--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/sat/memory/encryption.py	Sun Jul 29 19:22:56 2018 +0200
@@ -0,0 +1,119 @@
+#!/usr/bin/env python2
+# -*- coding: utf-8 -*-
+
+# SAT: a jabber client
+# Copyright (C) 2009-2018 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 sat.core.i18n import _
+from sat.core.constants import Const as C
+from sat.core import exceptions
+from collections import namedtuple
+from sat.core.log import getLogger
+log = getLogger(__name__)
+
+
+EncryptionPlugin = namedtuple("EncryptionPlugin", ("instance",
+                                                   "name",
+                                                   "namespace",
+                                                   "priority"))
+
+
+class EncryptionHandler(object):
+    """Class to handle encryption sessions for a client"""
+    plugins = []  # plugin able to encrypt messages
+
+    def __init__(self, host):
+        self._sessions = {}  # bare_jid ==> encryption_data
+
+    @classmethod
+    def registerPlugin(cls, plg_instance, name, namespace, priority=0):
+        """Register a plugin handling an encryption algorithm
+
+        @param plg_instance(object): instance of the plugin
+            it must have the following methods:
+                - startEncryption(jid.JID): start an encryption session with a bare jid
+                - stopEncryption(jid.JID): stop an encryption session with a bare jid
+        @param name(unicode): human readable name of the encryption alrgorithm
+        @param namespace(unicode): namespace of the encryption algorithm
+        @param priority(int): priority of this plugin to encrypt an message when not
+            selected manually
+        """
+        existing_ns = [p.namespace for p in cls.plugins]
+        if namespace in existing_ns:
+            raise exceptions.ConflictError("A plugin with this namespace already exists!")
+        plg = EncryptionPlugin(
+            instance=plg_instance,
+            name=name,
+            namespace=namespace,
+            priority=priority)
+        cls.plugins.append(plg)
+        cls.plugins.sort(key=lambda p: p.priority)
+
+    def start(self, entity, namespace=None):
+        """Start an encrypted session with an entity
+
+        @param entity(jid.JID): entity to start an encrypted session with
+            must be bare jid is the algorithm encrypt for all devices
+        @param namespace(unicode, None): namespace of the encryption algorithm to use
+            None to select automatically an algorithm
+        """
+        if not self.plugins:
+            raise exceptions.NotFound(_(u"No encryption plugin is registered, "
+                                        u"an encryption session can't be started"))
+
+        bare_jid = entity.userhostJID()
+        if bare_jid in self._sessions:
+            plg = self._sessions[bare_jid]['plugin']
+
+            msg = (_(u"Session with {bare_jid} is already encrypted with {name}."
+                     u"Please stop encryption session before changing algorithm.")
+                   .format(bare_jid=bare_jid, name=plg.name))
+            log.warning(msg)
+            raise exceptions.ConflictError(msg)
+
+        if namespace is None:
+            plg = self.plugins[0]
+        else:
+            try:
+                plg = next(p for p in self.plugins if p.namespace == namespace)
+            except StopIteration:
+                raise exceptions.NotFound(_(
+                    u"Can't find requested encryption plugin: {namespace}").format(
+                        namespace=namespace))
+
+        data = {"plugin": plg}
+        if entity.resource:
+            # indicate that we encrypt only for some devices
+            data['directed_devices'] = [entity.resource]
+
+        self._sessions[entity.userhostJID()] = data
+        log.info(_(u"Encryption session as been set for {bare_jid} with "
+                   u"{encryption_name}").format(
+                   bare_jid=bare_jid.userhost(), encryption_name=plg.name))
+
+    ## Triggers ##
+
+    def setEncryptionFlag(self, mess_data):
+        """Set "encryption" key in mess_data if session with destinee is encrypted"""
+
+        if mess_data["type"] == "groupchat":
+            # FIXME: to change when group chat encryption will be handled
+            return
+
+        to_jid = mess_data['to']
+        encryption = self._sessions.get(to_jid.userhostJID())
+        if encryption is not None:
+            mess_data[C.MESS_KEY_ENCRYPTION] = encryption