Re: pg_waldump: support decoding of WAL inside tarfile - Mailing list pgsql-hackers

On Thu, Apr 2, 2026 at 2:22 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Looking again at astreamer_tar.c, I suddenly realized that it doesn't
> do any meaningful input validation.  So if you feed it junk input,
> you get garbage errors that aren't even predictable:

Wow.

> So I think we need something like the attached, in addition
> to what I sent before.  This just makes astreamer_tar.c use
> the isValidTarHeader function that pg_dump already had.
> (I decided to const-ify isValidTarHeader's argument while
> moving it to a shared location, which in turn requires
> const-ifying tarChecksum.)

LGTM.

$ echo -n x | dd of=foo.tar bs=1 seek=257 count=1 conv=notrunc
$ strings foo.tar | grep tar | head -1
xstar
$ pg_waldump --path=foo.tar -s 0/1 -e 0/100
pg_waldump: error: input file does not appear to be a valid tar archive

$ echo -n u | dd of=foo.tar bs=1 seek=257 count=1 conv=notrunc
$ strings foo.tar | grep tar | head -1
ustar
$ pg_waldump --path=foo.tar -s 0/1 -e 0/100
... other output...