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

[Charles Lindsey]

On Wed, 20 Dec 2006 15:23:32 -0000, Mark Delany <markd+dkim at yahoo-inc.com>  
wrote:

> Charles Lindsey wrote:
>> Anyway, here is some wording:
>>     The "simple" body canonicalization removes empty lines from the end  
>> of the
>>    body until either the last line is non-empty, or no lines remain. An  
>> empty
>>    line is a line of zero length after removal of any terminating CRLF.  
>> If
>>    the body is not now empty and the last line is not already  
>> terminated by
>>    CRLF, a CRLF is added to it.
>>        INFORMATIVE NOTE: Following [RFC 2822}, the CRLF which separates  
>> the
>>       header fields from the body is NOT part of the body, and  
>> therefore is
>>       never presented to the signing or verification algorithm.
>
> I think I agree with the effect, but I wish I could offer something  
> terser, but that seems hard since this is dealing with the interaction  
> of potentially different header canon and body canon.
>
> Does the INFORMATIVE NOTE imply that the following two emails  
> canonicalize to the same thing?
>
>
> ---------------
> Last-Header: blahCRLF
> CRLF
> lineOne: blah1CRLF
> lineTwo: blah2CRLF
> ---------------
>
> ---------------
> Last-Header: blahCRLF
> lineOne: blah1CRLF
> lineTwo: blah2CRLF
> ---------------

Certainly not! Why should they?

The first is a message with one header and a body of two lines. The header  
canonicalizes into itself, and the body canonicalizes into

---------------
lineOne: blah1CRLF
lineTwo: blah2CRLF
---------------

The second is a message with three headers and no body at all. The headers  
canonicalize as themselves, and for the body you treat it as empty:

---------------
---------------

One could add text to say that an absent body is equivalent to an empty  
body, if you think that is necessary.

-- 
Charles H. Lindsey ---------At Home, doing my own thing------------------------
Tel: +44 161 436 6131                       
   Web: http://www.cs.man.ac.uk/~chl
Email: chl at clerew.man.ac.uk      Snail: 5 Clerewood Ave, CHEADLE, SK8 3JU, U.K.
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