Monkey patch some browser props

[Valleymu]

Hi,

I've written code which monkey patch of some browser props, website that I try to scrap takes browser fingerprint with canvas data url etc. I was able to patch it with this code:

PATCH_CANVAS_JS = f"""
(() => {{
  const CHOSEN_CANVAS_HASH = {CANVAS_HASH_JS};
  const NEW_LANGUAGE = '{NEW_LANGUAGE}';
  const NEW_LANGUAGES = {NEW_LANGUAGES_JS};
  const NEW_TZ_OFFSET = {NEW_TZ_OFFSET};
  const NEW_HW_THREADS = {NEW_HW_THREADS};
  const NEW_DEVICE_MEMORY = {NEW_DEVICE_MEMORY};

  const origToDataURL = HTMLCanvasElement.prototype.toDataURL;
  Object.defineProperty(HTMLCanvasElement.prototype, 'toDataURL', {{
    value: function (...args) {{
      try {{
        if (typeof CHOSEN_CANVAS_HASH === 'string' && CHOSEN_CANVAS_HASH.length) {{
          // If it’s already a data: URL, return it; else wrap as text.
          return /^data:/i.test(CHOSEN_CANVAS_HASH)
            ? CHOSEN_CANVAS_HASH
            : 'data:text/plain;charset=utf-8,' + encodeURIComponent(CHOSEN_CANVAS_HASH);
        }}
      }} catch (_) {{}}
      return origToDataURL.apply(this, args);
    }},
    configurable: false,
    writable: false,
  }});

  const overrideNavigatorProp = (prop, getter) => {{
    try {{
      const proto = Navigator && Navigator.prototype;
      const desc = proto ? Object.getOwnPropertyDescriptor(proto, prop) : null;
      if (desc && desc.configurable) {{
        Object.defineProperty(proto, prop, {{ get: getter, configurable: false }});
        return;
      }}
    }} catch (_) {{}}
    try {{
      Object.defineProperty(navigator, prop, {{ get: getter, configurable: false }});
    }} catch (_) {{}}
  }};

  // --- language / languages ---
  overrideNavigatorProp('language',  () => NEW_LANGUAGE);
  overrideNavigatorProp('languages', () => NEW_LANGUAGES);

  // --- hardwareConcurrency ---
  overrideNavigatorProp('hardwareConcurrency', () => NEW_HW_THREADS);

  // --- deviceMemory ---
  overrideNavigatorProp('deviceMemory', () => NEW_DEVICE_MEMORY);
  
  // --- platform ---
  overrideNavigatorProp('platform', () => 'Win32');

  // --- userAgent ---
  overrideNavigatorProp('userAgent', () => 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/138.0.0.0 Safari/537.36');

  // --- timezoneOffset ---
  const origGetTimezoneOffset = Date.prototype.getTimezoneOffset;
  Object.defineProperty(Date.prototype, 'getTimezoneOffset', {{
    value: function () {{ return NEW_TZ_OFFSET; }},
    writable: false,
    configurable: false,
  }});

  // (Optional) stash originals, non-enumerable
  try {{
    Object.defineProperty(window, '__origFingerprintFns__', {{
      value: Object.freeze({{
        fillText: origFillText,
        getTimezoneOffset: origGetTimezoneOffset,
      }}),
      writable: false,
      configurable: false,
      enumerable: false
    }});
  }} catch (_) {{}}
}})();
"""
        with SB(
                uc=True,
                incognito=True,
                locale_code="en",
                user_data_dir=user_data_dir,
                proxy=proxy,
        ) as sb:
                      # Enable the Network domain
        sb.driver.execute_cdp_cmd("Network.enable", {})

        # Override UA + UA-CH
        sb.driver.execute_cdp_cmd("Network.setUserAgentOverride", {
            "userAgent": (
                "Mozilla/5.0 (Windows NT 10.0; Win64; x64) "
                "AppleWebKit/537.36 (KHTML, like Gecko) "
                "Chrome/138.0.0.0 Safari/537.36"
            ),
            "userAgentMetadata": {
                "brands": [
                    {"brand": "Chromium", "version": "138"},
                    {"brand": "Google Chrome", "version": "138"},
                    {"brand": "Not)A;Brand", "version": "8"}
                ],
                "platform": "Windows",  # → sec-ch-ua-platform: "Windows"
                "platformVersion": "10.0.0",
                "architecture": "x86",
                "model": "",  # not sent on desktop
                "mobile": False,  # → sec-ch-ua-mobile: ?0
                "bitness": "64",
            }
        })
        sb.open(url)
        do_some_magic()

It works fine in IDE, although I get detected in docker container, docker container works when I use cdp mode, it's not being detected although I can't spoof all of those properties with cdp mode as it uses driver. Is there any cdp mode way of monkey patching those properties before website is being loaded?

