These tests were an attempt to establish that the content of the
"Legacy Display" part is the same as the actual protected headers of
the message. But this is more conservative than we need to be.
https://www.ietf.org/id/draft-autocrypt-lamps-protected-headers-02.html
section 5.3 makes clear that the Legacy Display part is purely
decorative, and section 5.2.1 clarifies that the detection can be done
purely by MIME structure and Content-Type alone.
Furthermore, now that we're accepting text/plain Legacy Display parts,
it's not clear the lines in the Legacy Display part should be
interpreted as needing an exact string match (e.g. "real" headers are
likely to be RFC 2047 encoded, but the text/plain Legacy Display part
probably should not be).
The concerns that motivated this test in the past were twofold: that
we might accidentally hide some information from the reader of the
message that they should have available to them, or that we could
introduce a covert channel that would be invisible to other clients.
I no longer think these are significant concerns:
a) There will be no accidental misidentification of a Legacy Display
part. The identification of the Legacy Display part is
unambiguous due to MIME structure and Content-Type. MIME
structure MUST be the first child part of a two-part
multipart/mixed Cryptographic Payload. And the
protected-headers=v1 content-type parameter must be present on
both the cryptographic payload and the legacy display part, so no
one would accidentally generate this structure and have it be
accidentally matched.
b) As for creating a covert channel, many such channels already
exist. For example, non-standard e-mail headers, custom MIME
types, unusual MIME structures, etc, all make it possible to ship
some content in a message that will be visible in some MUAs but
not in others. This doesn't make the situation demonstrably
worse.
Signed-off-by: Daniel Kahn Gillmor <dkg@fifthhorseman.net>
https://www.ietf.org/id/draft-autocrypt-lamps-protected-headers-02.html
Makes it clear that the "Legacy Display" part of an encrypted message
with protected headers can (and indeed, should) be of content-type
text/plain, though some clients still generate the Legacy Display part
as content-type text/rfc822-headers. Notmuch should recognize the
part whichever of the two content-types it uses.
See also discussion in
https://github.com/autocrypt/protected-headers/issues/23 for why the
community of implementers is moving in the direction of text/plain.
Signed-off-by: Daniel Kahn Gillmor <dkg@fifthhorseman.net>
We want freeing the returned stream to also free these underlying
objects. Compare tests/test-filters.c in the gmime 3.2.x source, which
uses this same idiom.
Thanks to James Troup for the report and the fix.
Implement a functional identification and repair process for "Mixed
Up" MIME messages as described in
https://tools.ietf.org/html/draft-dkg-openpgp-pgpmime-message-mangling-00#section-4.1
The detection test is not entirely complete, in that it does not
verify the contents of the latter two message subparts, but this is
probably safe to skip, because those two parts are unlikely to be
readable anyway, and the only part we are effectively omitting (the
first subpart) is guaranteed to be empty anyway, so its removal can be
reversed if you want to do so. I've left FIXMEs in the code so that
anyone excited about adding these additional checks can see where to
put them in.
Signed-off-by: Daniel Kahn Gillmor <dkg@fifthhorseman.net>
This is a utility function designed to make it easier to
"fast-forward" past a legacy-display part associated with a
cryptographic envelope, and show the user the intended message body.
The bulk of the ugliness in here is in the test function
_notmuch_crypto_payload_has_legacy_display, which tests all of the
things we'd expect to be true in a a cryptographic payload that
contains a legacy display part.
Signed-off-by: Daniel Kahn Gillmor <dkg@fifthhorseman.net>
Our _notmuch_message_crypto_potential_payload implementation could
only return a failure if bad arguments were passed to it. It is an
internal function, so if that happens it's an entirely internal bug
for notmuch.
It will be more useful for this function to return whether or not the
part is in fact a cryptographic payload, so we dispense with the
status return.
If some future change suggests adding a status return back, there are
only a handful of call sites, and no pressure to retain a stable API,
so it could be changed easily. But for now, go with the simpler
function.
We will use this return value in future patches, to make different
decisions based on whether a part is the cryptographic payload or not.
But for now, we just leave the places where it gets invoked marked
with (void) to show that the result is ignored.
Signed-off-by: Daniel Kahn Gillmor <dkg@fifthhorseman.net>
_notmuch_message_crypto_potential_payload is called on a GMimeObject
while walking the MIME tree of a message to determine whether that
object is the payload. It doesn't make sense to name the argument
"payload" if it might not be the payload, so we rename it to "part"
for clarity.
This is a non-functional change, just semantic cleanup.
Signed-off-by: Daniel Kahn Gillmor <dkg@fifthhorseman.net>
This adds no functionality directly, but is a useful starting point
for adding new repair functionality.
Signed-off-by: Daniel Kahn Gillmor <dkg@fifthhorseman.net>
When walking the MIME tree, if we discover that we are at the
cryptographic payload, then we would like to record at least the
Subject header of the current MIME part.
