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Fixed #14445 - Use HMAC and constant-time comparison functions where needed. 

All adhoc MAC applications have been updated to use HMAC, using SHA1 to
generate unique keys for each application based on the SECRET_KEY, which is
common practice for this situation. In all cases, backwards compatibility
with existing hashes has been maintained, aiming to phase this out as per
the normal deprecation process. In this way, under most normal
circumstances the old hashes will have expired (e.g. by session expiration
etc.) before they become invalid.

In the case of the messages framework and the cookie backend, which was
already using HMAC, there is the possibility of a backwards incompatibility
if the SECRET_KEY is shorter than the default 50 bytes, but the low
likelihood and low impact meant compatibility code was not worth it.

All known instances where tokens/hashes were compared using simple string
equality, which could potentially open timing based attacks, have also been
fixed using a constant-time comparison function.

There are no known practical attacks against the existing implementations,
so these security improvements will not be backported.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@14218 bcc190cf-cafb-0310-a4f2-bffc1f526a37
This commit is contained in:
Luke Plant 2010-10-14 20:54:30 +00:00
parent 36f2f7ee7c
commit 45c7f427ce
18 changed files with 476 additions and 51 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

22
django/contrib/auth/tests/tokens.py
View File

@ -50,3 +50,25 @@ class TokenGeneratorTest(TestCase):
p2 = Mocked(date.today() + timedelta(settings.PASSWORD_RESET_TIMEOUT_DAYS + 1))
self.assertFalse(p2.check_token(user, tk1))
def test_django12_hash(self):
"""
Ensure we can use the hashes generated by Django 1.2
"""
# Hard code in the Django 1.2 algorithm (not the result, as it is time
# dependent)
def _make_token(user):
from django.utils.hashcompat import sha_constructor
from django.utils.http import int_to_base36
timestamp = (date.today() - date(2001,1,1)).days
ts_b36 = int_to_base36(timestamp)
hash = sha_constructor(settings.SECRET_KEY + unicode(user.id) +
user.password + user.last_login.strftime('%Y-%m-%d %H:%M:%S') +
unicode(timestamp)).hexdigest()[::2]
return "%s-%s" % (ts_b36, hash)
user = User.objects.create_user('tokentestuser', 'test2@example.com', 'testpw')
p0 = PasswordResetTokenGenerator()
tk1 = _make_token(user)
self.assertTrue(p0.check_token(user, tk1))

22
django/contrib/auth/tokens.py
View File

@ -1,6 +1,9 @@
from datetime import date
from django.conf import settings
from django.utils.hashcompat import sha_constructor
from django.utils.http import int_to_base36, base36_to_int
from django.utils.crypto import constant_time_compare, salted_hmac
class PasswordResetTokenGenerator(object):
"""
@ -30,8 +33,12 @@ class PasswordResetTokenGenerator(object):
return False
# Check that the timestamp/uid has not been tampered with
if self._make_token_with_timestamp(user, ts) != token:
return False
if not constant_time_compare(self._make_token_with_timestamp(user, ts), token):
# Fallback to Django 1.2 method for compatibility.
# PendingDeprecationWarning <- here to remind us to remove this in
# Django 1.5
if not constant_time_compare(self._make_token_with_timestamp_old(user, ts), token):
return False
# Check the timestamp is within limit
if (self._num_days(self._today()) - ts) > settings.PASSWORD_RESET_TIMEOUT_DAYS:
@ -50,7 +57,16 @@ class PasswordResetTokenGenerator(object):
# last_login will also change), we produce a hash that will be
# invalid as soon as it is used.
# We limit the hash to 20 chars to keep URL short
from django.utils.hashcompat import sha_constructor
key_salt = "django.contrib.auth.tokens.PasswordResetTokenGenerator"
value = unicode(user.id) + \
user.password + user.last_login.strftime('%Y-%m-%d %H:%M:%S') + \
unicode(timestamp)
hash = salted_hmac(key_salt, value).hexdigest()[::2]
return "%s-%s" % (ts_b36, hash)
def _make_token_with_timestamp_old(self, user, timestamp):
# The Django 1.2 method
ts_b36 = int_to_base36(timestamp)
hash = sha_constructor(settings.SECRET_KEY + unicode(user.id) +
user.password + user.last_login.strftime('%Y-%m-%d %H:%M:%S') +
unicode(timestamp)).hexdigest()[::2]

