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mydns.py
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mydns.py
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import socket
import sys
from array import *
def ip_decoder(message1, message2, message3, message4):
ip1 = ord(message1) if len(message1) == 1 else int(message1, 16)
ip2 = ord(message2) if len(message2) == 1 else int(message2, 16)
ip3 = ord(message3) if len(message3) == 1 else int(message3, 16)
ip4 = ord(message4) if len(message4) == 1 else int(message4, 16)
ip = str(ip1) + '.' + str(ip2) + '.' + str(ip3) + '.' + str(ip4)
return ip
def copy(message, pos):
name = ''
pos = int(message[pos+1], 16) if len(message[pos+1]) == 2 else ord(message[pos+1])
pos += 1
while(message[pos] != '00'):
if(message[pos] == 'c0'):
name = name + '.' + copy(message, pos)
return (name)
elif(len(message[pos]) == 2):
name = name + '.'
else:
name = name + message[pos]
pos += 1
return(name)
def name_decoder(message, pos, length):
if(message[pos] == 'c0'):
return (copy(message, pos))
else:
if(length == 0):
name = ''
pos += 1
while(message[pos] != '00'):
if(len(message[pos]) == 2):
name = name + '.'
else:
name = name + message[pos]
pos += 1
return (name)
else:
pos += 1
length -= 2
name = ''
while(length > 0):
if(message[pos] == 'c0'):
length -= 2
name = name + '.' + copy(message, pos)
else:
if(len(message[pos]) == 2):
name = name + '.'
else:
name = name + message[pos]
length -= 1
pos += 1
return (name)
def display(message, extra):
print('----------------------------------------')
print('DNS server to query: ' + extra)
print('Reply received. Content overview:')
print('\t' + str(int(message[4]+message[5], 16)) + ' Queries')
Answers = int(message[6]+message[7], 16)
print('\t' + str(Answers) + ' Answers')
INS = int(message[8]+message[9], 16)
print('\t' + str(INS) + ' Intermediate Name Server')
AIR = int(message[10]+message[11], 16)
print('\t' + str(AIR) + ' Additional Information Records')
print('Answer section:')
pos = 12
notfound = True
while (notfound):
num = int(message[pos], 16)
pos += (num + 1)
if(message[pos] == '00'):
notfound = False
pos += 5
name = ''
while(Answers != 0):
name = ''
name = name_decoder(message, pos, 0)
pos += 15
ip = ip_decoder(message[pos-3], message[pos-2], message[pos-1], message[pos])
print('\tName : ' + name + '\t' + 'IP : ' + ip)
pos += 1
Answers -= 1
print('Authoritive section:')
while(INS != 0):
name = ''
server = name_decoder(message, pos, 0)
pos += 10
digit1 = message[pos] if (len(message[pos])) == 2 else str(ord(message[pos]))
pos += 1
digit2 = message[pos] if (len(message[pos])) == 2 else str(ord(message[pos]))
pos += 1
length = int((digit1 + digit2), 16)
name = name_decoder(message, pos, length)
pos += length
print('\tName : ' + server + '\t' + 'Name Server : ' + name)
INS -= 1
print('Additional Information section:')
while(AIR != 0):
name = ''
name = name_decoder(message, pos, 0)
pos = pos + 2
serverType = int((message[pos+1]), 16)
pos += 10
if(serverType == 1):
pos += 4
ip = ip_decoder(message[pos-4], message[pos-3], message[pos-2], message[pos-1])
print('\tName : ', name, '\t', 'IP : ', ip)
else:
pos += 16
print('\tName : ', name)
AIR -= 1
if(int(message[6]+message[7], 16) > 0):
return (str(int(message[6]+message[7], 16)))
else:
return (name)
def organize(response, extra):
message = []
message.append(response[2])
message.append(response[3])
count = 4
word = ''
while(count < len(response) - 1):
if(response[count] == '\\'):
count += 1
if(response[count] == 'x'):
count += 1
word = response[count:count+2]
message.append(word)
count += 2
if(response[count] != '\\'):
while((response[count] != '\\') & (count < len(response) - 1)):
message.append(response[count])
count += 1
else:
if(response[count] == 't'):
message.append('09')
elif(response[count] == 'n'):
message.append('0a')
elif(response[count] == 'r'):
message.append('0d')
elif(response[count] == 'v'):
message.append('0b')
elif(response[count] == 'f'):
message.append('0c')
else:
message.append('5c')
count += 1
if(response[count] != '\\'):
while((response[count] != '\\') & (count < len(response) - 1)):
message.append(response[count])
count += 1
return(display(message, extra))
def StrtoHex(name):
word = ''
words = []
midway = ''
result = ''
for i in name:
if (i != '.'):
word += i
else:
words.append(word)
word = ''
words.append(word)
count = len(words)
while (count > 0):
count -= 1
c_letters = len(words[count])
str_letters = hex(c_letters)
str_letters = str_letters[2:4]
if(len(str_letters) == 1):
str_letters = '0' + str_letters
for i in words[count]:
aux = hex(ord(i))
aux = aux[2:4]
midway = midway + aux
result = str_letters + midway + result
midway = ''
result = result + '00'
return (result)
Name = sys.argv[1]
name1 = '434701000001000000000000'
name2 = '00010001'
Port = 53
dns_server = sys.argv[2]
message = name1 + StrtoHex(Name) + name2
mysocket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
result = False
while (result == False):
request = bytes.fromhex(message)
mysocket.sendto(request,(dns_server, Port))
response = (mysocket.recvfrom(521))
dns_server = organize(str(response[0]), dns_server)
if(len(dns_server) == 1):
result = True