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[Ietf-dkim] Re: Malicious Modification was: My concerns

"Murray S. Kucherawy" <superuser@gmail.com> Fri, 18 April 2025 21:30 UTC

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From: "Murray S. Kucherawy" <superuser@gmail.com>
Date: Fri, 18 Apr 2025 14:30:39 -0700
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To: Alessandro Vesely <vesely@tana.it>
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Subject: [Ietf-dkim] Re: Malicious Modification was: My concerns
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On Fri, Apr 18, 2025 at 11:10 AM Alessandro Vesely <vesely@tana.it> wrote:

> > Indeed so, but reputation systems (because once again to state the
> > obvious, protocols cannot prevent bad email, but they can provide tools
> > for handling it efficiently) may take the view that a brand-new identity
> > that has acted as an intermediary to alter some email is not especially
> > trustworthy...
>
> This position leads to ARC-style authentication, where one must trust that
> the
> changes are benign.
>
> DKIM2 has change tracking.  Can't we tell whether a change is evil or not?
>

I'd put that question back to you: Short of pervasive deployment of RFC
3514, how does one classify, programmatically, whether a message mutation
is evil?  I can find a way to abuse each of the examples you provided.

We need to be careful here to acknowledge that identifying what mutations
might be acceptable isn't a matter of identifying "evil" so much as it is
risk mitigation.

Beyond that, here be dragons.

-MSK

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