`ForbiddenException` while using CardDAV when "Allow file system access" turned off and if encryption is enabled

⚠️ This issue respects the following points: ⚠️

• This is a bug, not a question or a configuration/webserver/proxy issue.
• This issue is not already reported on Github (I've searched it).
• Nextcloud Server is up to date. See Maintenance and Release Schedule for supported versions.
• Nextcloud Server is running on 64bit capable CPU, PHP and OS.
• I agree to follow Nextcloud's Code of Conduct.

Bug description

I am using Contacts app to sync contacts to an iPhone via CardDav. In order to access contacts from the iOS I created an app password. During creation I unset the checkbox "Allow file system access" for security reasons. Everything works fine but the log file is flooded with the exception listed below. When I check "Allow file system access" for the app password then the exception is gone but iOS thus have file access with the rights pertained to user.

Steps to reproduce

1. Create new app password
2. Unset "allow file system access"
3. Configure CardDav on iOS
4. Sync contacts on iOS

Expected behavior

No exceptions in the log file

Installation method

Community Manual installation with Archive

Nextcloud Server version

25

Operating system

Debian/Ubuntu

PHP engine version

PHP 8.1

Web server

Nginx

Database engine version

MariaDB

Is this bug present after an update or on a fresh install?

Updated to a major version (ex. 22.2.3 to 23.0.1)

Are you using the Nextcloud Server Encryption module?

Encryption is Enabled

What user-backends are you using?

• Default user-backend (database)
• LDAP/ Active Directory
• SSO - SAML
• Other

Configuration report

{
    "system": {
        "instanceid": "***REMOVED SENSITIVE VALUE***",
        "passwordsalt": "***REMOVED SENSITIVE VALUE***",
        "secret": "***REMOVED SENSITIVE VALUE***",
        "trusted_domains": [
            "***REMOVED SENSITIVE VALUE***"
        ],
        "datadirectory": "***REMOVED SENSITIVE VALUE***",
        "overwrite.cli.url": "https:\/\/***REMOVED SENSITIVE VALUE***\/nextcloud",
        "dbtype": "mysql",
        "version": "25.0.5.1",
        "dbname": "***REMOVED SENSITIVE VALUE***",
        "dbhost": "***REMOVED SENSITIVE VALUE***",
        "dbport": "",
        "dbtableprefix": "oc_",
        "dbuser": "***REMOVED SENSITIVE VALUE***",
        "dbpassword": "***REMOVED SENSITIVE VALUE***",
        "installed": true,
        "memcache.local": "\\OC\\Memcache\\Redis",
        "memcache.locking": "\\OC\\Memcache\\Redis",
        "redis": {
            "host": "***REMOVED SENSITIVE VALUE***",
            "port": 0,
            "dbindex": 0,
            "password": "***REMOVED SENSITIVE VALUE***",
            "timeout": 1.5
        },
        "enable_previews": true,
        "enabledPreviewProviders": [
            "OC\\Preview\\PNG",
            "OC\\Preview\\JPEG",
            "OC\\Preview\\GIF",
            "OC\\Preview\\HEIC",
            "OC\\Preview\\BMP",
            "OC\\Preview\\XBitmap",
            "OC\\Preview\\MP3",
            "OC\\Preview\\TXT",
            "OC\\Preview\\MarkDown"
        ],
        "log_type": "file",
        "logfile": "\/var\/log\/nextcloud\/nextcloud.log",
        "loglevel": 2,
        "logtimezone": "Europe\/Berlin",
        "log_rotate_size": 20971520,
        "encryption.legacy_format_support": false,
        "maintenance": false,
        "theme": "",
        "trashbin_retention_obligation": "auto, 30",
        "versions_retention_obligation": "30, auto",
        "default_phone_region": "DE",
        "mail_from_address": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpmode": "smtp",
        "mail_domain": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpauth": 1,
        "mail_smtpsecure": "ssl",
        "mail_smtphost": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpport": "465",
        "mail_smtpname": "***REMOVED SENSITIVE VALUE***",
        "mail_smtppassword": "***REMOVED SENSITIVE VALUE***",
        "mysql.utf8mb4": true,
        "mail_sendmailmode": "smtp",
        "mail_smtpauthtype": "LOGIN"
    }
}

