Attempt to fix Python 3.9 compatibility issue with array.array tostri…

…ng/fromstring methods (#1054)

Python 3.9 removed the `array.array` `tostring` and `fromstring` methods (see https://docs.python.org/3/whatsnew/3.9.html#removed).
Note that the `tostring` and `fromstring` methods were already deprecated since Python 3.2, but aliases to the new `tobytes` and `frombytes` were provided (see https://docs.python.org/3/library/array.html#array.array.tobytes).

This:
- Adds helper function to use `tostring` and `fromstring` in Python <3.2 versions and `tobytes` and `frombytes` in Python>=3.2.
- Replaces uses of `tostring` and `fromstring` with the new helper function.

examples/nmapAnswerMachine.py

@@ -8,7 +8,7 @@
 
 from impacket import ImpactPacket
 from impacket import ImpactDecoder
-from impacket.ImpactPacket import TCPOption
+from impacket.ImpactPacket import TCPOption, array_tobytes
 from impacket.examples import logger
 from impacket.examples import os_ident
 
@@ -354,7 +354,7 @@ def isMine(self, in_onion):
           #in_onion[O_UDP].get_uh_dport() == self.port)
 
    def buildAnswer(self, in_onion):
-       cmd = in_onion[O_UDP_DATA].get_bytes().tostring()
+       cmd = array_tobytes(in_onion[O_UDP_DATA].get_bytes())
        if cmd[:4] == 'cmd:': cmd = cmd[4:].strip()
        print("Got command: %r" % cmd)
 

impacket/ICMP6.py

@@ -8,7 +8,7 @@
 import array
 import struct
 
-from impacket.ImpactPacket import Header, Data
+from impacket.ImpactPacket import Header, Data, array_tobytes
 from impacket.IP6_Address import IP6_Address
 
 
@@ -234,7 +234,7 @@ def __build_echo_message(class_object, type, id, sequence_number, arbitrary_data
         icmp_bytes = struct.pack('>H', id)
         icmp_bytes += struct.pack('>H', sequence_number)
         if (arbitrary_data is not None):
-            icmp_bytes += array.array('B', arbitrary_data).tostring()
+            icmp_bytes += array_tobytes(array.array('B', arbitrary_data))
         icmp_payload = Data()
         icmp_payload.set_data(icmp_bytes)
 
@@ -273,9 +273,9 @@ def __build_error_message(class_object, type, code, data, originating_packet_dat
         icmp_packet.set_code(code)
 
         #Pack ICMP payload
-        icmp_bytes = array.array('B', data).tostring()
+        icmp_bytes = array_tobytes(array.array('B', data))
         if (originating_packet_data is not None):
-            icmp_bytes += array.array('B', originating_packet_data).tostring()
+            icmp_bytes += array_tobytes(array.array('B', originating_packet_data))
         icmp_payload = Data()
         icmp_payload.set_data(icmp_bytes)
 
@@ -302,11 +302,11 @@ def __build_neighbor_message(class_object, msg_type, target_address):
         icmp_packet.set_code(0)
 
         # Flags + Reserved
-        icmp_bytes = array.array('B', [0x00] * 4).tostring()       
+        icmp_bytes = array_tobytes(array.array('B', [0x00] * 4))
 
         # Target Address: The IP address of the target of the solicitation.
         # It MUST NOT be a multicast address.
-        icmp_bytes += array.array('B', IP6_Address(target_address).as_bytes()).tostring()
+        icmp_bytes += array_tobytes(array.array('B', IP6_Address(target_address).as_bytes()))
 
         icmp_payload = Data()
         icmp_payload.set_data(icmp_bytes)
@@ -394,10 +394,10 @@ def __build_node_information_message(class_object, type, code, payload = None):
 
         icmp_bytes = struct.pack('>H', qtype)
         icmp_bytes += struct.pack('>H', flags)
-        icmp_bytes += array.array('B', nonce).tostring()
+        icmp_bytes += array_tobytes(array.array('B', nonce))
 
         if payload is not None:
-            icmp_bytes += array.array('B', payload).tostring()
+            icmp_bytes += array_tobytes(array.array('B', payload))
 
         icmp_payload = Data()
         icmp_payload.set_data(icmp_bytes)

impacket/IP6.py

@@ -8,7 +8,7 @@
 import struct
 import array
 
-from impacket.ImpactPacket import Header
+from impacket.ImpactPacket import Header, array_frombytes
 from impacket.IP6_Address import IP6_Address
 from impacket.IP6_Extension_Headers import IP6_Extension_Header
 
