Windows Handles: Work in fixes from @attrc

These changes fix bugs encountered during regression testing related to
virtual offset validation and string length checks.

volatility3/framework/plugins/windows/handles.py

@@ -226,6 +226,14 @@ class Handles(interfaces.plugins.PluginInterface):
         masked_offset = offset & layer_object.maximum_address
 
         for entry in table:
+            # This triggered a backtrace in many testing samples
+            # in the level == 0 path
+            # The code above this calls `is_valid` on the `offset`
+            # It is sent but then does not validate `entry` before
+            # sending it to `_get_item`
+            if not self.context.layers[virtual].is_valid(entry.vol.offset):
+                continue
+
             if level > 0:
                 yield from self._make_handle_array(entry, level - 1, depth)
                 depth += 1

volatility3/framework/symbols/windows/extensions/pool.py

@@ -376,7 +376,16 @@ class OBJECT_HEADER(objects.StructType):
 
         try:
             # vista and earlier have a Type member
-            self._vol["object_header_object_type"] = self.Type.Name.String
+            length = self.Type.member("Name").Length
+            if length == 0 or length > 128:
+                string = None
+            else:
+                string = self.Type.Name.String
+                if len(string) == 0 or len(string) > 128:
+                    string = None
+
+            self._vol["object_header_object_type"] = string
+
         except AttributeError:
             # windows 7 and later have a TypeIndex, but windows 10
             # further encodes the index value with nt1!ObHeaderCookie