# Source code for poezio.plugin_e2ee

    #!/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 Callable, Dict, List, Optional, Union, Tuple, Set

    from slixmpp import InvalidJID, JID, Message
    from slixmpp.xmlstream import StanzaBase
    from poezio.tabs import (
        ChatTab,
        ConversationTab,
        DynamicConversationTab,
        MucTab,
        PrivateTab,
        StaticConversationTab,
    )
    from poezio.plugin import BasePlugin
    from poezio.theming import get_theme, dump_tuple
    from poezio.config import config
    from poezio.decorators import command_args_parser

    from asyncio import iscoroutinefunction

    import logging
    log = logging.getLogger(__name__)

    ChatTabs = Union[
        MucTab,
        DynamicConversationTab,
        StaticConversationTab,
        PrivateTab,
    ]

    EME_NS = 'urn:xmpp:eme:0'
    EME_TAG = 'encryption'

    JCLIENT_NS = 'jabber:client'
    HINTS_NS = 'urn:xmpp:hints'

    class NothingToEncrypt(Exception):
        """
        Exception to raise inside the _encrypt filter on stanzas that do not need
        to be processed.
        """

    class E2EEPlugin(BasePlugin):
        """Interface for E2EE plugins.

            This is a wrapper built on top of BasePlugin. It provides a base for
            End-to-end Encryption mechanisms in poezio.

            Plugin developers are excepted to implement the `decrypt` and
            `encrypt` function, provide an encryption name (and/or short name),
            and an eme namespace.

            Once loaded, the plugin will attempt to decrypt any message that
            contains an EME message that matches the one set.

            The plugin will also register a command (using the short name) to
            enable encryption per tab. It is only possible to have one encryption
            mechanism per tab, even if multiple e2ee plugins are loaded.

            The encryption status will be displayed in the status bar, using the
            plugin short name, alongside the JID, nickname etc.
        """

        #: Specifies that the encryption mechanism does more than encrypting
        #: `<body/>`.
        stanza_encryption = False

        #: Whitelist applied to messages when `stanza_encryption` is `False`.
        tag_whitelist = [
            (JCLIENT_NS, 'body'),
            (EME_NS, EME_TAG),
            (HINTS_NS, 'store'),
            (HINTS_NS, 'no-copy'),
            (HINTS_NS, 'no-store'),
            (HINTS_NS, 'no-permanent-store'),
            # TODO: Add other encryption mechanisms tags here
        ]

        #: Replaces body with `eme <https://xmpp.org/extensions/xep-0380.html>`_
        #: if set. Should be suitable for most plugins except those using
        #: `<body/>` directly as their encryption container, like OTR, or the
        #: example base64 plugin in poezio.
        replace_body_with_eme = True

        #: Encryption name, used in command descriptions, and logs. At least one
        #: of `encryption_name` and `encryption_short_name` must be set.
        encryption_name = None  # type: Optional[str]

        #: Encryption short name, used as command name, and also to display
        #: encryption status in a tab. At least one of `encryption_name` and
        #: `encryption_short_name` must be set.
        encryption_short_name = None  # type: Optional[str]

        #: Required. https://xmpp.org/extensions/xep-0380.html.
        eme_ns = None  # type: Optional[str]

        #: Used to figure out what messages to attempt decryption for. Also used
        #: in combination with `tag_whitelist` to avoid removing encrypted tags
        #: before sending.
        encrypted_tags = None  # type: Optional[List[Tuple[str, str]]]

        # Static map, to be able to limit to one encryption mechanism per tab at a
        # time
        _enabled_tabs = {}  # type: Dict[JID, Callable]

        # Tabs that support this encryption mechanism
        supported_tab_types = tuple()  # type: Tuple[ChatTabs]

        # States for each remote entity
        trust_states = {'accepted': set(), 'rejected': set()}  # type: Dict[str, Set[str]]

        def init(self):
            self._all_trust_states = self.trust_states['accepted'].union(
                self.trust_states['rejected']
            )
            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

            # Ensure decryption is done before everything, so that other handlers
            # don't have to know about the encryption mechanism.
            self.api.add_event_handler('muc_msg', self._decrypt, priority=0)
            self.api.add_event_handler('conversation_msg', self._decrypt, priority=0)
            self.api.add_event_handler('private_msg', self._decrypt, priority=0)

