Date: Mon, 26 Dec 2016 15:36:47 -0300
From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Michael Paquier <michael.paquier@gmail.com>,
	Joe Conway <mail@joeconway.com>,
	PostgreSQL mailing lists <pgsql-hackers@postgresql.org>
Subject: Re: Incautious handling of overlength identifiers
Message-ID: <20161226183647.hjlzi2vqyqvyevsa@alvherre.pgsql>
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Tom Lane wrote:
> I wrote:
> > Another idea worth considering is to just make the low-level functions
> > do truncation ...
> 
> After further thought, there's a bigger-picture issue here, which
> is whether the inputs to the SQL functions in question are intended to
> be raw user input --- in which case, not only would truncation be
> an appropriate service, but probably so would downcasing --- or whether
> they are more likely to be coming from a catalog scan, in which case
> you don't want any of that stuff.  Nobody's going to be happy if we
> start making them add quote_ident() around references to name columns.
> I think the privilege-inquiry functions are almost certainly mostly
> used in the latter style; there might be more room for debate about,
> say, pg_get_serial_sequence.

I expect that uses of pg_get_object_address() (one of the affected
interfaces) would mostly be through an event trigger or a similar
internal mechanism, that hopefully should appropriately quote names and
not produce anything overlength.  At least, pg_identify_object() (which
is what I mostly had in mind) complies.  I think removing the assert is
a good enough solution, myself.

I also admit it didn't occur to me to test the function(s) against
overlength input when developing it.  I wouldn't object to adding code
to deal with overlength identifies, but I'm not really sure I would
choose truncation over reporting an error.  But whatever it'd be, it'd
be at that level, not at the lower (hash function) level.

-- 
Álvaro Herrera                https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services


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