A Mitmproxy script to intercept DNS responses to a given domain.

mitmproxy_intercept_dns.py

# This is a Mitmproxy plugin that allows overwriting DNS responses to a given domain.
# Currently, it overwrites requests to thesupermac.local to 10.0.2.2
# There might be some typos -- I'll let this for you to fix; but I can confirm that it works.
# I added some comments to help future users :)
# IMPORTANT: you need to use the Wireguard mode for this to work, as far as I know.

import logging
from ipaddress import IPv4Address

import mitmproxy
from mitmproxy import dns

class OverrideDNS:
    def dns_request(self, flow: mitmproxy.dns.DNSFlow):
        # The DNS address we want to intercept.
        interception_url = "thesupermac.local"

        # There are multiple questions in a DNS request. Well, it's possible, but almost no software
        # actually does it. So, we consider that if we're matching any of the questions of a given request,
        # then, we'll inject our custom answer.
        # Do note that I'm using the "in" operator, so "aaathesupermac.local" and "thesupermac.local" will match
        # equally since they both contain "thesupermac.local". You could change this to a "==" operator if you
        # wanted to be more precise.
        if any(interception_url in q.name for q in flow.request.questions):
            # flow.request.succeed(...) crafts a DNS response, of type mitmproxy.dns.Message.
            # We then set it to flow, which is of type mitmproxy.dns.DNSFlow
            flow.response = flow.request.succeed(
                [
                    # In DNS, an "A" answer corresponds to an IPv4 address.
                    # AAAA, for instance, matches a domain name to an IPv6 address
                    dns.ResourceRecord.A(
                        interception_url, IPv4Address("10.0.2.2"), ttl=10
                    )
                ]
            )
            logging.info("Overwrite DNS response") # Log on the console to help you debug the script
            flow.comment = "Overwrote by OverrideAP" # Put a comment on the flow on Mitmweb
            flow.marked = ":black_nib:"  # Show a black pen emoj next to the response on Mitmweb
            
# make sure to include this line below so that Mitmproxy recognizes your addon
addons = [OverrideDNS()]