Now that the range of sensible decryption policies has come into full
view, we take a bit of space to document the distinctions.
Most people will use either "auto" or "true" -- but we provide "false"
and "nostash" to handle use cases that might reasonably be requested.
Note also that these can be combined in sensible ways. Like, if your
mail comes in regularly to a service that doesn't have access to your
secret keys, but does have access to your index, and you feel
comfortable adding selected encrypted messages to the index after
you've read them, you could stay in "auto" normally, and then when you
find yourself reading an indexable message (e.g. one you want to be
able to search for in the future, and that you don't mind exposing to
whatever entities have access to your inde), you can do:
notmuch reindex --decrypt=true id:whatever@example.biz
That leaves your default the same (still "auto") but you get the
cleartext index and stashed session key benefits for that particular
message.
Here's the configuration choice for people who want a cleartext index,
but don't want stashed session keys.
Interestingly, this "nostash" decryption policy is actually the same
policy that should be used by "notmuch show" and "notmuch reply",
since they never modify the index or database when they are invoked
with --decrypt.
We take advantage of this parallel to tune the behavior of those
programs so that we're not requesting session keys from GnuPG during
"show" and "reply" that we would then otherwise just throw away.
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.
There are some situations where the user wants to get rid of the
cleartext index of a message. For example, if they're indexing
encrypted messages normally, but suddenly they run across a message
that they really don't want any trace of in their index.
In that case, the natural thing to do is:
notmuch reindex --decrypt=false id:whatever@example.biz
But of course, clearing the cleartext index without clearing the
stashed session key is just silly. So we do the expected thing and
also destroy any stashed session keys while we're destroying the index
of the cleartext.
Note that stashed session keys are stored in the xapian database, but
xapian does not currently allow safe deletion (see
https://trac.xapian.org/ticket/742).
As a workaround, after removing session keys and cleartext material
from the database, the user probably should do something like "notmuch
compact" to try to purge whatever recoverable data is left in the
xapian freelist. This problem really needs to be addressed within
xapian, though, if we want it fixed right.
The new "auto" decryption policy is not only good for "notmuch show"
and "notmuch reindex". It's also useful for indexing messages --
there's no good reason to not try to go ahead and index the cleartext
of a message that we have a stashed session key for.
This change updates the defaults and tunes the test suite to make sure
that they have taken effect.
In our consolidation of _notmuch_crypto_decrypt, the callers lost
track a little bit of whether any actual decryption was attempted.
Now that we have the more-subtle "auto" policy, it's possible that
_notmuch_crypto_decrypt could be called without having any actual
decryption take place.
This change lets the callers be a little bit smarter about whether or
not any decryption was actually attempted.
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".
When showing a message, if the user doesn't specify --decrypt= at all,
but a stashed session key is known to notmuch, notmuch should just go
ahead and try to decrypt the message with the session key (without
bothering the user for access to their asymmetric secret key).
The user can disable this at the command line with --decrypt=false if
they really don't want to look at the e-mail that they've asked
notmuch to show them.
and of course, "notmuch show --decrypt" still works for accessing the
user's secret keys if necessary.
If the user doesn't specify --decrypt= at all, but a stashed session
key is known to notmuch, when replying to an encrypted message,
notmuch should just go ahead and decrypt.
The user can disable this at the command line with --decrypt=false,
though it's not clear why they would ever want to do that.
This new automatic decryption policy should make it possible to
decrypt messages that we have stashed session keys for, without
incurring a call to the user's asymmetric keys.
Future patches in this series will introduce new policies; this merely
readies the way for them.
We also convert --try-decrypt to a keyword argument instead of a boolean.
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.
"notmuch help" doesn't mention "notmuch-emacs-mua" even though we
support it through the try_external_command() mechanism.
In addition, "notmuch help emacs-mua" doesn't work, even though we
ship the appropriate manpage.
This changeset fixes both of these problems.
python2 is going to be deprecated, and python3-sphinx is available all
the way back to oldoldstable. let's use the more modern version.
To make this work and still ship the manpages, tell ./configure to
prefer python3 over python, if it exists.
If the version of GMime we're building against doesn't support session
key extraction or re-use, mark the tests that rely on session key
capabilities as known-broken.
This should resolve test suite failures on ubuntu trusty and debian
jessie and earlier, which have GMime 2.6.20 -- session key support was
introduced in GMime 2.6.21.
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.
Here we add a simple test that give some flavor of how that works.
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.
