MITM proxy with Twisted. Can be used to tamper with traffic by modifying the rules.json file while it is running.

proxy.py

LISTEN_PORT = 8085
SERVER_PORT = 8085
SERVER_ADDR = "37.187.171.215"
BIND_ADDR = ("10.14.88.15", 0)

from twisted.internet import protocol, reactor

import json

class RulesLoader():
    def reread(self, mode, data):
        with open("rules.json") as fp:
            rules = json.load(fp)

        for a, b in rules[mode].items():
            data = data.replace(a.decode("hex"), b.decode("hex"))
        return data

    def incoming(self, data):
        return self.reread("incoming", data)

    def outgoing(self, data):
        return self.reread("outgoing", data)

class ServerProtocol(protocol.Protocol):
    def __init__(self):
        self.buffer = None
        self.client = None
        self.rules = RulesLoader()

    def connectionMade(self):
        factory = protocol.ClientFactory()
        factory.protocol = ClientProtocol
        factory.server = self

        reactor.connectTCP(SERVER_ADDR, SERVER_PORT,
                           factory=factory, bindAddress=BIND_ADDR)

    # Client => Proxy
    def dataReceived(self, data):
        if self.client:
            self.client.write(data)
        else:
            self.buffer = data

    # Proxy => Client
    def write(self, data):
        print "IN ", repr(data)
        data = self.rules.incoming(data)
        self.transport.write(data)


class ClientProtocol(protocol.Protocol):
    def connectionMade(self):
        self.factory.server.client = self
        self.write(self.factory.server.buffer)
        self.factory.server.buffer = ''
        self.rules = RulesLoader()

    # Server => Proxy
    def dataReceived(self, data):
        self.factory.server.write(data)

    # Proxy => Server
    def write(self, data):
        if not data:
            return

        print "OUT", repr(data)
        data = self.rules.outgoing(data)
        self.transport.write(data)

def main():
    factory = protocol.ServerFactory()
    factory.protocol = ServerProtocol

    reactor.listenTCP(LISTEN_PORT, factory)
    reactor.run()

if __name__ == '__main__':
    main()

rules.json

{
    "incoming": {
        "526174": "436174"
    },
    "outgoing": {
        "686579": "627965"
    }
}