            # Ensure encryption is done after everything, so that whatever can be
            # encrypted is encrypted, and no plain element slips in.
            # Using a stream filter might be a bit too much, but at least we're
            # sure poezio is not sneaking anything past us.
            self.core.xmpp.add_filter('out', self._encrypt_wrapper)

            for tab_t in self.supported_tab_types:
                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),
                )

            trust_msg = 'Set {name} state to {state} for this fingerprint on this JID.'
            for state in self._all_trust_states:
                for tab_t in self.supported_tab_types:
                    self.api.add_tab_command(
                        tab_t,
                        self.encryption_short_name + '_' + state,
                        lambda args: self.__command_set_state_local(args, state),
                        usage='<fingerprint>',
                        short=trust_msg.format(name=self.encryption_short_name, state=state),
                        help=trust_msg.format(name=self.encryption_short_name, state=state),
                    )
                self.api.add_command(
                    self.encryption_short_name + '_' + state,
                    lambda args: self.__command_set_state_global(args, state),
                    usage='<JID> <fingerprint>',
                    short=trust_msg.format(name=self.encryption_short_name, state=state),
                    help=trust_msg.format(name=self.encryption_short_name, state=state),
                )

            self.api.add_command(
                self.encryption_short_name + '_fingerprint',
                self._command_show_fingerprints,
                usage='[jid]',
                short='Show %s fingerprint(s) for a JID.' % self.encryption_short_name,
                help='Show %s fingerprint(s) for a JID.' % self.encryption_short_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,
            )

            self.__load_encrypted_states()

        def __load_encrypted_states(self) -> None:
            """Load previously stored encryption states for jids."""
            for section in config.sections():
                value = config.get('encryption', section=section)
                if value and value == self.encryption_short_name:
                    self._enabled_tabs[section] = self.encrypt

        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 self._encryption_enabled(jid):
                return " " + self.encryption_short_name
            return ""

        def _toggle_tab(self, _input: str) -> None:
            jid = self.api.current_tab().jid  # type: JID

            if self._encryption_enabled(jid):
                del self._enabled_tabs[jid]
                config.remove_and_save('encryption', section=jid)
                self.api.information(
                    '{} encryption disabled for {}'.format(self.encryption_name, jid),
                    'Info',
                )
            else:
                self._enabled_tabs[jid] = self.encrypt
                config.set_and_save('encryption', self.encryption_short_name, section=jid)
                self.api.information(
                    '{} encryption enabled for {}'.format(self.encryption_name, jid),
                    'Info',
                )

        def _show_fingerprints(self, jid: JID) -> None:
            """Display encryption fingerprints for a JID."""
            fprs = self.get_fingerprints(jid)
            if len(fprs) == 1:
                self.api.information(
                    'Fingerprint for %s: %s' % (jid, fprs[0]),
                    'Info',
                )
            elif fprs:
                self.api.information(
                    'Fingerprints for %s:\n\t%s' % (jid, '\n\t'.join(fprs)),
                    'Info',
                )
            else:
                self.api.information(
                    'No fingerprints to display',
                    'Info',
                )

        @command_args_parser.quoted(0, 1)
        def _command_show_fingerprints(self, args: List[str]) -> None:
            if not args and isinstance(self.api.current_tab(), self.supported_tab_types):
                jid = self.api.current_tab().jid
            elif args:
                jid = args[0]
            else:
                self.api.information(
                    '%s_fingerprint: Couldn\'t deduce JID from context' % (
                        self.encryption_short_name),
                    'Error',
                )
                return None
            self._show_fingerprints(JID(jid))

        @command_args_parser.quoted(2)
        def __command_set_state_global(self, args, state='') -> None:
            jid, fpr = args
            if state not in self._all_trust_states:
                self.api.information(
                    'Unknown state for plugin %s: %s' % (
                        self.encryption_short_name, state),
                    'Error'
                )
                return
            self.store_trust(jid, state, fpr)

