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Re: [ietf-dkim] DKIM/ADSP edge case writeup at CircleID

2009-03-26 07:51:22
Charles Lindsey wrote:
On Wed, 25 Mar 2009 11:28:52 -0000, Hector Santos 
<hsantos(_at_)santronics(_dot_)com> wrote:


- eBay and PayPal: signs non-existent Resent-From, preventing resending

Another case of BLIND signing!  Read the freaking specs!!

Not necessarily. Signing a non-existent header is a valid way of 
preventing it being added subsequently, and maybe that is what you want 
(e.g. in this case if the mail is "for original recipient's eyes only"). 
Not that Ebay and Paypal were necessarily trying to do that, although 
they are the sort of organisations that just might want to do it in 
specific situations.

Good point Charles.

I guess I can see benefits of signing an non-existing header with the
intent to preempt some downlink injection.  But only from the
standpoint of the intent to force a failure handling process. i.e, 
eBay, Paypal and entities of the like do not expect these failures to 
be ignored.  Possible example is Reply-To.  They might not want a 
Reply-To and will rely on From: for any user feedback.  So they sign 
an non-existing Reply-to, this preventing any replays with an injected 
Reply-to for MUAs to use.

I can see that.


-- 
Sincerely

Hector Santos
http://www.santronics.com



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