FEATURE: Auto-remove users without permission from channel (discourse…

…#20344)

There are many situations that may cause users to lose permission to
send messages in a chat channel. Until now we have relied on security
checks in `Chat::ChatChannelFetcher` to remove channels which the
user may have a `UserChatChannelMembership` record for but which
they do not have access to.

This commit takes a more proactive approach. Now any of these following
`DiscourseEvent` triggers may cause `UserChatChannelMembership`
records to be deleted:

* `category_updated` - Permissions of the category changed
   (i.e. CategoryGroup records changed)
* `user_removed_from_group` - Means the user may not be able to access the
   channel based on `GroupUser` or also `chat_allowed_groups`
* `site_setting_changed` - The `chat_allowed_groups` was updated, some
   users may no longer be in groups that can access chat.
* `group_destroyed` - Means the user may not be able to access the
   channel based on `GroupUser` or also `chat_allowed_groups`

All of these are handled in a distinct service run in a background
job. Users removed are logged via `StaffActionLog` and then we
publish messages on a per-channel basis to users who had their
memberships deleted.

When the user has a channel they are kicked from open, we show
a dialog saying "You no longer have access to this channel".

When they click OK we redirect them either:

* To their first other public channel, if they have any followed
* The chat browse page if they don't

This is to save on tons of requests from kicked out users getting messages
from other channels.

When the user does not have the kicked channel open, we can just
silently yoink it out of their sidebar and turn off subscriptions.

app/models/group.rb

@@ -65,6 +65,7 @@ class Group < ActiveRecord::Base
   after_commit :automatic_group_membership, on: %i[create update]
   after_commit :trigger_group_created_event, on: :create
   after_commit :trigger_group_updated_event, on: :update
+  before_destroy :cache_group_users_for_destroyed_event, prepend: true
   after_commit :trigger_group_destroyed_event, on: :destroy
   after_commit :set_default_notifications, on: %i[create update]
 
@@ -911,13 +912,22 @@ def self.owner_of(groups, user)
     self.member_of(groups, user).where("gu.owner")
   end
 
-  %i[group_created group_updated group_destroyed].each do |event|
+  def cache_group_users_for_destroyed_event
+    @cached_group_user_ids = group_users.pluck(:user_id)
+  end
+
+  %i[group_created group_updated].each do |event|
     define_method("trigger_#{event}_event") do
       DiscourseEvent.trigger(event, self)
       true
     end
   end
 
+  def trigger_group_destroyed_event
+    DiscourseEvent.trigger(:group_destroyed, self, @cached_group_user_ids)
+    true
+  end
+
   def flair_type
     return :icon if flair_icon.present?
     return :image if flair_upload.present?

lib/job_time_spacer.rb

@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+##
+# In some cases we may want to enqueue_at several of the same job with
+# batches, spacing them out or incrementing by some amount of seconds,
+# in case the jobs do heavy work or send many MessageBus messages and the like.
+# This class handles figuring out the seconds increments.
+#
+# @example
+#   spacer = JobTimeSpacer.new
+#   user_ids.in_groups_of(200, false) do |user_id_batch|
+#     spacer.enqueue(:kick_users_from_topic, { topic_id: topic_id, user_ids: user_id_batch })
+#   end
+class JobTimeSpacer
+  def initialize(seconds_space_increment: 1, seconds_delay: 5)
+    @seconds_space_increment = seconds_space_increment
+    @seconds_space_modifier = seconds_space_increment
+    @seconds_step = seconds_delay
+  end
+
+  def enqueue(job_name, job_args = {})
+    Jobs.enqueue_at((@seconds_step * @seconds_space_modifier).seconds.from_now, job_name, job_args)
+    @seconds_space_modifier += @seconds_space_increment
+  end
+end

