On Wed, Jul 31, 2019 at 09:43:00AM -0400, Sehrope Sarkuni wrote: > On Wed, Jul 31, 2019 at 2:32 AM Masahiko Sawada <sawada.m...@gmail.com> wrote: > For WAL encryption, before flushing WAL we encrypt whole 8k WAL page > and then write only the encrypted data of the new WAL record using > pg_pwrite() rather than write whole encrypted page. So each time we > encrypt 8k WAL page we end up with encrypting different data with the > same key+nonce but since we don't write to the disk other than space > where we actually wrote WAL records it's not a problem. Is that right? > > Ah, this is what I was referring to in my previous mail. I'm not familiar with > how the writes happen yet (reading up...) but, yes, we would need to ensure > that encrypted data is not written more than once (i.e. no writing of encrypt > (zero) followed by writing of encrypt(non-zero) at the same spot).
No one replied to this comment, so I will state here that we never write zeros to the WAL and go back and write something else --- the WAL is append-only. We might do that for heap/index pages, but they would get a new LSN (and hence a new IV) when that happens. -- Bruce Momjian <br...@momjian.us> http://momjian.us EnterpriseDB http://enterprisedb.com + As you are, so once was I. As I am, so you will be. + + Ancient Roman grave inscription +