20
django/contrib/comments/forms.py
View File

@ -6,6 +6,7 @@ from django.forms.util import ErrorDict
from django.conf import settings
from django.contrib.contenttypes.models import ContentType
from models import Comment
from django.utils.crypto import salted_hmac, constant_time_compare
from django.utils.encoding import force_unicode
from django.utils.hashcompat import sha_constructor
from django.utils.text import get_text_list
@ -46,8 +47,13 @@ class CommentSecurityForm(forms.Form):
}
expected_hash = self.generate_security_hash(**security_hash_dict)
actual_hash = self.cleaned_data["security_hash"]
if expected_hash != actual_hash:
raise forms.ValidationError("Security hash check failed.")
if not constant_time_compare(expected_hash, actual_hash):
# Fallback to Django 1.2 method for compatibility
# PendingDeprecationWarning <- here to remind us to remove this
# fallback in Django 1.5
expected_hash_old = self._generate_security_hash_old(**security_hash_dict)
if not constant_time_compare(expected_hash_old, actual_hash):
raise forms.ValidationError("Security hash check failed.")
return actual_hash
def clean_timestamp(self):
@ -82,7 +88,17 @@ class CommentSecurityForm(forms.Form):
return self.generate_security_hash(**initial_security_dict)
def generate_security_hash(self, content_type, object_pk, timestamp):
"""
Generate a HMAC security hash from the provided info.
"""
info = (content_type, object_pk, timestamp)
key_salt = "django.contrib.forms.CommentSecurityForm"
value = "-".join(info)
return salted_hmac(key_salt, value).hexdigest()
def _generate_security_hash_old(self, content_type, object_pk, timestamp):
"""Generate a (SHA1) security hash from the provided info."""
# Django 1.2 compatibility
info = (content_type, object_pk, timestamp, settings.SECRET_KEY)
return sha_constructor("".join(info)).hexdigest()

25
django/contrib/formtools/preview.py
View File

@ -9,6 +9,7 @@ from django.http import Http404
from django.shortcuts import render_to_response
from django.template.context import RequestContext
from django.utils.hashcompat import md5_constructor
from django.utils.crypto import constant_time_compare
from django.contrib.formtools.utils import security_hash
AUTO_ID = 'formtools_%s' # Each form here uses this as its auto_id parameter.
@ -67,11 +68,33 @@ class FormPreview(object):
else:
return render_to_response(self.form_template, context, context_instance=RequestContext(request))
def _check_security_hash(self, token, request, form):
expected = self.security_hash(request, form)
if constant_time_compare(token, expected):
return True
else:
# Fall back to Django 1.2 method, for compatibility with forms that
# are in the middle of being used when the upgrade occurs. However,
# we don't want to do this fallback if a subclass has provided their
# own security_hash method - because they might have implemented a
# more secure method, and this would punch a hole in that.
# PendingDeprecationWarning <- left here to remind us that this
# compatibility fallback should be removed in Django 1.5
FormPreview_expected = FormPreview.security_hash(self, request, form)
if expected == FormPreview_expected:
# They didn't override security_hash, do the fallback:
old_expected = security_hash(request, form)
return constant_time_compare(token, old_expected)
else:
return False
def post_post(self, request):
"Validates the POST data. If valid, calls done(). Else, redisplays form."
f = self.form(request.POST, auto_id=AUTO_ID)
if f.is_valid():
if self.security_hash(request, f) != request.POST.get(self.unused_name('hash')):
if not self._check_security_hash(request.POST.get(self.unused_name('hash'), ''),
request, f):
return self.failed_hash(request) # Security hash failed.
return self.done(request, f.cleaned_data)
else:

