def get_rddata(self, l, type, dlen, beg_index):
if beg_index + dlen > len(l):
raise Trunc('(dns) truncated rdata')
# A
if type == 1:
if dlen != 4:
raise Exception('(dns) invalid a data size', system='packet')
return IPAddr(l[beg_index:beg_index + 4])
# AAAA
elif type == 28:
if dlen != 16:
raise Exception('(dns) invalid a data size', system='packet')
return IPAddr6(l[beg_index:beg_index + dlen])
# NS
elif type == 2:
return self.read_dns_name_from_index(l, beg_index)[1]
# PTR
elif type == 12:
return self.read_dns_name_from_index(l, beg_index)[1]
# CNAME
elif type == 5:
return self.read_dns_name_from_index(l, beg_index)[1]
# MX
elif type == 15:
#TODO: Save priority (don't just jump past it)
return self.read_dns_name_from_index(l, beg_index + 2)[1]
else:
return l[beg_index:beg_index + dlen]
def next_question(self, l, index):
array_len = len(l)
index, name = self.read_dns_name_from_index(l, index)
if index + 4 > array_len:
raise Trunc("next_question: truncated")
(qtype, qclass) = struct.unpack('!HH', l[index:index + 4])
self.questions.append(dns.question(name, qtype, qclass))
return index + 4
def next_rr(self, l, index, rr_list):
array_len = len(l)
# verify whether name is offset within packet
if index > array_len:
raise Trunc("next_rr: name truncated")
index,name = self.read_dns_name_from_index(l, index)
if index + 10 > array_len:
raise Trunc("next_rr: truncated")
(qtype,qclass,ttl,rdlen) = struct.unpack('!HHIH', l[index:index+10])
if index+10+rdlen > array_len:
raise Trunc("next_rr: data truncated")
rddata = self.get_rddata(l, qtype, rdlen, index + 10)
rr_list.append(dns.rr(name, qtype, qclass,ttl,rdlen,rddata))
return index + 10 + rdlen
def _read_dns_name_from_index(cls, l, index, retlist):
try:
while True:
chunk_size = ord(l[index])
# check whether we have an internal pointer
if (chunk_size & 0xc0) == 0xc0:
# pull out offset from last 14 bits
offset = ((ord(l[index]) & 0x3) << 8) | ord(l[index + 1])
cls._read_dns_name_from_index(l, offset, retlist)
index += 1
break
if chunk_size == 0:
break
index += 1
retlist.append(l[index:index + chunk_size])
index += chunk_size
return index
except IndexError:
raise Trunc("incomplete name")
