Re: DKIM: Canonicalization

[Frank Ellermann <nobody@xxxxxxxxxxxxxxxxx>]

Jim Fenton wrote:
 
> 1. Minimal changes to the message.
> 2. Only allow modifications explicitly permitted by RFC2822.
> 3. Do not alter the semantics of the message.
> 4. Do not provide a reasonable opportunity for abuse.
[...]
> the goal (well, mine at least) was to prevent abuse, not
> necessarily to maintain semantics.  Is that the right goal?

Depends on header vs. body, and maybe within the header on
unstructured vs. structured header fields (or on Subject: vs.
other header fields).  For a structured header field a simple
strategy is "treat FWS as SP and remove any trailing SP".

For an unstructered header field (incl. the Subject) a simple
strategy could be "handle this like structured header fields".

Add some ad hoc solutions for qouted-pairs with CR, HT, and LF,
and it should survive all WSP-related mangling.  For the body
it's of course much more interesting and very different.  Bye