In the future, we might want to record many other headers as well, but
for now we will stick with just the Subject.
See
https://dkg.fifthhorseman.net/blog/e-mail-cryptography.html#cryptographic-envelope
for more description of the Cryptographic Payload vs. the
Cryptographic Envelope.
Signed-off-by: Daniel Kahn Gillmor <dkg@fifthhorseman.net>
E-mail encryption and signatures reported by notmuch are at the MIME
part level. This makes sense in the dirty details, but for users we
need to have a per-message conception of the cryptographic state of
the e-mail. (see
https://dkg.fifthhorseman.net/blog/e-mail-cryptography.html for more
discussion of why this is important).
The object created in this patch is a useful for tracking the
cryptographic state of the underlying message as a whole, based on a
depth-first search of the message's MIME structure.
This object stores a signature list of the message, but we don't
handle it yet. Further patches in this series will make use of the
signature list.
This originally use Xapian::Unicode::is_wordchar, but that forces
clients to link directly to libxapian, which seems like it might be
busywork if nothing else.
The comment line here lingers from when we were using some fancy
version checking about session keys. Correct it to match the current
state.
Signed-off-by: Daniel Kahn Gillmor <dkg@fifthhorseman.net>
This is a functional change, not a straight translation, because we
are no longer directly invoking g_mime_parser_options_get_default(),
but the GMime source has indicated that the options parameter for
g_mime_parser_construct_message() is "nullable" since upstream commit
d0ebdd2ea3e6fa635a2a551c846e9bc8b6040353 (which itself precedes GMime
3.0).
Signed-off-by: Daniel Kahn Gillmor <dkg@fifthhorseman.net>
Several GMime 2.6 functions sprouted a change in the argument order in
GMime 3.0. We had a compatibility layer here to be able to handle
compiling against both GMime 2.6 and 3.0. Now that we're using 3.0
only, rip out the compatibility layer for those functions with changed
argument lists, and explicitly use the 3.0 argument lists.
Signed-off-by: Daniel Kahn Gillmor <dkg@fifthhorseman.net>
Several of these #defines were not actually used in the notmuch
codebase any longer. And as of GMime 3.0, g_mime_init takes no
arguments, so we can also drop the bogus RFC2047 argument that we were
passing and then #defining away.
signed-off-by: Daniel Kahn Gillmor <dkg@fifthhorseman.net>
This means dropping GMimeCryptoContext and notmuch_config arguments.
All the argument changes are to internal functions, so this is not an
API or ABI break.
We also get to drop the #define for g_mime_3_unused.
signed-off-by: Daniel Kahn Gillmor <dkg@fifthhorseman.net>
Note that we do keep ignoring the gpg_path configuration option,
though, to avoid breakage of existing installations. It is ignored
like any other unknown configuration option, but we at least document
that it is ignored so that people who find it in their legacy configs
can know that it's safe to drop.
signed-off-by: Daniel Kahn Gillmor <dkg@fifthhorseman.net>
libnotmuch_util.a is supposed to be usable from the library and the
CLI, but much the library is compiled as C++. Add in appropriate
wrapping to prevent symbol mangling. These wrappers already existed in
string-util.h; it seems better to be consistent.
When i'm trying to understand a message signature, i care that i know
who it came from (the "validity" of the identity associated with the
key), *not* whether i'm willing to accept the keyholder's other
identity assertions (the "trust" associated with the certificate).
We've been reporting User ID information based on the "trust"
associated with the certificate, because GMime didn't clearly expose
the validity of the User IDs.
This change relies on fixes made in GMime 3.0.3 and later which
include https://github.com/jstedfast/gmime/pull/18.
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.
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.
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.
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.
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.
In practice, we're going to see this function invoked differently
depending on which gmime we build against. The compatibility layer
forces our code into the lowest-common-denominator -- unable to make
use of new features even when built against a newer version.
Dropping the compatibility layer paves the way for clearer use of
features from GMime 3.0 in future commits.
"typedef GMimeAddressType GMimeRecipientType" is already present
further down in the compatibility wrapper (with other typedefs). We
don't need it twice.
Stripping trailing character is not that uncommon
operation. Particularly, the next patch has to perform it as
well. Lets move it to the separate function to avoid code duplication.
Also the new function has a little improvement: if the character to
strip is repeated several times in the end of a string, function
strips them all.
Signed-off-by: Yuri Volchkov <yuri.volchkov@gmail.com>
The problem shows up on 32 bit architectures where sizeof(time_t) !=
sizeof(gint64). Upcasting the 32 bit time_t to a 64 bit integer
should hopefully be safe.
When compiling as C code (instead of C++) against gmime 3.0, gcc gives
errors like the following:
error: invalid conversion from ‘int’ to ‘GMimeDecryptFlags’ [-fpermissive]
so use explicit *_NONE values instead.
The "key_id" field seems to used for userid in gmime-3.0, while the
keyid is dropped in the fingerprint field if the full fingerprint is
not available.
