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Re: [ietf-dkim] Re: Attempted summary

2006-01-24 08:28:14
On Mon, Jan 23, 2006 at 11:23:15PM -0800, Jim Fenton allegedly wrote:

If the list does sufficient damage to the message that any incoming
signature is invalid, it might as well throw away the original
signature.

How does the list know for sure? The only sure way is if it attempts
to re-verify the original signature after applying it's own
modifications.

And that assumes the original signature doesn't contain some future option
that the list doesn't know about - such as a variant l=.

So the actual rules would need to be:

 If original verifies
    and if I think I've modified badly
       and if I understand all tags in the original sig/selector
           re-verify list output to see if original sig now fails
           then if re-verify fails
              remove the original signature

If a list isn't fastidious about these checks then it risks removing a
"still-valid" signature because it thinks the modifications were
invalidating.

If it's still there, someone is likely to waste time trying
to verify it.

Is this the only benefit for this complexity? If so, does it risk
being a premature optimization?


Mark.
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