10
django/contrib/formtools/test_urls.py
View File

@ -1,10 +0,0 @@
"""
This is a URLconf to be loaded by tests.py. Add any URLs needed for tests only.
"""
from django.conf.urls.defaults import *
from django.contrib.formtools.tests import *
urlpatterns = patterns('',
(r'^test1/', TestFormPreview(TestForm)),
)

183
django/contrib/formtools/tests.py → django/contrib/formtools/tests/__init__.py
View File

@ -1,23 +1,37 @@
import os
from django import forms
from django import http
from django.conf import settings
from django.contrib.formtools import preview, wizard, utils
from django.test import TestCase
from django.utils import unittest
success_string = "Done was called!"
class TestFormPreview(preview.FormPreview):
def done(self, request, cleaned_data):
return http.HttpResponse(success_string)
class TestForm(forms.Form):
field1 = forms.CharField()
field1_ = forms.CharField()
bool1 = forms.BooleanField(required=False)
class UserSecuredFormPreview(TestFormPreview):
"""
FormPreview with a custum security_hash method
"""
def security_hash(self, request, form):
return "123"
class PreviewTests(TestCase):
urls = 'django.contrib.formtools.test_urls'
urls = 'django.contrib.formtools.tests.urls'
def setUp(self):
# Create a FormPreview instance to share between tests
@ -102,6 +116,39 @@ class PreviewTests(TestCase):
response = self.client.post('/test1/', self.test_data)
self.assertEqual(response.content, success_string)
def test_form_submit_django12_hash(self):
"""
Test contrib.formtools.preview form submittal, using the hash function
used in Django 1.2
"""
# Pass strings for form submittal and add stage variable to
# show we previously saw first stage of the form.
self.test_data.update({'stage':2})
response = self.client.post('/test1/', self.test_data)
self.failIfEqual(response.content, success_string)
hash = utils.security_hash(None, TestForm(self.test_data))
self.test_data.update({'hash': hash})
response = self.client.post('/test1/', self.test_data)
self.assertEqual(response.content, success_string)
def test_form_submit_django12_hash_custom_hash(self):
"""
Test contrib.formtools.preview form submittal, using the hash function
used in Django 1.2 and a custom security_hash method.
"""
# Pass strings for form submittal and add stage variable to
# show we previously saw first stage of the form.
self.test_data.update({'stage':2})
response = self.client.post('/test2/', self.test_data)
self.assertEqual(response.status_code, 200)
self.failIfEqual(response.content, success_string)
hash = utils.security_hash(None, TestForm(self.test_data))
self.test_data.update({'hash': hash})
response = self.client.post('/test2/', self.test_data)
self.failIfEqual(response.content, success_string)
class SecurityHashTests(unittest.TestCase):
def test_textfield_hash(self):
@ -127,10 +174,41 @@ class SecurityHashTests(unittest.TestCase):
hash2 = utils.security_hash(None, f2)
self.assertEqual(hash1, hash2)
class FormHmacTests(unittest.TestCase):
"""
Same as SecurityHashTests, but with form_hmac
"""
def test_textfield_hash(self):
"""
Regression test for #10034: the hash generation function should ignore
leading/trailing whitespace so as to be friendly to broken browsers that
submit it (usually in textareas).
"""
f1 = HashTestForm({'name': 'joe', 'bio': 'Nothing notable.'})
f2 = HashTestForm({'name': ' joe', 'bio': 'Nothing notable. '})
hash1 = utils.form_hmac(f1)
hash2 = utils.form_hmac(f2)
self.assertEqual(hash1, hash2)
def test_empty_permitted(self):
"""
Regression test for #10643: the security hash should allow forms with
empty_permitted = True, or forms where data has not changed.
"""
f1 = HashTestBlankForm({})
f2 = HashTestForm({}, empty_permitted=True)
hash1 = utils.form_hmac(f1)
hash2 = utils.form_hmac(f2)
self.assertEqual(hash1, hash2)
class HashTestForm(forms.Form):
name = forms.CharField()
bio = forms.CharField()
