socket_buffer)) {
 328              user_error('Connection closed attempting to forward data to SSH agent');
 329              return false;
 330          }
 331  
 332          $this->socket_buffer = '';
 333          $this->expected_bytes = 0;
 334  
 335          $temp = fread($this->fsock, 4);
 336          if (strlen($temp) != 4) {
 337              user_error('Connection closed while reading data response');
 338              return false;
 339          }
 340          $agent_reply_bytes = current(unpack('N', $temp));
 341  
 342          $agent_reply_data = fread($this->fsock, $agent_reply_bytes);
 343          if (strlen($agent_reply_data) != $agent_reply_bytes) {
 344              user_error('Connection closed while reading data response');
 345              return false;
 346          }
 347          $agent_reply_data = current(unpack('a*', $agent_reply_data));
 348  
 349          return pack('Na*', $agent_reply_bytes, $agent_reply_data);
 350      }
 351  }