login.py

# Based on http://djangosnippets.org/snippets/1158/

import json
import re

from django.conf import settings
from django.http import HttpResponse, HttpResponseRedirect

class EnforceLoginMiddleware(object):
    """
    Middlware class which requires the user to be authenticated for all urls except 
    those defined in PUBLIC_URLS in settings.py. PUBLIC_URLS should be a tuple of regular 
    expresssions for the urls you want anonymous users to have access to. If PUBLIC_URLS 
    is not defined, it falls back to LOGIN_URL or failing that '/accounts/login/'.  
    Requests for urls not matching PUBLIC_URLS get redirected to LOGIN_URL with next set 
    to original path of the unauthenticted request.
    """

    def __init__(self):
        self.login_url   = getattr(settings, 'LOGIN_URL', '/accounts/login/' )
        if hasattr(settings,'PUBLIC_URLS'):
            public_urls = [re.compile(url) for url in settings.PUBLIC_URLS]
        else:
            public_urls = [(re.compile("^%s$" % ( self.login_url[1:] )))]
        self.public_urls = tuple(public_urls)

    def process_request(self, request):
        """
        Redirect anonymous users to login_url from non public urls
        """
        redirect_to_login = False
        try:
            if request.user.is_anonymous():
                for url in self.public_urls:
                    if url.match(request.path):
                        return None
                    
                redirect_to_login = True
        except AttributeError:
            redirect_to_login = True
            
        if redirect_to_login:
            # Return a 401 for AJAX requests so it's easy to tell from JS that login is required
            if request.is_ajax() or \
               'application/json' in request.META.get('HTTP_ACCEPT', '') or \
               request.POST.get('httpAccept') == 'json':
                return HttpResponse(json.dumps({'loginRedirect': True}), status=401)
            return HttpResponseRedirect("%s?next=%s" % (self.login_url, request.path))

settings.py

PUBLIC_URLS = (
    r'^/login/',
    r'^/logout/',
    r'^/register/',
    r'^/forgotten/',
    r'^/reset/',
    r'^%s' % STATIC_URL,
    r'^/jsi18n/'
)