Re: [dmarc-ietf] Tickets 98 and 99 -- fake reports are not a problem and if they were authentication would not help

Michael Thomas <mike@mtcc.com> Mon, 25 January 2021 17:32 UTC

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To: Seth Blank <seth@valimail.com>
Cc: IETF DMARC WG <dmarc@ietf.org>, Douglas Foster <dougfoster.emailstandards@gmail.com>
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From: Michael Thomas <mike@mtcc.com>
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Date: Mon, 25 Jan 2021 09:32:01 -0800
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Subject: Re: [dmarc-ietf] Tickets 98 and 99 -- fake reports are not a problem and if they were authentication would not help
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Why is this controversial? Seriously. What is controversial about saying 
that the a report should authenticate? The onus is on the people who say 
it does not to lay out the case for why it's not a problem, not me. #98 
has a simple piece of text to remedy this. it's 2021. You don't use 
unauthenticated data if you can possibly help it.

Mike

On 1/25/21 9:25 AM, Seth Blank wrote:
> Mike, how do you believe DMARC reports are consumed and utilized? I 
> think you have a misunderstanding here which is why you're going down 
> this path and everyone else is pushing back.
>
> On Mon, Jan 25, 2021 at 9:22 AM Michael Thomas <mike@mtcc.com 
> <mailto:mike@mtcc.com>> wrote:
>
>     Taking in information from unauthenticated sources and acting on
>     it is an operational problem per se. Have we learned nothing in
>     the last 30 years?
>
>     Mike
>
>     On 1/25/21 9:19 AM, Seth Blank wrote:
>>     What operational problem are we solving here? Absent evidence of
>>     a problem and strong consensus on the solution, let's close these
>>     tickets and move on.
>>
>>     On Mon, Jan 25, 2021 at 9:10 AM Douglas Foster
>>     <dougfoster.emailstandards@gmail.com
>>     <mailto:dougfoster.emailstandards@gmail.com>> wrote:
>>
>>         Since the status quo is unauthenticated, I wonder if adding a
>>         signing requirement will help.
>>         Will recipients discad unsigned messages, or accept whatever
>>         is available to maximize their information capture?  I
>>         suspect they will conrinye to accept everything.
>>
>>         I think we would need an identified threat before recipients
>>         would be motivated to discard.
>>
>>         But what about John's problems with receiving reports that
>>         should not have gone to him?   I did not understand the root
>>         cause, but I would hope there is something that can be done.
>>         Would signing help receiving sites, those with less
>>         sophistication than he has, be able to sort out noise more
>>         effectively?
>>
>>
>>         On Mon, Jan 25, 2021, 11:51 AM Michael Thomas <mike@mtcc.com
>>         <mailto:mike@mtcc.com>> wrote:
>>
>>
>>             On 1/25/21 8:44 AM, Todd Herr wrote:
>>>             On Mon, Jan 25, 2021 at 10:18 AM Michael Thomas
>>>             <mike@mtcc.com <mailto:mike@mtcc.com>> wrote:
>>>
>>>
>>>                 The main thing I've learned over the years of
>>>                 dealing with security is to not underestimate what a
>>>                 motivated attacker can do. Your imagination is not
>>>                 the same as their imagination. Closing #98 in
>>>                 particular is absolutely ridiculous: the report
>>>                 should already have a DKIM signature or SPF so it's
>>>                 just a matter of making sure its valid. Why would
>>>                 you *not* want to insure that? The amount of
>>>                 justification for *not* having the receiver
>>>                 authenticate it is a mountain. The amount of effort
>>>                 to authenticate it is trivial for mail. Levine's
>>>                 dismissal of security concerns because he has
>>>                 anecdotal "evidence" from a backwater domain carries
>>>                 no weight at all.
>>>
>>>
>>>             That's all well and good, but you haven't answered the
>>>             question I asked.
>>>
>>>             What threats do you have in mind? Put another way, how
>>>             do you envision an attacker exploiting the lack of
>>>             authentication in a DMARC report to his or her gain?
>>>
>>             No, sorry, the onus is on the people who don't think it
>>             can be gamed. A bald assertion that it can't be gamed is
>>             very unconvincing. You need to lay out a miles long case
>>             for why it cannot be gamed. And to what end? #98 has a
>>             simple piece of text that should be added to DMARC to
>>             eliminate the possibility of forgery. You'd need a 10
>>             page threat I-D to explain why it's not necessary. What
>>             is the point of that? For email, it's trivial to prevent
>>             forgeries. Why would anybody argue against that?
>>
>>             Mike
>>
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>>
>>
>>     -- 
>>     *Seth Blank*| VP, Standards and New Technologies
>>     *e:*seth@valimail.com <mailto:seth@valimail.com>
>>     *p:*415.273.8818
>>
>>
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>
>
> -- 
> *Seth Blank*| VP, Standards and New Technologies
> *e:*seth@valimail.com <mailto:seth@valimail.com>
> *p:*415.273.8818
>
>
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