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In-Reply-To: <3118179.1775092964@sss.pgh.pa.us>
From: Thomas Munro <thomas.munro@gmail.com>
Date: Thu, 2 Apr 2026 15:14:09 +1300
Message-ID: 
 <CA+hUKG+-pn14s_tjEBO6YKHmc=uRhGVn=w2oM91KKnEUc7pH0Q@mail.gmail.com>
Subject: Re: pg_waldump: support decoding of WAL inside tarfile
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Tomas Vondra <tomas@vondra.me>, Andres Freund <andres@anarazel.de>,
	Michael Paquier <michael@paquier.xyz>, Andrew Dunstan <andrew@dunslane.net>,
 Amul Sul <sulamul@gmail.com>,
	Zsolt Parragi <zsolt.parragi@percona.com>,
 Robert Haas <robertmhaas@gmail.com>,
	Chao Li <li.evan.chao@gmail.com>,
	Anthonin Bonnefoy <anthonin.bonnefoy@datadoghq.com>,
 Fujii Masao <masao.fujii@gmail.com>,
	Jakub Wartak <jakub.wartak@enterprisedb.com>,
	PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
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On Thu, Apr 2, 2026 at 2:22=E2=80=AFPM 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=3Dfoo.tar bs=3D1 seek=3D257 count=3D1 conv=3Dnotrunc
$ strings foo.tar | grep tar | head -1
xstar
$ pg_waldump --path=3Dfoo.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=3Dfoo.tar bs=3D1 seek=3D257 count=3D1 conv=3Dnotrunc
$ strings foo.tar | grep tar | head -1
ustar
$ pg_waldump --path=3Dfoo.tar -s 0/1 -e 0/100
... other output...