Using OAuth 2.0 for Web Server Applications

[Natron42]

I am trying to get the "Using OAuth 2.0 for Web Server Applications" example program to work on my Google Cloud Shell. The url is at https://developers.google.com/identity/protocols/oauth2/web-server#example
It fails on line 113 flow.fetch_token(authorization_response=authorization_response)
The error is oauthlib.oauth2.rfc6749.errors.CustomOAuth2Error: (redirect_uri_mismatch) Bad Request

# https://developers.google.com/identity/protocols/oauth2/web-server#example

# -*- coding: utf-8 -*-

import os
import flask
import requests

import google.oauth2.credentials
import google_auth_oauthlib.flow
import googleapiclient.discovery

import logging
logging.basicConfig(level=logging.DEBUG, format='%(asctime)s %(levelname)s: %(message)s')
logger = logging.getLogger(__name__)
logger.debug("Line 16 debuger is working")

# This variable specifies the name of a file that contains the OAuth 2.0
# information for this application, including its client_id and client_secret.
#! CLIENT_SECRETS_FILE = "client_secret.json"
CLIENT_SECRETS_FILE = "./credentials.json"  #this is correct 

# This OAuth 2.0 access scope allows for full read/write access to the
# authenticated user's account and requires requests to use an SSL connection.

# the scopes must equate to the same scopes in the JSON file downloaded from GCP to prevent a warning.
#SCOPES = ['https://www.googleapis.com/auth/drive.metadata.readonly']
SCOPES = [
   'https://www.googleapis.com/auth/userinfo.profile',
   'https://www.googleapis.com/auth/calendar.readonly',
   'https://www.googleapis.com/auth/tasks.readonly',
   #this ones fails the program when refresh the pickle file if openid is not added
   'https://www.googleapis.com/auth/userinfo.email','openid',
   'https://www.googleapis.com/auth/drive.metadata.readonly'
   ]
API_SERVICE_NAME = 'drive'
API_VERSION = 'v2'

app = flask.Flask(__name__)
# Note: A secret key is included in the sample so that it works.
# If you use this code in your application, replace this with a truly secret
# key. See https://flask.palletsprojects.com/quickstart/#sessions.
#! app.secret_key = 'REPLACE ME - this value is here as a placeholder.'
app.secret_key    = os.environ.get("SECRET_KEY") or os.urandom(24)


@app.route('/')
def index():
  return print_index_table()


@app.route('/test')
def test_api_request():
  if 'credentials' not in flask.session:
    return flask.redirect('authorize')

  # Load credentials from the session.
  credentials = google.oauth2.credentials.Credentials(
      **flask.session['credentials'])

  drive = googleapiclient.discovery.build(
      API_SERVICE_NAME, API_VERSION, credentials=credentials)

  files = drive.files().list().execute()

  # Save credentials back to session in case access token was refreshed.
  # ACTION ITEM: In a production app, you likely want to save these
  #              credentials in a persistent database instead.
  flask.session['credentials'] = credentials_to_dict(credentials)

  return flask.jsonify(**files)


@app.route('/authorize')
def authorize():
  # Create flow instance to manage the OAuth 2.0 Authorization Grant Flow steps.
  flow = google_auth_oauthlib.flow.Flow.from_client_secrets_file(
      CLIENT_SECRETS_FILE, scopes=SCOPES)

  # The URI created here must exactly match one of the authorized redirect URIs
  # for the OAuth 2.0 client, which you configured in the API Console. If this
  # value doesn't match an authorized URI, you will get a 'redirect_uri_mismatch'
  # error.
  flow.redirect_uri = flask.url_for('oauth2callback', _external=True)

  authorization_url, state = flow.authorization_url(
      # Enable offline access so that you can refresh an access token without
      # re-prompting the user for permission. Recommended for web server apps.
      access_type='offline',
      # Enable incremental authorization. Recommended as a best practice.
      include_granted_scopes='true')

  # Store the state so the callback can verify the auth server response.
  flask.session['state'] = state

  return flask.redirect(authorization_url)