@@ -78,9 +78,9 @@ def get_pseudo_header(self):
         pseudo_header = array.array('B')        
         pseudo_header.extend(source_address)
         pseudo_header.extend(destination_address)
-        pseudo_header.fromstring(struct.pack('!L', upper_layer_packet_length))
+        array_frombytes(pseudo_header, struct.pack('!L', upper_layer_packet_length))
         pseudo_header.fromlist(reserved_bytes)
-        pseudo_header.fromstring(struct.pack('B', upper_layer_protocol_number))
+        array_frombytes(pseudo_header, struct.pack('B', upper_layer_protocol_number))
         return pseudo_header
 
 ############################################################################

impacket/ImpactPacket.py

@@ -22,6 +22,16 @@
 from binascii import hexlify
 from functools import reduce
 
+# Alias function for compatibility with both Python <3.2 `tostring` and `fromstring` methods, and
+# Python >=3.2 `tobytes` and `tostring`
+if sys.version_info[0] >= 3 and sys.version_info[1] >= 2:
+    array_tobytes = lambda array_object: array_object.tobytes()
+    array_frombytes = lambda array_object, bytes: array_object.frombytes(bytes)
+else:
+    array_tobytes = lambda array_object: array_object.tostring()
+    array_frombytes = lambda array_object, bytes: array_object.fromstring(bytes)
+
+
 """Classes to build network packets programmatically.
 
 Each protocol layer is represented by an object, and these objects are
@@ -60,7 +70,7 @@ def set_bytes_from_string(self, data):
 
     def get_buffer_as_string(self):
         "Returns the packet buffer as a string object"
-        return self.__bytes.tostring()
+        return array_tobytes(self.__bytes)
 
     def get_bytes(self):
         "Returns the packet buffer as an array"
@@ -97,7 +107,7 @@ def get_word(self, index, order = '!'):
             bytes = self.__bytes[index:]
         else:
             bytes = self.__bytes[index:index+2]
-        (value,) = struct.unpack(order + 'H', bytes.tostring())
+        (value,) = struct.unpack(order + 'H', array_tobytes(bytes))
         return value
 
     def set_long(self, index, value, order = '!'):
@@ -116,7 +126,7 @@ def get_long(self, index, order = '!'):
             bytes = self.__bytes[index:]
         else:
             bytes = self.__bytes[index:index+4]
-        (value,) = struct.unpack(order + 'L', bytes.tostring())
+        (value,) = struct.unpack(order + 'L', array_tobytes(bytes))
         return value
 
     def set_long_long(self, index, value, order = '!'):
@@ -135,7 +145,7 @@ def get_long_long(self, index, order = '!'):
             bytes = self.__bytes[index:]
         else:
             bytes = self.__bytes[index:index+8]
-        (value,) = struct.unpack(order + 'Q', bytes.tostring())
+        (value,) = struct.unpack(order + 'Q', array_tobytes(bytes))
         return value
 
 
@@ -146,7 +156,7 @@ def get_ip_address(self, index):
             bytes = self.__bytes[index:]
         else:
             bytes = self.__bytes[index:index+4]
-        return socket.inet_ntoa(bytes.tostring())
+        return socket.inet_ntoa(array_tobytes(bytes))
 
     def set_ip_address(self, index, ip_string):
         "Set 4-byte value at 'index' from 'ip_string'"
@@ -196,7 +206,7 @@ def __validate_index(self, index, size):
 
         diff = index + size - curlen
         if diff > 0:
-            self.__bytes.fromstring('\0' * diff)
+            array_frombytes(self.__bytes, '\0' * diff)
             if orig_index < 0:
                 orig_index -= diff
 
@@ -719,7 +729,7 @@ def set_addr(self, addr):
 
     def get_addr(self):
         "Returns the sender's address field"
-        return self.get_bytes()[6:14].tostring()
+        return array_tobytes(self.get_bytes()[6:14])
 
     def set_ether_type(self, aValue):
         "Set ethernet data type field to 'aValue'"
@@ -797,7 +807,7 @@ def get_packet(self):
         # Pad to a multiple of 4 bytes
         num_pad = (4 - (len(my_bytes) % 4)) % 4
         if num_pad:
-            my_bytes.fromstring(b"\0"* num_pad)
+            array_frombytes(my_bytes, b"\0" * num_pad)
 
