If you're going to store the cleartext index of an encrypted message,
in most situations you might just as well store the session key.
Doing this storage has efficiency and recoverability advantages.
Combined with a schedule of regular OpenPGP subkey rotation and
destruction, this can also offer security benefits, like "deletable
e-mail", which is the store-and-forward analog to "forward secrecy".
But wait, i hear you saying, i have a special need to store cleartext
indexes but it's really bad for me to store session keys! Maybe
(let's imagine) i get lots of e-mails with incriminating photos
attached, and i want to be able to search for them by the text in the
e-mail, but i don't want someone with access to the index to be
actually able to see the photos themselves.
Fret not, the next patch in this series will support your wacky
uncommon use case.
The stashed session keys are stored internally as notmuch properties.
So a user or developer who is reading about those properties might
want to understand how they fit into the bigger picture.
Note here that decrypting with a stored session key no longer needs
-decrypt for "notmuch show" and "notmuch reply".
the command-line interface for indexing (reindex, new, insert) used
--try-decrypt; and the configuration records used index.try_decrypt.
But by comparison with "show" and "reply", there doesn't seem to be
any reason for the "try" prefix.
This changeset adjusts the command-line interface and the
configuration interface.
For the moment, i've left indexopts_{set,get}_try_decrypt alone. The
subsequent changeset will address those.
When doing any decryption, if the notmuch database knows of any
session keys associated with the message in question, try them before
defaulting to using default symmetric crypto.
This changeset does the primary work in _notmuch_crypto_decrypt, which
grows some new parameters to handle it.
The primary advantage this patch offers is a significant speedup when
rendering large encrypted threads ("notmuch show") if session keys
happen to be cached.
Additionally, it permits message composition without access to
asymmetric secret keys ("notmuch reply"); and it permits recovering a
cleartext index when reindexing after a "notmuch restore" for those
messages that already have a session key stored.
Note that we may try multiple decryptions here (e.g. if there are
multiple session keys in the database), but we will ignore and throw
away all the GMime errors except for those that come from last
decryption attempt. Since we don't necessarily know at the time of
the decryption that this *is* the last decryption attempt, we'll ask
for the errors each time anyway.
This does nothing if no session keys are stashed in the database,
which is fine. Actually stashing session keys in the database will
come as a subsequent patch.
By default, notmuch won't try to decrypt on indexing. With this
patch, we make it possible to indicate a per-database preference using
the config variable "index.try_decrypt", which by default will be
false.
At indexing time, the database needs some way to know its internal
defaults for how to index encrypted parts. It shouldn't be contingent
on an external config file (since that can't be retrieved from the
database object itself), so we store it in the database.
This behaves similarly to the query.* configurations, which are also
stored in the database itself, so we're not introducing any new
dependencies by requiring that it be stored in the database.
If we see index options that ask us to decrypt when indexing a
message, and we encounter an encrypted part, we'll try to descend into
it.
If we can decrypt, we add the property index.decryption=success.
If we can't decrypt (or recognize the encrypted type of mail), we add
the property index.decryption=failure.
Note that a single message may have both values of the
"index.decryption" property: "success" and "failure". For example,
consider a message that includes multiple layers of encryption. If we
manage to decrypt the outer layer ("index.decryption=success"), but
fail on the inner layer ("index.decryption=failure").
Because of the property name, this will be automatically cleared (and
possibly re-set) during re-indexing. This means it will subsequently
correspond to the actual semantics of the stored index.
This allows us to create new properties that will be automatically set
during indexing, and cleared during re-indexing, just by choice of
property name.
the idea is that you can run
% notmuch search subject:/<your-favourite-regexp>/
% notmuch search from:/<your-favourite-regexp>/
or
% notmuch search subject:"your usual phrase search"
% notmuch search from:"usual phrase search"
This feature is only available with recent Xapian, specifically
support for field processors is needed.
It should work with bindings, since it extends the query parser.
This is easy to extend for other value slots, but currently the only
value slots are date, message_id, from, subject, and last_mod. Date is
already searchable; message_id is left for a followup commit.
This was originally written by Austin Clements, and ported to Xapian
field processors (from Austin's custom query parser) by yours truly.
We want to be able to query the properties directly, like:
notmuch count property:foo=bar
which should return a count of messages where the property with key
"foo" has value equal to "bar".
sphinx-build emits a minor warning:
[...]doc/man7/notmuch-search-terms.rst:223: WARNING: Block quote ends without a blank line; unexpected unindent.
And the tabular representation of boolean or probabilistic prefixes
currently renders like this when i view it in man:
┌───────────────────────────┬────────────────────────────┐
│Boolean │ Probabilistic │
└───────────────────────────┴────────────────────────────┘
│ tag: id: │ from: to: │
│ │ │
│ thread: folder: │ subject: attach‐ │
│ path: │ ment: mimetype: │
└───────────────────────────┴────────────────────────────┘
This isn't just ugly: it's confusing, because it seems to imply that
some of the prefixes in the left-hand column are somehow related to
specific other prefixes in the right-hand column.
The Definition List representation introduced by this patch should be
simpler for readers to understand, and doesn't have the warning.
<since> and <until> for the lastmod: prefix right below the date:
prefix description give the impression one could use last modified
dates to lastmod: which is not at all the case. Use
<initial-revision>..<final-revision> instead.
It doesn't seem likely we can support simple date:<expr> expanding to
date:<expr>..<expr> any time soon. (This can be done with a future
version of Xapian, or with a custom query query parser.) In the mean
time, provide shorthand date:<expr>..! to mean the same. This is
useful, as the expansion takes place before interpetation, and we can
use, for example, date:yesterday..! to match from beginning of
yesterday to end of yesterday.
Idea from Mark Walters <markwalters1009@gmail.com>.
Questions related to the way that probabilistic prefixes and phrases
are handled come up quite often and it is nicer to have the documentation self contained. Hopefully putting it in subsections prevents it from being overwhelming.
Adds new entry to the NEWS file, and updates the search terms section
of the man page. The search terms section needs to be updated again
once the new section in the documentation covering probablistic terms
has been committed.
This is the output from sphinx-quickstart, massaged a bit, along with
our existing man pages converted to rst.
A skeleton notmuch-emacs manual is also included. It is not suitable
for end user use yet.
