First shot of an E2EE plugin interface

Features:
- Decryption by default once the plugin is loaded if messages contains
the right EME magic
- Encryption of messages only if encryption is enabled for the current
tab

Missing pieces:
- No special treatment done on the order of the treatment for messages
yet
- No special handling of non-Partial(/Full) Stanza Encryption yet (i.e.,
removing stuff other than <body/>)

Signed-off-by: Maxime “pep” Buquet <pep@bouah.net>

plugins/b64.py

@@ -0,0 +1,50 @@
+#! /usr/bin/env python3
+# -*- coding: utf-8 -*-
+# vim:fenc=utf-8
+#
+# Copyright © 2019 Maxime “pep” Buquet <pep@bouah.net>
+#
+# Distributed under terms of the zlib license.
+
+"""
+Usage
+-----
+
+Base64 encryption plugin.
+
+This plugin also respects security guidelines listed in XEP-0419.
+
+.. glossary::
+    /b64
+        **Usage:** ``/b64``
+
+        This command enables encryption of outgoing messages for the current
+        tab.
+"""
+
+from base64 import b64decode, b64encode
+from poezio.plugin_e2ee import E2EEPlugin
+from slixmpp import Message
+
+
+class Plugin(E2EEPlugin):
+    """Base64 Plugin"""
+
+    encryption_name = 'base64'
+    encryption_short_name = 'b64'
+    eme_ns = 'urn:xmpps:base64:0'
+
+    def decrypt(self, message: Message, _tab) -> None:
+        """
+            Decrypt base64
+        """
+        body = message['body']
+        message['body'] = b64decode(body.encode()).decode()
+
+    def encrypt(self, message: Message, _tab) -> None:
+        """
+            Encrypt to base64
+        """
+        # TODO: Stop using <body/> for this. Put the encoded payload in another element.
+        body = message['body']
+        message['body'] = b64encode(body.encode()).decode()

poezio/plugin_e2ee.py

@@ -0,0 +1,155 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+# vim:fenc=utf-8 et ts=4 sts=4 sw=4
+#
+# Copyright © 2019 Maxime “pep” Buquet <pep@bouah.net>
+#
+# Distributed under terms of the zlib license. See COPYING file.
+
+"""
+    Interface for E2EE (End-to-end Encryption) plugins.
+"""
+
+from typing import Optional, Union
+
+from slixmpp import InvalidJID, JID, Message
+from poezio.tabs import ConversationTab, DynamicConversationTab, PrivateTab, MucTab
+from poezio.plugin import BasePlugin
+
+import logging
+log = logging.getLogger(__name__)
+
+
+ChatTabs = Union[
+    MucTab,
+    DynamicConversationTab,
+    PrivateTab,
+]
+
+
+class E2EEPlugin(BasePlugin):
+    """Interface for E2EE plugins"""
+
+    # At least one of encryption_name and encryption_short_name must be set
+    encryption_name = None  # type: Optional[str]
+    encryption_short_name = None  # type: Optional[str]
+
+    # Required.
+    eme_ns = None  # type: Optional[str]
+
+    def init(self):
+        if self.encryption_name is None and self.encryption_short_name is None:
+            raise NotImplementedError
+
+        if self.eme_ns is None:
+            raise NotImplementedError
+
+        if self.encryption_name is None:
+            self.encryption_name = self.encryption_short_name
+        if self.encryption_short_name is None:
+            self.encryption_short_name = self.encryption_name
+
+        self.api.add_event_handler('muc_msg', self._decrypt)
+        self.api.add_event_handler('muc_say', self._encrypt)
+        self.api.add_event_handler('conversation_msg', self._decrypt)
+        self.api.add_event_handler('conversation_say', self._encrypt)
+        self.api.add_event_handler('private_msg', self._decrypt)
+        self.api.add_event_handler('private_say', self._encrypt)
+
+        self._enabled_tabs = set()
+
+        for tab_t in (DynamicConversationTab, PrivateTab, MucTab):
+            self.api.add_tab_command(
+                tab_t,
+                self.encryption_short_name,
+                self._toggle_tab,
+                usage='',
+                short='Toggle {} encryption for tab.'.format(self.encryption_name),
+                help='Toggle automatic {} encryption for tab.'.format(self.encryption_name),
+            )
+
+        ConversationTab.add_information_element(
+            self.encryption_short_name,
+            self._display_encryption_status,
+        )
+        MucTab.add_information_element(
+            self.encryption_short_name,
+            self._display_encryption_status,
+        )
+        PrivateTab.add_information_element(
+            self.encryption_short_name,
+            self._display_encryption_status,
+        )
+
+    def cleanup(self):
+        ConversationTab.remove_information_element(self.encryption_short_name)
+        MucTab.remove_information_element(self.encryption_short_name)
+        PrivateTab.remove_information_element(self.encryption_short_name)
+
+    def _display_encryption_status(self, jid_s: str) -> str:
+        """
+            Return information to display in the infobar if encryption is
+            enabled for the JID.
+        """
+
+        try:
+            jid = JID(jid_s)
+        except InvalidJID:
+            return ""
+
+        if jid in self._enabled_tabs:
+            return self.encryption_short_name
+        return ""
+
+    def _toggle_tab(self, _input: str) -> None:
+        jid = self.api.current_tab().jid  # type: JID
+
+        if jid in self._enabled_tabs:
+            self._enabled_tabs.remove(jid)
+            self.api.information(
+                '{} encryption disabled for {}'.format(self.encryption_name, jid),
+                'Info',
+            )
+        else:
+            self._enabled_tabs.add(jid)
+            self.api.information(
+                '{} encryption enabled for {}'.format(self.encryption_name, jid),
+                'Info',
+            )
+
+    def _decrypt(self, message: Message, tab: ChatTabs) -> None:
+        if message['eme'] is None:
+            return None
+
+        if message['eme']['namespace'] != self.eme_ns:
+            return None
+
+        log.debug('Received %s message: %r', self.encryption_name, message['body'])
+
+        self.decrypt(message, tab)
+
+        log.debug('Decrypted %s message: %r', self.encryption_name, message['body'])
+        return None
+
+    def _encrypt(self, message: Message, tab: ChatTabs):
+        jid = tab.jid
+        if jid not in self._enabled_tabs:
+            return None
+
+        log.debug('Sending %s message: %r', self.encryption_name, message['body'])
+
+        message['eme']['namespace'] = self.eme_ns
+        message['eme']['name'] = self.encryption_name
+
+        self.encrypt(message, tab)
+
+        log.debug('Decrypted %s message: %r', self.encryption_name, message['body'])
+        return None
+
+    def decrypt(self, _message: Message, tab: ChatTabs):
+        """Decryption method"""
+        raise NotImplementedError
+
+    def encrypt(self, _message: Message, tab: ChatTabs):
+        """Encryption method"""
+        raise NotImplementedError