class HashTestBlankForm(forms.Form):
name = forms.CharField(required=False)
bio = forms.CharField(required=False)
@ -139,20 +217,38 @@ class HashTestBlankForm(forms.Form):
# FormWizard tests
#
class WizardPageOneForm(forms.Form):
field = forms.CharField()
class WizardPageTwoForm(forms.Form):
field = forms.CharField()
class WizardPageThreeForm(forms.Form):
field = forms.CharField()
class WizardClass(wizard.FormWizard):
def render_template(self, *args, **kw):
return http.HttpResponse("")
def get_template(self, step):
return 'formwizard/wizard.html'
def done(self, request, cleaned_data):
return http.HttpResponse(success_string)
class UserSecuredWizardClass(WizardClass):
"""
Wizard with a custum security_hash method
"""
def security_hash(self, request, form):
return "123"
class DummyRequest(http.HttpRequest):
def __init__(self, POST=None):
super(DummyRequest, self).__init__()
self.method = POST and "POST" or "GET"
@ -160,22 +256,87 @@ class DummyRequest(http.HttpRequest):
self.POST.update(POST)
self._dont_enforce_csrf_checks = True
class WizardTests(TestCase):
urls = 'django.contrib.formtools.tests.urls'
def setUp(self):
self.old_TEMPLATE_DIRS = settings.TEMPLATE_DIRS
settings.TEMPLATE_DIRS = (
os.path.join(
os.path.dirname(__file__),
'templates'
),
)
# Use a known SECRET_KEY to make security_hash tests deterministic
self.old_SECRET_KEY = settings.SECRET_KEY
settings.SECRET_KEY = "123"
def tearDown(self):
settings.TEMPLATE_DIRS = self.old_TEMPLATE_DIRS
settings.SECRET_KEY = self.old_SECRET_KEY
def test_step_starts_at_zero(self):
"""
step should be zero for the first form
"""
wizard = WizardClass([WizardPageOneForm, WizardPageTwoForm])
request = DummyRequest()
wizard(request)
self.assertEquals(0, wizard.step)
response = self.client.get('/wizard/')
self.assertEquals(0, response.context['step0'])
def test_step_increments(self):
"""
step should be incremented when we go to the next page
"""
wizard = WizardClass([WizardPageOneForm, WizardPageTwoForm])
request = DummyRequest(POST={"0-field":"test", "wizard_step":"0"})
response = wizard(request)
self.assertEquals(1, wizard.step)
response = self.client.post('/wizard/', {"0-field":"test", "wizard_step":"0"})
self.assertEquals(1, response.context['step0'])
def test_bad_hash(self):
"""
Form should not advance if the hash is missing or bad
"""
response = self.client.post('/wizard/',
{"0-field":"test",
"1-field":"test2",
"wizard_step": "1"})
self.assertEquals(0, response.context['step0'])
def test_good_hash_django12(self):
"""
Form should advance if the hash is present and good, as calculated using
django 1.2 method.
"""
# We are hard-coding a hash value here, but that is OK, since we want to
# ensure that we don't accidentally change the algorithm.
data = {"0-field": "test",
"1-field": "test2",
"hash_0": "2fdbefd4c0cad51509478fbacddf8b13",
"wizard_step": "1"}
response = self.client.post('/wizard/', data)
self.assertEquals(2, response.context['step0'])
def test_good_hash_django12_subclass(self):
"""
The Django 1.2 method of calulating hashes should *not* be used as a
fallback if the FormWizard subclass has provided their own method
of calculating a hash.
"""
# We are hard-coding a hash value here, but that is OK, since we want to
# ensure that we don't accidentally change the algorithm.
data = {"0-field": "test",
"1-field": "test2",
"hash_0": "2fdbefd4c0cad51509478fbacddf8b13",
"wizard_step": "1"}
response = self.client.post('/wizard2/', data)
self.assertEquals(0, response.context['step0'])
def test_good_hash_current(self):
"""
Form should advance if the hash is present and good, as calculated using
current method.
"""
data = {"0-field": "test",
"1-field": "test2",
"hash_0": "7e9cea465f6a10a6fb47fcea65cb9a76350c9a5c",
"wizard_step": "1"}
response = self.client.post('/wizard/', data)
self.assertEquals(2, response.context['step0'])

