[PATCH 05/18] crypto: Test restore of cleartext index from stashed session keys

[Daniel Kahn Gillmor]

On Tue 2017-11-14 09:13:52 -0400, David Bremner wrote:
> Daniel Kahn Gillmor <dkg at fifthhorseman.net> writes:
>
>> If you've got a notmuch dump that includes stashed session keys for
>> every decrypted message, and you've got your message archive, you
>> should be able to get back to the same index that you had before.
>
> Out of curiousity, have you given any thought to what happens when
> someone sends a message with the same message-id but a different
> session-key? it seems like the user can potentially lose access to the
> encrypted message.

yep!  I even have that case in my own mailbox due to messages i've sent
to schleuder encrypted mailing lists to which i'm also subscribed.

It works fine.  notmuch stashes both session keys against the message-id
(you can have multiple properties with the same name as long as they
have different values).  And upon decryption, it tries each session-key
in succession.  This is a little bit sloppy (maybe it would be less
sloppy to associate each message key with each version of the message
somehow?), but it's significantly simpler and basically unnoticeable
compared to the speedup gains provided by the rest of the series.

         --dkg