         # only change ip_hl value if options are present
         if len(self.__option_list):
@@ -809,9 +819,9 @@ def get_packet(self):
             self.set_ip_sum(self.compute_checksum(my_bytes))
 
         if child_data is None:
-            return my_bytes.tostring()
+            return array_tobytes(my_bytes)
         else:
-            return my_bytes.tostring() + child_data
+            return array_tobytes(my_bytes) + child_data
 
 
 
@@ -835,7 +845,7 @@ def get_pseudo_header(self):
 
         size_str = struct.pack("!H", tmp_size)
 
-        pseudo_buf.fromstring(size_str)
+        array_frombytes(pseudo_buf, size_str)
         return pseudo_buf
 
     def add_option(self, option):
@@ -1296,7 +1306,7 @@ def calculate_checksum(self):
             buffer += self.get_bytes()
             data = self.get_data_as_string()
             if(data):
-                buffer.fromstring(data)
+                array_frombytes(buffer, data)
             self.set_uh_sum(self.compute_checksum(buffer))
 
     def get_header_size(self):
@@ -1486,7 +1496,7 @@ def calculate_checksum(self):
 
         data = self.get_data_as_string()
         if(data):
-            buffer.fromstring(data)
+            array_frombytes(buffer, data)
 
         res = self.compute_checksum(buffer)
 
@@ -1505,9 +1515,9 @@ def get_packet(self):
         data = self.get_data_as_string()
 
         if data:
-            return bytes.tostring() + data
+            return array_tobytes(bytes) + data
         else:
-            return bytes.tostring()
+            return array_tobytes(bytes)
 
     def load_header(self, aBuffer):
         self.set_bytes_from_string(aBuffer[:20])
@@ -1562,7 +1572,7 @@ def get_padded_options(self):
             op_buf += op.get_bytes()
         num_pad = (4 - (len(op_buf) % 4)) % 4
         if num_pad:
-            op_buf.fromstring("\0" * num_pad)
+            array_frombytes(op_buf, "\0" * num_pad)
         return op_buf
 
     def __str__(self):

impacket/NDP.py

@@ -51,7 +51,7 @@ def Router_Advertisement(class_object, current_hop_limit,
     @classmethod
     def Neighbor_Solicitation(class_object, target_address):        
         message_data = struct.pack('>L', 0) #Reserved bytes
-        message_data += target_address.as_bytes().tostring()
+        message_data += ImpactPacket.array_tobytes(target_address.as_bytes())
         return class_object.__build_message(NDP.NEIGHBOR_SOLICITATION, message_data)
 
 
@@ -66,15 +66,15 @@ def Neighbor_Advertisement(class_object, router_flag, solicited_flag, override_f
             flag_byte |= 0x20
 
         message_data = struct.pack('>BBBB', flag_byte, 0x00, 0x00, 0x00) #Flag byte and three reserved bytes
-        message_data += target_address.as_bytes().tostring()
+        message_data += array_tobytes(target_address.as_bytes())
         return class_object.__build_message(NDP.NEIGHBOR_ADVERTISEMENT, message_data)
 
 
     @classmethod
     def Redirect(class_object, target_address, destination_address):        
         message_data = struct.pack('>L', 0)# Reserved bytes
-        message_data += target_address.as_bytes().tostring()
-        message_data += destination_address.as_bytes().tostring()
+        message_data += ImpactPacket.array_tobytes(target_address.as_bytes())
+        message_data += ImpactPacket.array_tobytes(destination_address.as_bytes())
         return class_object.__build_message(NDP.REDIRECT, message_data)
 
 
@@ -118,7 +118,7 @@ def Target_Link_Layer_Address(class_object, link_layer_address):
     #link_layer_address must have a size that is a multiple of 8 octets
     def __Link_Layer_Address(class_object, option_type, link_layer_address):
         option_length = (len(link_layer_address) / 8) + 1
-        option_data = array.array("B", link_layer_address).tostring()
+        option_data = ImpactPacket.array_tobytes(array.array("B", link_layer_address))
         return class_object.__build_option(option_type, option_length, option_data)
 
     @classmethod
@@ -134,15 +134,15 @@ def Prefix_Information(class_object, prefix_length, on_link_flag, autonomous_fla
 
         option_data = struct.pack('>BBLL', prefix_length, flag_byte, valid_lifetime, preferred_lifetime)
         option_data += struct.pack('>L', 0) #Reserved bytes
-        option_data += array.array("B", prefix).tostring()
+        option_data += ImpactPacket.array_tobytes(array.array("B", prefix))
         option_length = 4        
         return class_object.__build_option(NDP_Option.PREFIX_INFORMATION, option_length, option_data)
 
