def clean_security_hash(self):
"""Check the security hash."""
security_hash_dict = {
'content_type' : self.data.get("content_type", ""),
'object_pk' : self.data.get("object_pk", ""),
'timestamp' : self.data.get("timestamp", ""),
}
expected_hash = self.generate_security_hash(**security_hash_dict)
actual_hash = self.cleaned_data["security_hash"]
if not constant_time_compare(expected_hash, actual_hash):
raise forms.ValidationError("Security hash check failed.")
return actual_hash
def decode(self, session_data):
encoded_data = base64.b64decode(force_bytes(session_data))
try:
# could produce ValueError if there is no ':'
hash, pickled = encoded_data.split(b':', 1)
expected_hash = self._hash(pickled)
if not constant_time_compare(hash.decode(), expected_hash):
raise SuspiciousOperation("Session data corrupted")
else:
return pickle.loads(pickled)
except Exception:
# ValueError, SuspiciousOperation, unpickling exceptions. If any of
# these happen, just return an empty dictionary (an empty session).
return {}
def _decode(self, data):
"""
Safely decodes a encoded text stream back into a list of messages.
If the encoded text stream contained an invalid hash or was in an
invalid format, ``None`` is returned.
"""
if not data:
return None
bits = data.split('$', 1)
if len(bits) == 2:
hash, value = bits
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.
return json.loads(value, cls=MessageDecoder)
except ValueError:
pass
# Mark the data as used (so it gets removed) since something was wrong
# with the data.
self.used = True
return None
def check_token(self, user, token):
"""
Check that a password reset token is correct for a given user.
"""
# Parse the token
try:
ts_b36, hash = token.split("-")
except ValueError:
return False
try:
ts = base36_to_int(ts_b36)
except ValueError:
return False
# Check that the timestamp/uid has not been tampered with
if not constant_time_compare(self._make_token_with_timestamp(user, ts), token):
return False
# Check the timestamp is within limit
if (self._num_days(self._today()) - ts) > settings.PASSWORD_RESET_TIMEOUT_DAYS:
return False
return True
def test_constant_time_compare(self):
# It's hard to test for constant time, just test the result.
self.assertTrue(constant_time_compare(b"spam", b"spam"))
self.assertFalse(constant_time_compare(b"spam", b"eggs"))
self.assertTrue(constant_time_compare("spam", "spam"))
self.assertFalse(constant_time_compare("spam", "eggs"))
def _check_security_hash(self, token, request, form):
expected = self.security_hash(request, form)
return constant_time_compare(token, expected)
def process_view(self, request, callback, callback_args, callback_kwargs):
if getattr(request, 'csrf_processing_done', False):
return None
try:
csrf_token = _sanitize_token(
request.COOKIES[settings.CSRF_COOKIE_NAME])
# 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 RC2616 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 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
# 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
# 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.
referer = request.META.get('HTTP_REFERER')
if referer is None:
logger.warning('Forbidden (%s): %s',
REASON_NO_REFERER, request.path,
extra={
'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,
extra={
'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
# CSRF.
logger.warning('Forbidden (%s): %s',
REASON_NO_CSRF_COOKIE, request.path,
extra={
'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,
extra={
'status_code': 403,
'request': request,
}
)
return self._reject(request, REASON_BAD_TOKEN)
return self._accept(request)
def verify(self, password, encoded):
crypt = self._load_library()
algorithm, salt, data = encoded.split('$', 2)
assert algorithm == self.algorithm
return constant_time_compare(data, crypt.crypt(password, data))
def verify(self, password, encoded):
encoded_2 = self.encode(password, '')
return constant_time_compare(encoded, encoded_2)
def verify(self, password, encoded):
algorithm, salt, hash = encoded.split('$', 2)
assert algorithm == self.algorithm
encoded_2 = self.encode(password, salt)
return constant_time_compare(encoded, encoded_2)
def verify(self, password, encoded):
algorithm, data = encoded.split('$', 1)
assert algorithm == self.algorithm
bcrypt = self._load_library()
return constant_time_compare(data, bcrypt.hashpw(password, data))
