Add my agreement, policy should be at the discretion of the signer.
Bill Oxley
Messaging Engineer
Cox Communications, Inc.
Alpharetta GA
404-847-6397
bill(_dot_)oxley(_at_)cox(_dot_)com
-----Original Message-----
From: ietf-dkim-bounces(_at_)mipassoc(_dot_)org
[mailto:ietf-dkim-bounces(_at_)mipassoc(_dot_)org] On Behalf Of John Levine
Sent: Friday, November 18, 2005 11:12 AM
To: ietf-dkim(_at_)mipassoc(_dot_)org
Subject: Re: [ietf-dkim] SSP security relies upon the visual domain
appearance
The "From:" header should not be signed if it contains more than one
sending address. ...
Does anyone see such a statement as causing a problem?
I see it as needless and futile micromanagement. The point of a DKIM
signature is that the signer is taking responsibility for the message.
The only semantics that a DKIM signature has is "blame us if you don't
like this message." That's it.
We don't know all of the reasons that a signer might legitimately want
to sign multiple From: addresses, nor do we know all of the ways that
a bad guy might try to trick someone into signing his message, with
multiple From: addresses being rather low on that list.
I could easily imagine an SSP-like system limiting itself to a subset
of otherwise syntactically valid messages, e.g. only one address in
the From: line, sender matches signer, or any of a host of other
rules. But for the basic DKIM, a signer can sign anything he's
willing to, and please leave it at that.
R's,
John
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