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DNSProxyServer.py
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DNSProxyServer.py
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import socket
import sys
import struct
import thread
# convert the UDP DNS query to the TCP DNS query
def getTcpQuery(query):
message = "\x00"+ chr(len(query)) + query
return message
# send a TCP DNS query to the upstream DNS server
def sendTCP(DNSserverIP, query):
server = (DNSserverIP, 53)
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.connect(server)
tcp_query = getTcpQuery(query)
sock.send(tcp_query)
data = sock.recv(1024)
return data
# a new thread to handle the UPD DNS request to TCP DNS request
def handler(data, addr, socket, DNSserverIP):
#print "Request from client: ", data.encode("hex"), addr
#print ""
TCPanswer = sendTCP(DNSserverIP, data)
#print "TCP Answer from server: ", TCPanswer.encode("hex")
#print ""
if TCPanswer:
rcode = TCPanswer[:6].encode("hex")
rcode = str(rcode)[11:]
#print "RCODE: ", rcode
if (int(rcode, 16) == 1):
print "Request is not a DNS query. Format Error!"
else:
print "Success!"
UDPanswer = TCPanswer[2:]
#print "UDP Answer: ", UDPanswer.encode("hex")
socket.sendto(UDPanswer, addr)
else:
print "Request is not a DNS query. Format Error!"
if __name__ == '__main__':
DNSserverIP = sys.argv[1]
port = int(sys.argv[2])
host = ''
try:
# setup a UDP server to get the UDP DNS request
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
sock.bind((host, port))
while True:
data, addr = sock.recvfrom(1024)
thread.start_new_thread(handler, (data, addr, sock, DNSserverIP))
except Exception, e:
print e
sock.close()