Authentication using cookie key with asynchronous callback

Question

I need to write authentication function with asynchronous callback from remote Auth API. Simple authentication with login is working well, but authorization with cookie key, does not work. It should checks if in cookies present key "lp_login", fetch API url like async and execute on_response function.

The code almost works, but I see two problems. First, in on_response function I need to setup secure cookie for authorized user on every page. In code user_id returns correct ID, but line: self.set_secure_cookie("user", user_id) does't work. Why it can be?

And second problem. During async fetch API url, user's page has loaded before on_response setup cookie with key "user" and the page will has an unauthorized section with link to login or sign on. It will be confusing for users. To solve it, I can stop loading page for user who trying to load first page of site. Is it possible to do and how? Maybe the problem has more correct way to solve it?

class BaseHandler(tornado.web.RequestHandler):
    @tornado.web.asynchronous
    def get_current_user(self):
        user_id = self.get_secure_cookie("user")
        user_cookie = self.get_cookie("lp_login")
        if user_id:
            self.set_secure_cookie("user", user_id)
            return Author.objects.get(id=int(user_id))
        elif user_cookie:
            url = urlparse("http://%s" % self.request.host)
            domain = url.netloc.split(":")[0]
            try:
                username, hashed_password = urllib.unquote(user_cookie).rsplit(',',1)
            except ValueError:
                # check against malicious clients
                return None
            else:
                url = "http://%s%s%s/%s/" % (domain, "/api/user/username/", username, hashed_password)
                http = tornado.httpclient.AsyncHTTPClient()
                http.fetch(url, callback=self.async_callback(self.on_response))
        else:
            return None

    def on_response(self, response):
        answer = tornado.escape.json_decode(response.body)
        username = answer['username']
        if answer["has_valid_credentials"]:
            author = Author.objects.get(email=answer["email"])
            user_id = str(author.id)
            print user_id # It returns needed id
            self.set_secure_cookie("user", user_id) # but session can's setup

Answer 1

It seems you cross-posted this on the tornado mailing list here

One of the problems you are running into is that you can't start the async call inside of get_current_user, you can only start an async call from something that happens inside of get or post.

I've not tested it, but i think this should get you close to what you are looking for.

#!/bin/python
import tornado.web
import tornado.http
import tornado.escape
import functools
import logging
import urllib

import Author

def upgrade_lp_login_cookie(method):
    @functools.wraps(method)
    def wrapper(self, *args, **kwargs):
        if not self.current_user and self.get_cookie('lp_login'):
            self.upgrade_lp_login(self.async_callback(method, self, *args, **kwargs))
        else:
            return method(self, *args, **kwargs)
    return wrapper


class BaseHandler(tornado.web.RequestHandler):
    def get_current_user(self):
        user_id = self.get_secure_cookie("user")
        if user_id:
            return Author.objects.get(id=int(user_id))

    def upgrade_lp_login(self, callback):
        lp_login = self.get_cookie("lp_login")
        try:
            username, hashed_password = urllib.unquote(lp_login).rsplit(',',1)
        except ValueError:
            # check against malicious clients
            logging.info('invalid lp_login cookie %s' % lp_login)
            return callback()

        url = "http://%(host)s/api/user/username/%s/%s" % (self.request.host, 
                                                        urllib.quote(username), 
                                                        urllib.quote(hashed_password))
        http = tornado.httpclient.AsyncHTTPClient()
        http.fetch(url, self.async_callback(self.finish_upgrade_lp_login, callback))

    def finish_upgrade_lp_login(self, callback, response):
        answer = tornado.escape.json_decode(response.body)
        # username = answer['username']
        if answer['has_valid_credentials']:
            # set for self.current_user, overriding previous output of self.get_current_user()
            self._current_user = Author.objects.get(email=answer["email"])
            # set the cookie for next request
            self.set_secure_cookie("user", str(self.current_user.id))

        # now chain to the real get/post method
        callback()

    @upgrade_lp_login_cookie
    def get(self):
        self.render('template.tmpl')