Re: public key BATV isn't useful

Paul Smith wrote:
> Tony Hansen wrote:
> > Paul, The original idea behind BATV was so that 1) the original 
> > sending MTA can protect itself such that 2) non-delivery reports for 
> > messages originally sent from there can be differentiated from 3) 
> > non-delivery reports that are being sent in response to messages *not* 
> > originating from that sending MTA. That is, NDRs from your users (#2) 
> > will come back using your BATV tagging, whereas NDRs from spammers 
> > (#3) will come back without using your BATV tagging, and your system 
> > (#1) can happily ignore the #3 NDRs.
> Ah. I think I seem my problem... I looked at the BATV spec as a newcomer 
> to BATV rather than someone who had known about it for ages...
> The BATV introduction is misleading. It doesn't mention anything about 
> the reasoning behind BATV that you state, 

#2 and #3, above, are two types of bounce messages that are invalid, because 
they result from unauthorized creation of the bounce address (MailFrom).  The 
Introduction says:
     "existing Internet mail permits unauthorized use of addresses in the 
MailFrom command, which results in having notices sent to unwitting and 
unwilling recipients."
which seems to state exactly that condition, and:

     "Bounce Address Tag Validation (BATV) defines a framework for mechanisms 
that validate the value in this command."
says that BATV seeks to remedy that problem.

How should the Introduction be different?


and the introduction says
> things like "This assessment could aid in deciding whether to *send* a 
> bounce message, thereby reducing the Internet mail infrastructure cost 
> for transmitting notification messages in response to addresses used 
> without permission." (emphasis mine) - thus implying that the thing 
> sending the bounce message (ie NOT your own server - that should already 
> know that the address was used legitimately) is the thing checking the 
> BATV tags. To do that, you MUST have public key BATV tagging, private 
> key tagging doesn't make sense.
Right.  And since the sentence before the one you cite says:

     "Enhancements would permit processing agents that are along the original 
message's transfer path to determine whether the MailFrom adress is likely to 
be valid.",
it is meant to be clear that this portion of the discussion is referring to 
something beyond the current specification.  So I'm not sure I understand your 
concern.
This reaction to the reference to a public-key version of BATV once again 
demonstrates the dangers of having a specification discuss anything about a 
hypothetical future.  Best we remove all such references.  If and when there 
is an effort to specify and deploy and enhancement such as a public key 
version, we can document it separately.

> So, I think the introduction needs to have something in it about the 
> rationale, reasoning and purpose behind BATV, as I obviously 
> misunderstood it, and even though I've now had my mistake explained to 
> me, I still can't see anything in the spec which explains it...
I do not understand what it should say that it does not already say.  Please 
offer suggested text.
d/

--

  Dave Crocker
  Brandenburg InternetWorking
  bbiw.net