[ietf-dkim] Base issue: multiple linked signatures

[John Levine]

>>    Verifiers MUST NOT use the header field names or copied values
>>    for checking the signature in any way.  Copied header field
>>    values are for diagnostic use only.

>1) This condition is ACTUALLY REQUIRED for interoperation?

Well, yeah.  If the verifier is a separate module from the one that sorts
mail based on the verification result, the sorter is going to act
differently with results from a strict verifier vs. a squidgy one.

>2) This condition limits actual HARM?

If we consider unwittingly accepting mail with bad signatures as harm, yes.

I would prefer language along the lines of what I proposed last week, that
the copied values are not for signature validation, but you can do whatever
you want with them to decide what to do with a message whose signature
didn't validate.

R's,
John