gajim-otrplugin/modules/otr.py

## Copyright (C) 2008-2012 Kjell Braden <afflux@pentabarf.de>
## Copyright (C) 2019 Pavel R. <pd at narayana dot im>
#

# This file is part of Gajim OTR Plugin.
#
# Gajim OTR Plugin is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published
# by the Free Software Foundation; version 3 only.
#
# This software 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 General Public License for more details.
#
# You can always obtain full license text at <http://www.gnu.org/licenses/>.

name = 'OTR' 
zeroconf =  None
ENCRYPTION_NAME = 'OTR'
ERROR = None
OTR =  {
    'PROTOCOL': 'XMPP',
    'MMS': 1000,
    'POLICY': {
        'REQUIRE_ENCRYPTION': True,
        'ALLOW_V1': False,
        'ALLOW_V2': True,
        'SEND_TAG': True,
        'WHITESPACE_START_AKE': True,
        'ERROR_START_AKE': True,
    }
}    

import os
from collections import namedtuple
from nbxmpp.structs import StanzaHandler
from nbxmpp.protocol import Message, JID
from nbxmpp.const import MessageType
from gajim.common import app 
from gajim.common import configpaths
from gajim.common.nec import NetworkEvent 
from gajim.common.const import EncryptionData 
from gajim.common.modules.base import BaseModule
from gajim.plugins.plugins_i18n import _
from otrplugin.keystore import Keystore
try: 
    import potr as otr
except: 
    ERROR = 'Unable to import python-otr (python3-potr)'


#  otr channel prototype #
class OTRChannel(otr.context.Context):
    global OTR
    
    # init OTR channel here
    def __init__(self, account, peer):
        super(OTRChannel, self).__init__(account, peer)
        self.peer = peer 
        self.resend = [] 
        self.defaultQuery = account.getDefaultQueryMessage(self.getPolicy)
        self.trustName = peer.getBare() 
        self.println = lambda line: account.otrmodule.get_control(peer).conv_textview.print_conversation_line(line, 'status', '', None)

    # send message to jabber network
    def inject(self, msg, appdata=None):
        stanza = Message(to=self.peer, body=msg.decode(), typ='chat')
        stanza.setThread(appdata.get('thread')) if appdata and appdata.get('thread') else None
        self.user.otrmodule.stream.send_stanza(stanza)
    
    # we can catch state change here
    def setState(self, newstate):
        state, self.state = self.state, newstate 
        if self.getCurrentTrust() is None: # new fingerprint
            self.setCurrentTrust(0)
            self.println("OTR: new fingerprint received [%s]" % self.getCurrentKey())
        if newstate == otr.context.STATE_ENCRYPTED and state != newstate:  # channel established
            self.println("OTR: %s encrypted conversation started [%s]" % (self.getCurrentTrust() and 'trusted' or '**untrusted**', self.getCurrentKey()) )
        elif newstate == otr.context.STATE_FINISHED and state != newstate:  # channel closed 
            self.println("OTR: encrypted conversation closed") 
            
    def getPolicy(self, key):
        return OTR['POLICY'][key] if key in OTR['POLICY'] else None
    

# otr account prototype
class OTRAccount(otr.context.Account):
    global OTR 
    contextclass = OTRChannel

    # init otrfor gajim acct 
    def __init__(self, otrmodule):
        super(OTRAccount, self).__init__(otrmodule.jid, OTR['PROTOCOL'], OTR['MMS'])
        self.jid = otrmodule.jid
        self.keystore = otrmodule.keystore
        self.otrmodule = otrmodule 
        self.loadTrusts()

    def loadPrivkey(self):
        my = self.keystore.load({'jid': str(self.jid)})
        return otr.crypt.PK.parsePrivateKey(bytes.fromhex(my.privatekey))[0] if my and my.privatekey else None
    
    def savePrivkey(self):
        return self.keystore.save({'jid': self.jid, 'privatekey': self.getPrivkey().serializePrivateKey().hex()})
    
    def loadTrusts(self):
        for c in self.keystore.load(): self.setTrust(c.jid, c.fingerprint, c.trust)
    
    def saveTrusts(self):
        for jid, keys in self.trusts.items(): 
            for fingerprint, trust in keys.items(): self.keystore.save({'jid': jid, 'fingerprint': fingerprint, 'trust': trust})
                

