On 5/24/2024 4:38 PM, Jon Callas wrote:
"well, I attest to generating this message, but only the first 1234 bytes of it,
after that, well -- you're on your own."
Jon,
Sorry to be finicky, but I don't recall any statement in the DKIM
specification that matches or approximate that semantic for any aspect
of DKIM, never mind l=.
As for l= semantics, this is all of the relevant text, none of which is
nearly as interesting as the interpretation you've invoked:
l= Body length count (plain-text unsigned decimal integer; OPTIONAL,
default is entire body). This tag informs the Verifier of the
number of octets in the body of the email after canonicalization
included in the cryptographic hash, starting from 0 immediately
following the CRLF preceding the body.
...
and:
8.2 <https://www.rfc-editor.org/rfc/rfc6376.html#section-8.2>. Misuse
of Body Length Limits ("l=" Tag)
Use of the "l=" tag might allow display of fraudulent content without
appropriate warning to end users. The "l=" tag is intended for
increasing signature robustness when sending to mailing lists that
both modify their content and do not sign their modified messages.
and:
Appendix D <https://www.rfc-editor.org/rfc/rfc6376.html#appendix-D>.
MUA Considerations (INFORMATIVE)
...
If the message has an "l=" tag whose value does not
extend to the end of the message, the MUA might also hide or mark the
portion of the message body that was not signed.
d/
--
Dave Crocker
Brandenburg InternetWorking
bbiw.net
mast:@dcrocker@mastodon.social
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