How to implement nginx proxy_pass in gae standard?

Question

I'm using firebase-ui-web for authentication in my GAE app. There is an annoying issue recently where Safari is blocking 3rd party cookies and this breaks the login process.

The best solution ( described here ) seems to be implement a reverse-proxy config with nginx. Here are the details:

# reverse proxy for signin-helpers for popup/redirect sign in.
location /__/auth {
  proxy_pass https://<project>.firebaseapp.com;
}

Is it possible to accomplish the same thing in GAE where we are not able to add nginx rules? I'm using Python3/Flask if it matters.

Answer 1

With some Googling, I came up with this:

@app.route('/<path:path>', methods=['GET', 'POST'])
def proxy(path):
    url = f'https://www.example.com/{path}'
    excluded_headers = ['content-encoding', 'content-length', 
                        'transfer-encoding', 'connection']

    if request.method == 'GET':
        resp = requests.get(url)
    elif request.method == 'POST':
        resp = requests.post(url, data=request.form)

    headers = [(name, value) for (name, value) in resp.raw.headers.items() 
        if name.lower() not in excluded_headers]
    response = Response(resp.content, resp.status_code, headers)
    return response

Though I'm not confident that the sources are good so feedback is welcome.