        @command_args_parser.quoted(1)
        def __command_set_state_local(self, args, state='') -> None:
            if isinstance(self.api.current_tab(), MucTab):
                self.api.information(
                    'You can only trust each participant of a MUC individually.',
                    'Info',
                )
                return
            jid = self.api.current_tab().jid
            if not args:
                self.api.information(
                    'No fingerprint provided to the command..',
                    'Error',
                )
                return
            fpr = args[0]
            if state not in self._all_trust_states:
                self.api.information(
                    'Unknown state for plugin %s: %s' % (
                        self.encryption_short_name, state),
                    'Error',
                )
                return
            self.store_trust(jid, state, fpr)

        def _encryption_enabled(self, jid: JID) -> bool:
            return self._enabled_tabs.get(jid) == self.encrypt

        async def _encrypt_wrapper(self, stanza: StanzaBase) -> Optional[StanzaBase]:
            """
            Wrapper around _encrypt() to handle errors and display the message after encryption.
            """
            try:
                # pylint: disable=unexpected-keyword-arg
                result = await self._encrypt(stanza, passthrough=True)
            except NothingToEncrypt:
                return stanza
            except Exception as exc:
                jid = stanza['to']
                tab = self.core.tabs.by_name_and_class(jid, ChatTab)
                msg = ' \n\x19%s}Could not send message: %s' % (
                    dump_tuple(get_theme().COLOR_CHAR_NACK),
                    exc,
                )
                # XXX: check before commit. Do we not nack in MUCs?
                if not isinstance(tab, MucTab):
                    tab.nack_message(msg, stanza['id'], stanza['from'])
                # TODO: display exceptions to the user properly
                log.error('Exception in encrypt:', exc_info=True)
                return None
            return result

        def _decrypt(self, message: Message, tab: ChatTabs) -> None:

            has_eme = False
            if message.xml.find('{%s}%s' % (EME_NS, EME_TAG)) is not None and \
                    message['eme']['namespace'] == self.eme_ns:
                has_eme = True

            has_encrypted_tag = False
            if not has_eme and self.encrypted_tags is not None:
                for (namespace, tag) in self.encrypted_tags:
                    if message.xml.find('{%s}%s' % (namespace, tag)) is not None:
                        # TODO: count all encrypted tags.
                        has_encrypted_tag = True
                        break

            if not has_eme and not has_encrypted_tag:
                return None

            log.debug('Received %s message: %r', self.encryption_name, message['body'])

            # Get the original JID of the sender. The JID might be None if it
            # comes from a semi-anonymous MUC for example. Some plugins might be
            # fine with this so let them handle it.
            jid = message['from']
            muctab = tab

            if isinstance(muctab, PrivateTab):
                muctab = tab.parent_muc
                jid = None

            if isinstance(muctab, MucTab):
                nick = message['from'].resource
                for user in muctab.users:
                    if user.nick == nick:
                        jid = user.jid or None
                        break

            self.decrypt(message, jid, tab)

            log.debug('Decrypted %s message: %r', self.encryption_name, message['body'])
            return None

        async def _encrypt(self, stanza: StanzaBase) -> Optional[StanzaBase]:
            if not isinstance(stanza, Message) or stanza['type'] not in ('normal', 'chat', 'groupchat'):
                raise NothingToEncrypt()
            message = stanza

            # Find who to encrypt to. If in a groupchat this can be multiple JIDs.
            # It is possible that we are not able to find a jid (e.g., semi-anon
            # MUCs). Let the plugin decide what to do with this information.
            jids = [message['to']]  # type: Optional[List[JID]]
            tab = self.core.tabs.by_jid(message['to'])
            if tab is None:  # When does that ever happen?
                log.debug('Attempting to encrypt a message to \'%s\' '
                          'that is not attached to a Tab. ?! Aborting '
                          'encryption.', message['to'])
                return None

            parent = None
            if isinstance(tab, PrivateTab):
                parent = tab.parent_muc
                nick = tab.jid.resource
                jids = None

                for user in parent.users:
                    if user.nick == nick:
                        jids = user.jid or None
                        break