List of activated Apps

Enabled:
  - activity: 2.17.0
  - admin_audit: 1.15.0
  - audioplayer: 3.3.1
  - bruteforcesettings: 2.5.0
  - calendar: 4.3.3
  - circles: 25.0.0
  - cloud_federation_api: 1.8.0
  - comments: 1.15.0
  - contacts: 5.2.0
  - dashboard: 7.5.0
  - dav: 1.24.0
  - encryption: 2.13.0
  - federatedfilesharing: 1.15.0
  - federation: 1.15.0
  - files: 1.20.1
  - files_external: 1.17.0
  - files_pdfviewer: 2.6.0
  - files_rightclick: 1.4.0
  - files_sharing: 1.17.0
  - files_trashbin: 1.15.0
  - files_versions: 1.18.0
  - firstrunwizard: 2.14.0
  - logreader: 2.10.0
  - lookup_server_connector: 1.13.0
  - nextcloud_announcements: 1.14.0
  - notifications: 2.13.1
  - oauth2: 1.13.0
  - password_policy: 1.15.0
  - photos: 2.0.1
  - privacy: 1.9.0
  - provisioning_api: 1.15.0
  - recommendations: 1.4.0
  - related_resources: 1.0.4
  - serverinfo: 1.15.0
  - settings: 1.7.0
  - sharebymail: 1.15.0
  - support: 1.8.0
  - survey_client: 1.13.0
  - suspicious_login: 4.3.0
  - systemtags: 1.15.0
  - text: 3.6.0
  - theming: 2.0.1
  - twofactor_backupcodes: 1.14.0
  - updatenotification: 1.15.0
  - user_status: 1.5.0
  - viewer: 1.9.0
  - workflowengine: 2.7.0
Disabled:
  - contactsinteraction: 1.6.0
  - spreed: 15.0.5
  - twofactor_totp
  - user_ldap
  - weather_status: 1.5.0

Nextcloud Signing status

No errors have been found.

