--- a/sat/core/sat_main.py	Fri Mar 27 09:55:16 2020 +0100
+++ b/sat/core/sat_main.py	Fri Mar 27 10:02:14 2020 +0100
@@ -882,7 +882,8 @@
     def _encryptionTrustUIGet(self, to_jid_s, namespace, profile_key):
         client = self.getClient(profile_key)
         to_jid = jid.JID(to_jid_s)
-        d = client.encryption.getTrustUI(to_jid, namespace=namespace or None)
+        d = defer.ensureDeferred(
+            client.encryption.getTrustUI(to_jid, namespace=namespace or None))
         d.addCallback(lambda xmlui: xmlui.toXml())
         return d
 

--- a/sat/plugins/plugin_xep_0384.py	Fri Mar 27 09:55:16 2020 +0100
+++ b/sat/plugins/plugin_xep_0384.py	Fri Mar 27 10:02:14 2020 +0100
@@ -16,6 +16,11 @@
 # You should have received a copy of the GNU Affero General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
+import logging
+import random
+import base64
+from functools import partial
+from xml.sax.saxutils import quoteattr
 from sat.core.i18n import _, D_
 from sat.core.constants import Const as C
 from sat.core.log import getLogger
@@ -25,11 +30,7 @@
 from twisted.words.protocols.jabber import jid
 from twisted.words.protocols.jabber import error as jabber_error
 from sat.memory import persistent
-from functools import partial
 from sat.tools import xml_tools
-import logging
-import random
-import base64
 try:
     import omemo
     from omemo import exceptions as omemo_excpt
@@ -69,6 +70,11 @@
 KEY_DEVICE_ID = "DEVICE_ID"
 KEY_SESSION = "SESSION"
 KEY_TRUST = "TRUST"
+# devices which have been automatically trusted by policy like BTBV
+KEY_AUTO_TRUST = "AUTO_TRUST"
+# list of peer bare jids where trust UI has been used at least once
+# this is useful to activate manual trust with BTBV policy
+KEY_MANUAL_TRUST = "MANUAL_TRUST"
 KEY_ACTIVE_DEVICES = "DEVICES"
 KEY_INACTIVE_DEVICES = "INACTIVE_DEVICES"
 KEY_ALL_JIDS = "ALL_JIDS"
@@ -76,6 +82,9 @@
 # expressed in seconds, reset on each new MUC message
 MUC_CACHE_TTL = 60 * 5
 
+PARAM_CATEGORY = "Security"
+PARAM_NAME = "omemo_policy"
+
 
 # we want to manage log emitted by omemo module ourselves
 
@@ -111,15 +120,11 @@
 
 class OmemoStorage(omemo.Storage):
 
-    def __init__(self, client, device_id, all_jids, persistent_dict):
-        """
-        @param persistent_dict(persistent.LazyPersistentBinaryDict): object which will
-            store data in SàT database
-        """
+    def __init__(self, client, device_id, all_jids):
         self.own_bare_jid_s = client.jid.userhost()
         self.device_id = device_id
         self.all_jids = all_jids
-        self.data = persistent_dict
+        self.data = client._xep_0384_data
 
     @property
     def is_async(self):
@@ -262,7 +267,7 @@
         return d
 
     def deleteJID(self, callback, bare_jid):
-        """Retrieve all (in)actives of bare_jid, and delete all related keys"""
+        """Retrieve all (in)actives devices of bare_jid, and delete all related keys"""
         d_list = []
 
         key = '\n'.join([KEY_ACTIVE_DEVICES, bare_jid])
@@ -392,6 +397,27 @@
 
 class OMEMO:
 
+    params = """
+    <params>
+    <individual>
+    <category name="{category_name}" label="{category_label}">
+        <param name="{param_name}" label={param_label} type="list" security="3">
+            <option value="manual" label={opt_manual_lbl} />
+            <option value="btbv" label={opt_btbv_lbl} selected="true" />
+        </param>
+     </category>
+    </individual>
+    </params>
+    """.format(
+        category_name=PARAM_CATEGORY,
+        category_label=D_("Security"),
+        param_name=PARAM_NAME,
+        param_label=quoteattr(D_("OMEMO default trust policy")),
+        opt_manual_lbl=quoteattr(D_("Manual trust (more secure)")),
+        opt_btbv_lbl=quoteattr(
+            D_("Blind Trust Before Verification (more user friendly)")),
+    )
+
     def __init__(self, host):
         log.info(_("OMEMO plugin initialization (omemo module v{version})").format(
             version=omemo.__version__))
@@ -402,6 +428,7 @@
                 "minimum required, please update.").format(v=OMEMO_MIN_VER))
             raise exceptions.CancelError("module is too old")
         self.host = host
+        host.memory.updateParams(self.params)
         self._p_hints = host.plugins["XEP-0334"]
         self._p_carbons = host.plugins["XEP-0280"]
         self._p = host.plugins["XEP-0060"]
@@ -450,22 +477,55 @@
         self.text_cmds.feedBack(client, feedback, mess_data)
         return False
 
