Re: pg_walinspect - a new extension to get raw WAL data and WAL stats

On Tue, Feb 15, 2022 at 2:31 PM Bharath Rupireddy
<bharath(dot)rupireddyforpostgres(at)gmail(dot)com> wrote:
> > +/*
> > + * Verify the authenticity of the given raw WAL record.
> > + */
> > +Datum
> > +pg_verify_raw_wal_record(PG_FUNCTION_ARGS)
> > +{
> >
> >
> > Do we really need this function? I see that whenever the record is
> > read, we verify it. So could there be a scenario where any of these
> > functions would return an invalid WAL record?
>
> Yes, this function can be useful. Imagine a case where raw WAL records
> are fetched from one server using pg_get_wal_record_info and sent over
> the network to another server (for fixing some of the corrupted data
> pages or for whatever reasons), using pg_verify_raw_wal_record one can
> verify authenticity.

As I also said before, and so did Greg, I think giving the user a way
to supply WAL records that we will then try to decode is never going
to be OK. It's going to be a recipe for security bugs and crash bugs,
and there's no compelling use case for it that I can see. I support
this patch set only to the extent that it decodes locally generated
WAL read directly from the WAL stream.

--
Robert Haas
EDB: http://www.enterprisedb.com