Fix: check bulk mail delete permissions for the whole batch up front

ProcessedMailViewSet.bulk_delete checked permissions inside the delete
loop, so an unpermitted id returned 403 only after the mails ahead of it
had already been deleted. Resolve the permitted set once via
permitted_object_ids and reject before deleting anything, which also
drops the per-mail permission queries.

src/paperless_mail/tests/test_api.py

@@ -757,3 +757,30 @@ class TestAPIProcessedMails(DirectoriesMixin, APITestCase):
             format="json",
         )
         self.assertEqual(response.status_code, status.HTTP_400_BAD_REQUEST)
+
+    def test_bulk_delete_processed_mails_rejects_mixed_batch_atomically(self) -> None:
+        """
+        GIVEN:
+            - A permitted processed mail and one the user may not delete
+        WHEN:
+            - API call bulk deletes both in a single request
+        THEN:
+            - The request is rejected and neither mail is deleted
+        """
+        user2 = User.objects.create_user(username="temp_admin2")
+        rule = MailRuleFactory()
+        # Created first so it sorts ahead of the forbidden mail, i.e. the
+        # permission check has to cover the whole batch before deleting rather
+        # than rejecting only once it reaches the forbidden one.
+        pm_owned = ProcessedMailFactory(rule=rule, owner=self.user)
+        pm_forbidden = ProcessedMailFactory(rule=rule, owner=user2)
+
+        response = self.client.post(
+            f"{self.ENDPOINT}bulk_delete/",
+            data={"mail_ids": [pm_owned.id, pm_forbidden.id]},
+            format="json",
+        )
+
+        self.assertEqual(response.status_code, status.HTTP_403_FORBIDDEN)
+        self.assertTrue(ProcessedMail.objects.filter(id=pm_owned.id).exists())
+        self.assertTrue(ProcessedMail.objects.filter(id=pm_forbidden.id).exists())

src/paperless_mail/views.py

@@ -27,6 +27,7 @@ from documents.filters import PermittedObjectsFilter
 from documents.models import PaperlessTask
 from documents.permissions import PaperlessObjectPermissions
 from documents.permissions import has_perms_owner_aware
+from documents.permissions import permitted_object_ids
 from documents.views import PassUserMixin
 from paperless.views import StandardPagination
 from paperless_mail.filters import ProcessedMailFilterSet
@@ -211,10 +212,17 @@ class ProcessedMailViewSet(PassUserMixin, ReadOnlyModelViewSet[ProcessedMail]):
         ):
             return HttpResponseBadRequest("mail_ids must be a list of integers")
         mails = ProcessedMail.objects.filter(id__in=mail_ids)
-        for mail in mails:
-            if not has_perms_owner_aware(request.user, "delete_processedmail", mail):
-                return HttpResponseForbidden("Insufficient permissions")
-            mail.delete()
+        # Check every id up front so an unpermitted one rejects the whole
+        # request rather than deleting the mails ahead of it first.
+        if mails.exclude(
+            pk__in=permitted_object_ids(
+                request.user,
+                ProcessedMail,
+                "delete_processedmail",
+            ),
+        ).exists():
+            return HttpResponseForbidden("Insufficient permissions")
+        mails.delete()
         return Response({"result": "OK", "deleted_mail_ids": mail_ids})