server.py

from twisted.python import log
from twisted.web import http, proxy

__author__ = "Yashin Mehaboobe (@sp3ctr3)"

class ProxyClient(proxy.ProxyClient):
    """Modify response as well as header here.
    """
    def handleHeader(self, key, value):
        """
        Modify header here
        """
        log.msg("Header: %s: %s" % (key, value))
        proxy.ProxyClient.handleHeader(self, key, value)

    def handleResponsePart(self, buffer):
        """
        Modify buffer to modify response. For example replacing buffer with buffer[::-1] will lead to a reversed output.
        This might cause content encoding errors. Currently test only on text only websites
        """
        log.msg("Content: %s" % (buffer,))
        proxy.ProxyClient.handleResponsePart(self, buffer)

class ProxyClientFactory(proxy.ProxyClientFactory):
    protocol = ProxyClient

class ProxyRequest(proxy.ProxyRequest):
    protocols = dict(http=ProxyClientFactory)

class Proxy(proxy.Proxy):
    requestFactory = ProxyRequest

class ProxyFactory(http.HTTPFactory):
    protocol = Proxy
portstr = "tcp:8080:interface=localhost" # serve on localhost:8080

if __name__ == '__main__': 
    import sys
    from twisted.internet import endpoints, reactor

    def shutdown(reason, reactor, stopping=[]):
        """Stop the reactor."""
        if stopping: return
        stopping.append(True)
        if reason:
            log.msg(reason.value)
        reactor.callWhenRunning(reactor.stop)

    log.startLogging(sys.stdout)
    endpoint = endpoints.serverFromString(reactor, portstr)
    d = endpoint.listen(ProxyFactory())
    d.addErrback(shutdown, reactor)
    reactor.run()