Em qua., 29 de mai. de 2024 às 22:41, Long Song <songlon...@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, what are the padding fields like? But enough noise. Thanks for taking a look. best regards, Ranier Vilela
