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

Douglas Foster <dougfoster.emailstandards@gmail.com> Mon, 25 January 2021 17:10 UTC

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From: Douglas Foster <dougfoster.emailstandards@gmail.com>
Date: Mon, 25 Jan 2021 12:10:30 -0500
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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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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> 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> 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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