I think it's fair to say that doing an end run around the "Mail Gods" with
yet another attempt to canonicalize local parts will not make them any
less annoyed. Hand waving claims that it's doing something else doesn't
make it so.
I hope it's obvious why one approach to doing it in DANE and a different
incompatble approach in PKIX would be a bad idea.
On Mon, 7 Mar 2016, Sean Leonard wrote:
On 3/7/2016 4:54 AM, John Levine wrote:
In article <56DD1DB7(_dot_)7050305(_at_)seantek(_dot_)com> you write:
As the chairs graciously requested and got a meeting slot in Buenos
Aires, I would like to request DANE ALPS (Alternative Local-Part
Synthesis) discussion time at IETF 95.
This draft belongs in ietf-smtp or maybe appsarea, not DANE. It's an
interesting idea, but since it changes the rules about who interprets
local-parts, it's an update to RFC 5321.
Also, it's an issue that affects people in a lot of places other than DANE.
Pkix has been having somewhat similar discussions about the names in X.509
As the document itself states (repeatedly), the DANE ALPS proposal is very
specific to DANE. It does not affect how the mail infrastructure interprets
local-parts, because to do otherwise would anger the Mail Gods. We are
leaving the issue alone. Local-Part is and remains left to the interpretation
of the receiving MTA.
The point of DANE ALPS is to reduce the burden of maintaining a bajillion
variations of records, for operating a DANE/DNSSEC-enabled zone. Consider a
case where the owners want *all* messages sent to e-mail addresses in a
domain to use the same key. Perhaps that key is a master encryption key for
policy reasons, that will be decrypted by some gateway. Another case is where
one user maintains the whole domain: *@ietf.taugh.com e-mail addresses should
all be encrypted to the same key and read (ultimately) by the same user, even
if the messages get fanned out into different mailboxes on the back end. In
such cases, is it desirable for the DANE/DNSSEC-enabled zone to maintain a
bajillion different records with the same key info, or just to maintain one
record, and have a mechanism to point queries to that specific record? The
latter is simply more efficient (and more easily auditable).
Now, a possible outcome of the WG presentation/meeting is that the proposal
has broader application than just DANE. In that case, expanding or moving it
elsewhere would be fine. But we need to have that discussion.
Yes, it came up in PKIX recently...there is a broader question about how to
determine e-mail address equivalence, when the two inputs are not bit-for-bit
identical. This is an industry-wide problem. However, the DANE ALPS solution
is about alternate queries of the DNS zone between a DNS client and a DNS
server, not equivalence. It is specific to the way that DANE operates and is
not intended to be a published general statement about how the domain's MTA
fans out mail.
draft-osterweil-dmarc-dane-names also tries to address the matter using DMARC
records. However, it goes a step further by saying "canonicalization
policy"--which implies that it is promulgating interpretations of the
local-part that might cause a disturbance in the (Mail Gods') Force. See:
That approach should also be covered and discussed.
So now we have at least four different approaches: a) do nothing, b)
draft-seantek-dane-alps, c) draft-levine-dns-mailbox (a collection of
different approaches), d) draft-osterweil-dmarc-dane-names. Obviously the WG
is struggling to do something here, hence, discussion.
John Levine, johnl(_at_)taugh(_dot_)com, Taughannock Networks, Trumansburg NY
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