9
django/contrib/formtools/tests/templates/formwizard/wizard.html Normal file
View File

@ -0,0 +1,9 @@
<p>Step {{ step }} of {{ step_count }}</p>
<form action="." method="post">{% csrf_token %}
<table>
{{ form }}
</table>
<input type="hidden" name="{{ step_field }}" value="{{ step0 }}" />
{{ previous_fields|safe }}
<input type="submit">
</form>

17
django/contrib/formtools/tests/urls.py Normal file
View File

@ -0,0 +1,17 @@
"""
This is a URLconf to be loaded by tests.py. Add any URLs needed for tests only.
"""
from django.conf.urls.defaults import *
from django.contrib.formtools.tests import *
urlpatterns = patterns('',
(r'^test1/', TestFormPreview(TestForm)),
(r'^test2/', UserSecuredFormPreview(TestForm)),
(r'^wizard/$', WizardClass([WizardPageOneForm,
WizardPageTwoForm,
WizardPageThreeForm])),
(r'^wizard2/$', UserSecuredWizardClass([WizardPageOneForm,
WizardPageTwoForm,
WizardPageThreeForm]))
)

28
django/contrib/formtools/utils.py
View File

@ -4,8 +4,10 @@ except ImportError:
import pickle
from django.conf import settings
from django.utils.hashcompat import md5_constructor
from django.forms import BooleanField
from django.utils.crypto import salted_hmac
from django.utils.hashcompat import md5_constructor
def security_hash(request, form, *args):
"""
@ -15,7 +17,9 @@ def security_hash(request, form, *args):
order, pickles the result with the SECRET_KEY setting, then takes an md5
hash of that.
"""
import warnings
warnings.warn("security_hash is deprecated; use form_hmac instead",
PendingDeprecationWarning)
data = []
for bf in form:
# Get the value from the form data. If the form allows empty or hasn't
@ -37,3 +41,23 @@ def security_hash(request, form, *args):
return md5_constructor(pickled).hexdigest()
def form_hmac(form):
"""
Calculates a security hash for the given Form instance.
"""
data = []
for bf in form:
# Get the value from the form data. If the form allows empty or hasn't
# changed then don't call clean() to avoid trigger validation errors.
if form.empty_permitted and not form.has_changed():
value = bf.data or ''
else:
value = bf.field.clean(bf.data) or ''
if isinstance(value, basestring):
value = value.strip()
data.append((bf.name, value))
pickled = pickle.dumps(data, pickle.HIGHEST_PROTOCOL)
key_salt = 'django.contrib.formtools'
return salted_hmac(key_salt, pickled).hexdigest()