plugins/chat/app/jobs/regular/auto_join_channel_batch.rb

@@ -0,0 +1,81 @@
+# NOTE: When changing auto-join logic, make sure to update the `settings.auto_join_users_info` translation as well.
+# frozen_string_literal: true
+
+module Jobs
+  class AutoJoinChannelBatch < ::Jobs::Base
+    def execute(args)
+      return "starts_at or ends_at missing" if args[:starts_at].blank? || args[:ends_at].blank?
+      start_user_id = args[:starts_at].to_i
+      end_user_id = args[:ends_at].to_i
+
+      return "End is higher than start" if end_user_id < start_user_id
+
+      channel =
+        ChatChannel.find_by(
+          id: args[:chat_channel_id],
+          auto_join_users: true,
+          chatable_type: "Category",
+        )
+
+      return if !channel
+
+      category = channel.chatable
+      return if !category
+
+      query_args = {
+        chat_channel_id: channel.id,
+        start: start_user_id,
+        end: end_user_id,
+        suspended_until: Time.zone.now,
+        last_seen_at: 3.months.ago,
+        channel_category: channel.chatable_id,
+        mode: Chat::UserChatChannelMembership.join_modes[:automatic],
+      }
+
+      new_member_ids = DB.query_single(create_memberships_query(category), query_args)
+
+      # Only do this if we are running auto-join for a single user, if we
+      # are doing it for many then we should do it after all batches are
+      # complete for the channel in Jobs::AutoJoinChannelMemberships
+      if start_user_id == end_user_id
+        Chat::ChatChannelMembershipManager.new(channel).recalculate_user_count
+      end
+
+      Chat::Publisher.publish_new_channel(channel.reload, User.where(id: new_member_ids))
+    end
+
+    private
+
+    def create_memberships_query(category)
+      query = <<~SQL
+        INSERT INTO user_chat_channel_memberships (user_id, chat_channel_id, following, created_at, updated_at, join_mode)
+        SELECT DISTINCT(users.id), :chat_channel_id, TRUE, NOW(), NOW(), :mode
+        FROM users
+        INNER JOIN user_options uo ON uo.user_id = users.id
+        LEFT OUTER JOIN user_chat_channel_memberships uccm ON
+          uccm.chat_channel_id = :chat_channel_id AND uccm.user_id = users.id
+      SQL
+
+      query += <<~SQL if category.read_restricted?
+          INNER JOIN group_users gu ON gu.user_id = users.id
+          LEFT OUTER JOIN category_groups cg ON cg.group_id = gu.group_id
+        SQL
+
+      query += <<~SQL
+        WHERE (users.id >= :start AND users.id <= :end) AND
+          users.staged IS FALSE AND users.active AND
+          NOT EXISTS(SELECT 1 FROM anonymous_users a WHERE a.user_id = users.id) AND
+          (suspended_till IS NULL OR suspended_till <= :suspended_until) AND
+          (last_seen_at > :last_seen_at) AND
+          uo.chat_enabled AND
+          uccm.id IS NULL
+      SQL
+
+      query += <<~SQL if category.read_restricted?
+          AND cg.category_id = :channel_category
+        SQL
+
+      query += "RETURNING user_chat_channel_memberships.user_id"
+    end
+  end
+end

plugins/chat/app/jobs/regular/chat/auto_join_channel_batch.rb

@@ -37,7 +37,7 @@ def execute(args)
 
         # Only do this if we are running auto-join for a single user, if we
         # are doing it for many then we should do it after all batches are
-        # complete for the channel in Jobs::Chat::AutoManageChannelMemberships
+        # complete for the channel in Jobs::Chat::AutoJoinChannelMemberships
         if start_user_id == end_user_id
           ::Chat::ChannelMembershipManager.new(channel).recalculate_user_count
         end

plugins/chat/app/jobs/regular/chat/auto_manage_channel_memberships.rb → plugins/chat/app/jobs/regular/chat/auto_join_channel_memberships.rb

@@ -3,7 +3,7 @@
 
 module Jobs
   module Chat
-    class AutoManageChannelMemberships < ::Jobs::Base
+    class AutoJoinChannelMemberships < ::Jobs::Base
       def execute(args)
         channel =
           ::Chat::Channel.includes(:chatable).find_by(

plugins/chat/app/jobs/regular/chat/auto_remove_membership_handle_category_updated.rb

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+module Jobs
+  module Chat
+    class AutoRemoveMembershipHandleCategoryUpdated < ::Jobs::Base
+      def execute(args)
+        ::Chat::AutoRemove::HandleCategoryUpdated.call(**args)
+      end
+    end
+  end
+end

plugins/chat/app/jobs/regular/chat/auto_remove_membership_handle_chat_allowed_groups_change.rb

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+module Jobs
+  module Chat
+    class AutoRemoveMembershipHandleChatAllowedGroupsChange < ::Jobs::Base
+      def execute(args)
+        ::Chat::AutoRemove::HandleChatAllowedGroupsChange.call(**args)
+      end
+    end
+  end
+end

plugins/chat/app/jobs/regular/chat/auto_remove_membership_handle_destroyed_group.rb

