Fixed incorrect permissions check for admin's "Save as new".

This is a security fix.

django/contrib/admin/options.py

@@ -1399,6 +1399,10 @@ class ModelAdmin(BaseModelAdmin):
 
         model = self.model
         opts = model._meta
+
+        if request.method == 'POST' and '_saveasnew' in request.POST:
+            object_id = None
+
         add = object_id is None
 
         if add:
@@ -1416,10 +1420,6 @@ class ModelAdmin(BaseModelAdmin):
                 raise Http404(_('%(name)s object with primary key %(key)r does not exist.') % {
                     'name': force_text(opts.verbose_name), 'key': escape(object_id)})
 
-            if request.method == 'POST' and "_saveasnew" in request.POST:
-                object_id = None
-                obj = None
-
         ModelForm = self.get_form(request, obj)
         if request.method == 'POST':
             form = ModelForm(request.POST, request.FILES, instance=obj)
@@ -1482,6 +1482,8 @@ class ModelAdmin(BaseModelAdmin):
         if request.method == 'POST' and not form_validated and "_saveasnew" in request.POST:
             context['show_save'] = False
             context['show_save_and_continue'] = False
+            # Use the change template instead of the add template.
+            add = False
 
         context.update(extra_context or {})
 

docs/releases/1.9.2.txt

@@ -4,8 +4,17 @@ Django 1.9.2 release notes
 
 *Under development*
 
-Django 1.9.2 fixes several bugs in 1.9.1 and makes a small backwards
+Django 1.9.2 fixes a security regression in 1.9 and several bugs in 1.9.1. It
-incompatible change that hopefully doesn't affect any users.
+also makes a small backwards incompatible change that hopefully doesn't affect
+any users.
+
+Security issue: User with "change" but not "add" permission can create objects for ``ModelAdmin``’s with ``save_as=True``
+=========================================================================================================================
+
+If a ``ModelAdmin`` uses ``save_as=True`` (not the default), the admin
+provides an option when editing objects to "Save as new". A regression in
+Django 1.9 prevented that form submission from raising a "Permission Denied"
+error for users without the "add" permission.
 
 Backwards incompatible change: ``.py-tpl`` files rewritten in project/app templates
 ===================================================================================

tests/admin_views/tests.py

@@ -1673,6 +1673,35 @@ class AdminViewPermissionsTest(TestCase):
             self.assertContains(response, 'login-form')
             self.client.get(reverse('admin:logout'))
 
+    def test_change_view_save_as_new(self):
+        """
+        'Save as new' should raise PermissionDenied for users without the 'add'
+        permission.
+        """
+        change_dict_save_as_new = {
+            '_saveasnew': 'Save as new',
+            'title': 'Ikke fordømt',
+            'content': '<p>edited article</p>',
+            'date_0': '2008-03-18', 'date_1': '10:54:39',
+            'section': self.s1.pk,
+        }
+        article_change_url = reverse('admin:admin_views_article_change', args=(self.a1.pk,))
+
+        # Add user can perform "Save as new".
+        article_count = Article.objects.count()
+        self.client.force_login(self.adduser)
+        post = self.client.post(article_change_url, change_dict_save_as_new)
+        self.assertRedirects(post, self.index_url)
+        self.assertEqual(Article.objects.count(), article_count + 1)
+        self.client.logout()
+
+        # Change user cannot perform "Save as new" (no 'add' permission).
+        article_count = Article.objects.count()
+        self.client.force_login(self.changeuser)
+        post = self.client.post(article_change_url, change_dict_save_as_new)
+        self.assertEqual(post.status_code, 403)
+        self.assertEqual(Article.objects.count(), article_count)
+
     def test_delete_view(self):
         """Delete view should restrict access and actually delete items."""
         delete_dict = {'post': 'yes'}