--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libervia/backend/plugins/plugin_xep_0380.py	Fri Jun 02 11:49:51 2023 +0200
@@ -0,0 +1,102 @@
+#!/usr/bin/env python3
+
+
+# SAT plugin for Explicit Message Encryption
+# Copyright (C) 2009-2021 Jérôme Poisson (goffi@goffi.org)
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+
+# 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/>.
+
+from libervia.backend.core.i18n import _, D_
+from libervia.backend.core.constants import Const as C
+from libervia.backend.core.log import getLogger
+from twisted.words.protocols.jabber import jid
+
+log = getLogger(__name__)
+
+PLUGIN_INFO = {
+    C.PI_NAME: "Explicit Message Encryption",
+    C.PI_IMPORT_NAME: "XEP-0380",
+    C.PI_TYPE: "SEC",
+    C.PI_PROTOCOLS: ["XEP-0380"],
+    C.PI_DEPENDENCIES: [],
+    C.PI_MAIN: "XEP_0380",
+    C.PI_HANDLER: "no",
+    C.PI_DESCRIPTION: _("""Implementation of Explicit Message Encryption"""),
+}
+
+NS_EME = "urn:xmpp:eme:0"
+KNOWN_NAMESPACES = {
+    "urn:xmpp:otr:0": "OTR",
+    "jabber:x:encrypted": "Legacy OpenPGP",
+    "urn:xmpp:openpgp:0": "OpenPGP for XMPP",
+}
+
+
+class XEP_0380(object):
+
+    def __init__(self, host):
+        self.host = host
+        host.trigger.add("sendMessage", self._send_message_trigger)
+        host.trigger.add("message_received", self._message_received_trigger, priority=100)
+        host.register_namespace("eme", NS_EME)
+
+    def _add_eme_element(self, mess_data, namespace, name):
+        message_elt = mess_data['xml']
+        encryption_elt = message_elt.addElement((NS_EME, 'encryption'))
+        encryption_elt['namespace'] = namespace
+        if name is not None:
+            encryption_elt['name'] = name
+        return mess_data
+
+    def _send_message_trigger(self, client, mess_data, __, post_xml_treatments):
+        encryption = mess_data.get(C.MESS_KEY_ENCRYPTION)
+        if encryption is not None:
+            namespace = encryption['plugin'].namespace
+            if namespace not in KNOWN_NAMESPACES:
+                name = encryption['plugin'].name
+            else:
+                name = None
+            post_xml_treatments.addCallback(
+                self._add_eme_element, namespace=namespace, name=name)
+        return True
+
+    def _message_received_trigger(self, client, message_elt, post_treat):
+        try:
+            encryption_elt = next(message_elt.elements(NS_EME, 'encryption'))
+        except StopIteration:
+            return True
+
+        namespace = encryption_elt['namespace']
+        if namespace in client.encryption.get_namespaces():
+            # message is encrypted and we can decrypt it
+            return True
+
+        name = KNOWN_NAMESPACES.get(namespace, encryption_elt.getAttribute("name"))
+
+        # at this point, message is encrypted but we know that we can't decrypt it,
+        # we need to notify the user
+        sender_s = message_elt['from']
+        to_jid = jid.JID(message_elt['from'])
+        algorithm = "{} [{}]".format(name, namespace) if name else namespace
+        log.warning(
+            _("Message from {sender} is encrypted with {algorithm} and we can't "
+              "decrypt it.".format(sender=message_elt['from'], algorithm=algorithm)))
+
+        user_msg = D_(
+            "User {sender} sent you an encrypted message (encrypted with {algorithm}), "
+            "and we can't decrypt it.").format(sender=sender_s, algorithm=algorithm)
+
+        extra = {C.MESS_EXTRA_INFO: C.EXTRA_INFO_DECR_ERR}
+        client.feedback(to_jid, user_msg, extra)
+        return False