-    @defer.inlineCallbacks
-    def trustUICb(self, xmlui_data, trust_data, expect_problems=None,
-                  profile=C.PROF_KEY_NONE):
+    async def trustUICb(
+            self, xmlui_data, trust_data, expect_problems=None, profile=C.PROF_KEY_NONE):
         if C.bool(xmlui_data.get('cancelled', 'false')):
-            defer.returnValue({})
+            return {}
         client = self.host.getClient(profile)
         session = client._xep_0384_session
+        stored_data = client._xep_0384_data
+        manual_trust = await stored_data.get(KEY_MANUAL_TRUST, set())
+        auto_trusted_cache = {}
         answer = xml_tools.XMLUIResult2DataFormResult(xmlui_data)
+        blind_trust = C.bool(answer.get('blind_trust', C.BOOL_FALSE))
         for key, value in answer.items():
             if key.startswith('trust_'):
                 trust_id = key[6:]
             else:
                 continue
             data = trust_data[trust_id]
+            if blind_trust:
+                # user request to restore blind trust for this entity
+                # so if the entity is present in manual trust, we remove it
+                if data["jid"].full() in manual_trust:
+                    manual_trust.remove(data["jid"].full())
+                    await stored_data.aset(KEY_MANUAL_TRUST, manual_trust)
+            elif data["jid"].full() not in manual_trust:
+                # validating this trust UI implies that we activate manual mode for
+                # this entity (used for BTBV policy)
+                manual_trust.add(data["jid"].full())
+                await stored_data.aset(KEY_MANUAL_TRUST, manual_trust)
             trust = C.bool(value)
-            yield session.setTrust(
+
+            if not trust:
+                # if device is not trusted, we check if it must be removed from auto
+                # trusted devices list
+                bare_jid_s = data['jid'].userhost()
+                key = f"{KEY_AUTO_TRUST}\n{bare_jid_s}"
+                if bare_jid_s not in auto_trusted_cache:
+                    auto_trusted_cache[bare_jid_s] = await stored_data.get(
+                        key, default=set())
+                auto_trusted = auto_trusted_cache[bare_jid_s]
+                if data['device'] in auto_trusted:
+                    # as we don't trust this device anymore, we can remove it from the
+                    # list of automatically trusted devices
+                    auto_trusted.remove(data['device'])
+                    await stored_data.aset(key, auto_trusted)
+                    log.info(D_(
+                        "device {device} from {peer_jid} is not an auto-trusted device "
+                        "anymore").format(device=data['device'], peer_jid=bare_jid_s))
+
+            await session.setTrust(
                 data["jid"],
                 data["device"],
                 data["ik"],
@@ -475,10 +535,9 @@
                 expect_problems.setdefault(data['jid'].userhost(), set()).add(
                     data['device']
                 )
-        defer.returnValue({})
+        return {}
 
-    @defer.inlineCallbacks
-    def getTrustUI(self, client, entity_jid=None, trust_data=None, submit_id=None):
+    async def getTrustUI(self, client, entity_jid=None, trust_data=None, submit_id=None):
         """Generate a XMLUI to manage trust
 
         @param entity_jid(None, jid.JID): jid of entity to manage
@@ -502,6 +561,7 @@
             raise ValueError("A bare jid is expected")
 
         session = client._xep_0384_session
+        stored_data = client._xep_0384_data
 
         if trust_data is None:
             cache = client._xep_0384_cache.setdefault(entity_jid, {})
@@ -511,14 +571,14 @@
             else:
                 trust_jids = [entity_jid]
             for trust_jid in trust_jids:
-                trust_session_data = yield session.getTrustForJID(trust_jid)
+                trust_session_data = await session.getTrustForJID(trust_jid)
                 bare_jid_s = trust_jid.userhost()
                 for device_id, trust_info in trust_session_data['active'].items():
                     if trust_info is None:
                         # device has never been (un)trusted, we have to retrieve its
                         # fingerprint (i.e. identity key or "ik") through public bundle
                         if device_id not in cache:
-                            bundles, missing = yield self.getBundles(client,
+                            bundles, missing = await self.getBundles(client,
                                                                      trust_jid,
                                                                      [device_id])
                             if device_id not in bundles:
@@ -545,10 +605,11 @@
                         }
 
         if submit_id is None:
-            submit_id = self.host.registerCallback(partial(self.trustUICb,
-                                                           trust_data=trust_data),
-                                                   with_data=True,
-                                                   one_shot=True)
+            submit_id = self.host.registerCallback(
+                lambda data, profile: defer.ensureDeferred(
+                    self.trustUICb(data, trust_data=trust_data, profile=profile)),
+                with_data=True,
+                one_shot=True)
         xmlui = xml_tools.XMLUI(
             panel_type = C.XMLUI_FORM,
             title = D_("OMEMO trust management"),
@@ -573,8 +634,25 @@
         xmlui.addEmpty()
         xmlui.addEmpty()
 
