Re: one can re-sign without a permission to re-sign header

On Wed 23/Apr/2014 00:13:15 +0200 Ned Freed wrote:
> [...]
>>> I know people think I'm wrong, but I think it needs to be looked at a
>>> different way. As a recipient, I don't want 'proof' that this message
>>> came from Alessandro, I want 'proof' that it came from the
>>> [email protected] mailing list.
> 
>> I think you're right.
> 
> I concur as well.

Eh?  I agree a /receiver/ can do a better job by considering mailing
list messages as an already filtered/moderated mail stream, rather
than a collection of independent messages.  Talking domain-level
authentication, even the local part is irrelevant.  As a /recipient/,
however, the list where a message came from, ietf-822, ietf-smtp, or
whatever, is a rather circumstantial attribute of a message.  I
obviously care much more about who says what in which thread...

>> I've said for years that lists should sign their mail with their
>> own DKIM keys, and recipients should look at those list
>> signatures to filter the mail.
> 
> I'm not even sure that's necessary, but of course it can't hurt.
> Indeed, right now, with the exception of IETF lists, having a
> signature makes the odds it's spam more, not less, likely.

SPF authentication covers most subscribers, but not those who have
their mail forwarded to different sites (unless the forwarders use
SRS).  DKIM signatures survive forwarding.  Neither method is useful
for DMARC because the domain being authenticated is that of the
mailing list, which is aligned with "To:" rather than "From:".

Is it possible to introduce "To:" as a _secondary identifier_ in the
DMARC mechanism?  In that case a weak DKIM signature could be the
element which authorizes receivers to use the secondary identifier.

>> None of the theories about why you would care about preserving 
>> incoming signatures have ever impressed me as having any
>> relationship at all to the ways people actually use mailing
>> lists.  It's either a vague "more secure", or a passive
>> aggressive list manager who is skilled enough to jump through
>> hoops to preserve the signatures but too much of a doofus to keep
>> junk out of the list.
> 
> Nicely put and I agree.

Again, the people who actually use mailing lists are recipients; that
is subscribers, moderators, and ML admins.  MLMs and MTAs admins may
not be the same people.  Since users subscribe to MLs unbeknownst to
their servers, I see no natural whitelist-building method that could
be formalized.  However, John said mailing lists can be declared on
DNS using a name convention like the one in the DANE S/MIME draft,
with hashed mailboxes, e.g.:

   <hash of ietf-822>._mayday.ietf.org TXT "v=MR1; d=ietf.org"

That way a server can derive that a mailing list is valid because its
users post to that address.  This method is bad for lurkers, since a
mailing list gets whitelisted only after one or more posts.

Another method to let servers know about subscriptions was named
"water tight opt-in" by David Hofstee:
http://fixforwarding.org/wiki/Water_tight_opt-in

Is it time to standardize mailing lists already?
Ale

_______________________________________________
ietf-822 mailing list
[email protected]
https://www.ietf.org/mailman/listinfo/ietf-822