def parse(bytedata: bytes) -> tuple:
"""
:param bytedata data, from the dns packet stream
:return: tuple(AnswerItem, rest of bytedata)
:rtype AnswerItem, bytes
"""
name_field, bytedata = bread(bytedata, 2)
name_field = int.from_bytes(name_field, byteorder="big")
# 0bXY00000000000000 - X: 1 Y: 1 -> 11, X:0 Y:1 -> 1, X:1 Y:0 -> 10
name_type = 10 * ((name_field >> 15) & 0b1) + ((name_field >> 14) & 0b1)
name_offset = name_field & 0b001111111111111
assert name_type == 11
_type, bytedata = bread(bytedata, 2)
_type = int.from_bytes(_type, byteorder="big")
_class, bytedata = bread(bytedata, 2)
_class = int.from_bytes(_class, byteorder="big")
_ttl, bytedata = bread(bytedata, 4)
_ttl = int.from_bytes(_ttl, byteorder="big")
rdlen, bytedata = bread(bytedata, 2)
rdlen = int.from_bytes(rdlen, byteorder="big")
rddata, bytedata = bread(bytedata, rdlen)
rddata = QuestionTypes.unpack(_type, rddata)
return AnswerItem(QuestionItem(name_offset, _type, _class), _type, rddata, _ttl), bytedata
def __init__(self, qname, qtype: int, qclass: int):
"""
:param qname: question subject
:param qtype: question type
:param qclass: question class
:return:
"""
if isinstance(qname, str) and qtype == 1:
qname = qname.split(".")
self._qname = qname
self._qtype = int(qtype)
self._qclass = qclass
self._qtype_str = QuestionTypes.get(qtype).qname
def raw(self, offset):
"""
:param offset: offset from begin of the message for the name label
:return:
"""
body = b""
if offset < 1:
offset = 0
body += struct.pack(u16bit, 0b1100000000000000 + offset) # 16 bytes record, type 11, start 2 bytes
body += struct.pack(u16bit, self._type)
body += struct.pack(u16bit, self._class)
body += struct.pack(u32bit, self._ttl)
ipdata, size = QuestionTypes.pack(self._rtype, self._data)
if ipdata is None:
return None
body += struct.pack(u16bit, size)
body += ipdata
return body
def unpack_a_response(data: bytes) -> list:
ret = [-1] * 4
for i in range(0, 4):
octet, data = bread(data, 1, data_fx=lambda x: int.from_bytes(x, byteorder="big"))
ret[i] = octet
return ret
def unpack_ptr_response(data: bytes) -> str:
size = -1
_str = []
while size != 0: # ToDo: add check if packet is malformed and no zero flag at the end
size, data = bread(data, 1, data_fx=lambda x: int.from_bytes(x, byteorder="big"))
if size != 0:
lbl, data = bread(data, size)
try:
_str.append(lbl.decode(encoding="utf-8"))
except UnicodeDecodeError:
_str.append("<invalid format>")
return ".".join(_str)
# register packer/unpacker
QuestionTypes.set_fx("A", pack_a_response, unpack_a_response)
QuestionTypes.set_fx("PTR", pack_ptr_response, unpack_ptr_response)
QuestionTypes.set_fx("NS", pack_ptr_response, unpack_ptr_response)
