Merge pull request #1402 from ThomasWaldmann/fix-1351

Fix 1351

borg/archive.py

@@ -754,6 +754,9 @@ def valid_msgpacked_dict(d, keys_serialized):
 class RobustUnpacker:
     """A restartable/robust version of the streaming msgpack unpacker
     """
+    class UnpackerCrashed(Exception):
+        """raise if unpacker crashed"""
+
     def __init__(self, validator, item_keys):
         super().__init__()
         self.item_keys = [msgpack.packb(name) for name in item_keys]
@@ -776,6 +779,14 @@ class RobustUnpacker:
         return self
 
     def __next__(self):
+        def unpack_next():
+            try:
+                return next(self._unpacker)
+            except (TypeError, ValueError) as err:
+                # transform exceptions that might be raised when feeding
+                # msgpack with invalid data to a more specific exception
+                raise self.UnpackerCrashed(str(err))
+
         if self._resync:
             data = b''.join(self._buffered_data)
             while self._resync:
@@ -788,17 +799,17 @@ class RobustUnpacker:
                 self._unpacker = msgpack.Unpacker(object_hook=StableDict)
                 self._unpacker.feed(data)
                 try:
-                    item = next(self._unpacker)
+                    item = unpack_next()
+                except (self.UnpackerCrashed, StopIteration):
+                    # as long as we are resyncing, we also ignore StopIteration
+                    pass
+                else:
                     if self.validator(item):
                         self._resync = False
                         return item
-                # Ignore exceptions that might be raised when feeding
-                # msgpack with invalid data
-                except (TypeError, ValueError, StopIteration):
-                    pass
                 data = data[1:]
         else:
-            return next(self._unpacker)
+            return unpack_next()
 
 
 class ArchiveChecker:
@@ -1017,6 +1028,9 @@ class ArchiveChecker:
                                 yield item
                             else:
                                 report('Did not get expected metadata dict when unpacking item metadata', chunk_id, i)
+                    except RobustUnpacker.UnpackerCrashed as err:
+                        report('Unpacker crashed while unpacking item metadata, trying to resync...', chunk_id, i)
+                        unpacker.resync()
                     except Exception:
                         report('Exception while unpacking item metadata', chunk_id, i)
                         raise