Refs #32596 -- Added early return on safe methods in CsrfViewMiddleware.process_view().

This commit is contained in:
Chris Jerdonek 2021-04-03 02:02:47 -07:00 committed by Mariusz Felisiak
parent cfd8c91839
commit 214b36f50a
1 changed files with 63 additions and 64 deletions

View File

@ -317,75 +317,74 @@ class CsrfViewMiddleware(MiddlewareMixin):
return None return None
# Assume that anything not defined as 'safe' by RFC7231 needs protection # Assume that anything not defined as 'safe' by RFC7231 needs protection
if request.method not in ('GET', 'HEAD', 'OPTIONS', 'TRACE'): if request.method in ('GET', 'HEAD', 'OPTIONS', 'TRACE'):
if getattr(request, '_dont_enforce_csrf_checks', False): return self._accept(request)
# 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)
# Reject the request if the Origin header doesn't match an allowed if getattr(request, '_dont_enforce_csrf_checks', False):
# value. # Mechanism to turn off CSRF checks for test suite. It comes after
if 'HTTP_ORIGIN' in request.META: # the creation of CSRF cookies, so that everything else continues
if not self._origin_verified(request): # to work exactly the same (e.g. cookies are sent, etc.), but
return self._reject(request, REASON_BAD_ORIGIN % request.META['HTTP_ORIGIN']) # before any branches that call reject().
elif request.is_secure(): return self._accept(request)
# If the Origin header wasn't provided, reject HTTPS requests
# if the Referer header doesn't match an allowed value.
#
# Suppose user visits http://example.com/
# An active network attacker (man-in-the-middle, MITM) sends a
# POST form that targets https://example.com/detonate-bomb/ 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
# secret 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
# https://example.com/ we need additional protection that treats
# http://example.com/ 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.
try:
self._check_referer(request)
except RejectRequest as exc:
return self._reject(request, exc.reason)
# Access csrf_token via self._get_token() as rotate_token() may # Reject the request if the Origin header doesn't match an allowed
# have been called by an authentication middleware during the # value.
# process_request() phase. if 'HTTP_ORIGIN' in request.META:
csrf_token = self._get_token(request) if not self._origin_verified(request):
if csrf_token is None: return self._reject(request, REASON_BAD_ORIGIN % request.META['HTTP_ORIGIN'])
# No CSRF cookie. For POST requests, we insist on a CSRF cookie, elif request.is_secure():
# and in this way we can avoid all CSRF attacks, including login # If the Origin header wasn't provided, reject HTTPS requests if
# CSRF. # the Referer header doesn't match an allowed value.
return self._reject(request, REASON_NO_CSRF_COOKIE) #
# Suppose user visits http://example.com/
# An active network attacker (man-in-the-middle, MITM) sends a
# POST form that targets https://example.com/detonate-bomb/ 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 secret
# 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 https://example.com/ we need
# additional protection that treats http://example.com/ 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.
try:
self._check_referer(request)
except RejectRequest as exc:
return self._reject(request, exc.reason)
# Check non-cookie token for match. # Access csrf_token via self._get_token() as rotate_token() may have
request_csrf_token = "" # been called by an authentication middleware during the
if request.method == "POST": # process_request() phase.
try: csrf_token = self._get_token(request)
request_csrf_token = request.POST.get('csrfmiddlewaretoken', '') if csrf_token is None:
except OSError: # No CSRF cookie. For POST requests, we insist on a CSRF cookie,
# Handle a broken connection before we've completed reading # and in this way we can avoid all CSRF attacks, including login
# the POST data. process_view shouldn't raise any # CSRF.
# exceptions, so we'll ignore and serve the user a 403 return self._reject(request, REASON_NO_CSRF_COOKIE)
# (assuming they're still listening, which they probably
# aren't because of the error).
pass
if request_csrf_token == "": # Check non-cookie token for match.
# Fall back to X-CSRFToken, to make things easier for AJAX, request_csrf_token = ''
# and possible for PUT/DELETE. if request.method == 'POST':
request_csrf_token = request.META.get(settings.CSRF_HEADER_NAME, '') try:
request_csrf_token = request.POST.get('csrfmiddlewaretoken', '')
except OSError:
# Handle a broken connection before we've completed reading the
# POST data. process_view shouldn't raise any exceptions, so
# we'll ignore and serve the user a 403 (assuming they're still
# listening, which they probably aren't because of the error).
pass
request_csrf_token = _sanitize_token(request_csrf_token) if request_csrf_token == '':
if not _compare_masked_tokens(request_csrf_token, csrf_token): # Fall back to X-CSRFToken, to make things easier for AJAX, and
return self._reject(request, REASON_BAD_TOKEN) # possible for PUT/DELETE.
request_csrf_token = request.META.get(settings.CSRF_HEADER_NAME, '')
request_csrf_token = _sanitize_token(request_csrf_token)
if not _compare_masked_tokens(request_csrf_token, csrf_token):
return self._reject(request, REASON_BAD_TOKEN)
return self._accept(request) return self._accept(request)