+        if entity_jid is not None:
+            omemo_policy = self.host.memory.getParamA(
+                PARAM_NAME, PARAM_CATEGORY, profile_key=client.profile
+            )
+            if omemo_policy == 'btbv':
+                xmlui.addLabel(D_("Automatically trust new devices?"))
+                # blind trust is always disabled when UI is requested
+                # as submitting UI is a verification which should disable it.
+                xmlui.addBool("blind_trust", value=C.BOOL_FALSE)
+                xmlui.addEmpty()
+                xmlui.addEmpty()
+
+        auto_trust_cache = {}
 
         for trust_id, data in trust_data.items():
+            bare_jid_s = data['jid'].userhost()
+            if bare_jid_s not in auto_trust_cache:
+                key = f"{KEY_AUTO_TRUST}\n{bare_jid_s}"
+                auto_trust_cache[bare_jid_s] = await stored_data.get(key, set())
             xmlui.addLabel(D_("Contact"))
             xmlui.addJid(data['jid'])
             xmlui.addLabel(D_("Device ID"))
@@ -586,11 +664,15 @@
             xmlui.addLabel(D_("Trust this device?"))
             xmlui.addBool("trust_{}".format(trust_id),
                           value=C.boolConst(data.get('trusted', False)))
+            if data['device'] in auto_trust_cache[bare_jid_s]:
+                xmlui.addEmpty()
+                xmlui.addLabel(D_("(automatically trusted)"))
+
 
             xmlui.addEmpty()
             xmlui.addEmpty()
 
-        defer.returnValue(xmlui)
+        return xmlui
 
     @defer.inlineCallbacks
     def profileConnected(self, client):
@@ -607,6 +689,7 @@
         client._xep_0384_ready = defer.Deferred()
         # we first need to get devices ids (including our own)
         persistent_dict = persistent.LazyPersistentBinaryDict("XEP-0384", client.profile)
+        client._xep_0384_data = persistent_dict
         # all known devices of profile
         devices = yield self.getDevices(client)
         # and our own device id
@@ -630,7 +713,7 @@
 
         all_jids = yield persistent_dict.get(KEY_ALL_JIDS, set())
 
-        omemo_storage = OmemoStorage(client, device_id, all_jids, persistent_dict)
+        omemo_storage = OmemoStorage(client, device_id, all_jids)
         omemo_session = yield OmemoSession.create(client, omemo_storage, device_id)
         client._xep_0384_cache = {}
         client._xep_0384_session = omemo_session
@@ -862,8 +945,59 @@
 
     ## triggers
 
-    @defer.inlineCallbacks
-    def handleProblems(self, client, feedback_jid, bundles, expect_problems, problems):
+    async def policyBTBV(self, client, feedback_jid, expect_problems, undecided):
+        session = client._xep_0384_session
+        stored_data = client._xep_0384_data
+        for pb in undecided.values():
+            peer_jid = jid.JID(pb.bare_jid)
+            device = pb.device
+            ik = pb.ik
+            key = f"{KEY_AUTO_TRUST}\n{pb.bare_jid}"
+            auto_trusted = await stored_data.get(key, default=set())
+            auto_trusted.add(device)
+            await stored_data.aset(key, auto_trusted)
+            await session.setTrust(peer_jid, device, ik, True)
+
+        user_msg =  D_(
+            "Not all destination devices are trusted, unknown devices will be blind "
+            "trusted due to the OMEMO Blind Trust Before Verification policy. If you "
+            "want a more secure workflow, please activate \"manual\" OMEMO policy in "
+            "settings' \"Security\" tab.\nFollowing fingerprint have been automatically "
+            "trusted:\n{devices}"
+        ).format(
+            devices = ', '.join(
+                f"- {pb.device} ({pb.bare_jid}): {pb.ik.hex().upper()}"
+                for pb in undecided.values()
+            )
+        )
+        client.feedback(feedback_jid, user_msg)
+
+    async def policyManual(self, client, feedback_jid, expect_problems, undecided):
+        trust_data = {}
+        for trust_id, data in undecided.items():
+            trust_data[trust_id] = {
+                'jid': jid.JID(data.bare_jid),
+                'device':  data.device,
+                'ik': data.ik}
+
+        user_msg =  D_("Not all destination devices are trusted, we can't encrypt "
+                       "message in such a situation. Please indicate if you trust "
+                       "those devices or not in the trust manager before we can "
+                       "send this message")
+        client.feedback(feedback_jid, user_msg)
+        xmlui = await self.getTrustUI(client, trust_data=trust_data, submit_id="")
+
+        answer = await xml_tools.deferXMLUI(
+            self.host,
+            xmlui,
+            action_extra={
+                "meta_encryption_trust": NS_OMEMO,
+            },
+            profile=client.profile)
+        await self.trustUICb(answer, trust_data, expect_problems, client.profile)
+
+    async def handleProblems(
+        self, client, feedback_jid, bundles, expect_problems, problems):
         """Try to solve problems found by EncryptMessage
 
