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

On Wed, Feb 16, 2022 at 1:57 AM Robert Haas <robertmhaas@gmail.com> wrote:
>
> On Tue, Feb 15, 2022 at 2:31 PM Bharath Rupireddy
> <bharath.rupireddyforpostgres@gmail.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.

Agreed, I will remove pg_verify_raw_wal_record function in the next
version of the patch set. Thanks.

Regards,
Bharath Rupireddy.