Transparent proxy for rewriting web pages to include The Hoff

proxy.py

"""
Install twisted (pip install twisted) and PIL (pip install PIL), and run the script.

On your gateway, run the following commands:
iptables -t nat -A PREROUTING -i br0 -s ! 192.168.0.20 -p tcp --dport 80 -j DNAT --to 192.168.0.20:8080
iptables -t nat -A POSTROUTING -o br0 -s 192.168.0.0/24 -d 192.168.0.20 -j SNAT --to 192.168.0.1
iptables -A FORWARD -s 192.168.0.0/24 -d 192.168.0.20 -i br0 -o br0 -p tcp --dport 8080 -j ACCEPT

Substitute 192.168.0.20 for the computer running the proxy.
"""
from twisted.internet import reactor
from twisted.web import proxy, http
from PIL import Image
import StringIO
import zlib

img = Image.open("hoff.png")

class LoggingProxyClient(proxy.ProxyClient):
    def __init__(self, command, rest, version, headers, data, father):
        del headers["accept-encoding"]
        proxy.ProxyClient.__init__(self, command, rest, version, headers, data, father)
        self.isImage = False
        self.isHtml = False
        self.buffer = ""

    def handleStatus(self, version, code, message):
        proxy.ProxyClient.handleStatus(self, version, code, message)

    def handleHeader(self, key, value):
        if key.lower() == "content-type" and value.startswith("image/"):
            self.isImage = True
            self.isHtml = False
            self.imageType = value
        elif key.lower() == "content-type" and value.startswith("text/html"):
            self.isHtml = True
            self.isImage = False

        proxy.ProxyClient.handleHeader(self, key, value)

    def handleResponsePart(self, buffer):
        #proxy.ProxyClient.handleResponsePart(self, buffer)
        self.buffer += buffer

    def handleResponseEnd(self):
        if not self._finished:
            if self.isImage:
                try:
                    oldBuffer = StringIO.StringIO(self.buffer)
                    oldImg = Image.open(oldBuffer)

                    w, h = oldImg.size
                    if w > 50 and h > 50 and w >= h:
                        print "Inserting the hoff into image of size: ", str(oldImg.size)

                        nh = h/2
                        nw = nh * img.size[0] / img.size[1]

                        mask = Image.new("RGBA", oldImg.size)
                        maskData = mask.load()
                        for x in xrange(0, w):
                            for y in xrange(0, h):
                                maskData[x, y] = (0xFF, 0xFF, 0xFF, 0xFF)

                        newImg = oldImg.copy().convert("RGBA")
                        pasteImg = img.copy().resize((nw, nh))
                        newImg = Image.blend(newImg, mask, 0.5)
                        newImg.paste(pasteImg, (w - nw, h - nh), pasteImg)

                        newBuffer = StringIO.StringIO()
                        if self.imageType == "image/png":
                            newImg.save(newBuffer, "PNG")
                        elif self.imageType in ("image/jpg", "image/jpeg"):
                            newImg.save(newBuffer, "JPEG")

                        self.buffer = newBuffer.getvalue()

                        self.father.responseHeaders.setRawHeaders("Cache-Control", ["no-cache"])
                except Exception as e:
                    print repr(e)
            elif self.isHtml:
                print "Hoffifying HTML"
                #try:
                #    newBuffer = zlib.decompress(self.buffer)
                #except:
                #    newBuffer = self.buffer

                newBuffer = self.buffer
                self.buffer = newBuffer \
                                  .replace("He ", " The Hoff ") \
                                  .replace("She ", " The Hoff ") \
                                  .replace("Jag", " The Hoff ") \
                                  .replace("Han ", " The Hoff ") \
                                  .replace("han ", " The Hoff ") \
                                  .replace("Honom", " The Hoff ") \
                                  .replace("honom", " The Hoff ") \
                                  .replace("Hon ", " The Hoff ") \
                                  .replace("hon ", " The Hoff ") \
                                  .replace("Henne", " The Hoff ") \
                                  .replace("henne", " The Hoff ")
                #print self.buffer

            self.father.responseHeaders.setRawHeaders("Content-Length", [str(len(self.buffer))])
            self.father.write(self.buffer)
            proxy.ProxyClient.handleResponseEnd(self)

class LoggingProxyClientFactory(proxy.ProxyClientFactory):
    protocol = LoggingProxyClient

class LoggingProxyRequest(proxy.ProxyRequest):
    protocols = { "http": LoggingProxyClientFactory }

    def process(self):
        # when the client isn't aware it's talking to a proxy, it won't send
        # the full path to the web server. here we prepend http:// and the server
        # host to the uri
        if not self.uri.startswith("http://") and not self.uri.startswith("https://"):
            self.uri = "http://" + self.getHeader("Host") + self.uri
        print "Request from %s for %s" % (self.getClientIP(), self.uri)
        try:
            proxy.ProxyRequest.process(self)
        except KeyError:
            print "HTTPS is not supported at the moment!"

class LoggingProxy(proxy.Proxy):
    requestFactory = LoggingProxyRequest

class LoggingProxyFactory(http.HTTPFactory):
    def buildProtocol(self, addr):
        return LoggingProxy()

reactor.listenTCP(8080, LoggingProxyFactory())
reactor.run()