[ietf-dkim] Output summary

[Murray S. Kucherawy]

> -----Original Message-----
> From: John R. Levine [mailto:johnl at iecc.com]
> Sent: Thursday, April 28, 2011 10:52 AM
> To: Murray S. Kucherawy
> Cc: ietf-dkim at mipassoc.org
> Subject: Re: [ietf-dkim] Output summary
> 
> >> I wouldn't be opposed to doing so, except that 4871 says in two separate
> >> places not to do that.  Section 7 is, now that I look at it, really badly
> >> written, since it implies that a "verifier" is an SMTP server.
> >
> > I can take a run at fixing Section 7.  What's the other place that says
> > not to do that?
> 
> Last paragraph of sec 5.2: " Verifiers SHOULD ignore failed signatures as
> though they were not present in the message."

Is that inconsistent with the idea of only reporting signatures that verified or those that TEMPFAILed?  In that model, failed ones aren't reported which is logically equivalent to them being ignored.  Seems like a fit to me.

> > My preference would be to return a list of signatures that either passed
> > or TEMPFAILed, which could be the empty set if all of them PERMFAILed or
> > the message was unsigned, or none of them were acceptable in the first
> > place for whatever policy reasons.  The caller can decide whether it
> > wants to try the whole shebang again later, or continue with what it
> > got.  It's simple and complete.
> 
> That seems reasonable, but I wonder if that's a large enough change to
> provoke a recycle.  I suppose we can argue that the prior language was
> inconsistent.  What does opendkim do?  My verifier, which sometimes runs
> in the SMTP session and sometimes runs other places, treats tempfail
> and permfail the same.

The return code provided by the final evaluation function does make the distinction, although the caller could treat the two the same just as you do.  It also provides a mechanism for the caller to look through the signatures and get a result for each so that if the caller doesn't want to use that distilled result, it's free to do something more complicated.