On 8/26/19 2:53 AM, Masahiko Sawada wrote:
> I guess that this depends on the number of encryption keys we use. If
> we have encryption keys per tablespace or database the number of keys
> would be at most several dozen or several hundred. It's enough to have
> them in flat-file format on the disk and to load them to the hash
> table on the shared memory. We would not need a complex mechanism.
> OTOH if we have keys per tables, we would need to consider indexes and
> buffering as they might not fit in the memory.
Master key(s) need to be kept in memory, but derived keys (using KDF)
would be calculated at time of use, I would think.
>> Some kind of flat-file based approach with a temp file and renaming of
>> files using durable_rename(), like what we used to do with
>> pg_shadow/authid, and now do with replorigin_checkpoint and such?
>
> The PoC patch I created does that for the keyring file. When key
> rotation, the correspond WAL contains all re-encrypted keys with the
> master key identifier, and the recovery restores the keyring file. One
> good point of this approach is that external tools and startup process
> read it easier. It doesn't require backend codes such as system cache
> and heap functions.
That sounds like a good approach.
Joe
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