Scripting API Guide

Extend RelayCraft's capabilities using Python. The scripting API is fully compatible with mitmproxy.

Basic Structure

A script is a Python file that defines event handlers. The most common handlers are request and response.

from mitmproxy import http

def request(flow: http.HTTPFlow):
    # Called when a client request is received
    if "example.com" in flow.request.pretty_host:
        flow.request.headers["X-Debug"] = "True"

def response(flow: http.HTTPFlow):
    # Called when a server response is received
    if flow.response.status_code == 404:
        flow.response.status_code = 200
        flow.response.content = b"Fixed by RelayCraft!"

Common Use Cases

1. Redirecting Traffic

Useful for pointing a production app to a local development server.

def request(flow):
    if flow.request.host == "api.production.com":
        flow.request.host = "localhost"
        flow.request.port = 3000
        flow.request.scheme = "http"