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Re: [ietf-dkim] ISSUE: tag l=2 and dealing with leading blank lines for SIMPLE c14n.

2007-01-25 04:28:12
On Wed, 24 Jan 2007 18:01:48 -0000, Douglas Otis <dotis(_at_)mail-abuse(_dot_)org> wrote:

On Jan 24, 2007, at 9:24 AM, Scott Kitterman wrote:

IIRC, every time someone brings up l= problems, the response is don't use it. Is there a problem it solves that we need it? If it's inherently risky and
should not be used, I'm wondering if it should even be in the RFC?

This is a valid concern. Why allow something that can and most likely will be abused?

It all depends on what the sender of the message is trying to achieve, and on his level of paranoia. For the most obvious attacks (spoofing the source of a message), body signing is not important (since most bad guys do not have the ability to interfere with a message in transit), and the ability to permit mailing lists to add stuff like:

_______________________________________________
NOTE WELL: This list operates according tohttp://mipassoc.org/dkim/ietf-list-
rules.html

is more important. But if the sender is worried about possible Replay Attacks, then he has to do a little more (possibly loosing the ability to have the message pass smoothly through mailing lists).

But even there, there is a workaround. Simply include, as the last line of the signed part of the message, something like:

WARNING! THIS IS THE END OF THE MESSAGE. ANYTHING BELOW THIS LINE WAS ADDED IN TRANSIT.
------------------------------------------------------------------------------

If that looks a little alarmist, something more polite might do, such as a conventional signature following the customary "-- CRLF" might be good enough.

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