[bug] check if key is expired

For expired keys gnupg will not allow us to encrypt (to force it we'll
need to fake the system date). Let's bounce the email properly in this case,
and register the error.

Make sure as well that _encrypt_message does not return None, let's
raise exceptions in case of failure.

- Related: #8663

3 files changed, 124 insertions, 1 deletions

diff --git a/changes/next-changelog.txt b/changes/next-changelog.txt
index 2e13a84..4add2e4 100644
--- a/changes/next-changelog.txt
+++ b/changes/next-changelog.txt
@@ -15,6 +15,8 @@ Features
 
 Bugfixes
 ~~~~~~~~
+- `#8663 <https://0xacab.org/leap/leap_mx/issues/8663>`_: Bounce emails for expired keys
+
 - `#1235 <https://leap.se/code/issues/1235>`_: Description for the fixed stuff corresponding with issue #1235.
 - Bugfix without related issue number.
 
diff --git a/src/leap/mx/mail_receiver.py b/src/leap/mx/mail_receiver.py
index b200772..c8113c1 100644
--- a/src/leap/mx/mail_receiver.py
+++ b/src/leap/mx/mail_receiver.py
@@ -203,6 +203,13 @@ class MailReceiver(Service):
             gpg.import_keys(pubkey)
             key = gpg.list_keys().pop()
 
+            if key['expires']:
+                expires = datetime.fromtimestamp(int(key['expires']))
+                if expires < datetime.now():
+                    log.msg("_encrypt_message: the key is expired (%s), "
+                            "can't encrypt" % (str(expires),))
+                    raise Exception("Expired key")
+
             encryption_result = gpg.encrypt(
                 json.dumps(data, ensure_ascii=False),
                 key["fingerprint"],
@@ -211,7 +218,8 @@ class MailReceiver(Service):
             if not encryption_result.ok:
                 log.msg("_encrypt_message: Encryption failed with status: %r"
                         % (encryption_result.status,))
-                return None
+                raise Exception("Encryption failed: %r"
+                                % (encryption_result.status,))
 
             doc.content = {
                 self.INCOMING_KEY: True,
diff --git a/src/leap/mx/tests/test_mail_receiver.py b/src/leap/mx/tests/test_mail_receiver.py
index 6b274cd..68f8d0b 100644
--- a/src/leap/mx/tests/test_mail_receiver.py
+++ b/src/leap/mx/tests/test_mail_receiver.py
@@ -78,6 +78,8 @@ class MailReceiverTestCase(unittest.TestCase):
     def test_single_mail(self):
         msg, path = self.addMail("foo bar")
         uuid, doc = yield self.defer_put_doc
+        self.assertTrue("PGP MESSAGE" in doc.content['_enc_json'],
+                        "It's not encrypted")
         self.assertEqual(uuid, UUID)
         decmsg = self.decryptDoc(doc)
         self.assertEqual(msg, decmsg)
@@ -97,6 +99,23 @@ class MailReceiverTestCase(unittest.TestCase):
         self.assertTrue(os.path.exists(path))
 
     @defer.inlineCallbacks
+    def test_expired_key(self):
+        defer_bounce = defer.Deferred()
+
+        def bounce_mock(*args):
+            defer_bounce.callback(args)
+            return defer.succeed(None)
+
+        self.pubKey = EXPIRED_KEY
+        self.receiver._bounce_with_timeout = bounce_mock
+
+        msg, path = self.addMail("foo bar")
+        bpath, bmsg, berr = yield defer_bounce
+        self.assertEqual(path, bpath.path)
+        self.assertEqual(msg, bmsg.as_string())
+        self.assertEqual("Expired key", str(berr))
+
+    @defer.inlineCallbacks
     def test_misleading_encoding(self):
         msg, path = self.addMail(
             "ñáûä", headers={'Content-Transfer-Encoding': '7Bit'})
@@ -300,3 +319,97 @@ RZXoH+FTg9UAW87eqU610npOkT6cRaBxaMK/mDtGNdc=
 =JTFu
 -----END PGP PRIVATE KEY BLOCK-----
 """
+
+
+EXPIRED_FINGERPRINT = "7C1F68B0E14157B09B5F4ADE6F15F004A1885A7C"
+EXPIRED_KEY = """
+-----BEGIN PGP PUBLIC KEY BLOCK-----
+Version: GnuPG v1.4.12 (GNU/Linux)
+
+mQENBBvrfd0BCADGNpspaNhsbhSjKioCWrE2MTTYC+Sdpes22RabdhQyOCWvlSbj
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+Osuse7+NkyUHgMXMVW7cz+nU7iO+ht2rkBtv+Z5LGlzgHTeFjKci
+=WhX+
+-----END PGP PUBLIC KEY BLOCK-----
+"""
+EXPIRED_PRIVATE = """
+-----BEGIN PGP PRIVATE KEY BLOCK-----
+Version: GnuPG v1.4.12 (GNU/Linux)
+
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+=dZE8
+-----END PGP PRIVATE KEY BLOCK-----
+"""