oauth2

oauth_server.py

# python3 -mvenv venv && source venv/bin/activate && pip install flask requests && python3 server.py
# open http://localhost:8080
import flask
import requests

app = flask.Flask(__name__)

# To create a client ID/secret for Google oauth:
# 1. Go to the Google Cloud Console,
# 2. Create a project
# 3. Go to API credentials and Create a credentials of type OAuth Client ID
# 4. Make sure the URL http://localhost:8080/oauth2callback is part of the authorized redirect list.
# CLIENT_ID = '123456789.apps.googleusercontent.com'
# Read the client secret from a file or environmental variable in a real app
# CLIENT_SECRET = 'abc123'
# This is the scope you will require to have access to. Here we only need access to the user's email.
SCOPE = 'https://www.googleapis.com/auth/userinfo.email'
# This is the callback used to deal with google authentication indirection business.
REDIRECT_URI = 'http://localhost:8080/oauth2callback'
# This is the URL used to retrieve the email at the end of the oauth exchange.
EMAIL_URI = 'https://openidconnect.googleapis.com/v1/userinfo'

# Any good ol path into your application
@app.route('/')
def index():
  if 'credentials' not in flask.session:
    return flask.redirect(flask.url_for('oauth2callback'))
  credentials = json.loads(flask.session['credentials'])
  if credentials['expires_in'] <= 0:
    return flask.redirect(flask.url_for('oauth2callback'))
  else:
    headers = {'Authorization': 'Bearer {}'.format(credentials['access_token'])}
    r = requests.get(EMAIL_URI, headers=headers)
    return r.json().email

@app.route('/oauth2callback')
def oauth2callback():
  if 'code' not in flask.request.args:
    auth_uri = ('https://accounts.google.com/o/oauth2/v2/auth?response_type=code'
                '&client_id={}&redirect_uri={}&scope={}').format(CLIENT_ID, REDIRECT_URI, SCOPE)
    return flask.redirect(auth_uri)
  else:
    auth_code = flask.request.args.get('code')
    data = {'code': auth_code,
            'client_id': CLIENT_ID,
            'client_secret': CLIENT_SECRET,
            'redirect_uri': REDIRECT_URI,
            'grant_type': 'authorization_code'}
    r = requests.post('https://oauth2.googleapis.com/token', data=data)
    flask.session['credentials'] = r.text
    return flask.redirect(flask.url_for('index'))

if __name__ == '__main__':
  import uuid
  app.secret_key = str(uuid.uuid4())
  app.debug = False
  app.run(port=8080)