feat(hidden-moderator) Moderator can join hidden based on jwt

- hidden moderator is not seen by other participants
- hidden moderator does not see their own thumbnail
- hidden moderator cannot unmute their video/audio or share screen
- hidden moderator can see and control other participants in meet( stop video, kick etc)

conference.js

@@ -148,6 +148,7 @@ import { AudioMixerEffect } from './react/features/stream-effects/audio-mixer/Au
 import { createPresenterEffect } from './react/features/stream-effects/presenter';
 import { createRnnoiseProcessor } from './react/features/stream-effects/rnnoise';
 import { endpointMessageReceived } from './react/features/subtitles';
+import { muteLocal } from './react/features/video-menu/actions.any';
 import UIEvents from './service/UI/UIEvents';
 
 const logger = Logger.getLogger(__filename);
@@ -2600,13 +2601,21 @@ export default {
      * @returns {void}
      */
     _onConferenceJoined() {
+        const { dispatch } = APP.store;
+
         APP.UI.initConference();
 
         if (!config.disableShortcuts) {
             APP.keyboardshortcut.init();
         }
 
-        APP.store.dispatch(conferenceJoined(room));
+        dispatch(conferenceJoined(room));
+        if (room.isHidden()) {
+            dispatch(muteLocal(true, MEDIA_TYPE.AUDIO));
+            dispatch(muteLocal(true, MEDIA_TYPE.VIDEO));
+            dispatch(setAudioUnmutePermissions(true));
+            dispatch(setVideoUnmutePermissions(true));
+        }
     },
 
     /**

react/features/base/settings/functions.any.js

@@ -265,6 +265,12 @@ export function shouldHideShareAudioHelper(state: Object): boolean {
  * @returns {boolean}
  */
 export function shouldHideSelfView(state: Object) {
+    const { conference } = state['features/base/conference'];
+
+    if (conference?.isHidden()) {
+        return true;
+    }
+
     return getParticipantCount(state) === 1 ? false : getHideSelfView(state);
 }
 

react/features/follow-me/middleware.js

@@ -104,11 +104,11 @@ function _onFollowMeCommand(attributes = {}, id, store) {
 
     // The Command(s) API will send us our own commands and we don't want
     // to act upon them.
-    if (participantSendingCommand.local) {
+    if (participantSendingCommand?.local) {
         return;
     }
 
-    if (participantSendingCommand.role !== 'moderator') {
+    if (participantSendingCommand && participantSendingCommand.role !== 'moderator') {
         logger.warn('Received follow-me command not from moderator');
 
         return;

react/features/participants-pane/functions.js

@@ -210,6 +210,7 @@ export const shouldRenderInviteButton = (state: Object) => {
  * @returns {Array<string>}
  */
 export function getSortedParticipantIds(stateful: Object | Function): Array<string> {
+    const { conference } = stateful['features/base/conference'];
     const { id } = getLocalParticipant(stateful);
     const remoteParticipants = getRemoteParticipantsSorted(stateful);
     const reorderedParticipants = new Set(remoteParticipants);
@@ -226,7 +227,7 @@ export function getSortedParticipantIds(stateful: Object | Function): Array<stri
 
     const dominant = [];
     const dominantId = dominantSpeaker?.id;
-    const local = remoteRaisedHandParticipants.has(id) ? [] : [ id ];
+    let local = remoteRaisedHandParticipants.has(id) ? [] : [ id ];
 
     // In case dominat speaker has raised hand, keep the order in the raised hand queue.
     // In case they don't have raised hand, goes first in the participants list.
@@ -235,6 +236,11 @@ export function getSortedParticipantIds(stateful: Object | Function): Array<stri
         dominant.push(dominantId);
     }
 
+    if (conference.isHidden()) {
+        local = [];
+        remoteRaisedHandParticipants.delete(id);
+    }
+
     // Move self and participants with raised hand to the top of the list.
     return [
         ...dominant,

resources/prosody-plugins/mod_muc_moderator_hidden.lua

@@ -0,0 +1,36 @@
+--This module adds is_hidden tag when the user from jwt is moderator and when
+--jwt contains `hidden` flag set to true, or removes it in case it was
+--added maliciously from client sent presence.
+--The module must be enabled under the muc component.
+local is_user_hidden = module:require "util".is_user_hidden;
+local tag_name = "is_hidden"
+
+module:log("info", "Loading mod_muc_user_hidden!");
+
+function add_hidden_tag(event)
+    local stanza = event.stanza;
+    local session = event.origin;
+
+    if stanza == nil or stanza.name ~= "presence" then
+      return
+    end
+
+    stanza:maptags(function(tag)
+      if tag and tag.name == tag_name then
+          module:log("info", "Removing %s tag from presence stanza!", tag_name);
+          return nil;
+      else
+          return tag;
+      end
+    end)
+
+    if is_user_hidden(session) then
+        stanza:tag(tag_name):up()
+    end
+end
+
+module:hook("presence/bare", add_hidden_tag);
+module:hook("presence/full", add_hidden_tag);
+module:hook("presence/host", add_hidden_tag);
+
+module:log("info", "Loaded mod_muc_user_hidden!");

resources/prosody-plugins/util.lib.lua

@@ -239,6 +239,18 @@ function is_feature_allowed(session, feature)
     end
 end
 
+-- Utility function to check whether the user should be hidden.
+function is_user_hidden(session)
+    local context_user = session.jitsi_meet_context_user
+    if (context_user ~= nil
+        and (context_user['moderator'] == "true" or context_user['moderator'] == true)
+        and (context_user['hidden'] == "true" or context_user['hidden'] == true)) then
+        return true;
+    else
+        return false;
+    end
+end
+
 --- Extracts the subdomain and room name from internal jid node [foo]room1
 -- @return subdomain(optional, if extracted or nil), the room name
 function extract_subdomain(room_node)
@@ -356,6 +368,7 @@ end
 return {
     extract_subdomain = extract_subdomain;
     is_feature_allowed = is_feature_allowed;
+    is_user_hidden = is_user_hidden;
     is_healthcheck_room = is_healthcheck_room;
     get_room_from_jid = get_room_from_jid;
     get_room_by_name_and_subdomain = get_room_by_name_and_subdomain;