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

Michael Thomas <> Mon, 25 January 2021 16:51 UTC

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From: Michael Thomas <>
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Date: Mon, 25 Jan 2021 08:51:39 -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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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?