def parse_name(data, offset):
    p = offset
    labels = []
    # l为data数据流中的偏置offset的label的长度
    l = common.ord(data[p])
    while l > 0:
        # 为什么是128+64, 因为未经压缩的合法name长度在63内，因此
        # rfc定义0x11000000B为压缩指针的标志
        if (l & (128 + 64)) == (128 + 64):
            # 取出指针的位置
            pointer = struct.unpack('!H', data[p:p + 2])[0]
            # 指针取两个字节减去高两位（用于标志0x11000000B那两位）
            pointer &= 0x3FFF
            # 递归处理指针，找到上文的name记录，参考rfc1035
            r = parse_name(data, pointer)
            # 读取指针所指的数据，追加到labels中
            labels.append(r[1])
            # 指针偏移自增两个字节（跳过0x11000000B所在的两个字节的data数据段）
            p += 2
            # 递归返回
            return p - offset, b'.'.join(labels)
        # 若不是指针压缩，直接追加dns报文
        else:
            # 追加labels
            labels.append(data[p + 1:p + 1 + l])
            # 指针自增（1+len）
            p += 1 + l
        l = common.ord(data[p])
    # 递归返回
    return p - offset + 1, b'.'.join(labels)

    def server_post_decrypt(self, buf):
        if self.raw_trans:
            return (buf, False)
        self.recv_buf += buf
        out_buf = b''
        if not self.has_recv_header:
            if len(self.recv_buf) < 2:
                return (b'', False)
            if (ord(self.recv_buf[0]) & 0x10) != 0x10:
                return self.not_match_return(self.recv_buf)
            head_size = self.get_head_size(self.recv_buf, 65536)
            if len(self.recv_buf) < head_size + 10:
                return self.not_match_return(self.recv_buf)
            sha1data = hmac.new(self.server_info.recv_iv + self.server_info.key, self.recv_buf[:head_size], hashlib.sha1).digest()[:10]
            if sha1data != self.recv_buf[head_size:head_size + 10]:
                logging.error('server_post_decrype data uncorrect auth HMAC-SHA1')
                return self.not_match_return(self.recv_buf)
            out_buf = to_bytes(chr(ord(self.recv_buf[0]) & 0xEF)) + self.recv_buf[1:head_size]
            self.recv_buf = self.recv_buf[head_size + 10:]
            self.has_recv_header = True
        while len(self.recv_buf) > 2:
            length = struct.unpack('>H', self.recv_buf[:2])[0] + 12
            if length > len(self.recv_buf):
                break

            data = self.recv_buf[12:length]
            sha1data = hmac.new(self.server_info.recv_iv + struct.pack('>I', self.recv_id), data, hashlib.sha1).digest()[:10]
            if sha1data != self.recv_buf[2:12]:
                raise Exception('server_post_decrype data uncorrect chunk HMAC-SHA1')

            self.recv_id = (self.recv_id + 1) & 0xFFFFFFFF
            out_buf += data
            self.recv_buf = self.recv_buf[length:]

        return (out_buf, False)

def parse_name(data, offset):
    """
    提取NAME字段
    :param data:        接收到的数据
    :param offset:      name字段的偏移量
    :return:            (l, r) l name字段的长度，r 解析出的数据
    """
    p = offset
    labels = []
    l = common.ord(data[p])
    while l > 0:
        if (l & (128 + 64)) == (128 + 64):
            # pointer
            pointer = struct.unpack('!H', data[p:p + 2])[0]
            pointer &= 0x3FFF
            r = parse_name(data, pointer)
            labels.append(r[1])
            p += 2
            # pointer is the end
            return p - offset, b'.'.join(labels)
        else:
            labels.append(data[p + 1:p + 1 + l])
            p += 1 + l
        l = common.ord(data[p])
    return p - offset + 1, b'.'.join(labels)

 def get_head_size(self, buf, def_value):
     if len(buf) < 2:
         return def_value
     if ord(buf[0]) == 1:
         return 7
     if ord(buf[0]) == 4:
         return 19
     if ord(buf[0]) == 3:
         return 4 + ord(buf[1])
     return def_value

 def server_udp_post_decrypt(self, buf):
     if buf and ((ord(buf[0]) & 0x10) == 0x10):
         if len(buf) <= 11:
             return b''
         sha1data = hmac.new(self.server_info.recv_iv + self.server_info.key, buf[:-10], hashlib.sha1).digest()[:10]
         if sha1data != buf[-10:]:
             return b''
         return to_bytes(chr(ord(buf[0]) & 0xEF)) + buf[1:-10]
     else:
         return buf

 def get_head_size(self, buf, def_value):
     if len(buf) < 2:
         return def_value
     head_type = ord(buf[0]) & 0x7
     if head_type == 1:
         return 7
     if head_type == 4:
         return 19
     if head_type == 3:
         return 4 + ord(buf[1])
     return def_value

