It appears that <ned+dm...@mrochek.com> said: >> It appears that Wei Chuang <wei...@google.com> said: >> > If the RFC2045 canonical representation at the final destination can be the >> > same as the canonical representation at the original sender, ... > >> When we were working on DKIM canonicalization we had lengthy discussions >> about >> what to do about MIME and we decided not to even try. > >A mistake IMO.
This was part of the discussion about what sort of body modifications to allow. We ended up with optionally ignoring white space changes, and l= to ignore added text. My impression is that neither is useful. Very few messages pass with relaxed canonicalization that don't also pass strict. The goal of l= was to allow mailing lists to add footers, but as we've seen in this discussion, if a list adds a footer it's likely to make other changes too. I think the main use case for relaxed mode was an old bug in sendmail that added an extra \r\n on the way through, but it's long gone. For MIME, the question wasn't just whether two versions of messages were equivalent, but the impossible question of what other changes keep the message "the same" and which are too different. As you note there are lots of ways that a message could be recoded into equivalent MIME parts, but again it is my impression that those sorts of changes are rare without also adding or removing body parts which gets us into the swamp of how different is too different. So we didn't try. R's, John _______________________________________________ dmarc mailing list dmarc@ietf.org https://www.ietf.org/mailman/listinfo/dmarc