@app.route('/oauth2callback')
def oauth2callback():
  # Specify the state when creating the flow in the callback so that it can
  # verified in the authorization server response.
  state = flask.session['state']

  flow = google_auth_oauthlib.flow.Flow.from_client_secrets_file(
      CLIENT_SECRETS_FILE, scopes=SCOPES, state=state)
  flow.redirect_uri = flask.url_for('oauth2callback', _external=True)

  # Use the authorization server's response to fetch the OAuth 2.0 tokens.
  authorization_response = flask.request.url
  logger.debug("XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX authorization_response="+authorization_response)
  logger.debug("XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX117")
  flow.fetch_token(authorization_response=authorization_response)
  logger.debug("XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX119")  #did NOT get here
  # Store credentials in the session.
  # ACTION ITEM: In a production app, you likely want to save these
  #              credentials in a persistent database instead.
  credentials = flow.credentials
  flask.session['credentials'] = credentials_to_dict(credentials)

  return flask.redirect(flask.url_for('test_api_request'))


@app.route('/revoke')
def revoke():
  if 'credentials' not in flask.session:
    return ('You need to <a href="/authorize">authorize</a> before ' +
            'testing the code to revoke credentials.')

  credentials = google.oauth2.credentials.Credentials(
    **flask.session['credentials'])

  revoke = requests.post('https://oauth2.googleapis.com/revoke',
      params={'token': credentials.token},
      headers = {'content-type': 'application/x-www-form-urlencoded'})

  status_code = getattr(revoke, 'status_code')
  if status_code == 200:
    return('Credentials successfully revoked.' + print_index_table())
  else:
    return('An error occurred.' + print_index_table())


@app.route('/clear')
def clear_credentials():
  if 'credentials' in flask.session:
    del flask.session['credentials']
  return ('Credentials have been cleared.<br><br>' +
          print_index_table())


def credentials_to_dict(credentials):
  return {'token': credentials.token,
          'refresh_token': credentials.refresh_token,
          'token_uri': credentials.token_uri,
          'client_id': credentials.client_id,
          'client_secret': credentials.client_secret,
          'scopes': credentials.scopes}

def print_index_table():
  return ('<table>' +
          '<tr><td><a href="/test">Test an API request</a></td>' +
          '<td>Submit an API request and see a formatted JSON response. ' +
          '    Go through the authorization flow if there are no stored ' +
          '    credentials for the user.</td></tr>' +
          '<tr><td><a href="/authorize">Test the auth flow directly</a></td>' +
          '<td>Go directly to the authorization flow. If there are stored ' +
          '    credentials, you still might not be prompted to reauthorize ' +
          '    the application.</td></tr>' +
          '<tr><td><a href="/revoke">Revoke current credentials</a></td>' +
          '<td>Revoke the access token associated with the current user ' +
          '    session. After revoking credentials, if you go to the test ' +
          '    page, you should see an <code>invalid_grant</code> error.' +
          '</td></tr>' +
          '<tr><td><a href="/clear">Clear Flask session credentials</a></td>' +
          '<td>Clear the access token currently stored in the user session. ' +
          '    After clearing the token, if you <a href="/test">test the ' +
          '    API request</a> again, you should go back to the auth flow.' +
          '</td></tr></table>')


if __name__ == '__main__':
  # When running locally, disable OAuthlib's HTTPs verification.
  # ACTION ITEM for developers:
  #     When running in production *do not* leave this option enabled.
  os.environ['OAUTHLIB_INSECURE_TRANSPORT'] = '1'

  # Specify a hostname and port that are set as a valid redirect URI
  # for your API project in the Google API Console.
  app.run('0.0.0.0', 5000, debug=True)

[ronnelg]

Hi @Natron42,

Welcome to Google Cloud Community!

I understand that you're looking for help with the redirect_uri_mismatch error. While I don't have the specific expertise to answer your query, I recommend checking out Google Cloud Security Community Forum. They have a dedicated community and resources that might be more helpful in addressing your question.

[Natron42]

Hi Ronnelg,  Is it possible to move the posting to the Google Cloud Security Community Forum?