Simple python3 snippet for handling a oauth2 code callback by redeeming it and proxy back the response from the oauth2 server.

oauth2-code-callback-handler.py

#!/usr/bin/env python

import sys, http.client, ssl, urllib.parse
from http.server import HTTPServer, BaseHTTPRequestHandler
from urllib.parse import urlparse, parse_qs

class SimpleHTTPRequestHandler(BaseHTTPRequestHandler):

    def __init__(self, callback_url, token_url, client_id, client_secret):
        self.callback_url = callback_url
        self.token_url = token_url
        self.client_id = client_id
        self.client_secret = client_secret

    def __call__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)

    def do_GET(self):

        query_paramaters = parse_qs(urlparse(self.path).query)

        """ return if code query is not present. """
        if 'code' not in query_paramaters:
            return

        """ Redeem code from oauth2 server """
        code = str(query_paramaters['code'][0])
        parsed_token_url = urlparse(self.token_url)

        params = urllib.parse.urlencode({
            'code': str(code), 
            'client_id': self.client_id, 
            'client_secret': self.client_secret,
            'redirect_uri': self.callback_url,
            'grant_type': 'authorization_code'
        })
        headers = {
            'Content-type': 'application/x-www-form-urlencoded',
            'Accept': 'application/json'
        }
        conn = http.client.HTTPSConnection(
            parsed_token_url.netloc,
            context = ssl._create_unverified_context()
        ) if parsed_token_url.scheme == 'https' else http.client.HTTPConnection(
            parsed_token_url.netloc
        )
        conn.request(
            "POST", 
            parsed_token_url.path, 
            params, 
            headers
        )
        response = conn.getresponse()

        """ Respond to client with oauth2 token response """
        self.send_response(200)
        self.send_header(
            "Content-type", 
            response.headers['content-type']
        )
        self.end_headers()
        self.wfile.write(response.read())


callback_url = str(sys.argv[1])

handler = SimpleHTTPRequestHandler(
    callback_url, # callback_url
    str(sys.argv[2]), # target_url
    str(sys.argv[3]), # client_id
    str(sys.argv[4]) # client_secret
)

httpd = HTTPServer(
    (
        urlparse(callback_url).hostname, 
        urlparse(callback_url).port
    ), 
    handler
)

print("Hosting on " + callback_url)
    
httpd.serve_forever()

example:
python3 oauth2-code-callback-handler.py http://localhost:8000 https://localhost:8443/oauth/v2/oauth-token test-client client-secret