API: validate payment_info (#5944)

* API: validate payment_info

* improve dict-check

* Apply suggestions from code review

Co-authored-by: Raphael Michel <michel@pretix.eu>

---------

Co-authored-by: Raphael Michel <michel@pretix.eu>

src/pretix/api/serializers/order.py

@@ -19,6 +19,7 @@
 # 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 json
 import logging
 import os
 from collections import Counter, defaultdict
@@ -1215,6 +1216,18 @@ class OrderCreateSerializer(I18nAwareModelSerializer):
             raise ValidationError('The given payment provider is not known.')
         return pp
 
+    def validate_payment_info(self, info):
+        if info:
+            try:
+                obj = json.loads(info)
+            except ValueError:
+                raise ValidationError('payment_info must be valid JSON.')
+
+            if not isinstance(obj, dict):
+                # only objects are allowed
+                raise ValidationError('payment_info must be a JSON object.')
+        return info
+
     def validate_expires(self, expires):
         if expires < now():
             raise ValidationError('Expiration date must be in the future.')

src/tests/api/test_order_create.py

@@ -895,6 +895,41 @@ def test_order_create_payment_info_optional(token_client, organizer, event, item
     assert json.loads(p.info) == res['payment_info']
 
 
+@pytest.mark.django_db
+def test_order_create_payment_info_valid_object(token_client, organizer, event, item, quota, question):
+    res = copy.deepcopy(ORDER_CREATE_PAYLOAD)
+    res['positions'][0]['item'] = item.pk
+    res['positions'][0]['answers'][0]['question'] = question.pk
+
+    res["payment_info"] = [{"should": "fail"}]
+    resp = token_client.post(
+        '/api/v1/organizers/{}/events/{}/orders/'.format(
+            organizer.slug, event.slug
+        ), format='json', data=res
+    )
+    assert resp.status_code == 400
+
+    res['payment_info'] = {
+        'foo': {
+            'bar': [1, 2],
+            'test': False
+        }
+    }
+    resp = token_client.post(
+        '/api/v1/organizers/{}/events/{}/orders/'.format(
+            organizer.slug, event.slug
+        ), format='json', data=res
+    )
+    assert resp.status_code == 201
+    with scopes_disabled():
+        o = Order.objects.get(code=resp.data['code'])
+
+        p = o.payments.first()
+    assert p.provider == "banktransfer"
+    assert p.amount == o.total
+    assert json.loads(p.info) == res['payment_info']
+
+
 @pytest.mark.django_db
 def test_order_create_position_secret_optional(token_client, organizer, event, item, quota, question):
     res = copy.deepcopy(ORDER_CREATE_PAYLOAD)