| From: | Andres Freund <andres(at)anarazel(dot)de> |
|---|---|
| To: | Stephen Frost <sfrost(at)snowman(dot)net> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, David Steele <david(at)pgmasters(dot)net>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Suraj Kharage <suraj(dot)kharage(at)enterprisedb(dot)com>, tushar <tushar(dot)ahuja(at)enterprisedb(dot)com>, Rajkumar Raghuwanshi <rajkumar(dot)raghuwanshi(at)enterprisedb(dot)com>, Rushabh Lathia <rushabh(dot)lathia(at)gmail(dot)com>, Tels <nospam-pg-abuse(at)bloodgate(dot)com>, Andrew Dunstan <andrew(dot)dunstan(at)2ndquadrant(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>, Jeevan Chalke <jeevan(dot)chalke(at)enterprisedb(dot)com>, vignesh C <vignesh21(at)gmail(dot)com> |
| Subject: | Re: backup manifests |
| Date: | 2020-03-27 22:00:40 |
| Message-ID: | 20200327220040.lpinejiyktwtiay7@alap3.anarazel.de |
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| Lists: | pgsql-hackers |
Hi,
On 2020-03-27 17:07:42 -0400, Stephen Frost wrote:
> I had suggested up-thread, and I'm still fine with, having
> pg_validatebackup scan the WAL and check the internal checksums. I'd
> prefer an option that uses hashes to check when the user has asked for
> hashes with SHA256 or something, but at least scanning the WAL and
> making sure it validates its internal checksum (and is actually all
> there, which is pretty darn critical) would be enough to say that we're
> pretty sure the backup is valid.
I'd say that actually parsing the WAL will give you a lot higher
confidence than verifying a sha256 for each file. There's plenty of ways
to screw up the pg_wal on the source server (I've seen several
restore_commands doing so, particularly when eagerly fetching). Sure,
it'll not help against an attacker, but I'm not sure I see the threat
model.
There's imo a cost argument against doing WAL verification by reading
it, but that'd mostly be a factor when comparing against a faster
whole-file checksum.
Greetings,
Andres Freund
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