[notmuch] indexing encrypted messages (was: OpenPGP support)

[James Westby]

On Fri, 8 Jan 2010 15:56:10 +1300, martin f krafft <madduck at madduck.net> wrote:
> also sprach Jameson Graef Rollins <jrollins at finestructure.net> [2009.11.26.1901 +1300]:
> > I would really like to start using notmuch with emacs beyond just
> > testing, but I really need to be able to handle/read/send mail with
> > PGP/MIME encoded attachments.  Do folks have any suggestions on how to
> > handle this?  Is there a separate emacs mode that people use for
> > signing/verifying/{de,en}crypting mail buffers, or is this something
> > that is going to have to be integrated into the notmuch mode?  I guess
> > the notmuch-show mode at least will need to do some verifying and
> > decrypting.
> 
> How about indexing GPG-encrypted messages?

I think the difficulty will be interactivity. If notmuch-new can
potentially block watiting for a passphrase then it's not going to be
much use for non-interactive use, and whether someone can respond to a
GPG prompt is harder to determine that isatty().

Configuration may be a possible way around that, but looking at other
things such as opportunistic indexing could be good. For instance,
it could be the job of the UIs to decrypt content, and there could be a
nomuch function which takes a message id and decrypted content and
indexes it in to the DB. That means it's under the UI's control, where
the decryption UI should be, gets you indexing of encrypted content.

That would leave an open question over whether future notmuch show
invocations would return the plaintext or ciphertext. If it is the
latter then it requires decrypting every time you want to view it, but
it does mean that there is less information leakage (you could find out
whether an encrypted message contained a particular term, but not read
the whole message directly).

Thanks,

James