Flask-CAS is a Flask extension which makes it easy to authenticate with a CAS.

The Central Authentication Service (CAS) is a single sign-on protocol for the web. Its purpose is to permit a user to access multiple applications while providing their credentials (such as userid and password) only once. It also allows web applications to authenticate users without gaining access to a user's security credentials, such as a password. The name CAS also refers to a software package that implements this protocol.

http://www.jasig.org/cas

Want to see it in action? Here is a live demo that lets you authenticate against your favorite CAS Server!

http://flask-cas-extension-demo.cameronbwhite.com/

Flask-CAS is available on PyPI! You can install it with pip.

pip install Flask-CAS

If you want to do it the hard way you can clone the repository and install Flask-CAS in a virtualenv.

1. Clone it git clone git@github.com:cameronbwhite/Flask-CAS.git
2. Enter it cd Flask-CAS
3. Create a virtualenv and enter it (Optional) virtualenv venv && source venv/bin/activate
4. Install it python setup.py install

After Flask-CAS is installed you will be able to import the flask.ext.cas packages. There is only one thing you care about inside the package which is the CAS class.

from flask.ext.cas import CAS

There are two ways to use the CAS class.

1. Add the application object at construction time

   app = Flask(__name__)
   CAS(app)

2. Or initialize the application with CAS.init_app

   cas = CAS()
   app = Flask(__name__)
   cas.init_app(app)

The CAS class will add two routes /login/ and /logout/. You can prefix these routes if you pass a second argument to the CAS constructor or init_app depending on the method you choose.

The /login/ route will redirect the user to the CAS specified by the CAS_SERVER configuration value. If login is successful the user will be redirect to the endpoint specified by the CAS_AFTER_LOGIN configuration value, and the logged in user's username will be store in the session under the key specified by the CAS_USERNAME_SESSION_KEY configuration value.

The /logout/ route will redirect the user to the CAS logout page and the username will be removed from the session.

import flask
from flask import Flask
from flask.ext.cas import CAS

app = Flask(__name__)
cas = CAS(app, '/cas')
app.config['CAS_SERVER'] = 'https://sso.pdx.edu' 
app.config['CAS_AFTER_LOGIN'] = 'route_root'

@app.route('/')
def route_root():
    return flask.render_template(
        'layout.html',
        username = cas.username,
    )