On 2019-Jul-10, Bruce Momjian wrote:
> * Using the LSN as part of the nonce fixes both problems, and has a
> third benefit:
>
> * We don't need to decrypt/re-encrypt during CREATE DATABASE since
> the page contents are the same in both places, and once one
> database changes its pages, it gets a new LSN, and hence a new
> nonce/IV.
>
> * For each change of an 8k page, you get a new nonce/IV, so you
> are not encrypting different data with the same nonce/IV
>
> * This avoids requiring pg_upgrade to preserve database oids.
An ignorant question -- what is it that gets stored in the page for
decryption use, the nonce or the IV derived from it? I think if you
want to store the nonce, you'd have to store the database OID, because
otherwise how do you know which database OID to use to determine the
full nonce after cloning a database? You already have the table OID in
the catalog and the LSN in the page header, so you're only missing the
database OID. (Assuming you make the nonce be database OID || relation
OID || page LSN)
Also, how are key changes handled? Do we need to store a key identifier
in each page?
--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services