mitmproxy_replace.py

# mitmproxy addon to serve modified content
# how to use:
#  1. create replace.txt file in your current working directory
#  2. add urls you want to replace to that file, one line per url; urls can be regular expresions; lines starting with # are ignored
#  3. start mitmproxy with parameter -s mitmproxy_replace.py to load this addon
#  4. configure your OS or browser to use your running mitmproxy instance (default port 8080)
#  5. install mitmproxy certificate to allow proxying https by navigating to http://mitm.it/
#  5. navigate to the url you want to replace; a dump of the response content is created in the replace folder in your current working directory
#  6. modify the content dump and reload the page

from mitmproxy import ctx
import re
import os
# import base64
import errno

class Replacer:
    def __init__(self):
        self.matchers = []
        self.listFilePath = 'replace.txt'
        self.copiesDir = 'replace'
        self.loadedFileTimestamp = 0
        
    def isListFileModified(self):
        try:
            return self.loadedFileTimestamp < os.path.getmtime(self.listFilePath)
        except OSError:
            ctx.log.info("Replacer addon list file could not be opened")
        return False
        
    def parseListFile(self):
        if self.isListFileModified():
            self.loadedFileTimestamp = os.path.getmtime(self.listFilePath)
            with open(self.listFilePath) as f:
                content = f.readlines()
                self.matchers = [re.compile("^{}$".format(x.strip())) for x in content if x.strip() and not x.strip().startswith("#")]
                
    def getFileName(self, flow):
        return flow.request.host + re.sub(r"[^a-zA-Z0-9-+\./_]", "", flow.request.path).replace("/", "__") # + "_" + base64.urlsafe_b64encode(flow.request.url.encode()).decode()

    def response(self, flow):
        self.parseListFile()
        if any(re.match(m, flow.request.url) for m in self.matchers):
            try:
                os.makedirs(self.copiesDir)
            except OSError as e:
                if e.errno != errno.EEXIST:
                    raise
            ctx.log.alert("replace: " + flow.request.url)
            filename = self.getFileName(flow)
            filepath = self.copiesDir + "/" + filename
            if os.path.isfile(filepath):
                with open(filepath, "rb", buffering=0) as f:
                    flow.response.content = f.readall()
            else:
                with open(filepath, "wb") as f:
                    f.write(flow.response.content)

addons = [
    Replacer()
]