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Negligible spacing changes to docs/csrf.txt to be consistent 

git-svn-id: http://code.djangoproject.com/svn/django/trunk@4224 bcc190cf-cafb-0310-a4f2-bffc1f526a37
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Adrian Holovaty 2006-12-18 03:59:45 +00:00
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@ -1,9 +1,9 @@
===================================== =====================================
Cross Site Request Forgery Protection Cross Site Request Forgery protection
===================================== =====================================
The CsrfMiddleware class provides easy-to-use protection against The CsrfMiddleware class provides easy-to-use protection against
`Cross Site Request Forgeries`_. This type of attack occurs when a malicious `Cross Site Request Forgeries`_. This type of attack occurs when a malicious
web site creates a link or form button that is intended to perform some action web site creates a link or form button that is intended to perform some action
on your web site, using the credentials of a logged-in user who is tricked on your web site, using the credentials of a logged-in user who is tricked
into clicking on the link in their browser. into clicking on the link in their browser.
@ -12,12 +12,12 @@ The first defense against CSRF attacks is to ensure that GET requests
are side-effect free. POST requests can then be protected by adding this are side-effect free. POST requests can then be protected by adding this
middleware into your list of installed middleware. middleware into your list of installed middleware.
.. _Cross Site Request Forgeries: http://www.squarefree.com/securitytips/web-developers.html#CSRF .. _Cross Site Request Forgeries: http://www.squarefree.com/securitytips/web-developers.html#CSRF
How to use it How to use it
============= =============
Add the middleware ``'django.contrib.csrf.middleware.CsrfMiddleware'`` to
Add the middleware ``'django.contrib.csrf.middleware.CsrfMiddleware'`` to
your list of middleware classes, ``MIDDLEWARE_CLASSES``. It needs to process your list of middleware classes, ``MIDDLEWARE_CLASSES``. It needs to process
the response after the SessionMiddleware, so must come before it in the the response after the SessionMiddleware, so must come before it in the
list. It also must process the response before things like compression list. It also must process the response before things like compression
@ -25,16 +25,17 @@ happen to the response, so it must come after GZipMiddleware in the list.
How it works How it works
============ ============
CsrfMiddleware does two things: CsrfMiddleware does two things:
1. It modifies outgoing requests by adding a hidden form field to all 1. It modifies outgoing requests by adding a hidden form field to all
'POST' forms, with the name 'csrfmiddlewaretoken' and a value which is 'POST' forms, with the name 'csrfmiddlewaretoken' and a value which is
a hash of the session ID plus a secret. If there is no session ID set, a hash of the session ID plus a secret. If there is no session ID set,
this modification of the response isn't done, so there is very little this modification of the response isn't done, so there is very little
performance penalty for those requests that don't have a session. performance penalty for those requests that don't have a session.
2. On all incoming POST requests that have the session cookie set, it 2. On all incoming POST requests that have the session cookie set, it
checks that the 'csrfmiddlewaretoken' is present and correct. If it checks that the 'csrfmiddlewaretoken' is present and correct. If it
isn't, the user will get a 403 error. isn't, the user will get a 403 error.
This ensures that only forms that have originated from your web site This ensures that only forms that have originated from your web site
@ -43,26 +44,26 @@ can be used to POST data back.
It deliberately only targets HTTP POST requests (and the corresponding It deliberately only targets HTTP POST requests (and the corresponding
POST forms). GET requests ought never to have side effects (if you are POST forms). GET requests ought never to have side effects (if you are
using HTTP GET and POST correctly), and so a CSRF attack with a GET using HTTP GET and POST correctly), and so a CSRF attack with a GET
request will always be harmless. request will always be harmless.
POST requests that are not accompanied by a session cookie are not protected, POST requests that are not accompanied by a session cookie are not protected,
but they do not need to be protected, since the 'attacking' web site but they do not need to be protected, since the 'attacking' web site
could make these kind of requests anyway. could make these kind of requests anyway.
The Content-Type is checked before modifying the response, and only The Content-Type is checked before modifying the response, and only
pages that are served as 'text/html' or 'application/xml+xhtml' pages that are served as 'text/html' or 'application/xml+xhtml'
are modified. are modified.
Limitations Limitations
=========== ===========
CsrfMiddleware requires Django's session framework to work. If you have CsrfMiddleware requires Django's session framework to work. If you have
a custom authentication system that manually sets cookies and the like, a custom authentication system that manually sets cookies and the like,
it won't help you. it won't help you.
If your app creates HTML pages and forms in some unusual way, (e.g. If your app creates HTML pages and forms in some unusual way, (e.g.
it sends fragments of HTML in javascript document.write statements) it sends fragments of HTML in javascript document.write statements)
you might bypass the filter that adds the hidden field to the form, you might bypass the filter that adds the hidden field to the form,
in which case form submission will always fail. It may still be possible in which case form submission will always fail. It may still be possible
to use the middleware, provided you can find some way to get the to use the middleware, provided you can find some way to get the
CSRF token and ensure that is included when your form is submitted. CSRF token and ensure that is included when your form is submitted.