Re: [Proposal] Table-level Transparent Data Encryption (TDE) and Key Management Service (KMS)

On Fri, Jul 12, 2019 at 7:37 AM Bruce Momjian <bruce(at)momjian(dot)us> wrote:
>
> On Wed, Jul 10, 2019 at 12:26:24PM -0400, Bruce Momjian wrote:
> > On Wed, Jul 10, 2019 at 08:31:17AM -0400, Joe Conway wrote:
> > > Please see my other reply (and
> > > https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-38a.pdf
> > > appendix C as pointed out by Ryan downthread).
> > >
> > > At least in my mind, I trust a published specification from the
> > > nation-state level over random blogs or wikipedia. If we can find some
> > > equivalent published standards that contradict NIST we should discuss
> > > it, but for my money I would prefer to stick with the NIST recommended
> > > method to produce the IVs.
> >
> > So, we have had a flurry of activity on this thread in the past day, so
> > let me summarize:
>
> Seems we have an updated approach:
>
> First, we need to store the symmetric encryption key in the data
> directory, like we do for SSL certificates and private keys. (Crash
> recovery needs access to this key, so we can't easily store it in a
> database table.) We will pattern it after the GUC
> ssl_passphrase_command. We will need to decide on a format for the
> symmetric encryption key in the file so we can check that the supplied
> passphrase properly unlocks the key.
>
> Our first implementation will encrypt the entire cluster. We can later
> consider encryption per table or tablespace. It is unclear if
> encrypting different parts of the system with different keys is useful
> or feasible. (This is separate from key rotation.)
>
> We will use CBC AES128 mode for tables/indexes, and CTR AES128 for WAL.
> 8k pages will use the LSN as a nonce, which will be encrypted to
> generate the initialization vector (IV). We will not encrypt the first
> 16 bytes of each pages so the LSN can be used in this way. The WAL will
> use the WAL file segment number as the nonce and the IV will be created
> in the same way.
>
> wal_log_hints will be enabled automatically in encryption mode, like we
> do for checksum mode, so we never encrypt different 8k pages with the
> same IV.

I guess that different two pages can have the same LSN when a heap
update modifies both a page for old tuple and another page for new
tuple.

heapam.c:3707
recptr = log_heap_update(relation, buffer,
newbuf, &oldtup, heaptup,
old_key_tuple,
all_visible_cleared,
all_visible_cleared_new);
if (newbuf != buffer)
{
PageSetLSN(BufferGetPage(newbuf), recptr);
}
PageSetLSN(BufferGetPage(buffer), recptr);

Wouldn't it a problem?

Regards,

--
Masahiko Sawada
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center