lib/django-1.4/docs/ref/clickjacking.txt

========================
Clickjacking Protection
========================

.. module:: django.middleware.clickjacking
   :synopsis: Protects against Clickjacking

The clickjacking middleware and decorators provide easy-to-use protection
against `clickjacking`_.  This type of attack occurs when a malicious site
tricks a user into clicking on a concealed element of another site which they
have loaded in a hidden frame or iframe.

.. versionadded:: 1.4
   The clickjacking middleware and decorators were added.

.. _clickjacking: http://en.wikipedia.org/wiki/Clickjacking

An example of clickjacking
==========================

Suppose an online store has a page where a logged in user can click "Buy Now" to
purchase an item. A user has chosen to stay logged into the store all the time
for convenience. An attacker site might create an "I Like Ponies" button on one
of their own pages, and load the store's page in a transparent iframe such that
the "Buy Now" button is invisibly overlaid on the "I Like Ponies" button. If the
user visits the attacker site and clicks "I Like Ponies" he will inadvertently
click on the online store's "Buy Now" button and unknowingly purchase the item.

.. _clickjacking-prevention:

Preventing clickjacking
=======================

Modern browsers honor the `X-Frame-Options`_ HTTP header that indicates whether
or not a resource is allowed to load within a frame or iframe. If the response
contains the header with a value of SAMEORIGIN then the browser will only load
the resource in a frame if the request originated from the same site. If the
header is set to DENY then the browser will block the resource from loading in a
frame no matter which site made the request.

.. _X-Frame-Options: https://developer.mozilla.org/en/The_X-FRAME-OPTIONS_response_header

Django provides a few simple ways to include this header in responses from your
site:

1. A simple middleware that sets the header in all responses.

2. A set of view decorators that can be used to override the middleware or to
   only set the header for certain views.

How to use it
=============

Setting X-Frame-Options for all responses
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

To set the same X-Frame-Options value for all responses in your site, add
``'django.middleware.clickjacking.XFrameOptionsMiddleware'`` to
:setting:`MIDDLEWARE_CLASSES`::

    MIDDLEWARE_CLASSES = (
        ...
        'django.middleware.clickjacking.XFrameOptionsMiddleware',
        ...
    )

By default, the middleware will set the X-Frame-Options header to SAMEORIGIN for
every outgoing ``HttpResponse``. If you want DENY instead, set the
:setting:`X_FRAME_OPTIONS` setting::

    X_FRAME_OPTIONS = 'DENY'

When using the middleware there may be some views where you do **not** want the
X-Frame-Options header set. For those cases, you can use a view decorator that
tells the middleware not to set the header::

    from django.http import HttpResponse
    from django.views.decorators.clickjacking import xframe_options_exempt

    @xframe_options_exempt
    def ok_to_load_in_a_frame(request):
        return HttpResponse("This page is safe to load in a frame on any site.")


Setting X-Frame-Options per view
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

To set the X-Frame-Options header on a per view basis, Django provides these
decorators::

    from django.http import HttpResponse
    from django.views.decorators.clickjacking import xframe_options_deny
    from django.views.decorators.clickjacking import xframe_options_sameorigin

    @xframe_options_deny
    def view_one(request):
        return HttpResponse("I won't display in any frame!")

    @xframe_options_sameorigin
    def view_two(request):
        return HttpResponse("Display in a frame if it's from the same origin as me.")

Note that you can use the decorators in conjunction with the middleware. Use of
a decorator overrides the middleware.

Limitations
===========

The `X-Frame-Options` header will only protect against clickjacking in a modern
browser. Older browsers will quietly ignore the header and need `other
clickjacking prevention techniques`_.

Browsers that support X-Frame-Options
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

* Internet Explorer 8+
* Firefox	3.6.9+
* Opera	10.5+
* Safari	4+
* Chrome	4.1+

See also
~~~~~~~~

A `complete list`_ of browsers supporting X-Frame-Options.

.. _complete list: https://developer.mozilla.org/en/The_X-FRAME-OPTIONS_response_header#Browser_compatibility
.. _other clickjacking prevention techniques: http://en.wikipedia.org/wiki/Clickjacking#Prevention