PoC: PG-1442 Encrypt catalog tables using the default key

[jeltz]

Quick and dirty PoC which implements encryption of the system catalog if there is a default key configured. To test it do the following.

CREATE DATABASE foo;

CREATE EXTENSION IF NOT EXISTS pg_tde;
SELECT pg_tde_add_key_provider_file('PG_TDE_GLOBAL', 'file-provider','/tmp/default.per');
SELECT pg_tde_set_default_principal_key('default-principal-key', 'PG_TDE_GLOBAL', 'file-provider', false);

CREATE DATABASE bar;

CHECKPOINT;

In foo:

CREATE TABLE zzz_foo AS SELECT generate_series(1, 10000); CHECKPOINT;

In bar:

CREATE TABLE zzz_bar AS SELECT generate_series(1, 10000); CHECKPOINT;

Check:

$ strings data/base/16384/1259 | grep ^pg_ | wc -l
484
$ strings data/base/16384/1259 | grep zzz
zzz_foo
$ strings data/base/16452/1259 | grep ^pg_ | wc -l
0
$ strings data/base/16452/1259 | grep zzz