 def _get_head_size(self, buf, def_value):
     if len(buf) < 2:
         return def_value
     head_type = common.ord(buf[0]) & 0xF
     if head_type == 1:
         return 7
     if head_type == 4:
         return 19
     if head_type == 3:
         return 4 + common.ord(buf[1])
     return def_value

 def server_udp_post_decrypt(self, buf):
     if buf and ((ord(buf[0]) & 0x10) == 0x10):
         if len(buf) <= 11:
             return b'E'
         sha1data = hmac.new(self.server_info.recv_iv + self.server_info.key, buf[:-10], hashlib.sha1).digest()[:10]
         if sha1data != buf[-10:]:
             logging.error('server_udp_post_decrypt data uncorrect auth HMAC-SHA1')
             return b'E'
         return to_bytes(chr(ord(buf[0]) & 0xEF)) + buf[1:-10]
     else:
         return buf

def test_nonce_increment():
    buf = create_string_buffer(12)
    print("".join("%02x" % ord(b) for b in buf))
    nonce_increment(buf, 12)
    nonce_increment(buf, 12)
    nonce_increment(buf, 12)
    nonce_increment(buf, 12)
    print("".join("%02x" % ord(b) for b in buf))
    for i in range(256):
        nonce_increment(buf, 12)
        print("".join("%02x" % ord(b) for b in buf))

    def server_post_decrypt(self, buf):
        if self.raw_trans:
            return buf
        self.recv_buf += buf
        out_buf = b''
        while len(self.recv_buf) > 2:
            length = struct.unpack('>H', self.recv_buf[:2])[0]
            if length >= 8192:
                self.raw_trans = True
                self.recv_buf = b''
                if self.decrypt_packet_num == 0:
                    logging.info('auth_simple: over size')
                    return b'E'
                else:
                    raise Exception('server_post_decrype data error')
            if length > len(self.recv_buf):
                break

            if (binascii.crc32(self.recv_buf[:length]) & 0xffffffff) != 0xffffffff:
                logging.info('auth_simple: crc32 error, data %s' % (binascii.hexlify(self.recv_buf[:length]),))
                self.raw_trans = True
                self.recv_buf = b''
                if self.decrypt_packet_num == 0:
                    return b'E'
                else:
                    raise Exception('server_post_decrype data uncorrect CRC32')

            pos = common.ord(self.recv_buf[2]) + 2
            out_buf += self.recv_buf[pos:length - 4]
            if not self.has_recv_header:
                if len(out_buf) < 12:
                    self.raw_trans = True
                    self.recv_buf = b''
                    logging.info('auth_simple: too short')
                    return b'E'
                utc_time = struct.unpack('<I', out_buf[:4])[0]
                client_id = struct.unpack('<I', out_buf[4:8])[0]
                connection_id = struct.unpack('<I', out_buf[8:12])[0]
                time_dif = common.int32((int(time.time()) & 0xffffffff) - utc_time)
                if time_dif < 60 * -3 or time_dif > 60 * 3 or common.int32(utc_time - self.server_info.data.startup_time) < 0:
                    self.raw_trans = True
                    self.recv_buf = b''
                    logging.info('auth_simple: wrong timestamp, time_dif %d, data %s' % (time_dif, binascii.hexlify(out_buf),))
                    return b'E'
                elif self.server_info.data.insert(client_id, connection_id):
                    self.has_recv_header = True
                    out_buf = out_buf[12:]
                    self.client_id = client_id
                    self.connection_id = connection_id
                else:
                    self.raw_trans = True
                    self.recv_buf = b''
                    logging.info('auth_simple: auth fail, data %s' % (binascii.hexlify(out_buf),))
                    return b'E'
            self.recv_buf = self.recv_buf[length:]

        if out_buf:
            self.server_info.data.update(self.client_id, self.connection_id)
            self.decrypt_packet_num += 1
        return out_buf

 def pack_data(self, buf):
     rnd_data = os.urandom(common.ord(os.urandom(1)[0]) % 16)
     data = common.chr(len(rnd_data) + 1) + rnd_data + buf
     data = struct.pack('>H', len(data) + 6) + data
     adler32 = zlib.adler32(data) & 0xFFFFFFFF
     data += struct.pack('<I', adler32)
     return data

    def client_post_decrypt(self, buf):
        if self.raw_trans:
            return buf
        self.recv_buf += buf
        out_buf = b''
        while len(self.recv_buf) > 4:
            mac_key = self.user_key + struct.pack('<I', self.recv_id)
            mac = hmac.new(mac_key, self.recv_buf[:2], self.hashfunc).digest()[:2]
            if mac != self.recv_buf[2:4]:
                raise Exception('client_post_decrypt data uncorrect mac')
            length = struct.unpack('<H', self.recv_buf[:2])[0]
            if length >= 8192 or length < 7:
                self.raw_trans = True
                self.recv_buf = b''
                raise Exception('client_post_decrypt data error')
            if length > len(self.recv_buf):
                break

