Re: Row Level Security − leakproof-ness and performance implications

On 2/28/19 9:12 AM, Robert Haas wrote:
> On Wed, Feb 27, 2019 at 6:03 PM Joe Conway <mail(at)joeconway(dot)com> wrote:
>> Patch for discussion attached.
>
> So... you're just going to replace ALL error messages of any kind with
> "ERROR: missing error text" when this option is enabled? That sounds
> unusable. I mean if I'm reading it right this would get not only
> messages from SQL-callable functions but also things like "deadlock
> detected" and "could not read block %u in file %s" and "database is
> not accepting commands to avoid wraparound data loss in database with
> OID %u". You can't even shut it off conveniently, because the way
> you've designed it it has to be PGC_POSTMASTER to avoid TOCTTOU
> vulnerabilities. Maybe I'm misreading the patch?

You have it correct.

I completely disagree that is is unusable though. The way I envision
this is that you enable force_leakproof on your development machine
without suppress_client_messages being turned on. Do your debugging there.

On production, both are turned on. You still get full unredacted
messages in your pg log. The client on a prod system does not need these
details. If you *really* need to, you can restart to turn it on for a
short while on prod, but hopefully you have a non prod system where you
reproduce issues for debugging anyway.

I am not married to making this only changeable via restart though --
that's why I posted the patch for discussion. Perhaps a superuserset
would be better so debugging could be done on one session only on the
prod machine.

> I don't think it would be crazy to have a mode where we try to redact
> the particular error messages that might leak information, but I think
> we'd need to make it only those. A wild idea might be to let
> proleakproof take on three values: yes, no, and maybe. When 'maybe'
> functions are involved, we tell them whether or not the current query
> involves any security barriers, and if so they self-censor.

Again, I disagree. See above -- you have all you need in the server logs.

Joe
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