Nextcloud Logs

{"reqId":"7BruMtr4SbU2rjCnHicr","level":3,"time":"2023-04-15T12:42:35+02:00","remoteAddr":"*** sensitive parameters replaced ***","user":"*** sensitive parameters replaced ***","app":"no app in context","method":"REPORT","url":"/nextcloud/remote.php/dav/addressbooks/users/*** sensitive parameters replaced ***/kontakte/","message":"This request is not allowed to access the filesystem","userAgent":"iOS/16.4.1 (20E252) dataaccessd/1.0","version":"25.0.5.1","exception":{"Exception":"OC\\ForbiddenException","Message":"This request is not allowed to access the filesystem","Code":0,"Trace":[{"file":"/var/www/nextcloud/lib/private/Files/View.php","line":1181,"function":"mkdir","class":"OC\\Lockdown\\Filesystem\\NullStorage","type":"->"},{"file":"/var/www/nextcloud/lib/private/Files/View.php","line":270,"function":"basicOperation","class":"OC\\Files\\View","type":"->"},{"file":"/var/www/nextcloud/lib/private/Encryption/Keys/Storage.php","line":484,"function":"mkdir","class":"OC\\Files\\View","type":"->"},{"file":"/var/www/nextcloud/lib/private/Encryption/Keys/Storage.php","line":337,"function":"keySetPreparation","class":"OC\\Encryption\\Keys\\Storage","type":"->"},{"file":"/var/www/nextcloud/lib/private/Encryption/Keys/Storage.php","line":131,"function":"setKey","class":"OC\\Encryption\\Keys\\Storage","type":"->"},{"file":"/var/www/nextcloud/apps/encryption/lib/KeyManager.php","line":333,"function":"setUserKey","class":"OC\\Encryption\\Keys\\Storage","type":"->"},{"file":"/var/www/nextcloud/apps/encryption/lib/KeyManager.php","line":292,"function":"setPublicKey","class":"OCA\\Encryption\\KeyManager","type":"->"},{"file":"/var/www/nextcloud/apps/encryption/lib/Users/Setup.php","line":53,"function":"storeKeyPair","class":"OCA\\Encryption\\KeyManager","type":"->","args":["*** sensitive parameters replaced ***"]},{"file":"/var/www/nextcloud/apps/encryption/lib/Hooks/UserHooks.php","line":179,"function":"setupUser","class":"OCA\\Encryption\\Users\\Setup","type":"->","args":["*** sensitive parameters replaced ***"]},{"file":"/var/www/nextcloud/lib/private/legacy/OC_Hook.php","line":106,"function":"login","class":"OCA\\Encryption\\Hooks\\UserHooks","type":"->","args":["*** sensitive parameters replaced ***"]},{"file":"/var/www/nextcloud/lib/private/Server.php","line":621,"function":"emit","class":"OC_Hook","type":"::"},{"function":"OC\\{closure}","class":"OC\\Server","type":"->","args":["*** sensitive parameters replaced ***"]},{"file":"/var/www/nextcloud/lib/private/Hooks/EmitterTrait.php","line":106,"function":"call_user_func_array"},{"file":"/var/www/nextcloud/lib/private/Hooks/PublicEmitter.php","line":40,"function":"emit","class":"OC\\Hooks\\BasicEmitter","type":"->"},{"file":"/var/www/nextcloud/lib/private/User/Session.php","line":401,"function":"emit","class":"OC\\Hooks\\PublicEmitter","type":"->"},{"file":"/var/www/nextcloud/lib/private/User/Session.php","line":671,"function":"completeLogin","class":"OC\\User\\Session","type":"->","args":["*** sensitive parameters replaced ***"]},{"file":"/var/www/nextcloud/lib/private/User/Session.php","line":354,"function":"loginWithToken","class":"OC\\User\\Session","type":"->","args":["*** sensitive parameters replaced ***"]},{"file":"/var/www/nextcloud/lib/private/User/Session.php","line":452,"function":"login","class":"OC\\User\\Session","type":"->","args":["*** sensitive parameters replaced ***"]},{"file":"/var/www/nextcloud/apps/dav/lib/Connector/Sabre/Auth.php","line":113,"function":"logClientIn","class":"OC\\User\\Session","type":"->","args":["*** sensitive parameters replaced ***"]},{"file":"/var/www/nextcloud/3rdparty/sabre/dav/lib/DAV/Auth/Backend/AbstractBasic.php","line":103,"function":"validateUserPass","class":"OCA\\DAV\\Connector\\Sabre\\Auth","type":"->","args":["*** sensitive parameters replaced ***"]},{"file":"/var/www/nextcloud/apps/dav/lib/Connector/Sabre/Auth.php","line":229,"function":"check","class":"Sabre\\DAV\\Auth\\Backend\\AbstractBasic","type":"->"},{"file":"/var/www/nextcloud/apps/dav/lib/Connector/Sabre/Auth.php","line":136,"function":"auth","class":"OCA\\DAV\\Connector\\Sabre\\Auth","type":"->"},{"file":"/var/www/nextcloud/3rdparty/sabre/dav/lib/DAV/Auth/Plugin.php","line":180,"function":"check","class":"OCA\\DAV\\Connector\\Sabre\\Auth","type":"->"},{"file":"/var/www/nextcloud/3rdparty/sabre/dav/lib/DAV/Auth/Plugin.php","line":135,"function":"check","class":"Sabre\\DAV\\Auth\\Plugin","type":"->"},{"file":"/var/www/nextcloud/3rdparty/sabre/event/lib/WildcardEmitterTrait.php","line":89,"function":"beforeMethod","class":"Sabre\\DAV\\Auth\\Plugin","type":"->"},{"file":"/var/www/nextcloud/3rdparty/sabre/dav/lib/DAV/Server.php","line":456,"function":"emit","class":"Sabre\\DAV\\Server","type":"->"},{"file":"/var/www/nextcloud/3rdparty/sabre/dav/lib/DAV/Server.php","line":253,"function":"invokeMethod","class":"Sabre\\DAV\\Server","type":"->"},{"file":"/var/www/nextcloud/3rdparty/sabre/dav/lib/DAV/Server.php","line":321,"function":"start","class":"Sabre\\DAV\\Server","type":"->"},{"file":"/var/www/nextcloud/apps/dav/lib/Server.php","line":360,"function":"exec","class":"Sabre\\DAV\\Server","type":"->"},{"file":"/var/www/nextcloud/apps/dav/appinfo/v2/remote.php","line":35,"function":"exec","class":"OCA\\DAV\\Server","type":"->"},{"file":"/var/www/nextcloud/remote.php","line":171,"args":["/var/www/nextcloud/apps/dav/appinfo/v2/remote.php"],"function":"require_once"}],"File":"/var/www/nextcloud/lib/private/Lockdown/Filesystem/NullStorage.php","Line":41,"CustomMessage":"--"},"id":"643a7ff2d99a1"}

Additional info

No response

Start with lib/private/Lockdown/Filesystem/NullStorage.php and trace the failing path through lib/private/Encryption/Keys/Storage.php, apps/encryption/lib/KeyManager.php, and apps/dav/lib/Connector/Sabre/Auth.php. Reproduce CardDAV authentication with encryption enabled and filesystem access disabled, then add regression coverage so the sync completes without the ForbiddenException or repeated log errors.