auth.py

#!/usr/bin/env python

# ----------------------------------------------------------------------
# auth.py
# Author: Bob Dondero
# ----------------------------------------------------------------------

from urllib.request import urlopen
from urllib.parse import quote
from re import sub
from sys import stderr
from flask import request, redirect, session, abort
from app import app
import database
import models

# ----------------------------------------------------------------------

# Authors: Alex Halderman, Scott Karlin, Brian Kernighan, Bob Dondero
# Editors: Arnav Kumar

# ----------------------------------------------------------------------

_CAS_URL = 'https://fed.princeton.edu/cas/'


# ----------------------------------------------------------------------

# Return url after stripping out the "ticket" parameter that was
# added by the CAS server.


def strip_ticket(url):
    if url is None:
        return "something is badly wrong"
    url = sub(r'ticket=[^&]*&?', '', url)
    url = sub(r'\?&?$|&$', '', url)
    return url


# ----------------------------------------------------------------------

# Validate a login ticket by contacting the CAS server. If
# valid, return the user's username; otherwise, return None.


def validate(ticket):
    val_url = (_CAS_URL + "validate"
               + '?service=' + quote(strip_ticket(request.url))
               + '&ticket=' + quote(ticket))
    lines = []
    with urlopen(val_url) as flo:
        lines = flo.readlines()  # Should return 2 lines.
    if len(lines) != 2:
        return None
    first_line = lines[0].decode('utf-8')
    second_line = lines[1].decode('utf-8')
    if not first_line.startswith('yes'):
        return None
    return second_line


# ----------------------------------------------------------------------

# Authenticate the remote user, and return the user's username.
# Do not return unless the user is successfully authenticated.

def authenticate():
    # If the username is in the session, then the user was
    # authenticated previously.  So return the username.
    if 'username' in session:
        username = session.get('username').strip()
        user = database.get_user(username)
        if user is not None:
            admin = user.admin
        if user is None:
            user = models.Users(
                netid = username,
                major = '',
                certificates = '',
                grade = '',
                admin = False
            )
            database.add_user(user)
            admin = False
        return (username, admin)
    # If the request does not contain a login ticket, then redirect
    # the browser to the login page to get one.
    ticket = request.args.get('ticket')
    if ticket is None:
        login_url = (_CAS_URL + 'login?service=' + quote(request.url))
        abort(redirect(login_url))
    
    # If the login ticket is invalid, then redirect the browser
    # to the login page to get a new one.
    username = validate(ticket).strip()
    if username is None:
        login_url = (_CAS_URL + 'login?service='
                     + quote(strip_ticket(request.url)))
        abort(redirect(login_url))
    user = database.get_user(username)
    if user is not None:
        admin = user.admin
    if user is None:
        user = models.Users(
            netid = username,
            major = '',
            certificates = '',
            grade = '',
            admin = False
        )
        admin = False
        database.add_user(user)
    # The user is authenticated, so store the username in
    # the session.
    session['username'] = username
    return (username, admin)

# ----------------------------------------------------------------------


@app.route('/logout', methods=['GET'])
def logout():
    authenticate()

    # Delete the user's username from the session.
    session.pop('username')

    # Logout, and redirect the browser to the index page.
    logout_url = (_CAS_URL + 'logout?service='
                  + quote(sub('logout', 'index', request.url)))
    return redirect(logout_url)