Re: Bypassing Directory Ownership Check in PostgreSQL 16.6 with Secure z/OS NFS (AT-TLS)

Thanks Laurenz.

On Mon, Jul 14, 2025 at 8:11 PM Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at>
wrote:

> On Mon, 2025-07-14 at 18:32 +0530, Amol Inamdar wrote:
> > > The data directory can either be created by "initdb", in which case
> > > the mount point must allow the PostgreSQL user to create a directory.
> > > You could set the group of the mount point to the group of the
> > > PostgreSQL user and use permissions 1770, which should be perfectly
> safe.
> >
> > This exactly is the problem we are facing, to give you a summary,
> > our NFS server is enabled with AT-TLS authentication
> > and we are accessing the server via a proxy server (Haproxy).
> > This acts as our NFS client and it is configured with the
> > required client certificates.
> >
> > The outcome of above configuration is that any directory created
> > in the NFS mount is always owned by the user in the certificates
> > and if that user isn't present in the proxy container it is marked
> > as nobody:nogroup, we tried various things like
> > created the user similar to postgres user so that the users ids match
> but
> > always ended up giving error “data directory “/var/lib” has wrong
> ownership
> >
> > Hence, we thought of skipping this check (Directory owner and postgres
> user validation) and
> > wanted to understand the implication of the same.
>
> No; don't.
>
> Simply mount the directory once, create a subdirectory with the
> appropriate ownership and permissions, and there you go.
> Problem solved.
>
> Yours,
> Laurenz Albe
>

--
-regards
Amol