Re: [Dcrup] Adam Roach's No Objection on draft-ietf-dcrup-dkim-usage-04: (with COMMENT)

[Scott Kitterman <[e-mail]>]

On October 24, 2017 4:46:28 PM PDT, Brandon Long <[e-mail]> wrote:
>On Tue, Oct 24, 2017 at 4:35 PM, Kurt Andersen <[e-mail]>
>wrote:
>
>> On Tue, Oct 24, 2017 at 8:03 PM, Murray S. Kucherawy
><[e-mail]>
>> wrote:
>>
>>> On Tue, Oct 24, 2017 at 12:58 PM, Murray S. Kucherawy <
>>> [e-mail]> wrote:
>>>
>>>> On Thu, Oct 19, 2017 at 3:54 AM, Scott Kitterman
><[e-mail]>
>>>> wrote:
>>>>
>>>>> My assumption had been that since there's no valid signature with
>>>>> rsa-sha1, there's nothing to even consider putting in an A-R
>header field.
>>>>>
>>>>> I think the only result that can go in this case is None.  I
>hadn't
>>>>> thought we'd need to say that, but I guess maybe we do.
>>>>>
>>>>
>>>> I think "policy" is the right way to go.  There's nothing
>technically
>>>> wrong with an rsa-sha1 signature, but you're deciding not to accept
>it.
>>>> It's the same as you deciding you're not going to accept a
>perfectly valid
>>>> rsa-sha256 signature on a message simply because that signature
>didn't
>>>> include the Subject field.
>>>>
>>>
>>> In fact I would claim that by the definitions in Section 2.7.1 of
>>> RFC7601, "policy" is the only option.
>>>
>>
>> Are we talking about before or after this group consigns sha1 to the
>ash
>> heap? Perhaps I'm confused about the sequencing of events that we are
>> discussing. If the original DKIM spec had allowed rsa-md5 and a
>previous
>> (hypothetical) instance of DCRUP had similarly deprecated MD5, what
>sort of
>> designation would we expect to be recorded today for such usage?
>>
>
>This is obviously a bit different, but today google uses policy for
>keys
>under 1024 bits.  I say "different", because prior to the dcrup work
>being
>published, that's our policy choice.  After, it's the standard, so
>permerror might be more appropriate.
>
>Brandon

I prefer None, but I think permerror is reasonable.  Policy means local policy (as you are doing now).  Once this is approved, not accepting short keys ( < 1024 ) or rsa-sha1 is not just a local policy call.

Scott K