Em qua., 29 de mai. de 2024 às 22:41, Long Song <songlong88@126.com> escreveu:
Hi Ranier,
> IMO, I think that pg_rewind can have a security issue, > if two files are exactly the same, they are considered different. > Because use of structs with padding values is unspecified. Logically you are right. But I don't understand what scenario would require memcmp to compare ControlFileData. In general, we read ControlFileData from a pg_control file and then use members of ControlFileData directly. So the two ControlFileData are not directly compared by byte.
Actually in pg_rewind there is a comparison using memcmp.
> Fix by explicitly initializing with memset to avoid this. And, even if there are scenarios that use memcmp comparisons, your modifications are not complete. There are three calls to the digestControlFile in the main() of pg_rewind.c, and as your said(if right), these should do memory initialization every time.
In fact, initializing structures with memset does not solve anything. Once the entire structure is populated again by a call to memcpy shortly thereafter.
My concern now is that when the structure is saved to disk,
