--On 28 April 2010 08:23:52 -0700 Dave CROCKER <dhc(_at_)dcrocker(_dot_)net>
wrote:
On 4/28/2010 8:02 AM, MH Michael Hammer (5304) wrote:
A few thoughts to fuel the discussion:
1) It may be that the BCP document would appropriately have a section
for end users of mail lists. One possible recommendation is that for
domains which have strong security concerns, they may want to have a
policy against posting to lists using the domain in question. (I'm
throwing this out as a straw man).
Are you suggesting a bit of draft text that recipient sites might include
in the email practices documentation they supply to the (human) users?
2) One possible recommendation to list managers is that if a message to
the list is DKIM signed AND has an ADSP discardable policy AND the
signature cannot be maintained intact then the list should bounce the
message.
What is the particular benefit of doing this, rather than letting the
receiving site do the bouncing? This is extra mechanism for the MLM,
and most MLMs won't be supporting it. I'm trying to get a clear sense
of the value proposition for this.
The receiving site would bounce to the list. The message ought to be
bounced to the original sender, who (with adsp=discard) probably doesn't
want messages redistributed, and should be informed of the problem.
Certainly *my* MTA/MLM setup (Exim/Mailman) can be configured to do this.
In fact, Exim could be configured to do this with any MLM behind it.
3) Is there a way for us (perhaps in a future version) to provide for
some sort of "encapsulation" that will allow the original
signature/message to be maintained even as the list does certain (as yet
unspecified) actions which might currently break the signature? Just
blue skying here.
I think you are raising the (much) larger question of constraining the
nature of changes made by MLMs. Since the are actually posting an
entirely new message, they have the legitimate freedom to do what they
want to it. However, some can choose to participate in that much more
constrained role, looking more like a relaying MTA than a modifying
intermediary.
4) I recognize the chorus which says "mail lists have always done things
a certain way and who are you to tell us how or what we have to do".
Having given that recognition, in creating an authentication model it
Strictly speaking, DKIM does not "authenticate" any part of the message,
othe than the d= parameter.
I realize that this is an irritating observation, but it is semantically
precise and accurate. Absent the presence of ADSP usage, assuming that
anything else is "authenticated" goes beyond the DKIM specification.
d/
--
Ian Eiloart
IT Services, University of Sussex
01273-873148 x3148
For new support requests, see http://www.sussex.ac.uk/its/help/
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