            if isinstance(tab, MucTab):
                jids = []
                for user in tab.users:
                    # If the JID of a user is None, assume all others are None and
                    # we are in a (at least) semi-anon room. TODO: Really check if
                    # the room is semi-anon. Currently a moderator of a semi-anon
                    # room will possibly encrypt to everybody, leaking their
                    # public key/identity, and they wouldn't be able to decrypt it
                    # anyway if they don't know the moderator's JID.
                    # TODO: Change MUC to give easier access to this information.
                    if user.jid is None:
                        jids = None
                        break
                    # If we encrypt to all of these JIDs is up to the plugin, we
                    # just tell it who is in the room.
                    # XXX: user.jid shouldn't be empty. That's a MucTab/slixmpp
                    # bug.
                    if user.jid.bare:
                        jids.append(user.jid)

            if not self._encryption_enabled(tab.jid):
                raise NothingToEncrypt()

            log.debug('Sending %s message', self.encryption_name)

            has_body = message.xml.find('{%s}%s' % (JCLIENT_NS, 'body')) is not None

            # Drop all messages that don't contain a body if the plugin doesn't do
            # Stanza Encryption
            if not self.stanza_encryption and not has_body:
                log.debug(
                    '%s plugin: Dropping message as it contains no body, and '
                    'not doesn\'t do stanza encryption',
                    self.encryption_name,
                )
                return None

            # Call the enabled encrypt method
            func = self._enabled_tabs[tab.jid]
            if iscoroutinefunction(func):
                # pylint: disable=unexpected-keyword-arg
                await func(message, jids, tab, passthrough=True)
            else:
                # pylint: disable=unexpected-keyword-arg
                func(message, jids, tab, passthrough=True)

            if has_body:
                # Only add EME tag if the message has a body.
                # Per discussion in jdev@:
                # The receiving client needs to know the message contains
                # meaningful information or not to display notifications to the
                # user, and not display anything when it's e.g., a chatstate.
                # This does leak the fact that the encrypted payload contains a
                # message.
                message['eme']['namespace'] = self.eme_ns
                message['eme']['name'] = self.encryption_name

                if self.replace_body_with_eme:
                    self.core.xmpp['xep_0380'].replace_body_with_eme(message)

            # Filter stanza with the whitelist. Plugins doing stanza encryption
            # will have to include these in their encrypted container beforehand.
            whitelist = self.tag_whitelist
            if self.encrypted_tags is not None:
                whitelist += self.encrypted_tags

            tag_whitelist = {'{%s}%s' % tag for tag in whitelist}

            for elem in message.xml[:]:
                if elem.tag not in tag_whitelist:
                    message.xml.remove(elem)

            log.debug('Encrypted %s message', self.encryption_name)
            return message

        def store_trust(self, jid: JID, state: str, fingerprint: str) -> None:
            """Store trust for a fingerprint and a jid."""
            option_name = '%s:%s' % (self.encryption_short_name, fingerprint)
            config.silent_set(option=option_name, value=state, section=jid)

        def fetch_trust(self, jid: JID, fingerprint: str) -> str:
            """Fetch trust of a fingerprint and a jid."""
            option_name = '%s:%s' % (self.encryption_short_name, fingerprint)
            return config.get(option=option_name, section=jid)

        async def decrypt(self, message: Message, jid: Optional[JID], tab: ChatTab):
            """Decryption method

            This is a method the plugin must implement.  It is expected that this
            method will edit the received message and return nothing.

            :param message: Message to be decrypted.
            :param jid: Real Jid of the sender if available. We might be
                        talking through a semi-anonymous MUC where real JIDs are
                        not available.
            :param tab: Tab the message is coming from.

            :returns: None
            """

            raise NotImplementedError

        async def encrypt(self, message: Message, jids: Optional[List[JID]], tab: ChatTabs):
            """Encryption method

            This is a method the plugin must implement.  It is expected that this
            method will edit the received message and return nothing.

            :param message: Message to be encrypted.
            :param jids: Real Jids of all possible recipients.
            :param tab: Tab the message is going to.

            :returns: None
            """

            raise NotImplementedError

        def get_fingerprints(self, jid: JID) -> List[str]:
            """Show fingerprint(s) for this encryption method and JID.

            To overload in plugins.

            :returns: A list of fingerprints to display
            """
            return []