Daniel Kahn Gillmor <dkg@fifthhorseman.net> writes:

> On Sun 2017-06-04 09:32:29 -0300, David Bremner wrote:
>> The corresponding xapian document just gets more terms added to it,
>> but this doesn't seem to break anything. Values on the other hand get
>> overwritten, which is a bit annoying, but arguably it is not worse to
>> take the values (from, subject, date) from the last file indexed
>> rather than the first.
[snip]
> for example, i could follow up on the current message with another
> message with Message-Id: 20170604123235.24466-7-david@tethera.net and
> give it a subject "Re: [patch v3 06/12] lib: do *not* index message
> files with duplicate message-ids".  that's a bit odd, no?

Yes, I agree that's a bit strange.  We should make some effort to
display the subject that belongs with a given message body. I think it's
not too hard [1] to preserve the old behaviour of keeping the first
subject, date, and from. This leaves us with a version of the original
hiding message attack, but only for the special case of regex searches,
since those rely exclusively on the value slots.

[1]: should be just a matter of guarding the call to
_notmuch_message_set_header_values() with if (is_new || is_ghost), but
that needs testing.