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import json
import copy
import struct
import binascii
from Crypto.Cipher import AES
from cStringIO import StringIO
class BinaryDataStream(object):
"""Directional binary data stream
Reads and writes binary data from any stream-like object. This object is
not bi-directional. Does no interpertation just unpacking and packing.
"""
def __init__(self, data):
self.data = data
@classmethod
def for_output(cls):
return cls(StringIO())
def read_int(self):
return struct.unpack(">i", self.data.read(4))[0]
def read_short(self):
return struct.unpack(">h", self.data.read(2))[0]
def read_string(self, length):
return self.data.read(length)
def write_int(self, data):
self.data.write(struct.pack(">i", data))
def write_short(self, data):
self.data.write(struct.pack(">h", data))
def write_string(self, data):
self.data.write(data)
def get_output(self):
return self.data.getvalue()
class Cryptor(object):
"""AES encryption strategy
Handles AES crypto by wrapping pycrypto. Does padding and un-padding as
well as key conversions when needed.
"""
def __init__(self, key, iv):
self.iv = iv
self.key = key
self.cipher = AES.new(key.decode("hex"), AES.MODE_CBC, iv)
@staticmethod
def unpad(s):
return s[0:-ord(s[-1])]
@staticmethod
def pad(s, BS=16):
return s + (BS - len(s) % BS) * chr(BS - len(s) % BS)
def decrypt(self, payload):
return self.unpad(self.cipher.decrypt(payload))
def encrypt(self, payload):
return self.cipher.encrypt(self.pad(payload))
class InformPacket(object):
"""Inform model object
Holds basic, parsed, inform packet data. Does some interpertation for
fields like flags. Can be passed to and from the serialiser. This class
only fully supports version 1 of the inform data protocol. Version 0
payload parsing is not supported.
"""
ENCRYPTED_FLAG = 0x1
COMPRESSED_FLAG = 0x2
def __init__(self):
self.magic_number = None
self.version = None
self.mac_addr = None
self.flags = None
self.iv = None
self.data_version = None
self.data_length = None
self.raw_payload = None
self._used_key = None
def response_copy(self):
"""Copy object for use in response
Generates a deep copy of the object and removes the payload so that it
can be used to respond to the station that send this inform request.
"""
new_obj = copy.deepcopy(self)
new_obj.raw_payload = None
return new_obj
@staticmethod
def _format_mac_addr(mac_bytes):
return ":".join([binascii.hexlify(i) for i in mac_bytes])
def _has_flag(self, flag):
return self.flags & flag != 0
@property
def formatted_mac_addr(self):
return self._format_mac_addr(self.mac_addr)
@property
def is_encrypted(self):
return self._has_flag(self.ENCRYPTED_FLAG)
@property
def is_compressed(self):
return self._has_flag(self.COMPRESSED_FLAG)
@property
def payload(self):
if self.data_version == 1:
return json.loads(self.raw_payload.decode("latin-1"))
else:
return self.raw_payload
@payload.setter
def payload(self, value):
self.raw_payload = json.dumps(value)
class InformSerializer(object):
"""Inform protocol version 1 parser/serializer
Handles the parsing of the inform binary protocol to python objects and
seralization of python objects to inform binary protocol. Handles
cryptography and data formats. Compatible only with version 1 of the data
format.
"""
MASTER_KEY = "ba86f2bbe107c7c57eb5f2690775c712"
PROTOCOL_MAGIC = 1414414933
MAX_VERSION = 1
def __init__(self, key=None, key_bag=None):
self.key = key
self.key_bag = key_bag or {}
def _decrypt_payload(self, packet):
i = 0
key = self.key_bag.get(packet.formatted_mac_addr)
for key in (key, self.key, self.MASTER_KEY):
if key is None:
continue
decrypted = Cryptor(key, packet.iv).decrypt(packet.raw_payload)
json.loads(decrypted.decode("latin-1"))
packet.raw_payload = decrypted
packet._used_key = key
break
def parse(self, input):
input_stream = BinaryDataStream(input)
packet = InformPacket()
packet.magic_number = input_stream.read_int()
assert packet.magic_number == self.PROTOCOL_MAGIC
packet.version = input_stream.read_int()
assert packet.version < self.MAX_VERSION
packet.mac_addr = input_stream.read_string(6)
packet.flags = input_stream.read_short()
packet.iv = input_stream.read_string(16)
packet.data_version = input_stream.read_int()
packet.data_length = input_stream.read_int()
packet.raw_payload = input_stream.read_string(packet.data_length)
if packet.is_encrypted:
self._decrypt_payload(packet)
return packet
def _encrypt_payload(self, packet):
if packet.data_version != 1:
raise ValueError("Can no encrypt contents of pre 1.0 packets")
key = packet._used_key if packet._used_key else self.MASTER_KEY
return Cryptor(key, packet.iv).encrypt(json.dumps(packet.payload))
def serialize(self, packet):
output = BinaryDataStream.for_output()
output.write_int(packet.magic_number)
output.write_int(packet.version)
output.write_string(packet.mac_addr)
output.write_short(packet.flags)
output.write_string(packet.iv)
output.write_int(packet.data_version)
output.write_int(packet.data_length)
output.write_string(self._encrypt_payload(packet))
return output.get_output()
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