[ietf-dkim] Final update to 4871bis for working group review
ietf-dkim at kitterman.com
Thu Jul 7 09:43:43 PDT 2011
On Thursday, July 07, 2011 12:22:20 PM Murray S. Kucherawy wrote:
> > -----Original Message-----
> > From: ietf-dkim-bounces at mipassoc.org
> > [mailto:ietf-dkim-bounces at mipassoc.org] On Behalf Of Scott Kitterman
> > Sent: Thursday, July 07, 2011 6:32 AM
> > To: ietf-dkim at mipassoc.org
> > Subject: Re: [ietf-dkim] Final update to 4871bis for working group review
> > I'm working with someone on an implementation and I think we're going to
> > assume one more From than listed in h= when verifying to ensure nothing
> > has been added.
> This intentionally causes the verifier to assume what the signer really
> meant when it signed a message using a single From: field. That may look
> safe but it isn't what DKIM actually says.
> We might do this for libopendkim somewhere down the line, but it would
> default "off".
> In any case, interesting idea.
It only assumes that the signer signed all the From: fields present in the
message (note: I said one more than in h=, not two). I think it's fair to say
that if someone is sending messages with multiple From: fields (or
Date:/Subject:) and trying to sign something less than all of them they are
fairly deep into unsupported territory and shouldn't find any result
I agree it's not exactly what is specified in the protocol, but this is an
implementation design issue. I think it's safe. If the DKIM protocol says I
can't do something like this, then I think we have a problem with the current
"describe it and let implementors deal with it" plan.
More information about the ietf-dkim