class UserAuthMiddleware(object):
    def process_request(self, request):
        if 'auth_hash' in request.GET:
            auth_hash = request.GET['auth_hash']
            try:
                data = signing.loads(auth_hash, max_age=7*24*60*60)
            except signing.BadSignature:
                data = {}
            if data:
                try:
                    user = User.objects.get(username=data['username'])
                except User.DoesNotExist:
                    user = None
                if user:
                    user.backend = 'core.backend.Backend' 
                    login(request, user)