phpseclib\Net\SSH2::_filter PHP Method

    function _filter($payload)
    {
        switch (ord($payload[0])) {
            case NET_SSH2_MSG_DISCONNECT:
                Strings::shift($payload, 1);
                if (strlen($payload) < 8) {
                    return false;
                }
                extract(unpack('Nreason_code/Nlength', Strings::shift($payload, 8)));
                $this->errors[] = 'SSH_MSG_DISCONNECT: ' . $this->disconnect_reasons[$reason_code] . "\r\n" . utf8_decode(Strings::shift($payload, $length));
                $this->bitmap = 0;
                return false;
            case NET_SSH2_MSG_IGNORE:
                $payload = $this->_get_binary_packet();
                break;
            case NET_SSH2_MSG_DEBUG:
                Strings::shift($payload, 2);
                if (strlen($payload) < 4) {
                    return false;
                }
                extract(unpack('Nlength', Strings::shift($payload, 4)));
                $this->errors[] = 'SSH_MSG_DEBUG: ' . utf8_decode(Strings::shift($payload, $length));
                $payload = $this->_get_binary_packet();
                break;
            case NET_SSH2_MSG_UNIMPLEMENTED:
                return false;
            case NET_SSH2_MSG_KEXINIT:
                if ($this->session_id !== false) {
                    if (!$this->_key_exchange($payload)) {
                        $this->bitmap = 0;
                        return false;
                    }
                    $payload = $this->_get_binary_packet();
                }
        }
        // see http://tools.ietf.org/html/rfc4252#section-5.4; only called when the encryption has been activated and when we haven't already logged in
        if ($this->bitmap & self::MASK_CONNECTED && !($this->bitmap & self::MASK_LOGIN) && ord($payload[0]) == NET_SSH2_MSG_USERAUTH_BANNER) {
            Strings::shift($payload, 1);
            if (strlen($payload) < 4) {
                return false;
            }
            extract(unpack('Nlength', Strings::shift($payload, 4)));
            $this->banner_message = utf8_decode(Strings::shift($payload, $length));
            $payload = $this->_get_binary_packet();
        }
        // only called when we've already logged in
        if ($this->bitmap & self::MASK_CONNECTED && $this->bitmap & self::MASK_LOGIN) {
            switch (ord($payload[0])) {
                case NET_SSH2_MSG_GLOBAL_REQUEST:
                    // see http://tools.ietf.org/html/rfc4254#section-4
                    if (strlen($payload) < 4) {
                        return false;
                    }
                    extract(unpack('Nlength', Strings::shift($payload, 4)));
                    $this->errors[] = 'SSH_MSG_GLOBAL_REQUEST: ' . Strings::shift($payload, $length);
                    if (!$this->_send_binary_packet(pack('C', NET_SSH2_MSG_REQUEST_FAILURE))) {
                        return $this->_disconnect(NET_SSH2_DISCONNECT_BY_APPLICATION);
                    }
                    $payload = $this->_get_binary_packet();
                    break;
                case NET_SSH2_MSG_CHANNEL_OPEN:
                    // see http://tools.ietf.org/html/rfc4254#section-5.1
                    Strings::shift($payload, 1);
                    if (strlen($payload) < 4) {
                        return false;
                    }
                    extract(unpack('Nlength', Strings::shift($payload, 4)));
                    $data = Strings::shift($payload, $length);
                    if (strlen($payload) < 4) {
                        return false;
                    }
                    extract(unpack('Nserver_channel', Strings::shift($payload, 4)));
                    switch ($data) {
                        case 'auth-agent':
                        case '[email protected]':
                            if (isset($this->agent)) {
                                $new_channel = self::CHANNEL_AGENT_FORWARD;
                                if (strlen($payload) < 8) {
                                    return false;
                                }
                                extract(unpack('Nremote_window_size', Strings::shift($payload, 4)));
                                extract(unpack('Nremote_maximum_packet_size', Strings::shift($payload, 4)));
                                $this->packet_size_client_to_server[$new_channel] = $remote_window_size;
                                $this->window_size_server_to_client[$new_channel] = $remote_maximum_packet_size;
                                $this->window_size_client_to_server[$new_channel] = $this->window_size;
                                $packet_size = 0x4000;
                                $packet = pack('CN4', NET_SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, $server_channel, $new_channel, $packet_size, $packet_size);
                                $this->server_channels[$new_channel] = $server_channel;
                                $this->channel_status[$new_channel] = NET_SSH2_MSG_CHANNEL_OPEN_CONFIRMATION;
                                if (!$this->_send_binary_packet($packet)) {
                                    return false;
                                }
                            }
                            break;
                        default:
                            $packet = pack('CN3a*Na*', NET_SSH2_MSG_REQUEST_FAILURE, $server_channel, NET_SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED, 0, '', 0, '');
                            if (!$this->_send_binary_packet($packet)) {
                                return $this->_disconnect(NET_SSH2_DISCONNECT_BY_APPLICATION);
                            }
                    }
                    $payload = $this->_get_binary_packet();
                    break;
                case NET_SSH2_MSG_CHANNEL_WINDOW_ADJUST:
                    Strings::shift($payload, 1);
                    if (strlen($payload) < 8) {
                        return false;
                    }
                    extract(unpack('Nchannel', Strings::shift($payload, 4)));
                    extract(unpack('Nwindow_size', Strings::shift($payload, 4)));
                    $this->window_size_client_to_server[$channel] += $window_size;
                    $payload = $this->bitmap & self::MASK_WINDOW_ADJUST ? true : $this->_get_binary_packet();
            }
        }
        return $payload;
    }