I have no programming knowledge. The below code is written with the help of AI neural network. In the code, I am performing the task of spoofing the ipv4 dns response with a fake ip ipv4 to access inaccessible sites. I need to fix the code so that it returns rcode servfail if all dns servers are unreachable, and otherwise copies the behavior of external dns servers and their responses where possible, except for ipv4 dns responses if 192.168.2.1:9054 is reachable and the request does not contain DNSSEC. If external dns servers give unusual rcode not being Noerror, NXDomain then if possible then give ipv4 response only from 192.168.2.1:9054.
import socket
import threading
from dnslib import DNSRecord, DNSHeader, DNSQuestion, A, AAAA, DNSKEY, RR
# DNS server configuration
LOCAL_DNS_SERVER = ('192.168.2.1', 9053)
FALLBACK_DNS_SERVERS = [
('5.34.34.5', 53),
('37.99.99.37', 53),
('8.8.8.8', 53)
]
UDP_PORT = 5353
TIMEOUT = 0.4 # 400 ms
def query_dns(server, message):
"""Sending a query to a DNS server and receiving a response."""
try:
with socket.socket(socket.AF_INET, socket.SOCK_DGRAM) as s:
s.settimeout(TIMEOUT)
s.sendto(message, server)
response, _ = s.recvfrom(512)
return response
except (socket.timeout, socket.error):
return None
def handle_client_request(data, addr, server_socket):
# Initialisation of tor_dns variable
tor_dns = None
# Parsing an incoming request
request = DNSRecord.parse(data)
# Querying the local DNS server
local_dns_response = query_dns(LOCAL_DNS_SERVER, data)
if local_dns_response:
local_response = DNSRecord.parse(local_dns_response)
if local_response.header.rcode == 0: # NoError
# Extracting A record
for rr in local_response.rr:
if rr.rtype == 1: # A record
tor_dns = rr
break
# Attempting queries to external DNS servers
external_dns_responses = []
for server in FALLBACK_DNS_SERVERS:
response = query_dns(server, data)
if response:
external_dns_responses.append(response)
external_response = DNSRecord.parse(response)
if external_response.header.rcode == 3: # NXDomain
server_socket.sendto(response, addr)
return
if not external_dns_responses:
# No response from external DNS servers, generate response from tor_dns
if tor_dns:
response = DNSRecord.parse(data)
if response.header.rcode == 0: # NoError
answer_section = [rr for rr in response.rr if rr.rtype != 1]
answer_section.append(tor_dns)
response.rr = answer_section
server_socket.sendto(response.pack(), addr)
return
# Processing responses from external DNS servers
for external_response_data in external_dns_responses:
external_response = DNSRecord.parse(external_response_data)
if external_response.header.rcode == 0: # NoError
# DNSSEC verification
dnssec = any(rr.rtype == 48 for rr in external_response.ar)
if not dnssec:
# Record processing
answer_section = [rr for rr in external_response.rr if rr.rtype != 1]
if any(rr.rtype in [28, 6] for rr in external_response.rr):
answer_section += [tor_dns] if tor_dns else []
else:
answer_section = [tor_dns] + answer_section if tor_dns else answer_section
external_response.rr = answer_section
server_socket.sendto(external_response.pack(), addr)
return
# If there is no response and tor_dns is also not installed, send ServFail
if not tor_dns:
response = DNSRecord.parse(data)
response.header.rcode = 2 # ServFail
server_socket.sendto(response.pack(), addr)
return
# Forming a response
response = DNSRecord.parse(data)
if tor_dns:
answer_section = [rr for rr in response.rr if rr.rtype != 1]
if any(rr.rtype in [28, 6] for rr in response.rr):
answer_section += [tor_dns]
else:
answer_section = [tor_dns] + answer_section
response.rr = answer_section
else:
response.header.rcode = 2 # ServFail
# Sending a reply to the client
response_data = response.pack()
server_socket.sendto(response_data, addr)
def start_server():
"""Starting a DNS server."""
with socket.socket(socket.AF_INET, socket.SOCK_DGRAM) as server_socket:
server_socket.bind(('192.168.2.1', UDP_PORT))
print(f"DNS server started on 192.168.2.1:{UDP_PORT}")
while True:
data, addr = server_socket.recvfrom(512)
threading.Thread(target=handle_client_request, args=(data, addr, server_socket)).start()
if __name__ == "__main__":
start_server()
Then I want to get a separate Python code that starts a dns server on a specific ip and port, then check if there is a list.txt file in the /tmp directory and if not, create it and write { +block } in the first line. The task of the new DNS to query the specified dns servers and then from this dns response to delete ipv6 dns records, provided there are ipv4 dns responses and if there is no DNSSEC. Otherwise the DNS server should copy the behaviour of external dns servers and copy the rest without change. If it turns out that we delete ipv6 dns responses, we write the domain and ip ipv6 addresses to the list.txt file in a column and if the file has more than 1000 lines, we delete all lines except the first one. I hope among Privoxy, Squid, Polipo or Tinyproxy there is a programme that can take into account frequent changes in the list.txt file, otherwise I have to restart the programme frequently