Saving decoded Protobuf content

Question

I'm trying to setup a .py plugin that will save decoded Protobuf responses to file, but whatever I do, the result is always file in byte format (not decoded). I have also tried to do the same by using "w" in Mitmproxy - although on screen I saw decoded data, in the file it was encoded again. Any thoughts how to do it correctly?

Sample code for now:

import mitmproxy
def response(flow):
    # if flow.request.pretty_url.endswith("some-url.com/endpoint"):
    if flow.request.pretty_url.endswith("some-url.com/endpoint"):
        f = open("test.log","ab")
        with decoded(flow.response)
            f.write(flow.request.content)
            f.write(flow.response.content)

Answer 1

I was able to find the way to do that. Seems mitmdump or mitmproxy wasn't able to save raw decoded Protobuf, so I used:

mitmdump -s decode_script.py

with the following script to save the decoded data to a file:

import mitmproxy
import subprocess
import time

def response(flow):
    if flow.request.pretty_url.endswith("HERE/IS/SOME/API/PATH"):
        protobuffedResponse=flow.response.content
        (out, err) = subprocess.Popen(['protoc', '--decode_raw'], stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE).communicate(protobuffedResponse)
        outStr = str(out, 'utf-8')
        outStr = outStr.replace('\\"', '"')
        timestr = time.strftime("%Y%m%d-%H%M%S")
        with open("decoded_messages/" + timestr + ".decode_raw.log","w") as f:
            f.write(outStr)