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

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.