Compatibility fixes

- PHP4 doesn't allow method chaining
- $_SESSION isn't always defined
- on PHP5.1 and earlier using 0x100000000 instead of 4294967296 gives E_NOTICE
- array('Net_SSH2', 'func_name') doesn't work so we fix this by passing $this to it.
  to make that work on PHP4 pass by call-time reference. normally this would result
  in a fatal error on PHP5.4+ but doesn't seem to in this case. the following URL
  elaborates:

  http://stackoverflow.com/q/20732563/569976

phpseclib/Crypt/Random.php

@@ -131,9 +131,7 @@ function crypt_random_string($length)
         $old_session_id = session_id();
         $old_use_cookies = ini_get('session.use_cookies');
         $old_session_cache_limiter = session_cache_limiter();
-        if (isset($_SESSION)) {
+        $_OLD_SESSION = isset($_SESSION) ? $_SESSION : false;
-            $_OLD_SESSION = $_SESSION;
-        }
         if ($old_session_id != '') {
             session_write_close();
         }
@@ -166,7 +164,7 @@ function crypt_random_string($length)
             ini_set('session.use_cookies', $old_use_cookies);
             session_cache_limiter($old_session_cache_limiter);
         } else {
-           if (isset($_OLD_SESSION)) {
+           if ($_OLD_SESSION !== false) {
                $_SESSION = $_OLD_SESSION;
                unset($_OLD_SESSION);
             } else {

phpseclib/Net/SFTP.php

@@ -402,7 +402,7 @@ class Net_SFTP extends Net_SSH2
     function login($username)
     {
         $args = func_get_args();
-        if (!call_user_func_array(array('Net_SSH2', 'login'), $args)) {
+        if (!call_user_func_array(array(&$this, '_login'), $args)) {
             return false;
         }
 
@@ -1042,7 +1042,7 @@ class Net_SFTP extends Net_SSH2
      */
     function truncate($filename, $new_size)
     {
-        $attr = pack('N3', NET_SFTP_ATTR_SIZE, $new_size / 0x100000000, $new_size);
+        $attr = pack('N3', NET_SFTP_ATTR_SIZE, $new_size / 4294967296, $new_size);
 
         return $this->_setstat($filename, $attr, false);
     }
@@ -1539,7 +1539,7 @@ class Net_SFTP extends Net_SSH2
         while ($sent < $size) {
             $temp = $mode & NET_SFTP_LOCAL_FILE ? fread($fp, $sftp_packet_size) : substr($data, $sent, $sftp_packet_size);
             $subtemp = $offset + $sent;
-            $packet = pack('Na*N3a*', strlen($handle), $handle, $subtemp / 0x100000000, $subtemp, strlen($temp), $temp);
+            $packet = pack('Na*N3a*', strlen($handle), $handle, $subtemp / 4294967296, $subtemp, strlen($temp), $temp);
             if (!$this->_send_sftp_packet(NET_SFTP_WRITE, $packet)) {
                 fclose($fp);
                 return false;
@@ -1687,7 +1687,7 @@ class Net_SFTP extends Net_SSH2
 
         $size = $this->max_sftp_packet < $length || $length < 0 ? $this->max_sftp_packet : $length;
         while (true) {
-            $packet = pack('Na*N3', strlen($handle), $handle, $offset / 0x100000000, $offset, $size);
+            $packet = pack('Na*N3', strlen($handle), $handle, $offset / 4294967296, $offset, $size);
             if (!$this->_send_sftp_packet(NET_SFTP_READ, $packet)) {
                 if ($local_file !== false) {
                     fclose($fp);
@@ -1925,7 +1925,7 @@ class Net_SFTP extends Net_SSH2
                     // (0xFFFFFFFF bytes), anyway.  as such, we'll just represent all file sizes that are bigger than
                     // 4GB as being 4GB.
                     extract(unpack('Nupper/Nsize', $this->_string_shift($response, 8)));
-                    $attr['size'] = $upper ? 0x100000000 * $upper : 0;
+                    $attr['size'] = $upper ? 4294967296 * $upper : 0;
                     $attr['size']+= $size < 0 ? ($size & 0x7FFFFFFF) + 0x80000000 : $size;
                     break;
                 case NET_SFTP_ATTR_UIDGID: // 0x00000002 (SFTPv3 only)

phpseclib/Net/SSH2.php

@@ -1284,7 +1284,8 @@ class Net_SSH2
            -- http://tools.ietf.org/html/rfc4419#section-6.2 */
         $one = new Math_BigInteger(1);
         $keyLength = min($keyLength, $kexHash->getLength());
-        $max = $one->bitwise_leftShift(16 * $keyLength)->subtract($one); // 2 * 8 * $keyLength
+        $max = $one->bitwise_leftShift(16 * $keyLength); // 2 * 8 * $keyLengt
+        $max->subtract($one);
 
         $x = $one->random($one, $max);
         $e = $g->modPow($x, $prime);
@@ -1671,10 +1672,26 @@ class Net_SSH2
      * @param Mixed $password
      * @param Mixed $...
      * @return Boolean
-     * @see _login_helper
+     * @see _login
      * @access public
      */
     function login($username)
+    {
+        $args = func_get_args();
+        return call_user_func_array(array(&$this, '_login'), $args);
+    }
+
+    /**
+     * Login Helper
+     *
+     * @param String $username
+     * @param Mixed $password
+     * @param Mixed $...
+     * @return Boolean
+     * @see _login_helper
+     * @access private
+     */
+    function _login($username)
     {
         $args = array_slice(func_get_args(), 1);
         if (empty($args)) {