CASClient.py

#!/usr/bin/env python

#-----------------------------------------------------------------------
# CASClient.py
# Authors: Alex Halderman, Scott Karlin, Brian Kernighan, Bob Dondero
#-----------------------------------------------------------------------

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

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

class CASClient:

    #-------------------------------------------------------------------
    
    # Initialize a new CASClient object so it uses the given CAS
    # server, or fed.princeton.edu if no server is given.
    
    def __init__(self, url='https://fed.princeton.edu/cas/'):
        self.cas_url = url

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

    # Return the URL of the current request after stripping out the
    # "ticket" parameter added by the CAS server.
	
    def stripTicket(self):
        url = request.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(self, ticket):
        val_url = self.cas_url + "validate" + \
            '?service=' + quote(self.stripTicket()) + \
            '&ticket=' + quote(ticket)
        r = urlopen(val_url).readlines()   # returns 2 lines
        if len(r) != 2:
            return None     
        firstLine = r[0].decode('utf-8')
        secondLine = r[1].decode('utf-8')
        if not firstLine.startswith('yes'):
            return None
        return secondLine
        
    #-------------------------------------------------------------------

    def redirectLanding(self):
        
        # If the user's username is in the session, then the user was
        # authenticated previously.  So return the user's username.
        if 'username' in session:
            return 0
           
        # If the request contains a login ticket, then try to
        # validate it.
        ticket = request.args.get('ticket')
        if ticket is not None:
            username = self.validate(ticket)
            if username is not None:             
                # The user is authenticated, so store the user's
                # username in the session.               
                session['username'] = username        
                return 0
      
        # The request does not contain a valid login ticket
        return 1

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

    # Authenticate the remote user, and return the user's username.
    # Do not return unless the user is successfully authenticated.
   	
    def authenticate(self):
        
        # If the user's username is in the session, then the user was
        # authenticated previously.  So return the user's username.
        if 'username' in session:
            return session.get('username')
           
        # If the request contains a login ticket, then try to
        # validate it.
        ticket = request.args.get('ticket')
        if ticket is not None:
            username = self.validate(ticket)
            if username is not None:             
                # The user is authenticated, so store the user's
                # username in the session.               
                session['username'] = username        
                return username
      
        # The request does not contain a valid login ticket, so
        # redirect the browser to the login page to get one.
        login_url = self.cas_url + 'login' \
            + '?service=' + quote(self.stripTicket())
            
        abort(redirect(login_url))

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

    # Logout the user.
    
    def logout(self):
        
        # Delete the user's username from the session.
        session.pop('username')
        
        # Redirect the browser to the application's home page.
        logout_url = self.cas_url +  'logout?service=' + \
            quote(sub('logout', 'index', request.url))
        abort(redirect(logout_url))
        
#-----------------------------------------------------------------------

def main():
    print("CASClient does not run standalone")

if __name__ == '__main__':
    main()