[PATCH 1/4] test: add test for "Mixed-Up Mime" message mangling

Daniel Kahn Gillmor dkg at fifthhorseman.net
Tue May 28 15:54:49 PDT 2019

Some MTAs mangle e-mail messages in transit in ways that are

Microsoft Exchange (in particular, the version running today on
Office365's mailservers) appears to mangle multipart/encrypted
messages in a way that makes them undecryptable by the recipient.

I've documented this in section 4.1 "Mixed-up encryption" of draft -00

Fortunately, it's possible to repair such a message, and notmuch can
do that so that a user who receives an encrypted message from a user
of office365.com can still decrypt the message.

Enigmail already knows about this particular kind of mangling.  It
describes it as "broken PGP email format probably caused by an old
Exchange server", and it tries to repair by directly changing the
message held by the user.  if this kind of repair goes wrong, the
repair process can cause data loss
(https://sourceforge.net/p/enigmail/bugs/987/, yikes).

The tests introduced here are currently broken.  In subsequent
patches, i'll introduce a non-destructive form of repair for notmuch
so that notmuch users can read mail that has been mangled in this way,
and the tests will succeed.

Signed-off-by: Daniel Kahn Gillmor <dkg at fifthhorseman.net>
 test/T351-pgpmime-mangling.sh      | 28 +++++++++++++++++++++++++
 test/corpora/mangling/mixed-up.eml | 33 ++++++++++++++++++++++++++++++
 2 files changed, 61 insertions(+)
 create mode 100755 test/T351-pgpmime-mangling.sh
 create mode 100644 test/corpora/mangling/mixed-up.eml

diff --git a/test/T351-pgpmime-mangling.sh b/test/T351-pgpmime-mangling.sh
new file mode 100755
index 00000000..17f94a31
--- /dev/null
+++ b/test/T351-pgpmime-mangling.sh
@@ -0,0 +1,28 @@
+#!/usr/bin/env bash
+test_description='PGP/MIME message mangling'
+. $(dirname "$0")/test-lib.sh || exit 1
+add_email_corpus mangling
+test_begin_subtest "handle 'Mixed-Up' mangled PGP/MIME message"
+output=$(notmuch show --format=json --decrypt=true id:mixed-up at mangling.notmuchmail.org)
+test_json_nodes <<<"$output" \
+                'body:[0][0][0]["body"][0]["content"][1]["content"]="The password is \"abcd1234!\", please do not tell anyone.\n"'
+test_begin_subtest "repaired 'Mixed-up' messages can be found with index.repaired=mixedup"
+output=$(notmuch search --output=messages property:index.repaired=mixedup)
+test_expect_equal "$output" id:mixed-up at mangling.notmuchmail.org
+test_begin_subtest "reindex 'Mixed-Up' mangled PGP/MIME message"
+test_expect_success 'notmuch reindex --decrypt=true id:mixed-up at mangling.notmuchmail.org'
+test_begin_subtest "search cleartext of 'Mixed-Up' mangled PGP/MIME message"
+output=$(notmuch search --output=messages body:password)
+test_expect_equal "$output" id:mixed-up at mangling.notmuchmail.org
diff --git a/test/corpora/mangling/mixed-up.eml b/test/corpora/mangling/mixed-up.eml
new file mode 100644
index 00000000..a09f6191
--- /dev/null
+++ b/test/corpora/mangling/mixed-up.eml
@@ -0,0 +1,33 @@
+From: test_suite at notmuchmail.org
+To: test_suite at notmuchmail.org
+Subject: Here is the password
+Date: Sat, 01 Jan 2000 12:00:00 +0000
+Message-ID: <mixed-up at mangling.notmuchmail.org>
+MIME-Version: 1.0
+Content-Type: multipart/mixed; boundary="=-=-="
+Content-Type: text/plain; charset="us-ascii"
+Content-Transfer-Encoding: quoted-printable
+Content-Type: application/pgp-encrypted
+Content-Transfer-Encoding: base64
+Content-Type: application/octet-stream
+Content-Transfer-Encoding: base64

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