Horton

Re: storing an explicit nonce

Bruce Momjian <bruce@momjian.us>

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From: Bruce Momjian <bruce@momjian.us>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Stephen Frost <sfrost@snowman.net>, Andres Freund <andres@anarazel.de>, Alvaro Herrera <alvherre@alvh.no-ip.org>, Masahiko Sawada <sawada.mshk@gmail.com>, Tom Kincaid <tomjohnkincaid@gmail.com>, Amit Kapila <amit.kapila16@gmail.com>, Thomas Munro <thomas.munro@gmail.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>, Masahiko Sawada <masahiko.sawada@2ndquadrant.com>
Date: 2021-05-26T20:45:15Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Rethink method for assigning OIDs to the template0 and postgres DBs.

  2. pg_upgrade: Preserve database OIDs.

  3. pg_upgrade: Preserve relfilenodes and tablespace OIDs.

  4. Fix for new Boolean node

  5. Improve error handling of HMAC computations

  6. Add macro RelationIsPermanent() to report relation permanence

  7. Enhance nbtree index tuple deletion.

On Wed, May 26, 2021 at 04:40:48PM -0400, Bruce Momjian wrote:
> On Wed, May 26, 2021 at 01:56:38PM -0400, Robert Haas wrote:
> > However, I believe that if we store the nonce in the page explicitly,
> > as proposed here, rather trying to derive it from the LSN, then we
> > don't need to worry about this kind of masking, which I think is
> > better from both a security perspective and a performance perspective.
> 
> You are saying that by using a non-LSN nonce, you can write out the page
> with a new nonce, but the same LSN, and also discard the page during
> crash recovery and use the WAL copy?
> 
> I am confused why checksums, which are widely used, acceptably require
> wal_log_hints, but there is concern that file encryption, which is
> heavier, cannot acceptably require wal_log_hints.  I must be missing
> something.
> 
> Why can't checksums also throw away hint bit changes like you want to do
> for file encryption and not require wal_log_hints?

One detail might be this extra hint bit FPW case:

	https://github.com/postgres/postgres/compare/bmomjian:cfe-01-doc..bmomjian:_cfe-02-internaldoc.patch
	
	However, if a hint-bit-modified page is written to the file system
	during a checkpoint, and there is a later hint bit change switching
	the same page from clean to dirty during the same checkpoint, we
	need a new LSN, and wal_log_hints doesn't give us a new LSN here.
	The fix for this is to update the page LSN by writing a dummy
	WAL record via xloginsert.c::LSNForEncryption() in such cases.

Is this how file encryption is different from checksum wal_log_hints,
and the big concern?

-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EDB                                      https://enterprisedb.com

  If only the physical world exists, free will is an illusion.