Improve order secret handling (#4139)

- use hmac.compare_digest for all secret comparisons
- use salted_hmac with sha256 instead of plain sha1 for hashed secrets
- move secret handling into helper functions

src/pretix/plugins/paypal2/payment.py

@@ -19,7 +19,6 @@
 # You should have received a copy of the GNU Affero General Public License along with this program.  If not, see
 # <https://www.gnu.org/licenses/>.
 #
-import hashlib
 import json
 import logging
 import urllib.parse
@@ -1096,5 +1095,5 @@ class PaypalAPM(PaypalMethod):
         return eventreverse(self.event, 'plugins:paypal2:pay', kwargs={
             'order': payment.order.code,
             'payment': payment.pk,
-            'hash': hashlib.sha1(payment.order.secret.lower().encode()).hexdigest(),
+            'hash': payment.order.tagged_secret('plugins:paypal2:pay'),
         })

src/pretix/plugins/paypal2/views.py

@@ -31,7 +31,6 @@
 # Unless required by applicable law or agreed to in writing, software distributed under the Apache License 2.0 is
 # distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 # License for the specific language governing permissions and limitations under the License.
-import hashlib
 import json
 import logging
 from decimal import Decimal
@@ -81,15 +80,11 @@ logger = logging.getLogger('pretix.plugins.paypal2')
 class PaypalOrderView:
     def dispatch(self, request, *args, **kwargs):
         try:
-            self.order = request.event.orders.get(code=kwargs['order'])
-            if hashlib.sha1(self.order.secret.lower().encode()).hexdigest() != kwargs['hash'].lower():
-                raise Http404('Unknown order')
+            self.order = request.event.orders.get_with_secret_check(
+                code=kwargs['order'], received_secret=kwargs['hash'].lower(), tag='plugins:paypal2:pay'
+            )
         except Order.DoesNotExist:
-            # Do a hash comparison as well to harden timing attacks
-            if 'abcdefghijklmnopq'.lower() == hashlib.sha1('abcdefghijklmnopq'.encode()).hexdigest():
-                raise Http404('Unknown order')
-            else:
-                raise Http404('Unknown order')
+            raise Http404('Unknown order')
         return super().dispatch(request, *args, **kwargs)
 
     @cached_property

src/pretix/plugins/stripe/payment.py

@@ -32,7 +32,6 @@
 # distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 # License for the specific language governing permissions and limitations under the License.
 
-import hashlib
 import json
 import logging
 import re
@@ -636,7 +635,7 @@ class StripeMethod(BasePaymentProvider):
             'order': payment.order,
             'payment': payment,
             'payment_info': payment_info,
-            'payment_hash': hashlib.sha1(payment.order.secret.lower().encode()).hexdigest()
+            'payment_hash': payment.order.tagged_secret('plugins:stripe')
         }
         return template.render(ctx)
 
@@ -890,7 +889,7 @@ class StripeMethod(BasePaymentProvider):
                     return_url=build_absolute_uri(self.event, 'plugins:stripe:sca.return', kwargs={
                         'order': payment.order.code,
                         'payment': payment.pk,
-                        'hash': hashlib.sha1(payment.order.secret.lower().encode()).hexdigest(),
+                        'hash': payment.order.tagged_secret('plugins:stripe'),
                     }),
                     expand=['latest_charge'],
                     **params
@@ -988,7 +987,7 @@ class StripeMethod(BasePaymentProvider):
         url = build_absolute_uri(self.event, 'plugins:stripe:sca', kwargs={
             'order': payment.order.code,
             'payment': payment.pk,
-            'hash': hashlib.sha1(payment.order.secret.lower().encode()).hexdigest(),
+            'hash': payment.order.tagged_secret('plugins:stripe'),
         })
         if not self.redirect_in_widget_allowed and request.session.get('iframe_session', False):
             return build_absolute_uri(self.event, 'plugins:stripe:redirect') + '?data=' + signing.dumps({
@@ -1009,7 +1008,7 @@ class StripeMethod(BasePaymentProvider):
                 return_url=build_absolute_uri(self.event, 'plugins:stripe:sca.return', kwargs={
                     'order': payment.order.code,
                     'payment': payment.pk,
-                    'hash': hashlib.sha1(payment.order.secret.lower().encode()).hexdigest(),
+                    'hash': payment.order.tagged_secret('plugins:stripe'),
                 }),
                 expand=["latest_charge"],
                 **self.api_kwargs
@@ -1829,7 +1828,7 @@ class StripeMultibanco(StripeSourceMethod):
                 'return_url': build_absolute_uri(self.event, 'plugins:stripe:return', kwargs={
                     'order': payment.order.code,
                     'payment': payment.pk,
-                    'hash': hashlib.sha1(payment.order.secret.lower().encode()).hexdigest(),
+                    'hash': payment.order.tagged_secret('plugins:stripe'),
                 })
             },
             **self.api_kwargs

src/pretix/plugins/stripe/views.py

@@ -32,7 +32,6 @@
 # distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 # License for the specific language governing permissions and limitations under the License.
 
-import hashlib
 import json
 import logging
 import urllib.parse
@@ -486,15 +485,11 @@ def oauth_disconnect(request, **kwargs):
 class StripeOrderView:
     def dispatch(self, request, *args, **kwargs):
         try:
-            self.order = request.event.orders.get(code=kwargs['order'])
-            if hashlib.sha1(self.order.secret.lower().encode()).hexdigest() != kwargs['hash'].lower():
-                raise Http404('')
+            self.order = request.event.orders.get_with_secret_check(
+                code=kwargs['order'], received_secret=kwargs['hash'].lower(), tag='plugins:stripe'
+            )
         except Order.DoesNotExist:
-            # Do a hash comparison as well to harden timing attacks
-            if 'abcdefghijklmnopq'.lower() == hashlib.sha1('abcdefghijklmnopq'.encode()).hexdigest():
-                raise Http404('')
-            else:
-                raise Http404('')
+            raise Http404('Unknown order')
         self.payment = get_object_or_404(
             self.order.payments,
             pk=self.kwargs['payment'],