[ietf-dkim] canonicalized null body and dkim

Mon Jan 8 09:27:49 PST 2007

--On January 8, 2007 11:51:13 AM +0000 Charles Lindsey 
<chl at clerew.man.ac.uk> wrote:

> On Sun, 07 Jan 2007 18:49:50 -0000, Eric Allman
> <eric+dkim at sendmail.org>  wrote:
>
>> I have (finally) managed to slog my way through all the messages
>> on this   topic.  Let me start out by saying that I don't see the
>> ambiguity in the   current text:
>>
>>         If there is no trailing CRLF on the message, a CRLF is
>>         added. It makes no other changes to the message body. In
>>         more formal terms, the "simple" body canonicalization
>>         algorithm converts "0*CRLF" at the end of the body to a
>>         single "CRLF".
>>
> ...
>
> Indeed there is no ambiguity in that, but that is because you have
> only  quoted half the text. The full text is:
>
>     The "simple" body canonicalization algorithm ignores all empty
> lines
>     at the end of the message body.  An empty line is a line of zero
>     length after removal of the line terminator.  If there is no
> trailing
>     CRLF on the message, a CRLF is added.  It makes no other
> changes to
>     the message body.  In more formal terms, the "simple" body
>     canonicalization algorithm converts "0*CRLF" at the end of the
> body
>     to a single "CRLF".
>
> Observe carefully that the text some times tells you to consider
> the  "message", and somtimes the "message body" (which I take to
> mean exactly  the <body>, if any, defined by RFC 2822).

OK, I'll change the single instance of "message" to "message body".

> Consider the example, in DATA format:
>
>     Field: foobar<CRLF>.
>     <CRLF>
>     <CRLF>
>     .<CRLF>
>
> The ".<CRLF>" is evidently not a part of either the message or of
> the  message body. The "message body" consists of "<CRLF>". Let us
> apply the  sentences of 3.4.3 one by one.

As Hector points out, this is not a valid 2822 message to begin with, 
so sending it would be undefined.  At that point how it gets 
canonicalized is the least of your problems.

I can't come up with a scenario that starts with a valid message that 
has the problem you describe.  None the less, changing "message" to 
"message body" will improve consistency, and it would make 
interpretation of this degenerate case consistent.

eric 