On Tue, Jul 7, 2020 at 2:19 PM Alessandro Vesely <[email protected]> wrote:
> On Tue 07/Jul/2020 18:27:40 +0200 John R Levine wrote: > >> There's a distinction though. ARC tells you "that guy over there said > the > >> original message passed", and you have to trust it. On the other hand, > the > >> transformations draft, when it works, hands you the original message, > and > >> you don't have to make that trust assessment. > > > > I understand that, and I still don't see why it's useful. > > At what overhead cost? You have to hold the connection open while reversing the transformations or you are not in a position to reject (vs accepting then rejecting). There are folks currently holding the connection while evaluating the DKIM signature but that is lighter weight than reversing the transforms AND doing the DNS lookup to validate the DKIM signature. > > It would allow me, for one, to honor remote DMARC policies. Of course, > I'd > still need to manually whitelist non compliant MLMs. However, when the > number > of those drops below a reasonable figure, whitelisting might become > feasible. > > An interesting dependency. When might that reasonable figure occur? What is a reasonable number? Would other receivers agree with you on reasonableness? Should a standard be predicated on this basis? > > > It's hard to imagine a realistic situation where a recipient system > would > > strip off the changes and show the original message, so the recipient > has to > > trust that the mediator doesn't make malicious transformations. > > > Agreed. Undoing the changes has to be done on a temporary file, solely > for > verification purposes. Undoing the changes would be illegal, if the > footer > contains legal claims. > Your claim is interesting. What possible legal claims might an intermediator make that would be legally binding on a receiver and be illegal to undo in a temporary file for processing? Are you a lawyer? Are you a lawyer making such an assertion for all jurisdictions? > > > > So if you trust them that far, why wouldn't you also trust them to report > > the status of incoming mail? > > I cannot trust ARC operators, unless I manually compile a trusted list, > which > is as unfeasible as whitelisting each MLM. > Or you use a trusted list compiled by someone else. The use of blocklists such as Spamhaus ones or RPZ come to mind. > > I trust the original message as any other message. Allowed > transformations are > designed to not pervert the original message. Consider my notes 1 and 2 > about > l=, in a message upthread[*]. We can also specify limits on the size of > subject tags and footers. Transformations that insert stuff before the > original content should not be allowed —rewrite From: in such cases. > This is getting unduly complicated. Now we have to hold up progress on the effort while folks argue out what the size limits on subject lines and footers should be? Michael Hammer
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