43
django/contrib/formtools/wizard.py
View File

@ -8,12 +8,13 @@ import cPickle as pickle
from django import forms
from django.conf import settings
from django.contrib.formtools.utils import security_hash, form_hmac
from django.http import Http404
from django.shortcuts import render_to_response
from django.template.context import RequestContext
from django.utils.crypto import constant_time_compare
from django.utils.hashcompat import md5_constructor
from django.utils.translation import ugettext_lazy as _
from django.contrib.formtools.utils import security_hash
from django.utils.decorators import method_decorator
from django.views.decorators.csrf import csrf_protect
@ -53,6 +54,27 @@ class FormWizard(object):
# hook methods might alter self.form_list.
return len(self.form_list)
def _check_security_hash(self, token, request, form):
expected = self.security_hash(request, form)
if constant_time_compare(token, expected):
return True
else:
# Fall back to Django 1.2 method, for compatibility with forms that
# are in the middle of being used when the upgrade occurs. However,
# we don't want to do this fallback if a subclass has provided their
# own security_hash method - because they might have implemented a
# more secure method, and this would punch a hole in that.
# PendingDeprecationWarning <- left here to remind us that this
# compatibility fallback should be removed in Django 1.5
FormWizard_expected = FormWizard.security_hash(self, request, form)
if expected == FormWizard_expected:
# They didn't override security_hash, do the fallback:
old_expected = security_hash(request, form)
return constant_time_compare(token, old_expected)
else:
return False
@method_decorator(csrf_protect)
def __call__(self, request, *args, **kwargs):
"""
@ -72,7 +94,7 @@ class FormWizard(object):
# TODO: Move "hash_%d" to a method to make it configurable.
for i in range(current_step):
form = self.get_form(i, request.POST)
if request.POST.get("hash_%d" % i, '') != self.security_hash(request, form):
if not self._check_security_hash(request.POST.get("hash_%d" % i, ''), request, form):
return self.render_hash_failure(request, i)
self.process_step(request, form, i)
@ -95,6 +117,21 @@ class FormWizard(object):
# Validate all the forms. If any of them fail validation, that
# must mean the validator relied on some other input, such as
# an external Web site.
# It is also possible that validation might fail under certain
# attack situations: an attacker might be able to bypass previous
# stages, and generate correct security hashes for all the
# skipped stages by virtue of:
# 1) having filled out an identical form which doesn't have the
# validation (and does something different at the end),
# 2) or having filled out a previous version of the same form
# which had some validation missing,
# 3) or previously having filled out the form when they had
# more privileges than they do now.
#
# Since the hashes only take into account values, and not other
# other validation the form might do, we must re-do validation
# now for security reasons.
for i, f in enumerate(final_form_list):
if not f.is_valid():
return self.render_revalidation_failure(request, i, f)
@ -155,7 +192,7 @@ class FormWizard(object):
Subclasses may want to take into account request-specific information,
such as the IP address.
"""
return security_hash(request, form)
return form_hmac(form)
def determine_step(self, request, *args, **kwargs):
"""

10
django/contrib/messages/storage/cookie.py
View File

@ -1,11 +1,9 @@
import hmac
from django.conf import settings
from django.contrib.messages import constants
from django.contrib.messages.storage.base import BaseStorage, Message
from django.http import CompatCookie
from django.utils import simplejson as json
from django.utils.hashcompat import sha_hmac
from django.utils.crypto import salted_hmac, constant_time_compare
class MessageEncoder(json.JSONEncoder):
@ -111,8 +109,8 @@ class CookieStorage(BaseStorage):
Creates an HMAC/SHA1 hash based on the value and the project setting's
SECRET_KEY, modified to make it unique for the present purpose.
"""
key = 'django.contrib.messages' + settings.SECRET_KEY
return hmac.new(key, value, sha_hmac).hexdigest()
key_salt = 'django.contrib.messages'
return salted_hmac(key_salt, value).hexdigest()
def _encode(self, messages, encode_empty=False):
"""
@ -139,7 +137,7 @@ class CookieStorage(BaseStorage):
bits = data.split('$', 1)
if len(bits) == 2:
hash, value = bits
if hash == self._hash(value):
if constant_time_compare(hash, self._hash(value)):
try:
# If we get here (and the JSON decode works), everything is
# good. In any other case, drop back and return None.

