Conversation looses all moderators

[joendres]

Steps to reproduce

1. Create a conversation (Optionally enable guest access)
2. Add another user
3. Promote the user to moderator
4. Both moderators leave the conversation in a short period of time (before the state ist updated)

Expected behaviour

It should not be possible for all moderators to leave the conversation

Actual behaviour

If the last moderators leaves before the menu item is disabled, the conversation has no moderator. It is not possible to delete it from the Web interface. But if guest access was enabled anyone who has the link can still use the conversation.

Server configuration detail

Operating system: Linux 4.19.89 #1 SMP Mon Dec 16 00:24:57 CET 2019 x86_64

Webserver: Apache (cgi-fcgi)

Database: mysql 10.2.29

PHP version:

7.3.14
Modules loaded: Core, date, libxml, openssl, pcre, sqlite3, zlib, bcmath, bz2, calendar, ctype, curl, dba, dom, hash, fileinfo, filter, ftp, gd, gettext, gmp, SPL, iconv, session, intl, json, mbstring, standard, mysqlnd, pcntl, mysqli, PDO, pdo_mysql, pdo_sqlite, Phar, posix, readline, Reflection, imap, SimpleXML, soap, sockets, exif, tokenizer, xml, xmlreader, xmlwriter, xsl, zip, cgi-fcgi, apcu, imagick, memcached, redis, Zend OPcache

Nextcloud version: 18.0.4 - 18.0.4.2

Updated from an older Nextcloud/ownCloud or fresh install: Updated from 17.0.? in several steps

Where did you install Nextcloud from: Hosting provider's template

Signing status

Integrity checker has been disabled. Integrity cannot be verified.

List of activated apps

Enabled:
 - activity: 2.11.0
 - admin_audit: 1.8.0
 - bruteforcesettings: 1.6.0
 - calendar: 2.0.3
 - circles: 0.18.5
 - cloud_federation_api: 1.1.0
 - contacts: 3.3.0
 - dav: 1.14.0
 - federatedfilesharing: 1.8.0
 - files: 1.13.1
 - files_external: 1.9.0
 - files_rightclick: 0.15.2
 - files_sharing: 1.10.1
 - files_trashbin: 1.8.0
 - files_versions: 1.11.0
 - groupfolders: 6.0.6
 - issuetemplate: 0.6.0
 - logreader: 2.3.0
 - lookup_server_connector: 1.6.0
 - nextcloud_announcements: 1.7.0
 - notifications: 2.6.0
 - oauth2: 1.6.0
 - occweb: 0.0.7
 - password_policy: 1.8.0
 - polls: 1.4.3
 - privacy: 1.2.0
 - provisioning_api: 1.8.0
 - serverinfo: 1.8.0
 - settings: 1.0.0
 - spreed: 8.0.9
 - tasks: 0.13.1
 - text: 2.0.0
 - theming: 1.9.0
 - twofactor_backupcodes: 1.7.0
 - twofactor_totp: 4.1.3
 - updatenotification: 1.8.0
 - viewer: 1.2.0
 - workflowengine: 2.0.0
Disabled:
 - accessibility
 - comments
 - encryption
 - federation
 - files_pdfviewer
 - files_videoplayer
 - firstrunwizard
 - photos
 - recommendations
 - sharebymail
 - support
 - survey_client
 - systemtags
 - user_ldap

Configuration (config/config.php)

{
    "instanceid": "***REMOVED SENSITIVE VALUE***",
    "passwordsalt": "***REMOVED SENSITIVE VALUE***",
    "secret": "***REMOVED SENSITIVE VALUE***",
    "trusted_domains": [
        "cloud.johannes-endres.de"
    ],
    "datadirectory": "***REMOVED SENSITIVE VALUE***",
    "dbtype": "mysql",
    "version": "18.0.4.2",
    "integrity.check.disabled": true,
    "default_language": "de",
    "default_locale": "de",
    "trashbin_retention_obligation": "auto, 30",
    "version_retention_obligation": "auto, 30",
    "memcache.local": "\\OC\\Memcache\\APCu",
    "overwrite.cli.url": "https:\/\/cloud.johannes-endres.de",
    "dbname": "***REMOVED SENSITIVE VALUE***",
    "dbhost": "***REMOVED SENSITIVE VALUE***",
    "dbport": "",
    "dbtableprefix": "nc_6068_",
    "mysql.utf8mb4": true,
    "dbuser": "***REMOVED SENSITIVE VALUE***",
    "dbpassword": "***REMOVED SENSITIVE VALUE***",
    "installed": true,
    "maintenance": false,
    "theme": "",
    "loglevel": 2,
    "mail_smtpmode": "smtp",
    "mail_smtpauth": 1,
    "mail_sendmailmode": "smtp",
    "app_install_overwrite": [
        "occweb"
    ],
    "updater.release.channel": "stable"
}

Are you using external storage, if yes which one: no

Are you using encryption:

Are you using an external user-backend, if yes which one: no

Client configuration

Browser: any, verified with Firefox, Chrome, Edge and Android

Operating system: any, verified with Windows and Android

Logs

Web server error log

Nextcloud log

Browser log

[nickvergessen]

If the last moderators leaves before the menu item is disabled, the conversation has no moderator.

This is checked on an API level. You might run into concurrency of course if both first pass the check for the number of moderators and then the remove-from-self happens. But other than that it should not be possible.

But if guest access was enabled anyone who has the link can still use the conversation.

Just for the record: as soon as there is no person in the call at some point, the next cron job will delete the conversation

[joendres]

If the last moderators leaves before the menu item is disabled, the conversation has no moderator.

This is checked on an API level. You might run into concurrency of course if both first pass the check for the number of moderators and then the remove-from-self happens. But other than that it should not be possible.

OK, sorry for my wrong interpretation of the condition. Still the concurrency really happens. I ran into a unmoderated conversation in real life.

What's worse: The conversatin does not appear in the Web interface. I guess that's because no user (with an account) is in it. So nobody notices that it's still around.

But if guest access was enabled anyone who has the link can still use the conversation.

Just for the record: as soon as there is no person in the call at some point, the next cron job will delete the conversation

That's what I thought happende to the initial conversation. But what is the condition for "no person in the call"?

When I reproduced the problem, after the two moderators left, I closed the guest's browser (edge) and called /cron.php (I use webcron) on in a different browser (firefox). That was 5 hours ago and I can still open the conversation by the guest link.

[nickvergessen]

I think I managed to reproduce the issue last week, but I forgot to write it.
Will have to check again, but yeah it should just not be possible.

[nickvergessen]

Doesn't work anymore on master/stable19 so closing