[ietf-dkim] bh=; l=0;

[Michael Thomas]

Paul Hoffman wrote:

>
>
>> #13 3.4.5, 3.5 and 3.7. "l=0" is allowed, but "bh=" is REQUIRED, 
>> which is a bit
>> of a contradiction.
>
>
> "l=0;bh=;" seems valid.


It doesn't seem valid to me, and it's certainly not the natural thing that
an implementor would do which is to just take the value of SHA[1|256]_Final
and compare it against the bh= value. Leaving it as is doesn't create an
unnecessary new case.

>
>> And "l=" is not mentioned when saying how to calculate
>> "bh=". I guess the right thing to do might be to add some mention of 
>> "l=" when
>> talking about calculating "bh=",
>
>
> Agree.


I don't see what the problem is: l= is the canonical byte count, and that's
just as true with bh as is was before bh was invented.

>
>> I think I'd prefer to outlaw "l=0" and make "bh="
>> optional for just that case, but that might be a bit broken for 
>> backwards
>> compatability.
>
>
> It also adds another special case.


Not to mention that l=0 is a perfectly valid 2822 mail message.

          Mike