Subject: Re: I-D ACTION:draft-ietf-dnsext-ad-is-secure-03.txt

From: "Stephan Jager" <[email-masked]>
Date: Sat, 21 Jul 2001 00:14:22 -0700

On Fri, 20 Jul 2001, Brian Wellington wrote:

> On Fri, 20 Jul 2001, Roy Arends wrote:
> 
> > Ah, so without cryptographicly authenticating the data which is read
> > from disk, the primary could set the AD bit on responses since it may
> > consider locally configured data to be in authenticated state.
> >
> > I totally object to this.
> >

So do I.

> This discussion has already been had several times.  If you don't trust
> the on-disk zone data, why would you trust anything else about the server?

Suppose the server is hacked. The malisious operater can change the
zonefile on disk (can change a SIG, change the RR, remove the SIG), but in
all cases, the zone is then BAD, since he cannot make a new correct SIG.
(He doesn't have access to the private key) If the zone is loaded again
from disk, it is "secure", and when a secondary gets the zone with the AD
bit, the zone will still be bad.

Is that want we want to happen?

-- Stephan

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---

From: Roy Arends <[email-masked]>
Date: Sat, 21 Jul 2001 09:07:52 -0700

> Is that want we want to happen?

Well, I objected to this at first because I thought the AD bit
interpretation changed from Authenticated to something less.

This is not the case.

Suppose the server is hacked, malicious operator and changed zonefiles and
all that. If everything could be compromised, the server-software could be
compromised too. So extra sig-validation does not help you there.

The _only_ situation when a client depends on the AD bit from an
Authoritative (!) server is when this client talk directly, with
TSIG/SIG(0) to this authoritative server.

In that situation, the server must be preconfigured with the shared-TSIG
or the public-SIG(0) of the client and vice versa. That means the client
conforms to the local policy of the server. If the server trusts the
contents on disk, so should the client.

In a perfect world, clients do not talk immediatly to authoritative
servers. They talk to some local cache.

Roy Arends
Nominum