 
     @classmethod    
     def Redirected_Header(class_object, original_packet):
         option_data = struct.pack('>BBBBBB', 0x00, 0x00, 0x00, 0x00, 0x00, 0x00)# Reserved bytes
-        option_data += array.array("B", original_packet).tostring()
+        option_data += ImpactPacket.array_tobytes(array.array("B", original_packet))
         option_length = (len(option_data) + 4) / 8  
         return class_object.__build_option(NDP_Option.REDIRECTED_HEADER, option_length, option_data)
 

impacket/cdp.py

@@ -14,7 +14,7 @@
 from struct import unpack
 import socket
 
-from impacket.ImpactPacket import Header
+from impacket.ImpactPacket import Header, array_tobytes
 from impacket import LOG
 
 IP_ADDRESS_LENGTH = 4
@@ -124,11 +124,11 @@ def get_length(self):
         return self.get_word(2)
 
     def get_data(self):        
-        return self.get_bytes().tostring()[4:self.get_length()]
+        return array_tobytes(self.get_bytes())[4:self.get_length()]
 
     def get_ip_address(self, offset = 0, ip = None):
         if not ip:
-            ip = self.get_bytes().tostring()[offset : offset + IP_ADDRESS_LENGTH]
+            ip = array_tobytes(self.get_bytes())[offset : offset + IP_ADDRESS_LENGTH]
         return socket.inet_ntoa( ip )
 
 class CDPDevice(CDPElement):
@@ -149,7 +149,7 @@ class Address(CDPElement):
     def __init__(self, aBuffer = None):
         CDPElement.__init__(self, aBuffer)
         if aBuffer:
-            data = self.get_bytes().tostring()[8:]
+            data = array_tobytes(self.get_bytes())[8:]
             self._generateAddressDetails(data)
 
     def _generateAddressDetails(self, buff):
@@ -353,10 +353,10 @@ def get_status(self):
         return self.get_byte(19)
 
     def get_cluster_command_mac(self):
-        return self.get_bytes().tostring()[20:20+6]
+        return array_tobytes(self.get_bytes())[20:20+6]
 
     def get_switch_mac(self):
-        return self.get_bytes().tostring()[28:28+6]
+        return array_tobytes(self.get_bytes())[28:28+6]
 
     def get_management_vlan(self):
         return self.get_word(36)

impacket/dot11.py

@@ -13,7 +13,7 @@
 import struct
 from binascii import crc32
 
-from impacket.ImpactPacket import ProtocolPacket
+from impacket.ImpactPacket import ProtocolPacket, array_tobytes
 from impacket.Dot11Crypto import RC4
 frequency = {
     2412: 1,    2417: 2,    2422: 3,    2427: 4,    2432: 5,    2437: 6,    2442: 7,    2447: 8,    2452: 9,
@@ -997,9 +997,9 @@ def __init__(self, aBuffer = None):
 
     def get_OUI(self):
         "Get the three-octet Organizationally Unique Identifier (OUI) SNAP frame"
-        b=self.header.get_bytes()[0:3].tostring()
+        b = array_tobytes(self.header.get_bytes()[0:3])
         #unpack requires a string argument of length 4 and b is 3 bytes long
-        (oui,)=struct.unpack('!L', b'\x00'+b)
+        (oui,) = struct.unpack('!L', b'\x00'+b)
         return oui
 
     def set_OUI(self, value):
@@ -1040,9 +1040,9 @@ def is_WEP(self):
 
     def get_iv(self):
         'Return the \'WEP IV\' field'
-        b=self.header.get_bytes()[0:3].tostring()
+        b = array_tobytes(self.header.get_bytes()[0:3])
         #unpack requires a string argument of length 4 and b is 3 bytes long
-        (iv,)=struct.unpack('!L', b'\x00'+b)
+        (iv,) = struct.unpack('!L', b'\x00'+b)
         return iv
 
     def set_iv(self, value):

impacket/helper.py

@@ -100,9 +100,9 @@ def __init__(self, index):
         Field.__init__(self, index)
 
     def getter(self, o):
-        b=o.header.get_bytes()[self.index:self.index+3].tostring()
+        b = ip.array_tobytes(o.header.get_bytes()[self.index:self.index+3])
         #unpack requires a string argument of length 4 and b is 3 bytes long
-        (value,)=struct.unpack('!L', b'\x00'+b)
+        (value,) = struct.unpack('!L', b'\x00'+b)
         return value
 
     def setter(self, o, value):