[ietf-dkim] Re: canonicalized null body and dkim

[Eric Allman]

--On January 10, 2007 3:34:27 PM -0500 Hector Santos 
<hsantos at santronics.com> wrote:

> Eric Allman wrote:
>
>> I've changed the text to read "If there is no body or no trailing
>> CRLF  on the message body, a CRLF is added" in order to avoid any
>> confusion.
>
> Eric, this is good. I will comment that the only confusion is there
> is an indirect implication that the final two bytes of the FEED
> must have a <CRLF>.
>
> Which is not true, right?

I'm not sure what you mean by the "FEED" here.  If you mean the data 
transmitted using either DATA or BDAT you can have a message without 
a trailing CRLF using BDAT.

> Because a) A signer can canonicalized the message, including adding
> a <CRLF> if necessary, that yields size X, but B) the signer
> decides to hash only L=N  bytes where N < X bytes.
>
> That was the only "scratch head" thought I had about all this - The
> reason to add a <CRLF> if a signer was not going to hash the entire
> body.

It's true that if the signer uses l= then you don't actually have to 
add the trailing CRLF --- in fact, it doesn't have to canonicalize 
anything at all after it has sent N bytes (where l=N).  We could say 
that, but it would be an implementation detail that probably doesn't 
belong in the spec, and certainly not in normative language.

> So I guess, if anything, a statement, sentence or comment that
> states "the need to add a <CRLF> is only necessary if the entire
> body is going to be hashed."

See above.

eric