43
django/contrib/sessions/backends/base.py
View File

@ -12,6 +12,7 @@ except ImportError:
from django.conf import settings
from django.core.exceptions import SuspiciousOperation
from django.utils.hashcompat import md5_constructor
from django.utils.crypto import constant_time_compare, salted_hmac
# Use the system (hardware-based) random number generator if it exists.
if hasattr(random, 'SystemRandom'):
@ -83,23 +84,45 @@ class SessionBase(object):
def delete_test_cookie(self):
del self[self.TEST_COOKIE_NAME]
def _hash(self, value):
key_salt = "django.contrib.sessions" + self.__class__.__name__
return salted_hmac(key_salt, value).hexdigest()
def encode(self, session_dict):
"Returns the given session dictionary pickled and encoded as a string."
pickled = pickle.dumps(session_dict, pickle.HIGHEST_PROTOCOL)
pickled_md5 = md5_constructor(pickled + settings.SECRET_KEY).hexdigest()
return base64.encodestring(pickled + pickled_md5)
hash = self._hash(pickled)
return base64.encodestring(hash + ":" + pickled)
def decode(self, session_data):
encoded_data = base64.decodestring(session_data)
pickled, tamper_check = encoded_data[:-32], encoded_data[-32:]
if md5_constructor(pickled + settings.SECRET_KEY).hexdigest() != tamper_check:
raise SuspiciousOperation("User tampered with session cookie.")
try:
return pickle.loads(pickled)
# Unpickling can cause a variety of exceptions. If something happens,
# just return an empty dictionary (an empty session).
except:
return {}
# could produce ValueError if there is no ':'
hash, pickled = encoded_data.split(':', 1)
expected_hash = self._hash(pickled)
if not constant_time_compare(hash, expected_hash):
raise SuspiciousOperation("Session data corrupted")
else:
return pickle.loads(pickled)
except Exception:
# ValueError, SuspiciousOperation, unpickling exceptions
# Fall back to Django 1.2 method
# PendingDeprecationWarning <- here to remind us to
# remove this fallback in Django 1.5
try:
return self._decode_old(session_data)
except Exception:
# Unpickling can cause a variety of exceptions. If something happens,
# just return an empty dictionary (an empty session).
return {}
def _decode_old(self, session_data):
encoded_data = base64.decodestring(session_data)
pickled, tamper_check = encoded_data[:-32], encoded_data[-32:]
if not constant_time_compare(md5_constructor(pickled + settings.SECRET_KEY).hexdigest(),
tamper_check):
raise SuspiciousOperation("User tampered with session cookie.")
return pickle.loads(pickled)
def update(self, dict_):
self._session.update(dict_)

21
django/contrib/sessions/tests.py
View File

@ -1,4 +1,6 @@
import base64
from datetime import datetime, timedelta
import pickle
import shutil
import tempfile
@ -12,6 +14,7 @@ from django.contrib.sessions.models import Session
from django.core.exceptions import ImproperlyConfigured
from django.test import TestCase
from django.utils import unittest
from django.utils.hashcompat import md5_constructor
class SessionTestsMixin(object):
@ -237,6 +240,24 @@ class SessionTestsMixin(object):
finally:
settings.SESSION_EXPIRE_AT_BROWSER_CLOSE = original_expire_at_browser_close
def test_decode(self):
# Ensure we can decode what we encode
data = {'a test key': 'a test value'}
encoded = self.session.encode(data)
self.assertEqual(self.session.decode(encoded), data)
def test_decode_django12(self):
# Ensure we can decode values encoded using Django 1.2
# Hard code the Django 1.2 method here:
def encode(session_dict):
pickled = pickle.dumps(session_dict, pickle.HIGHEST_PROTOCOL)
pickled_md5 = md5_constructor(pickled + settings.SECRET_KEY).hexdigest()
return base64.encodestring(pickled + pickled_md5)
data = {'a test key': 'a test value'}
encoded = encode(data)
self.assertEqual(self.session.decode(encoded), data)
class DatabaseSessionTests(SessionTestsMixin, TestCase):

5
django/middleware/csrf.py
View File

@ -15,6 +15,7 @@ from django.utils.cache import patch_vary_headers
from django.utils.hashcompat import md5_constructor
from django.utils.log import getLogger
from django.utils.safestring import mark_safe
from django.utils.crypto import constant_time_compare
_POST_FORM_RE = \
re.compile(r'(<form\W[^>]*\bmethod\s*=\s*(\'|"|)POST(\'|"|)\b[^>]*>)', re.IGNORECASE)
@ -216,8 +217,8 @@ class CsrfViewMiddleware(object):
csrf_token = request.META["CSRF_COOKIE"]
# check incoming token
request_csrf_token = request.POST.get('csrfmiddlewaretoken', None)
if request_csrf_token != csrf_token:
request_csrf_token = request.POST.get('csrfmiddlewaretoken', '')
if not constant_time_compare(request_csrf_token, csrf_token):
if cookie_is_new:
# probably a problem setting the CSRF cookie
logger.warning('Forbidden (%s): %s' % (REASON_NO_CSRF_COOKIE, request.path),

