Re: [TLS] Proposed text for dnsssec chain extension draft

[Nico Williams <[e-mail]>]

On Wed, Apr 25, 2018 at 11:51:58AM +0200, Melinda Shore wrote:
> On 4/25/18 7:33 AM, Viktor Dukhovni wrote:
> > Perhaps a concrete proposal will make it
> > easier to reach a mutually-agreeable consensus position, and make it
> > clear that the requested 16-bits are a reasonable consensus outcome.
> 
> Hi, Viktor:
> 
> This doesn't actually reflect the consensus called by the
> chairs, as I understand what was posted.  It may be useful
> to start work on a new draft describing your proposal.

The chair said there is consensus for (A) with no pinning.  Viktor's
proposal is (A) with no pinning.  It's not at all clear to me that the
two reserved bytes are outside the consensus, and anyways, their cost is
minimal.

However, if you object to turning the extension contents into a struct,
then I would propose a slight tweak to Viktor's proposal:

   Two-byte elements of the AuthenticationChain are reserved for future
   use.  Pending future specifications, clients MUST discard any two-
   byte elements of the AuthenticationChain, and servers MUST NOT send
   any such elements.

We might as well say that all too-small-to-be-DNS-payloads elements of
the AuthenticationChain are reserved and discarded:

   Any elements of the AuthenticationChain that are too small to contain
   DNS RRset payloads are reserved for future use.  Pending future
   specifications, clients MUST discard any such AuthenticationChain
   elements, and servers MUST NOT send any such elements.

The nice thing about this is that it makes it easier to extend this
extension later, while also adding minimal complexity now ("clients MUST
discard such elements").

Nico
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