            if hmac.new(mac_key, self.recv_buf[:length - 4], self.hashfunc).digest()[:4] != self.recv_buf[length - 4:length]:
                self.raw_trans = True
                self.recv_buf = b''
                raise Exception('client_post_decrypt data uncorrect checksum')

            self.recv_id = (self.recv_id + 1) & 0xFFFFFFFF
            pos = common.ord(self.recv_buf[4])
            if pos < 255:
                pos += 4
            else:
                pos = struct.unpack('<H', self.recv_buf[5:7])[0] + 4
            out_buf += self.recv_buf[pos:length - 4]
            self.recv_buf = self.recv_buf[length:]

        return out_buf

    def client_post_decrypt(self, buf):
        if self.raw_trans:
            return buf
        self.recv_buf += buf
        out_buf = b''
        while len(self.recv_buf) > 2:
            length = struct.unpack('>H', self.recv_buf[:2])[0]
            if length >= 8192 or length < 7:
                self.raw_trans = True
                self.recv_buf = b''
                raise Exception('client_post_decrypt data error')
            if length > len(self.recv_buf):
                break

            if struct.pack('<I', zlib.adler32(self.recv_buf[:length - 4]) & 0xFFFFFFFF) != self.recv_buf[length - 4:length]:
                self.raw_trans = True
                self.recv_buf = b''
                raise Exception('client_post_decrypt data uncorrect checksum')

            pos = common.ord(self.recv_buf[2])
            if pos < 255:
                pos += 2
            else:
                pos = struct.unpack('>H', self.recv_buf[3:5])[0] + 2
            out_buf += self.recv_buf[pos:length - 4]
            self.recv_buf = self.recv_buf[length:]

        if out_buf:
            self.decrypt_packet_num += 1
        return out_buf

    def client_decode(self, buf):
        if self.handshake_status == -1:
            return (buf, False)

        if self.handshake_status == 8:
            ret = b''
            self.recv_buffer += buf
            while len(self.recv_buffer) > 5:
                if ord(self.recv_buffer[0]) != 0x17:
                    logging.info("data = %s" % (binascii.hexlify(self.recv_buffer)))
                    raise Exception('server_decode appdata error')
                size = struct.unpack('>H', self.recv_buffer[3:5])[0]
                if len(self.recv_buffer) < size + 5:
                    break
                buf = self.recv_buffer[5:size+5]
                ret += buf
                self.recv_buffer = self.recv_buffer[size+5:]
            return (ret, False)

        if len(buf) < 11 + 32 + 1 + 32:
            raise Exception('client_decode data error')
        verify = buf[11:33]
        if hmac.new(self.server_info.key + self.server_info.data.client_id, verify, hashlib.sha1).digest()[:10] != buf[33:43]:
            raise Exception('client_decode data error')
        return (b'', True)

    def _handle_stage_addr(self, data):
        try:
            if self._is_local:
                cmd = common.ord(data[1])
                if cmd == CMD_UDP_ASSOCIATE:
                    logging.debug('UDP associate')
                    if self._local_sock.family == socket.AF_INET6:
                        header = b'\x05\x00\x00\x04'
                    else:
                        header = b'\x05\x00\x00\x01'
                    addr, port = self._local_sock.getsockname()[:2]
                    addr_to_send = socket.inet_pton(self._local_sock.family,
                                                    addr)
                    port_to_send = struct.pack('>H', port)
                    self._write_to_sock(header + addr_to_send + port_to_send,
                                        self._local_sock)
                    self._stage = STAGE_UDP_ASSOC
                    # just wait for the client to disconnect
                    return
                elif cmd == CMD_CONNECT:
                    # just trim VER CMD RSV
                    data = data[3:]
                else:
                    logging.error('unknown command %d', cmd)
                    self.destroy()
                    return
            header_result = parse_header(data)
            if header_result is None:
                raise Exception('can not parse header')
            addrtype, remote_addr, remote_port, header_length = header_result
            logging.info('connecting %s:%d' % (common.to_str(remote_addr),
                                               remote_port))
            self._remote_address = (remote_addr, remote_port)
            # pause reading
            self._update_stream(STREAM_UP, WAIT_STATUS_WRITING)
            self._stage = STAGE_DNS
            if self._is_local:
                # forward address to remote
                self._write_to_sock((b'\x05\x00\x00\x01'
                                     b'\x00\x00\x00\x00\x10\x10'),
                                    self._local_sock)
                data_to_send = self._encryptor.encrypt(data)
                self._data_to_write_to_remote.append(data_to_send)
                # notice here may go into _handle_dns_resolved directly