45
django/utils/crypto.py Normal file
View File

@ -0,0 +1,45 @@
"""
Django's standard crypto functions and utilities.
"""
import hmac
from django.conf import settings
from django.utils.hashcompat import sha_constructor
def salted_hmac(key_salt, value, secret=None):
"""
Returns the HMAC-SHA1 of 'value', using a key generated from key_salt and a
secret (which defaults to settings.SECRET_KEY).
A different key_salt should be passed in for every application of HMAC.
"""
if secret is None:
secret = settings.SECRET_KEY
# We need to generate a derived key from our base key. We can do this by
# passing the key_salt and our base key through a pseudo-random function and
# SHA1 works nicely.
key = sha_constructor(key_salt + secret).digest()
# If len(key_salt + secret) > sha_constructor().block_size, the above
# line is redundant and could be replaced by key = key_salt + secret, since
# the hmac module does the same thing for keys longer than the block size.
# However, we need to ensure that we *always* do this.
return hmac.new(key, msg=value, digestmod=sha_constructor)
def constant_time_compare(val1, val2):
"""
Returns True if the two strings are equal, False otherwise.
The time taken is independent of the number of characters that match.
"""
if len(val1) != len(val2):
return False
result = 0
for x, y in zip(val1, val2):
result |= ord(x) ^ ord(y)
return result == 0

4
docs/internals/deprecation.txt
View File

@ -114,6 +114,10 @@ their deprecation, as per the :ref:`Django deprecation policy
:class:`~django.test.simple.DjangoTestRunner` will be removed in
favor of using the unittest-native class.
* The undocumented function
:func:`django.contrib.formtools.utils.security_hash`
is deprecated, in favour of :func:`django.contrib.formtools.utils.form_hmac`
* 2.0
* ``django.views.defaults.shortcut()``. This function has been moved
to ``django.contrib.contenttypes.views.shortcut()`` as part of the

2
docs/ref/contrib/formtools/form-wizard.txt
View File

@ -240,7 +240,7 @@ Advanced ``FormWizard`` methods
Calculates the security hash for the given request object and
:class:`~django.forms.Form` instance.
By default, this uses an MD5 hash of the form data and your
By default, this generates a SHA1 HMAC using your form data and your
:setting:`SECRET_KEY` setting. It's rare that somebody would need to
override this.

18
tests/regressiontests/comment_tests/tests/comment_form_tests.py
View File

@ -2,6 +2,7 @@ import time
from django.conf import settings
from django.contrib.comments.models import Comment
from django.contrib.comments.forms import CommentForm
from django.utils.hashcompat import sha_constructor
from regressiontests.comment_tests.models import Article
from regressiontests.comment_tests.tests import CommentTestCase
@ -43,6 +44,23 @@ class CommentFormTests(CommentTestCase):
def testObjectPKTampering(self):
self.tamperWithForm(object_pk="3")
def testDjango12Hash(self):
# Ensure we can use the hashes generated by Django 1.2
a = Article.objects.get(pk=1)
d = self.getValidData(a)
content_type = d['content_type']
object_pk = d['object_pk']
timestamp = d['timestamp']
# The Django 1.2 method hard-coded here:
info = (content_type, object_pk, timestamp, settings.SECRET_KEY)
security_hash = sha_constructor("".join(info)).hexdigest()
d['security_hash'] = security_hash
f = CommentForm(a, data=d)
self.assertTrue(f.is_valid(), f.errors)
def testSecurityErrors(self):
f = self.tamperWithForm(honeypot="I am a robot")
self.assert_("honeypot" in f.security_errors())