From 4b82578a6045746e7c470b7881dfcf182fd57048 Mon Sep 17 00:00:00 2001
From: Nick Pope <nick@nickpope.me.uk>
Date: Fri, 3 Sep 2021 11:26:27 +0200
Subject: [PATCH] Refs #33060 -- Ensured cache backends validate keys.

The validate_key() function should be called after make_key() to ensure
that the validation is performed on the key that will actually be
stored in the cache.

Co-authored-by: Mariusz Felisiak <felisiak.mariusz@gmail.com>
---
 django/core/cache/backends/db.py | 11 +++++++----
 tests/cache/tests.py             | 17 +++++++++++++++--
 2 files changed, 22 insertions(+), 6 deletions(-)

diff --git a/django/core/cache/backends/db.py b/django/core/cache/backends/db.py
index b84885f1ef..63598007d0 100644
--- a/django/core/cache/backends/db.py
+++ b/django/core/cache/backends/db.py
@@ -56,8 +56,9 @@ class DatabaseCache(BaseDatabaseCache):
 
         key_map = {}
         for key in keys:
-            self.validate_key(key)
-            key_map[self.make_key(key, version)] = key
+            new_key = self.make_key(key, version)
+            self.validate_key(new_key)
+            key_map[new_key] = key
 
         db = router.db_for_read(self.cache_model_class)
         connection = connections[db]
@@ -196,14 +197,16 @@ class DatabaseCache(BaseDatabaseCache):
                 return True
 
     def delete(self, key, version=None):
+        key = self.make_key(key, version)
         self.validate_key(key)
-        return self._base_delete_many([self.make_key(key, version)])
+        return self._base_delete_many([key])
 
     def delete_many(self, keys, version=None):
         key_list = []
         for key in keys:
+            key = self.make_key(key, version)
             self.validate_key(key)
-            key_list.append(self.make_key(key, version))
+            key_list.append(key)
         self._base_delete_many(key_list)
 
     def _base_delete_many(self, keys):
diff --git a/tests/cache/tests.py b/tests/cache/tests.py
index 1b40def85a..0e2f5f7d1f 100644
--- a/tests/cache/tests.py
+++ b/tests/cache/tests.py
@@ -675,7 +675,7 @@ class BaseCacheTests:
         finally:
             cull_cache._max_entries = old_max_entries
 
-    def _perform_invalid_key_test(self, key, expected_warning):
+    def _perform_invalid_key_test(self, key, expected_warning, key_func=None):
         """
         All the builtin backends should warn (except memcached that should
         error) on keys that would be refused by memcached. This encourages
@@ -688,7 +688,7 @@ class BaseCacheTests:
             return key
 
         old_func = cache.key_func
-        cache.key_func = func
+        cache.key_func = key_func or func
 
         tests = [
             ('add', [key, 1]),
@@ -725,6 +725,19 @@ class BaseCacheTests:
         )
         self._perform_invalid_key_test(key, expected_warning)
 
+    def test_invalid_with_version_key_length(self):
+        # Custom make_key() that adds a version to the key and exceeds the
+        # limit.
+        def key_func(key, *args):
+            return key + ':1'
+
+        key = 'a' * 249
+        expected_warning = (
+            'Cache key will cause errors if used with memcached: '
+            '%r (longer than %s)' % (key_func(key), 250)
+        )
+        self._perform_invalid_key_test(key, expected_warning, key_func=key_func)
+
     def test_cache_versioning_get_set(self):
         # set, using default version = 1
         cache.set('answer1', 42)