This flag should make it easier to write the code for session-key
handling.
Note that this only works for GMime 2.6.21 and later (the session key
interface wasn't available before then). It should be fine to build
the rest of notmuch if this functionality isn't available.
Note that this also adds the "session_key" built_with() aspect to
libnotmuch.
We will use this centralized function to consolidate the awkward
behavior around different gmime versions.
It's only invoked from two places: mime-node.c's
node_decrypt_and_verify() and lib/index.cc's
_index_encrypted_mime_part().
However, those two places have some markedly distinct logic, so the
interface for this _notmuch_crypto_decrypt function is going to get a
little bit clunky. It's worthwhile, though, for the sake of keeping
these #if directives reasonably well-contained.
Move transitional package to to "oldlibs/optional"
This resolves two lintian warnings:
W: notmuch-emacs: transitional-package-should-be-oldlibs-optional oldlibs/extra
W: notmuch-emacs: priority-extra-is-replaced-by-priority-optional
In 8e7fb88237 Jani replaced the use of $(pwd -P) to find the
TEST_DIRECTORY in order to better support out of tree
builds. Unfortunately the performance-tests need a different value for
the variable and were thus broken.
This commit splits out the setting of this variable for the two sets
of tests. Performance tests still don't work out of tree, because
the handling of the downloaded corpus needs to be updated.
Now that it's easy to add argument specific modifiers in opt
descriptions, add a new .allow_empty field to allow empty strings for
individual string arguments while retaining strict checks
elsewhere. Use this for notmuch insert --folder, where the empty
string means top level folder.
Commit 1fdc08d0ff ("cli/crypto: treat failure to create a crypto
context as fatal.") started treating crypto context creation failures
"as fatal", returning NULL from _mime_node_create().
Unfortunately, we do not have NULL checks for _mime_node_create()
failures. The only caller, mime_node_child(), could check and return
NULL (as it's documented to do on errors) but none of the several call
sites have NULL checks either. And none of them really have a trivial
but feasible and graceful way of recovery.
So while the right thing to do would be to handle NULL returns
properly all over the place, and we have other scenarios that do
return NULL from above mentioned functions, the crypto context
creation failure is something that does seem to show up regularly in
some scenarios, revert back to the functionality before commit
1fdc08d0ff as an interim fix.
backup_database() and restore_database() used to store the backups in
the test specific temporary directory, through the current working
directory being there. Commit 8e7fb88237 ("test: use source and
build paths in test-lib-common.sh") started using a test specific
backup directories under the build tree test directory. This was in
error. Switch back to the old location, but using paths to the
location instead of relying on current working directory.
Reported by Daniel Kahn Gillmor <dkg@fifthhorseman.net>.
Enable override of the index.try_decrypt setting on a per-run basis
when invoking "notmuch reindex". This allows the possibility of (for
example) an emacs keybinding that adds the cleartext of the currently
shown decrypted message to the index, making it searchable in the
future.
It also enables one-time indexing of all messages matching some query,
like so:
notmuch reindex tag:encrypted and\
not property:index.decryption=success and\
from:alice@example.org
We also update the documentation and tab completion, and add a few
more tests.
Enable override of the index.try_decrypt setting on a per-message
basis when invoking "notmuch insert".
We also update the documentation and tab completion, and add more tests.
Enable override of the index.try_decrypt setting during "notmuch new"
on a per-invocation basis.
We update the documentation and tab completion, and also add a test.
Subsequent patches may want to send GNU-style --long-arguments to
notmuch new in the test suite, in particular when invoking
emacs_fcc_message. This changeset makes that possible.
We have an indexopts structure for manipulating indexing in different
ways, but we also have three command-line invocations that can trigger
indexing: new, insert, and reindex.
This changeset prepares a common parser that these subcommands can
share.
Note: if the deprecated crypto.gpg_path configuration option is set to
anything other than "gpg", we ignore it (and print a warning on
stderr, if built against gmime < 3.0).
At the moment, it's just --try-decrypt, but others will likely follow.
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.
QUERY_STRING was only used in two places, both to test whether a
variable should be stored in (or retrieved from) the database.
Since other configuration variables might be stored in the database in
the future, consolidate that test into a single function.
We also document that these configuration options should not be placed
in the config file.
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.
This is currently mostly a wrapper around _notmuch_crypto_t that keeps
its internals private and doesn't expose any of the GMime API.
However, non-crypto indexing options might also be added later
(e.g. filters or other transformations).
