Script for mitmproxy to replace response bodies with the content of arbitrary other files

replacefiles.py

"""
This script replaces a response body with the contents of a specific file.
"""
import mimetypes
import os
import typing

from mitmproxy import ctx
from mitmproxy import exceptions
from mitmproxy import flowfilter
from mitmproxy import http
from mitmproxy import optmanager


class ReplaceFiles:
    def __init__(self):
        mimetypes.init()
        self.lst = []

    def load(self, loader: optmanager.OptManager) -> None:
        loader.add_option(
            name="replacefiles",
            typespec=typing.Sequence[str],
            default=[],
            help="""Replacements of files of the form
            [filter expression]:[path to file]
            """
        )

    def configure(self, updated):
        if "replacefiles" in updated:
            lst = []
            for rep in ctx.options.replacefiles:
                fpatt, filename = rep.split(":", 1)
                filename = os.path.expanduser(filename)
                flt = flowfilter.parse(fpatt)
                if not flt:
                    raise exceptions.OptionsError(
                        "Invalid filter pattern: %s" % fpatt
                    )
                if not os.path.isfile(filename):
                    raise exceptions.OptionsError(
                        "Invalid file path: {}".format(filename)
                    )
                lst.append((flt, filename))
            self.lst = lst

    def response(self, flow: http.HTTPFlow) -> None:
        for flt, filename in self.lst:
            if flt(flow):
                try:
                    with open(filename, "rb") as f:
                        c = f.read()
                except IOError:
                    ctx.log.warn(
                        "Could not read replacement file {}".format(filename)
                    )
                    return
                flow.response.status_code = 200
                flow.response.reason = "OK"
                ctype, enc = mimetypes.guess_type(filename, strict=False)
                if ctype is not None:
                    flow.response.headers["Content-Type"] = ctype
                if enc is not None:
                    flow.response.headers["Content-Encoding"] = enc
                elif "Content-Encoding" in flow.response.headers:
                    del(flow.response.headers["Content-Encoding"])
                flow.response.content = c


addons = [ReplaceFiles()]