Re: [DNSOP] RFC 2136 pre-requisite checks before client authorization checks

Mukund Sivaraman <muks@mukund.org> Fri, 07 December 2018 14:56 UTC

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Date: Fri, 7 Dec 2018 20:26:11 +0530
From: Mukund Sivaraman <muks@mukund.org>
To: Chris Thompson <cet1@cam.ac.uk>
Cc: dnsop@ietf.org
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Subject: Re: [DNSOP] RFC 2136 pre-requisite checks before client authorization checks
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On Fri, Dec 07, 2018 at 02:37:31PM +0000, Chris Thompson wrote:
> On Dec 6 2018, Mukund Sivaraman wrote:
> 
> > On Thu, Dec 06, 2018 at 04:29:13PM +0100, p vixie wrote:
> > > It's an error in the specification.
> > 
> > Thank you Paul. That clears it. I asked because BIND follows the RFC to
> > the letter, and an admin may see some log messages that are unexpected
> > for an address that's not in the update ACL.
> 
> This is actually a (long-standing, if rather mild) security exposure.
> By distinguishing the error codes returned for suitably crafted update
> operations, a client not authorised to even query a zone can determine
> the existence or otherwise of names, RRsets, and even specific RRs with
> guessed rdata, within it.

IIRC BIND checks if a client can query the zone before it proceeds with
the update algorithm. Don't know about other implementations.

		Mukund