[mdmintz]

There are fingerprints that you can change in CDP Mode, such as timezone and geolocation. Example:
https://github.com/seleniumbase/SeleniumBase/blob/master/examples/cdp_mode/raw_timezone_sb.py

Docker leaves hardcoded fingerprints that can't be changed, so I wouldn't use that if you need stealth.

[Valleymu]

my problem is canvas fingerprint which is being sent as payload. What I'm trying to do is to override headers and payload with on paused event but I can't make it work, looks like script is stale after log print("New body preview:", preview):

FINGERPRINT = generate_fingerprint()

def _to_header_entries(hdict):
    return [mycdp.fetch.HeaderEntry(name=k, value=v) for k, v in hdict.items()]


async def on_request_paused(evt: mycdp.fetch.RequestPaused, tab):
    req = evt.request

    # Build headers for ALL requests
    h = dict(req.headers or {})
    h["User-Agent"] = UA
    h["sec-ch-ua"] = '"Chromium";v="138", "Google Chrome";v="138", "Not A(Brand";v="8"'
    h["sec-ch-ua-mobile"] = "?0"
    h["sec-ch-ua-platform"] = '"Windows"'
    h["sec-ch-ua-arch"] = '"x86"'
    h["sec-ch-ua-bitness"] = '"64"'
    h["sec-ch-ua-full-version"] = '"138.0.0.0"'
    # Let Chromium compute content-length
    h.pop("Content-Length", None)
    h.pop("content-length", None)

    post_data = None

    try:
        if req.method == "POST" and "someText" in req.url:
            post_data = json.dumps({"ui": FINGERPRINT})

            print("Intercepted POST to", req.url)
            preview = (post_data[:140] + "...") if len(post_data) > 140 else post_data
            print("New body preview:", preview)

        tab.feed_cdp(
            mycdp.fetch.continue_request(
                request_id=evt.request_id,
                post_data=post_data,
                headers=[mycdp.fetch.HeaderEntry(name=k, value=v) for k, v in h.items()],
            )
        )
    except Exception as e:
        try:
            tab.feed_cdp(mycdp.fetch.continue_request(request_id=evt.request_id))
        finally:
            print("continue_request failed:", repr(e))



        sb.activate_cdp_mode("about:blank")

        sb.cdp.add_handler(mycdp.fetch.RequestPaused, on_request_paused)

        tab = sb.cdp.page
        loop = sb.cdp.get_event_loop()

        async def cdp_setup():
            await tab.send(mycdp.target.set_discover_targets(discover=True))
            await tab.send(
                mycdp.target.set_auto_attach(auto_attach=True, wait_for_debugger_on_start=False, flatten=True))

            await tab.send(mycdp.network.enable())
            await tab.send(mycdp.network.set_bypass_service_worker(bypass=True))

            await tab.send(mycdp.fetch.enable(patterns=[
                mycdp.fetch.RequestPattern(url_pattern="*", request_stage=mycdp.fetch.RequestStage.REQUEST)
            ]))

        loop.run_until_complete(cdp_setup())

        sb.cdp.open(url)

[mdmintz]

You can try working with the existing examples that use mycdp.fetch.RequestPaused...
https://github.com/search?q=repo%3Aseleniumbase%2FSeleniumBase%20mycdp.fetch.RequestPaused&type=code

...and the ones that use mycdp.fetch.continue_request:
https://github.com/search?q=repo%3Aseleniumbase%2FSeleniumBase+mycdp.fetch.continue_request&type=code

I'm no CDP expert, but SeleniumBase does provide the tools for using CDP if you understand how it works and how to formulate the proper CDP commands/actions for what you're trying to accomplish, assuming that those actions are allowed by CDP.

[Valleymu]

thanks, will try to dig into cdp