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+module Jobs
+  module Chat
+    class AutoRemoveMembershipHandleDestroyedGroup < ::Jobs::Base
+      def execute(args)
+        ::Chat::AutoRemove::HandleDestroyedGroup.call(**args)
+      end
+    end
+  end
+end

plugins/chat/app/jobs/regular/chat/auto_remove_membership_handle_user_removed_from_group.rb

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+module Jobs
+  module Chat
+    class AutoRemoveMembershipHandleUserRemovedFromGroup < ::Jobs::Base
+      def execute(args)
+        ::Chat::AutoRemove::HandleUserRemovedFromGroup.call(**args)
+      end
+    end
+  end
+end

plugins/chat/app/jobs/regular/chat/kick_users_from_channel.rb

@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+module Jobs
+  module Chat
+    class KickUsersFromChannel < Jobs::Base
+      def execute(args)
+        return if !::Chat::Channel.exists?(id: args[:channel_id])
+        return if args[:user_ids].blank?
+        ::Chat::Publisher.publish_kick_users(args[:channel_id], args[:user_ids])
+      end
+    end
+  end
+end

plugins/chat/app/models/chat/user_chat_channel_membership.rb

@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 module Chat
-  class UserChatChannelMembership < ActiveRecord::Base
+  class Chat::UserChatChannelMembership < ActiveRecord::Base
     self.table_name = "user_chat_channel_memberships"
 
     NOTIFICATION_LEVELS = { never: 0, mention: 1, always: 2 }

plugins/chat/app/serializers/chat/channel_serializer.rb

@@ -112,12 +112,9 @@ def meta
       {
         message_bus_last_ids: {
           channel_message_bus_last_id: MessageBus.last_id("/chat/#{object.id}"),
-          new_messages:
-            @opts[:new_messages_message_bus_last_id] ||
-              MessageBus.last_id(Chat::Publisher.new_messages_message_bus_channel(object.id)),
-          new_mentions:
-            @opts[:new_mentions_message_bus_last_id] ||
-              MessageBus.last_id(Chat::Publisher.new_mentions_message_bus_channel(object.id)),
+          new_messages: new_messages_message_bus_id,
+          new_mentions: new_mentions_message_bus_id,
+          kick: kick_message_bus_id,
         },
       }
     end
@@ -127,5 +124,22 @@ def meta
     alias_method :include_archived_messages?, :include_archive_status?
     alias_method :include_archive_failed?, :include_archive_status?
     alias_method :include_archive_completed?, :include_archive_status?
+
+    private
+
+    def new_messages_message_bus_id
+      @opts[:new_messages_message_bus_last_id] ||
+        MessageBus.last_id(Chat::Publisher.new_messages_message_bus_channel(object.id))
+    end
+
+    def new_mentions_message_bus_id
+      @opts[:new_mentions_message_bus_last_id] ||
+        MessageBus.last_id(Chat::Publisher.new_mentions_message_bus_channel(object.id))
+    end
+
+    def kick_message_bus_id
+      @opts[:kick_message_bus_last_id] ||
+        MessageBus.last_id(Chat::Publisher.kick_users_message_bus_channel(object.id))
+    end
   end
 end

plugins/chat/app/serializers/chat/structured_channel_serializer.rb

@@ -30,6 +30,8 @@ def direct_message_channels
             chat_message_bus_last_ids[Chat::Publisher.new_messages_message_bus_channel(channel.id)],
           new_mentions_message_bus_last_id:
             chat_message_bus_last_ids[Chat::Publisher.new_mentions_message_bus_channel(channel.id)],
+          kick_message_bus_last_id:
+            chat_message_bus_last_ids[Chat::Publisher.kick_users_message_bus_channel(channel.id)],
         )
       end
     end
@@ -84,6 +86,7 @@ def chat_message_bus_last_ids
           object[:public_channels].each do |channel|
             message_bus_channels.push(Chat::Publisher.new_messages_message_bus_channel(channel.id))
             message_bus_channels.push(Chat::Publisher.new_mentions_message_bus_channel(channel.id))
+            message_bus_channels.push(Chat::Publisher.kick_users_message_bus_channel(channel.id))
           end
 
           object[:direct_message_channels].each do |channel|