Re: [DNSOP] DNSOP Call for Adoption draft-vixie-dns-rpz

Ted Lemon <mellon@fugue.com> Mon, 09 January 2017 14:19 UTC

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From: Ted Lemon <mellon@fugue.com>
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Date: Mon, 9 Jan 2017 09:19:37 -0500
In-Reply-To: <alpine.LRH.2.20.1701082342250.18316@bofh.nohats.ca>
To: Paul Wouters <paul@nohats.ca>
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Cc: dnsop <dnsop@ietf.org>, Barry Raveendran Greene <bgreene@senki.org>
Subject: Re: [DNSOP] DNSOP Call for Adoption draft-vixie-dns-rpz
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On Jan 8, 2017, at 11:49 PM, Paul Wouters <paul@nohats.ca> wrote:
> It is actually the other way around. If an end-node performs DNSSEC
> validation, it can only see RPZ modified answers as an attack. It is
> in the interest of RPZ to give such clients the confidence that the RPZ
> produced answer is not an attack but a handbreak action in the user's
> interest.

I think you missed what Barry was saying: you are correct that an end-node that performs DNSSEC validation will see RPZ on a domain that is signed as an attack.   The point Barry is making is that this only matters if they sign their zones, and they won't, because doing so produces a clear audit trail leading back to them.

I think this is actually not true: why is a DS record any more of an audit train than an NS record?   Nevertheless, let's be clear on what RPZ does and does not do.   I think the main reason attackers won't sign is that it's too much trouble, and provides no real benefit in the presence of an effective RPZ block.

Your point here, that in order for RPZ to function in the presence of widespread DNSSEC signing, there has to be some mechanism for authenticating RPZ answers _as_ RPZ answers, doesn't seem clearly true.   It may be perfectly functional for RPZ answers to look like an attack.   But it's certainly worth considering, and has been talked about earlier in this thread.   The question is, does it make sense to add code to the validating resolver to detect and validate an RPZ block, so the user can be informed that a block occurred, and who did it?   Would people actually code this up?   Would it be better or worse?

To me it seems like a bad idea: it's a larger attack surface, more complexity, a single point of attack: if I can compromise the RPZ keys, I can make an attack look like protection to the end user.   Ultimately, if we were to specify a solution for this, I think we doul actually be doing something harmful to human rights.   Isn't blocking the domain enough?