An alternative patch for https://bugs.launchpad.net/swift/+bug/1257330 (see https://gist.github.com/gholt/7771150).

patch-for-1257330.diff

diff --git a/swift/common/exceptions.py b/swift/common/exceptions.py
index 5943f89..e0361cf 100644
--- a/swift/common/exceptions.py
+++ b/swift/common/exceptions.py
@@ -54,6 +54,10 @@ class DiskFileDeleted(DiskFileNotExist):
     pass
 
 
+class DiskFileExpired(DiskFileNotExist):
+    pass
+
+
 class DiskFileNoSpace(DiskFileError):
     pass
 
diff --git a/swift/obj/diskfile.py b/swift/obj/diskfile.py
index ffdcafd..82fa311 100644
--- a/swift/obj/diskfile.py
+++ b/swift/obj/diskfile.py
@@ -56,7 +56,7 @@ from swift.common.utils import mkdirs, normalize_timestamp, \
 from swift.common.exceptions import DiskFileQuarantined, DiskFileNotExist, \
     DiskFileCollision, DiskFileNoSpace, DiskFileDeviceUnavailable, \
     DiskFileDeleted, DiskFileError, DiskFileNotOpen, PathNotDir, \
-    ReplicationLockTimeout
+    ReplicationLockTimeout, DiskFileExpired
 from swift.common.swob import multi_range_iterator
 
 
@@ -1165,7 +1165,10 @@ class DiskFile(object):
                     self._metadata['X-Delete-At']))
         else:
             if x_delete_at <= time.time():
-                raise DiskFileNotExist('Expired')
+                exc = DiskFileExpired()
+                exc.x_delete_at = x_delete_at
+                exc.timestamp = self._metadata['X-Timestamp']
+                raise exc
         try:
             metadata_size = int(self._metadata['Content-Length'])
         except KeyError:
diff --git a/swift/obj/server.py b/swift/obj/server.py
index cfb7695..cb4ce07 100644
--- a/swift/obj/server.py
+++ b/swift/obj/server.py
@@ -34,7 +34,7 @@ from swift.common.constraints import check_object_creation, \
     check_float, check_utf8
 from swift.common.exceptions import ConnectionTimeout, DiskFileQuarantined, \
     DiskFileNotExist, DiskFileCollision, DiskFileNoSpace, DiskFileDeleted, \
-    DiskFileDeviceUnavailable
+    DiskFileDeviceUnavailable, DiskFileExpired
 from swift.obj import ssync_receiver
 from swift.common.http import is_success
 from swift.common.request_helpers import split_and_validate_path
@@ -584,11 +584,15 @@ class ObjectController(object):
             orig_metadata = disk_file.read_metadata()
         except DiskFileDeleted as e:
             orig_timestamp = e.timestamp
-            orig_metadata = {}
+            orig_delete_at = 0
+            response_class = HTTPNotFound
+        except DiskFileExpired as e:
+            orig_timestamp = e.timestamp
+            orig_delete_at = e.x_delete_at
             response_class = HTTPNotFound
         except (DiskFileNotExist, DiskFileQuarantined):
             orig_timestamp = 0
-            orig_metadata = {}
+            orig_delete_at = 0
             response_class = HTTPNotFound
         else:
             orig_timestamp = orig_metadata.get('X-Timestamp', 0)
@@ -596,13 +600,23 @@ class ObjectController(object):
                 response_class = HTTPNoContent
             else:
                 response_class = HTTPConflict
-        if 'x-if-delete-at' in request.headers and \
-                int(request.headers['x-if-delete-at']) != \
-                int(orig_metadata.get('X-Delete-At') or 0):
-            return HTTPPreconditionFailed(
-                request=request,
-                body='X-If-Delete-At and X-Delete-At do not match')
-        orig_delete_at = int(orig_metadata.get('X-Delete-At') or 0)
+            orig_delete_at = int(orig_metadata.get('X-Delete-At') or 0)
+        try:
+            req_if_delete_at = request.headers['x-if-delete-at']
+        except KeyError:
+            pass
+        else:
+            try:
+                req_if_delete_at = int(req_if_delete_at)
+            except ValueError:
+                return HTTPBadRequest(body='Missing timestamp',
+                                      request=request,
+                                      content_type='text/plain')
+            else:
+                if orig_delete_at != req_if_delete_at:
+                    return HTTPPreconditionFailed(
+                        request=request,
+                        body='X-If-Delete-At and X-Delete-At do not match')
         if orig_delete_at:
             self.delete_at_update('DELETE', orig_delete_at, account,
                                   container, obj, request, device)