Re: Patch proposal: make use of regular expressions for the username in pg_hba.conf

On Tue, Sep 20, 2022 at 12:09:33AM -0400, Tom Lane wrote:
> You have to assume that somebody (a) has a role or DB name starting
> with slash, (b) has an explicit reference to that name in their
> pg_hba.conf, (c) doesn't read the release notes, and (d) doesn't
> notice that things are misbehaving until after some hacker manages
> to break into their installation on the strength of the misbehaving
> entry.  OK, I'll grant that the probability of (c) is depressingly
> close to unity; but each of the other steps seems quite low probability.
> All four of them happening in one installation is something I doubt
> will happen.

It is the kind of things that could blow up as a CVE and some bad PR
for the project, so I cannot get excited about enforcing this new rule
in an authentication file (aka before a role is authenticated) while
we are talking about 3~4 code paths (?) that would need an extra check
to make sure that no instances have such object names.

> On the contrary side, if we make this work differently from the
> pg_ident.conf precedent, or install weird rules to try to prevent
> accidental misinterpretations, that could also lead to security
> problems because things don't work as someone would expect.  I see
> no a-priori reason to believe that this risk is negligible compared
> to the other one.

I also do like a lot the idea of making things consistent across all
the auth configuration files for all the fields where this can be
applied.
--
Michael