# Module name
class OTRModule(BaseModule):

    def __init__(self, con):
        BaseModule.__init__(self, con)
        self.handlers = [ 
            StanzaHandler(name='message', callback=self.receive_message, priority=9), 
        ]
        self.jid = self._con.get_own_jid() # JID
        self.stream = self._con # XMPP stream
        self.keystore = Keystore(os.path.join(configpaths.get('MY_DATA'), 'otr_' + self.jid.getBare()))  # Key storage
        self.otr = OTRAccount(self) # OTR object
        self.channels = {}
        self.controls = {}
    
    # get chat control for <peer>
    def get_control(self, peer):
        return self.controls.setdefault(peer, app.interface.msg_win_mgr.get_control(peer.getBare(), self._account))
    
    # get otr channel for <peer>
    def get_channel(self, peer):
        self.channels.get(peer) and self.channels[peer].state == otr.context.STATE_FINISHED and self.channels.pop(peer).disconnect()        
        return self.channels.setdefault(peer, self.otr.getContext(peer))

    # receive and decrypt message 
    def receive_message(self, con, stanza, message):
        if message.type != MessageType.CHAT or not stanza.getBody() or stanza.getBody().encode().find(otr.proto.OTRTAG) == -1: return # it is not OTR message 
        if message.is_mam_message:  return stanza.setBody('')  # it is OTR message from archive, we can not decrypt it 
        self._log.debug('got otr message: %s' % stanza) # everything is fine, we can try to decrypt it 
        try:
            channel = self.get_channel(stanza.getFrom())
            text, tlvs = channel.receiveMessage(stanza.getBody().encode(), {'thread': stanza.getThread()})
            stanza.setBody(text and text.decode() or '')
            message.encrypted = EncryptionData({'name':'OTR'})
        except otr.context.UnencryptedMessage:
            channel.println("OTR: received plain message [%s]" % stanza.getBody())
            self._log.error('** got plain text over encrypted channel ** %s' % stanza.getBody())
        except otr.context.ErrorReceived as e:
            channel.println("OTR: received error [%s]" % e)
            self._log.error('** otr error ** %s' % e)
        except otr.crypt.InvalidParameterError:
            channel.println("OTR: received unreadable message (session expired?)")
            self._log.error('** unreadable message **')
        except otr.context.NotEncryptedError:
            channel.println("OTR: session lost")
            self._log.error('** otr channel lost **')
        channel.resend and channel.state == otr.context.STATE_ENCRYPTED and channel.sendMessage(otr.context.FRAGMENT_SEND_ALL, **(channel.resend.pop()))  # resend any spooled messages
        return

    # encrypt and send message 
    def encrypt_message(self, obj, callback):
        self._log.warning('sending otr message: %s ' % obj.msg_iq)
        try:
            peer = obj.msg_iq.getTo()
            channel = self.get_channel(peer)
            session = obj.session or self.stream.make_new_session(peer)
            message = obj.message.encode()
            encrypted = channel.sendMessage(otr.context.FRAGMENT_SEND_ALL_BUT_LAST, message, appdata = {'thread': session.thread_id}) or b''
            encrypted == channel.defaultQuery and channel.resend.append({'msg': message, 'appdata': {'thread': session.thread_id}})
        except otr.context.NotEncryptedError:
            self._log.warning('message was not sent.')
            return
        
        obj.encrypted = 'OTR'
        obj.additional_data['encrypted'] = {'name': 'OTR'}
        obj.msg_iq.setBody(encrypted.decode())
        callback(obj)

    
def get_instance(*args, **kwargs):
    return OTRModule(*args, **kwargs), name