[3.1.x] Fixed CVE-2021-35042 -- Prevented SQL injection in QuerySet.order_by().

charettes · felixxm · commit 0bd57a879a0d · 2021-07-01T08:36:17.000+02:00
Regression introduced in 5139487 by marking the raw SQL column reference feature for deprecation in Django 4.0 while lifting the column format validation. In retrospective the validation should have been kept around and the user should have been pointed at using RawSQL expressions during the deprecation period. The main branch is not affected because the raw SQL column reference support has been removed in 06eec31 per the 4.0 deprecation life cycle. Thanks Joel Saunders for the report.
diff --git a/django/db/models/sql/constants.py b/django/db/models/sql/constants.py
@@ -1,6 +1,7 @@
 """
 Constants specific to the SQL storage portion of the ORM.
 """
+from django.utils.regex_helper import _lazy_re_compile
 
 # Size of each "chunk" for get_iterator calls.
 # Larger values are slightly faster at the expense of more storage space.
@@ -18,6 +19,7 @@
     'ASC': ('ASC', 'DESC'),
     'DESC': ('DESC', 'ASC'),
 }
+ORDER_PATTERN = _lazy_re_compile(r'[-+]?[.\w]+$')
 
 # SQL join types.
 INNER = 'INNER JOIN'
diff --git a/django/db/models/sql/query.py b/django/db/models/sql/query.py
@@ -30,7 +30,9 @@
 from django.db.models.query_utils import (
     Q, check_rel_lookup_compatibility, refs_expression,
 )
-from django.db.models.sql.constants import INNER, LOUTER, ORDER_DIR, SINGLE
+from django.db.models.sql.constants import (
+    INNER, LOUTER, ORDER_DIR, ORDER_PATTERN, SINGLE,
+)
 from django.db.models.sql.datastructures import (
     BaseTable, Empty, Join, MultiJoin,
 )
@@ -1897,7 +1899,7 @@ def add_ordering(self, *ordering):
         errors = []
         for item in ordering:
             if isinstance(item, str):
-                if '.' in item:
+                if '.' in item and ORDER_PATTERN.match(item):
                     warnings.warn(
                         'Passing column raw column aliases to order_by() is '
                         'deprecated. Wrap %r in a RawSQL expression before '
diff --git a/docs/releases/3.1.13.txt b/docs/releases/3.1.13.txt
@@ -6,4 +6,16 @@ Django 3.1.13 release notes
 
 Django 3.1.13 fixes a security issues with severity "high" in 3.1.12.
 
-...
+CVE-2021-35042: Potential SQL injection via unsanitized ``QuerySet.order_by()`` input
+=====================================================================================
+
+Unsanitized user input passed to ``QuerySet.order_by()`` could bypass intended
+column reference validation in path marked for deprecation resulting in a
+potential SQL injection even if a deprecation warning is emitted.
+
+As a mitigation the strict column reference validation was restored for the
+duration of the deprecation period. This regression appeared in 3.1 as a side
+effect of fixing :ticket:`31426`.
+
+The issue is not present in the main branch as the deprecated path has been
+removed.
diff --git a/tests/queries/tests.py b/tests/queries/tests.py
@@ -3134,6 +3134,14 @@ def test_invalid_order_by(self):
         with self.assertRaisesMessage(FieldError, msg):
             Article.objects.order_by('*')
 
+    def test_order_by_escape_prevention(self):
+        msg = (
+            "Cannot resolve keyword 'queries.name);' into field. Choices are: "
+            "created, id, name"
+        )
+        with self.assertRaisesMessage(FieldError, msg):
+            Article.objects.order_by('queries.name);')
+
     def test_invalid_queryset_model(self):
         msg = 'Cannot use QuerySet for "Article": Use a QuerySet for "ExtraInfo".'
         with self.assertRaisesMessage(ValueError, msg):
