2006-05-09 07:03:08 +08:00
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"""
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Cross Site Request Forgery Middleware.
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This module provides a middleware that implements protection
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against request forgeries from other sites.
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"""
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from django.conf import settings
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from django.http import HttpResponseForbidden
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2007-11-14 20:58:53 +08:00
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from django.utils.safestring import mark_safe
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2006-05-09 07:03:08 +08:00
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import md5
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import re
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2006-05-12 06:32:47 +08:00
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import itertools
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2006-05-09 07:03:08 +08:00
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2007-11-14 20:58:53 +08:00
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_ERROR_MSG = mark_safe('<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en"><body><h1>403 Forbidden</h1><p>Cross Site Request Forgery detected. Request aborted.</p></body></html>')
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2006-05-09 07:03:08 +08:00
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_POST_FORM_RE = \
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re.compile(r'(<form\W[^>]*\bmethod=(\'|"|)POST(\'|"|)\b[^>]*>)', re.IGNORECASE)
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_HTML_TYPES = ('text/html', 'application/xhtml+xml')
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def _make_token(session_id):
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return md5.new(settings.SECRET_KEY + session_id).hexdigest()
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2006-05-12 06:32:47 +08:00
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2006-05-09 07:03:08 +08:00
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class CsrfMiddleware(object):
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"""Django middleware that adds protection against Cross Site
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Request Forgeries by adding hidden form fields to POST forms and
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checking requests for the correct value.
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In the list of middlewares, SessionMiddleware is required, and must come
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after this middleware. CsrfMiddleWare must come after compression
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middleware.
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If a session ID cookie is present, it is hashed with the SECRET_KEY
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setting to create an authentication token. This token is added to all
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outgoing POST forms and is expected on all incoming POST requests that
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have a session ID cookie.
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If you are setting cookies directly, instead of using Django's session
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framework, this middleware will not work.
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"""
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def process_request(self, request):
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if request.method == 'POST':
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2006-05-09 07:03:08 +08:00
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try:
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session_id = request.COOKIES[settings.SESSION_COOKIE_NAME]
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except KeyError:
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# No session, no check required
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return None
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csrf_token = _make_token(session_id)
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# check incoming token
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try:
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request_csrf_token = request.POST['csrfmiddlewaretoken']
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except KeyError:
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return HttpResponseForbidden(_ERROR_MSG)
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if request_csrf_token != csrf_token:
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return HttpResponseForbidden(_ERROR_MSG)
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return None
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2006-05-09 07:03:08 +08:00
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def process_response(self, request, response):
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csrf_token = None
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try:
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cookie = response.cookies[settings.SESSION_COOKIE_NAME]
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csrf_token = _make_token(cookie.value)
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except KeyError:
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# No outgoing cookie to set session, but
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# a session might already exist.
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try:
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session_id = request.COOKIES[settings.SESSION_COOKIE_NAME]
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csrf_token = _make_token(session_id)
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except KeyError:
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# no incoming or outgoing cookie
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pass
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if csrf_token is not None and \
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response['Content-Type'].split(';')[0] in _HTML_TYPES:
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# ensure we don't add the 'id' attribute twice (HTML validity)
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idattributes = itertools.chain(("id='csrfmiddlewaretoken'",),
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itertools.repeat(''))
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def add_csrf_field(match):
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"""Returns the matched <form> tag plus the added <input> element"""
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return mark_safe(match.group() + "<div style='display:none;'>" + \
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2006-05-12 06:32:47 +08:00
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"<input type='hidden' " + idattributes.next() + \
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" name='csrfmiddlewaretoken' value='" + csrf_token + \
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2007-11-14 20:58:53 +08:00
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"' /></div>")
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2006-05-12 06:32:47 +08:00
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2006-05-09 07:03:08 +08:00
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# Modify any POST forms
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response.content = _POST_FORM_RE.sub(add_csrf_field, response.content)
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2006-05-09 07:03:08 +08:00
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return response
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