DKIM and email address proof-of-control

[Lachlan Gunn]

Le 2016-08-02 à 23:35, MFPA a écrit :
> But to bring it back
> on-topic, would a DKIM signature on such a message be for the
> gmail.com domain or the twopif.net domain?

It the key is from twopif.net, though obviously Google have the private
key rather than myself.

> Is this a Denial of Service attack, rather than an attempt to get
> roboca to certify something it shouldn't?

No, the idea is that you send an email to victim at example.com and
roboca at roboca.com and when the victim hits reply-to-all the
response goes to the CA as well.  If such an email is considered
acceptable, then an attacker who can get hold of the email now has a
proof-of-sending.


> I thought the message-ID had to end in a fully qualified domain name.

Yes, you would do something like
<a-shortish-ecdsa-signature-of-some-parameter>@roboca.net.  But thinking
about it further, this would mean that you couldn't mandate a clean
subject line (no Re: etc.) without user intervention.

I guess I'll go ahead and start building, then we'll see how it looks in
practice.

Thanks,
Lachlan

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