Blogged by buffi

The internet is stupid, and your users will misbehave. Therefore every homepage should have some way of banning users from posting content, or perhaps in some cases from viewing your page altogether.
I wanted a simple way to ban users from accessing one of my django made homepages, and then having them redirected to a page with an explanation why. The IP’s and explanations should be entered through the django admin interface. For this django middleware is a decent choice.

First of all, lets create a Ban model in your models file. Something like this should do (you might want timestamps and other stuff as well, I don’t really need it).

class Ban(models.Model):
    ip = models.IPAddressField()
    reason = models.TextField()

    def __str__(self):
        return self.ip

    class Admin: pass

Do a python manage.py syncdb to insert the model into your database.

Now it’s time to create the middleware. The middleware can be placed anywhere reachable from your python path.
I named my middleware file ipban.py and placed in in a subfolder called “middleware”. Also create an empty __init__.py file in this directory if you do so as well to indicate that it holds python files. The content of my ipban.py is

from django import http
from pici.picipage.models import Ban

class IPBanMiddleware(object):
  """
  Simple middleware for taking care of bans from specific IP's
  Redirects the banned user to a ban-page with an explanation
  """
  def process_request(self, request):
    ip = request.META['REMOTE_ADDR'] # user's IP
    path = request.path # requested path

    # see if user is banned
    try:
      # if this doesnt throw an exception, user is banned
      Ban.objects.get(ip=ip) 

      # only redirect when not already at the ban page
      if not path.startswith("/banned/"):
        return http.HttpResponseRedirect("/banned/%s/" % ip)
    except Ban.DoesNotExist: # not banned! goodie
      pass

pici.picipage.models should of course be changed to point to your own models module containing the Ban model.
This middleware checks if the users IP is in the list of banned users at every request. If the user is banned, then he is redirected to the ban-page “/banned/ipgoeshere/”.

Now open your settings.py file and add this class to your MIDDLEWARE_CLASSES.
In my case I added

'pici.middleware.ipban.IPBanMiddleware',

Add a urls.py entry with something like this (I’m somewhat lazy at regular expressions). Obviously replace miscviews.banned with whatever you are going to call your view-handling method and it’s module.

(r"^banned/([^/]+)/$", miscviews.banned),

Add the handler for the banning in your view. Mine looks like this. Replace “subpages/banned/banned.html” with the path to your template.

def banned(request, banip):
  try:
    ban = Ban.objects.get(ip=banip)
    reason = ban.reason
  except Ban.DoesNotExist:
    reason = "None given"
  return render_to_response("subpages/banned/banned.html",
    {"reason": reason}, context_instance=RequestContext(request))

Finally add the template and you are done!
Adding the template should be straight forward if you know anything about django, but it can look something like this

{% extends "index.html" %}

{% block main_content %}
  <div class="normal_content_centered">
    <h1>BANNED!</h1>
    <p>The reason for your banning is:</p>
    <p><b>{{ reason }}</b></p>
    <img src="url_to_crying_baby_goes_here.jpg" />
  </div>
{% endblock %}

The image of a crying baby is essential.

This can of course quite easily be optimized by using sessions to avoid having to do the lookup for each request, however a very simple database hit per request is not a big deal in my case so I’ll save that for later. Premature optimization is evil and all that.

Have fun banning users from your homepage

edit: Improved version up

buffi Programming & scripting, Python