Re: [ietf-dkim] Concerns about DKIM and mailiing lists, etc.

Michael Thomas wrote:
> John Levine wrote:
> > > How does a receiver know the difference between a "mailer" and a
> > > "random third party"?
> >
> > It doesn't, and it doesn't care.  It looks up the signing domain in
> > its handy local list of signers worth paying attention to.  Maybe at
> > some future time there will also be external sources of worthy
> > signers, but that's way outside the scope of any discussion here.
> Which handy local list of signers is that? Where do I find Cisco's?
Michael,

The signature that you are so worried about preserving is only useful if there 
is some database to consult, about it.
That's the list John is referring to.

So whatever you are planning to consult, after validating the originator's 
signature, is what should be consulted after validating the list's signature.
In other words, a valid signature is a valid signature.  An invalid signature is 
an invalid signature.
And, as I've raised many times, I do not understand the compulsion to preserve a 
signature for a message that is re-posted by an automaton user agent, when there 
is no equivalent expectation of preservation, for a message that is manually 
re-posted -- such as when I forward a message on to someone else.  The 
architectural role is the same.  The semantics are the same.
Mailing lists can do, and do do, whatever violence to a message they wish and 
their subscribers find useful, because the mailing list agent is really posting 
a new message, no matter how close it might seem to the original.  A small 
amount of hacking to make the close ones preserve the signature is one thing.  A 
large amount is quite another. So is attempting to declare the ones making 
larger changes "wayward".
It is not reasonable to try to declare that the ones doing small changes are 
somehow acceptable but that the ones doing larger are not, since a) there is no 
specification or established practice to justify that declaration, and has been 
pointed out rather directly, b) such a declaration will have no beneficial effect.
So, as vigorously as you are arguing your position, I am not seeing how it 
produces anything that will work in the real Internet.
d/

--

Dave Crocker
Brandenburg InternetWorking
<http://bbiw.net>
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