                # Here uses the resolve in dns_server, dns_server could perform like a portable module
                self._dns_resolver.resolve(self._chosen_server[0],
                                           self._handle_dns_resolved)
            else:
                if len(data) > header_length:
                    self._data_to_write_to_remote.append(data[header_length:])
                # notice here may go into _handle_dns_resolved directly
                self._dns_resolver.resolve(remote_addr,
                                           self._handle_dns_resolved)
        except Exception as e:
            logging.error(e)
            if self._config['verbose']:
                traceback.print_exc()
            # TODO use logging when debug completed
            self.destroy()

    def _handle_server(self):
        server = self._server_socket
        data, r_addr = server.recvfrom(BUF_SIZE)
        ogn_data = data
        if not data:
            logging.debug('UDP handle_server: data is empty')
        if self._stat_callback:
            self._stat_callback(self._listen_port, len(data))
        uid = None
        if self._is_local:
            frag = common.ord(data[2])
            if frag != 0:
                logging.warn('drop a message since frag is not 0')
                return
            else:
                data = data[3:]
        else:
            ref_iv = [0]
            data = encrypt.encrypt_all_iv(self._protocol.obfs.server_info.key, self._method, 0, data, ref_iv)
            # decrypt data
            if not data:
                logging.debug('UDP handle_server: data is empty after decrypt')
                return
            self._protocol.obfs.server_info.recv_iv = ref_iv[0]
            data, uid = self._protocol.server_udp_post_decrypt(data)

        #logging.info("UDP data %s" % (binascii.hexlify(data),))
        if not self._is_local:
            data = pre_parse_header(data)
            if data is None:
                return

        try:
            header_result = parse_header(data)
        except:
            self._handel_protocol_error(r_addr, ogn_data)
            return

        if header_result is None:
            self._handel_protocol_error(r_addr, ogn_data)
            return
        connecttype, addrtype, dest_addr, dest_port, header_length = header_result

        if self._is_local:
            addrtype = 3
            server_addr, server_port = self._get_a_server()
        else:
            server_addr, server_port = dest_addr, dest_port

        if (addrtype & 7) == 3:
            af = common.is_ip(server_addr)
            if af == False:
                handler = common.UDPAsyncDNSHandler((data, r_addr, uid, header_length))
                handler.resolve(self._dns_resolver, (server_addr, server_port), self._handle_server_dns_resolved)
            else:
                self._handle_server_dns_resolved("", (server_addr, server_port), server_addr, (data, r_addr, uid, header_length))
        else:
            self._handle_server_dns_resolved("", (server_addr, server_port), server_addr, (data, r_addr, uid, header_length))

 def pack_data(self, buf):
     if len(buf) == 0:
         return b''
     rnd_data = os.urandom(common.ord(os.urandom(1)[0]) % 16)
     data = common.chr(len(rnd_data) + 1) + rnd_data + buf
     data = struct.pack('>H', len(data) + 6) + data
     crc = (0xffffffff - binascii.crc32(data)) & 0xffffffff
     data += struct.pack('<I', crc)
     return data

def parse_name(data, offset):
	p = offset
	labels = []
	l = common.ord(data[p])
	while l > 0:
		if (l & (128 + 64)) == (128 + 64):
			# pointer
			pointer = struct.unpack('!H', data[p:p + 2])[0]
			pointer &= 0x3FFF
			r = parse_name(data, pointer)
			labels.append(r[1])
			p += 2
			# pointer is the end
			return p - offset, b'.'.join(labels)
		else:
			labels.append(data[p + 1:p + 1 + l])
			p += 1 + l
		l = common.ord(data[p])
	return p - offset + 1, b'.'.join(labels)

def get_table(key):
    m = hashlib.md5()
    m.update(key)
    s = m.digest()
    a, b = struct.unpack('<QQ', s)
    table = maketrans(b'', b'')
    table = [table[i: i + 1] for i in range(len(table))]
    for i in range(1, 1024):
        table.sort(key=lambda x: int(a % (ord(x) + i)))
    return table

 def pack_auth_data(self, buf):
     if len(buf) == 0:
         return b''
     rnd_data = os.urandom(common.ord(os.urandom(1)[0]) % 128)
     data = common.chr(len(rnd_data) + 1) + rnd_data + buf
     data = struct.pack('>H', len(data) + 16) + data
     crc = binascii.crc32(self.server_info.key) & 0xFFFFFFFF
     data = struct.pack('<I', crc) + data
     data += hmac.new(self.server_info.iv + self.server_info.key, data, hashlib.sha1).digest()[:10]
     return data