user data is not updated to forum_user table of osqa causes the link to be still login even after successful login through cas

After much trial and error, I have a working CAS-authenticated instance of OSQA.

First of all, I had to modify the source for django_cas. What I needed was a method to verify the CAS ticket without creating a user - the default will try to create a User object and that doesn't do things the right way with respect to OSQA:

site-packages/django_cas-2.0.3-py2.7.egg/django_cas/backends.py (this is just a snippet - the key point is that I refactored out a verify method from authenticate)

def verify(self, ticket, service):
    return _verify(ticket, service)

def authenticate(self, ticket, service):
    """Verifies CAS ticket and gets or creates User object"""

username = self.verify(ticket, service)
    if not username:
        return None

Next, I created a PopulatedCASBackend as suggested in the Google Code installation docs, however, the exception handler is somewhat different. I cribbed this code from the LDAP handler examples that I've found on here. The UserJoinsAction seems to be a key bit.

forum/PopulatedCASBackend.py

    from django_cas.backends import CASBackend
    from forum.authentication.base import  AuthenticationConsumer, InvalidAuthentication, ConsumerTemplateContext
    from forum.models import User
    from forum.actions import UserJoinsAction
    import logging

class PopulatedCASBackend(CASBackend):
    """CAS authentication backend with user data populated from AD"""
def authenticate(self, ticket, service):
    """Authenticates CAS ticket and retrieves user data"""

    username = super(PopulatedCASBackend, self).verify(
        ticket, service)

    if not username:
    return None

# Connect to AD, modify user object, etc.
logger = logging.getLogger(__name__)
try: # If user is in datatbase carry on
        _user = User.objects.get(email=username)
    except User.DoesNotExist:# not in the database add user to database
        _user =  User(username=username, email=username)
        _user.email_isvalid = True
        _user.set_unusable_password()
        _user.save()
        UserJoinsAction(user=_user).save()

    return _user

Settings.py has a few new settings:

 MIDDLEWARE_CLASSES = [

... other stuff
'django.contrib.sessions.middleware.SessionMiddleware',
 'django.contrib.auth.middleware.AuthenticationMiddleware',
 'django_cas.middleware.CASMiddleware',
     'forum.middleware.extended_user.ExtendedUser',
 ] 
AUTHENTICATION_BACKENDS =
     ['django.contrib.auth.backends.ModelBackend',
     'forum.PopulatedCASBackend.PopulatedCASBackend',
     ]

Also note that you have to modify urls.py as mentioned in the original question.

There may be an easier way to do this, but this is what I found that works. The bit about modifying django_cas is a bit hacky but it seems like the path of least resistance, maybe they'll accept a patch to refactor the verify method, or maybe they'll be open to creating a callback for doing extended user creation.