Authlib client error: State not equal in request and response - flask

Question

I'm trying to implement authlib client and server. I took example OAuth2.0 example and making my own client authorization on Flask site following tutorial. This is my code:
from flask import Flask, redirect, url_for, session, request
from authlib.flask.client import OAuth
from authlib.client.errors import OAuthException
APP_ID = 'KBtRDO3r2HETjw4TcLznthoj'
APP_SECRET = '3g4C6nbJcTIYX3jyCIEmf6KE8h8pzxUhjy6ArlY3AEgj1snv'
app = Flask('testa_client')
app.debug = True
app.secret_key = 'development'
oauth = OAuth()
oauth.init_app(app)
remote = oauth.register(
'testa',
client_id=APP_ID,
client_secret=APP_SECRET,
# request_token_params={'scope': 'base'},
base_url='http://127.0.0.1:5000',
access_token_url='http://127.0.0.1:5000/auth/token',
authorize_url='http://127.0.0.1:5000/auth/connect'
)
#app.route('/')
def index():
return redirect(url_for('login'))
#app.route('/login')
def login():
callback = url_for(
'websa_authorized',
next=request.args.get('next') or request.referrer or None,
_external=True
)
return remote.authorize_redirect(callback=callback)
#app.route('/login/authorized')
def websa_authorized():
resp = remote.authorize_access_token()
if resp is None:
return 'Access denied: reason=%s error=%s' % (
request.args['error_reason'],
request.args['error_description']
)
if isinstance(resp, OAuthException):
return 'Access denied: %s' % resp.message
session['oauth_token'] = (resp['access_token'], '')
me = remote.get('/user/me')
return 'Logged in as id=%s name=%s redirect=%s' % \
(me.data['id'], me.data['name'], request.args.get('next'))
app.run(port=9001)
Server code as I said almost the same as in https://github.com/authlib/example-oauth2-server repository.
When I'm trying to make an authorization I'm getting to the authorization server (on port 5000) and confirm that I allow access. But when I got redirect back to the client site on page http://127.0.0.1:9001/login/authorized?code=...&state=... (on 9001) I'm getting the error:
127.0.0.1 - - [20/Jun/2018 09:33:12] "GET /login/authorized?code=1jw8niqDdzSLpnYHGvT1NIulTwRdVoy22UNm3G4xEaTOWE9Y&state=JUuJtmnseITz8WZYaDeHcAsiIL6KfS HTTP/1.1" 500 -
Traceback (most recent call last):
File "/Users/xen/envs/auth-s4eELiZl/lib/python3.6/site-packages/flask/app.py", line 2309, in __call__
return self.wsgi_app(environ, start_response)
File "/Users/xen/envs/auth-s4eELiZl/lib/python3.6/site-packages/flask/app.py", line 2295, in wsgi_app
response = self.handle_exception(e)
File "/Users/xen/envs/auth-s4eELiZl/lib/python3.6/site-packages/flask/app.py", line 1741, in handle_exception
reraise(exc_type, exc_value, tb)
File "/Users/xen/envs/auth-s4eELiZl/lib/python3.6/site-packages/flask/_compat.py", line 35, in reraise
raise value
File "/Users/xen/envs/auth-s4eELiZl/lib/python3.6/site-packages/flask/app.py", line 2292, in wsgi_app
response = self.full_dispatch_request()
File "/Users/xen/envs/auth-s4eELiZl/lib/python3.6/site-packages/flask/app.py", line 1815, in full_dispatch_request
rv = self.handle_user_exception(e)
File "/Users/xen/envs/auth-s4eELiZl/lib/python3.6/site-packages/flask/app.py", line 1718, in handle_user_exception
reraise(exc_type, exc_value, tb)
File "/Users/xen/envs/auth-s4eELiZl/lib/python3.6/site-packages/flask/_compat.py", line 35, in reraise
raise value
File "/Users/xen/envs/auth-s4eELiZl/lib/python3.6/site-packages/flask/app.py", line 1813, in full_dispatch_request
rv = self.dispatch_request()
File "/Users/xen/envs/auth-s4eELiZl/lib/python3.6/site-packages/flask/app.py", line 1799, in dispatch_request
return self.view_functions[rule.endpoint](**req.view_args)
File "/Users/xen/Dev/auth/client_example/client_testa.py", line 52, in testa_authorized
resp = remote.authorize_access_token()
File "/Users/xen/envs/auth-s4eELiZl/lib/python3.6/site-packages/authlib/flask/client/oauth.py", line 257, in authorize_access_token
raise MismatchingStateError()
authlib.client.errors.MismatchingStateError: mismatching_state: CSRF Warning! State not equal in request and response.
What can be wrong? Both parts use Authlib 0.8.

Answer 1

I've spent a lot of time to find an error in my code. The problem was not in the code, but in the way I use it. I accessed both applications by local IP address 127.0.0.1 and different ports. Browser mix sessions and cookies for such related URIs. I give another local domain name (http://test:9001 in my case) for the service and that fixed my problem.
When you work with OAuth don't use the local address and same domains.