gistfile1.txt

from django.conf import settings
from django.contrib.auth.models import User, check_password
from django.contrib.sites.models import Site
from django.contrib.auth.backends import ModelBackend

from apps.common.models import User2Site

class SitesBackend(ModelBackend):

    def authenticate(self, username=None, password=None):
        try:
            user = User.objects.get(username=username)
            if user.check_password(password):
                if user.is_superuser:
                    return user

                try:
                    site = Site.objects.get(id=settings.SITE_ID)
                    user2site = User2Site.objects.get(site=site, user=user)
                except User2Site.DoesNotExist:
                    return None
                return user
        except User.DoesNotExist:
            return None