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

Seth Blank <> Mon, 25 January 2021 17:19 UTC

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From: Seth Blank <>
Date: Mon, 25 Jan 2021 09:19:09 -0800
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Cc: Douglas Foster <>, Michael Thomas <>
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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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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 <> 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 <> wrote:
>> On 1/25/21 8:44 AM, Todd Herr wrote:
>> On Mon, Jan 25, 2021 at 10:18 AM Michael Thomas <> 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
>> _______________________________________________
>> dmarc mailing list
> _______________________________________________
> dmarc mailing list


*Seth Blank* | VP, Standards and New Technologies
*p:* 415.273.8818

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