Skip to content


Subversion checkout URL

You can clone with HTTPS or Subversion.

Download ZIP
Fetching contributors…

Cannot retrieve contributors at this time

219 lines (183 sloc) 8.87 kb
Cross Site Request Forgery Middleware.
This module provides a middleware that implements protection
against request forgeries from other sites.
from __future__ import unicode_literals
import hashlib
import logging
import re
import random
from django.conf import settings
from django.core.urlresolvers import get_callable
from django.utils.cache import patch_vary_headers
from django.utils.encoding import force_text
from django.utils.http import same_origin
from django.utils.crypto import constant_time_compare, get_random_string
logger = logging.getLogger('django.request')
REASON_NO_REFERER = "Referer checking failed - no Referer."
REASON_BAD_REFERER = "Referer checking failed - %s does not match %s."
REASON_NO_CSRF_COOKIE = "CSRF cookie not set."
REASON_BAD_TOKEN = "CSRF token missing or incorrect."
def _get_failure_view():
Returns the view to be used for CSRF rejections
return get_callable(settings.CSRF_FAILURE_VIEW)
def _get_new_csrf_key():
return get_random_string(CSRF_KEY_LENGTH)
def get_token(request):
Returns the the CSRF token required for a POST form. The token is an
alphanumeric value.
A side effect of calling this function is to make the the csrf_protect
decorator and the CsrfViewMiddleware add a CSRF cookie and a 'Vary: Cookie'
header to the outgoing response. For this reason, you may need to use this
function lazily, as is done by the csrf context processor.
request.META["CSRF_COOKIE_USED"] = True
return request.META.get("CSRF_COOKIE", None)
def _sanitize_token(token):
# Allow only alphanum
if len(token) > CSRF_KEY_LENGTH:
return _get_new_csrf_key()
token = re.sub('[^a-zA-Z0-9]+', '', force_text(token))
if token == "":
# In case the cookie has been truncated to nothing at some point.
return _get_new_csrf_key()
return token
class CsrfViewMiddleware(object):
Middleware that requires a present and correct csrfmiddlewaretoken
for POST requests that have a CSRF cookie, and sets an outgoing
CSRF cookie.
This middleware should be used in conjunction with the csrf_token template
# The _accept and _reject methods currently only exist for the sake of the
# requires_csrf_token decorator.
def _accept(self, request):
# Avoid checking the request twice by adding a custom attribute to
# request. This will be relevant when both decorator and middleware
# are used.
request.csrf_processing_done = True
return None
def _reject(self, request, reason):
return _get_failure_view()(request, reason=reason)
def process_view(self, request, callback, callback_args, callback_kwargs):
if getattr(request, 'csrf_processing_done', False):
return None
csrf_token = _sanitize_token(
# Use same token next time
request.META['CSRF_COOKIE'] = csrf_token
except KeyError:
csrf_token = None
# Generate token and store it in the request, so it's
# available to the view.
request.META["CSRF_COOKIE"] = _get_new_csrf_key()
# Wait until request.META["CSRF_COOKIE"] has been manipulated before
# bailing out, so that get_token still works
if getattr(callback, 'csrf_exempt', False):
return None
# Assume that anything not defined as 'safe' by RFC2616 needs protection
if request.method not in ('GET', 'HEAD', 'OPTIONS', 'TRACE'):
if getattr(request, '_dont_enforce_csrf_checks', False):
# Mechanism to turn off CSRF checks for test suite.
# It comes after the creation of CSRF cookies, so that
# everything else continues to work exactly the same
# (e.g. cookies are sent, etc.), but before any
# branches that call reject().
return self._accept(request)
if request.is_secure():
# Suppose user visits
# An active network attacker (man-in-the-middle, MITM) sends a
# POST form that targets and
# submits it via JavaScript.
# The attacker will need to provide a CSRF cookie and token, but
# that's no problem for a MITM and the session-independent
# nonce we're using. So the MITM can circumvent the CSRF
# protection. This is true for any HTTP connection, but anyone
# using HTTPS expects better! For this reason, for
# we need additional protection that treats
# as completely untrusted. Under HTTPS,
# Barth et al. found that the Referer header is missing for
# same-domain requests in only about 0.2% of cases or less, so
# we can use strict Referer checking.
referer = request.META.get('HTTP_REFERER')
if referer is None:
logger.warning('Forbidden (%s): %s',
REASON_NO_REFERER, request.path,
'status_code': 403,
'request': request,
return self._reject(request, REASON_NO_REFERER)
# Note that request.get_host() includes the port.
good_referer = 'https://%s/' % request.get_host()
if not same_origin(referer, good_referer):
reason = REASON_BAD_REFERER % (referer, good_referer)
logger.warning('Forbidden (%s): %s', reason, request.path,
'status_code': 403,
'request': request,
return self._reject(request, reason)
if csrf_token is None:
# No CSRF cookie. For POST requests, we insist on a CSRF cookie,
# and in this way we can avoid all CSRF attacks, including login
logger.warning('Forbidden (%s): %s',
REASON_NO_CSRF_COOKIE, request.path,
'status_code': 403,
'request': request,
return self._reject(request, REASON_NO_CSRF_COOKIE)
# Check non-cookie token for match.
request_csrf_token = ""
if request.method == "POST":
request_csrf_token = request.POST.get('csrfmiddlewaretoken', '')
if request_csrf_token == "":
# Fall back to X-CSRFToken, to make things easier for AJAX,
# and possible for PUT/DELETE.
request_csrf_token = request.META.get('HTTP_X_CSRFTOKEN', '')
if not constant_time_compare(request_csrf_token, csrf_token):
logger.warning('Forbidden (%s): %s',
REASON_BAD_TOKEN, request.path,
'status_code': 403,
'request': request,
return self._reject(request, REASON_BAD_TOKEN)
return self._accept(request)
def process_response(self, request, response):
if getattr(response, 'csrf_processing_done', False):
return response
# If CSRF_COOKIE is unset, then CsrfViewMiddleware.process_view was
# never called, probaby because a request middleware returned a response
# (for example, contrib.auth redirecting to a login page).
if request.META.get("CSRF_COOKIE") is None:
return response
if not request.META.get("CSRF_COOKIE_USED", False):
return response
# Set the CSRF cookie even if it's already set, so we renew
# the expiry timer.
max_age = 60 * 60 * 24 * 7 * 52,
# Content varies with the CSRF cookie, so set the Vary header.
patch_vary_headers(response, ('Cookie',))
response.csrf_processing_done = True
return response
Jump to Line
Something went wrong with that request. Please try again.