         @param feedback_jid(jid.JID): bare jid where the feedback message must be sent
@@ -910,7 +1044,7 @@
                 if problem.device in entity_cache:
                     entity_bundles[problem.device] = entity_cache[problem.device]
                 else:
-                    found_bundles, missing = yield self.getBundles(
+                    found_bundles, missing = await self.getBundles(
                         client, pb_entity, [problem.device])
                     entity_cache.update(bundles)
                     entity_bundles.update(found_bundles)
@@ -942,31 +1076,38 @@
                    peer=peer_jid.full(), devices=", ".join(devices_s)))
 
         if undecided:
-            trust_data = {}
-            for trust_id, data in undecided.items():
-                trust_data[trust_id] = {
-                    'jid': jid.JID(data.bare_jid),
-                    'device':  data.device,
-                    'ik': data.ik}
+            omemo_policy = self.host.memory.getParamA(
+                PARAM_NAME, PARAM_CATEGORY, profile_key=client.profile
+            )
+            if omemo_policy == 'btbv':
+                # we first separate entities which have been trusted manually
+                manual_trust = await client._xep_0384_data.get(KEY_MANUAL_TRUST)
+                if manual_trust:
+                    manual_undecided = {}
+                    for hash_, pb in undecided.items():
+                        if pb.bare_jid in manual_trust:
+                            manual_undecided[hash_] = pb
+                    for hash_ in manual_undecided:
+                        del undecided[hash_]
+                else:
+                    manual_undecided = None
 
-            user_msg =  D_("Not all destination devices are trusted, we can't encrypt "
-                           "message in such a situation. Please indicate if you trust "
-                           "those devices or not in the trust manager before we can "
-                           "send this message")
-            client.feedback(feedback_jid, user_msg)
-            xmlui = yield self.getTrustUI(client, trust_data=trust_data, submit_id="")
+                if undecided:
+                    # we do the automatic trust here
+                    await self.policyBTBV(
+                        client, feedback_jid, expect_problems, undecided)
+                if manual_undecided:
+                    # here user has to manually trust new devices from entities already
+                    # verified
+                    await self.policyManual(
+                        client, feedback_jid, expect_problems, manual_undecided)
+            elif omemo_policy == 'manual':
+                await self.policyManual(
+                    client, feedback_jid, expect_problems, undecided)
+            else:
+                raise exceptions.InternalError(f"Unexpected OMEMO policy: {omemo_policy}")
 
-            answer = yield xml_tools.deferXMLUI(
-                self.host,
-                xmlui,
-                action_extra={
-                    "meta_encryption_trust": NS_OMEMO,
-                },
-                profile=client.profile)
-            yield self.trustUICb(answer, trust_data, expect_problems, client.profile)
-
-    @defer.inlineCallbacks
-    def encryptMessage(self, client, entity_bare_jids, message, feedback_jid=None):
+    async def encryptMessage(self, client, entity_bare_jids, message, feedback_jid=None):
         if feedback_jid is None:
             if len(entity_bare_jids) != 1:
                 log.error(
@@ -985,14 +1126,14 @@
                     raise exceptions.InternalError(msg)
                 # encryptMessage may fail, in case of e.g. trust issue or missing bundle
                 try:
-                    encrypted = yield omemo_session.encryptMessage(
+                    encrypted = await omemo_session.encryptMessage(
                         entity_bare_jids,
                         message,
                         bundles,
                         expect_problems = expect_problems)
                 except omemo_excpt.EncryptionProblemsException as e:
                     # we know the problem to solve, we can try to fix them
-                    yield self.handleProblems(
+                    await self.handleProblems(
                         client,
                         feedback_jid=feedback_jid,
                         bundles=bundles,
@@ -1240,8 +1381,8 @@
             if self._sid is not None:
                 self._sid.addOriginId(message_elt, mess_data['uid'])
 
-        encryption_data = yield self.encryptMessage(
-            client, to_jids, body, feedback_jid=feedback_jid)
+        encryption_data = yield defer.ensureDeferred(self.encryptMessage(
+            client, to_jids, body, feedback_jid=feedback_jid))
 
         encrypted_elt = message_elt.addElement((NS_OMEMO, 'encrypted'))
         header_elt = encrypted_elt.addElement('header')