[Bug]: 'OCP\Files\NotPermittedException' and 403 Error - Unable to Write Files or Folders to External Storage

⚠️ This issue respects the following points: ⚠️

[X] This is a bug, not a question or a configuration/webserver/proxy issue.
[X] This issue is not already reported on Github OR Nextcloud Community Forum (I've searched it).
[X] Nextcloud Server is up to date. See Maintenance and Release Schedule for supported versions.
[X] I agree to follow Nextcloud's Code of Conduct.

Bug description

I encountered an issue after upgrading to Nextcloud 28.0.1, which persisted even after updating to 28.0.2.RC5.

The internal storage owned by the user works well, with no problems in syncing.

However, when I try to create a file or folder in External Storage, I receive an error message. In the web browser, it shows a 403 error with the message 'Unable to create new file from template'. On the desktop, the NextCloud sync also fails; downloading is possible, but writing is not.

I checked the NextCloud log and found an error labeled 'OCP\Files\NotPermittedException'.

The permissions for the external storage appear to be correctly set, as shown below:

chown -R www-data:www-data MY_EXTERNAL_STORAGE chmod -R 770 MY_EXTERNAL_STORAGE

Creating a folder via the terminal works without issues:

sudo -u www-data mkdir MY_EXTERNAL_STORAGE/MyFolder

Additionally, there are no SELinux issues.

The external storage is located on the same drive as the NextCloud data folder, and there is ample disk space.

I find this problem quite peculiar.

Steps to reproduce

Admin Account: Configure external storages by navigating to Admin Settings > Administration > External Storage.
User Account: Sign in and access the external storage folder. Attempt to create a folder or add a 'New Text File' by clicking the '+ New' button at the top of the interface.

Expected behavior

Writing files and folders to the external storage folder without encountering any errors.

Installation method

Community Manual installation with Archive

Nextcloud Server version

Operating system

RHEL/CentOS

PHP engine version

PHP 8.3

Web server

Nginx

Database engine version

MariaDB

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

Upgraded to a MAJOR version (ex. 22 to 23)

Are you using the Nextcloud Server Encryption module?

Encryption is Disabled

What user-backends are you using?

[X] 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": [
            "MY.SERVER.DOMAIN"
        ],
        "overwrite.cli.url": "https:\/\/MY.SERVER.DOMAIN",
        "datadirectory": "***REMOVED SENSITIVE VALUE***",
        "dbtype": "mysql",
        "version": "28.0.2.4",
        "dbname": "***REMOVED SENSITIVE VALUE***",
        "dbhost": "***REMOVED SENSITIVE VALUE***",
        "dbport": "3306",
        "dbtableprefix": "oc_",
        "mysql.utf8mb4": true,
        "dbuser": "***REMOVED SENSITIVE VALUE***",
        "dbpassword": "***REMOVED SENSITIVE VALUE***",
        "installed": true,
        "maintenance": false,
        "filesystem_check_changes": 1,
        "tempdirectory": "\/ServerMain\/service\/nextcloud\/data_tmp\/alt",
        "loglevel": 3,
        "memcache.local": "\\OC\\Memcache\\APCu",
        "memcache.locking": "\\OC\\Memcache\\Redis",
        "memcache.distributed": "\\OC\\Memcache\\Redis",
        "redis": {
            "host": "***REMOVED SENSITIVE VALUE***",
            "port": 0,
            "password": "***REMOVED SENSITIVE VALUE***",
            "timeout": 1.5
        },
        "enable_previews": true,
        "preview_max_x": "2048",
        "preview_max_y": "2048",
        "jpeg_quality": "60",
        "enabledPreviewProviders": [
            "OC\\Preview\\PNG",
            "OC\\Preview\\JPEG",
            "OC\\Preview\\GIF",
            "OC\\Preview\\BMP",
            "OC\\Preview\\XBitmap",
            "OC\\Preview\\MP3",
            "OC\\Preview\\TXT",
            "OC\\Preview\\MarkDown",
            "OC\\Preview\\Illustrator",
            "OC\\Preview\\Photoshop",
            "OC\\Preview\\PDF",
            "OC\\Preview\\TIFF",
            "OC\\Preview\\SVG",
            "OC\\Preview\\Movie",
            "OC\\Preview\\MSOffice2007",
            "OC\\Preview\\MSOffice",
            "OC\\Preview\\HEIC",
            "OC\\Preview\\TGA"
        ],
        "updater.release.channel": "beta",
        "theme": "",
        "data-fingerprint": "cf1ac45a1fc53af42dddc0ef66a4ed80",
        "twofactor_enforced": "false",
        "twofactor_enforced_groups": [
            "home"
        ],
        "twofactor_enforced_excluded_groups": [],
        "ldapProviderFactory": "OCA\\User_LDAP\\LDAPProviderFactory",
        "app_install_overwrite": [
            "files_rightclick",
            "imageconverter",
            "files_texteditor",
            "files_markdown"
        ],
        "updater.secret": "***REMOVED SENSITIVE VALUE***"
    }
}

List of activated Apps

No response

Nextcloud Signing status

No response

Nextcloud Logs

{
  "reqId": "Abqt6cHe1hpu8QQ4bZHL",
  "level": 3,
  "time": "2024-01-30T07:08:59+00:00",
  "remoteAddr": "211.114.206.72",
  "user": "THE_USER",
  "app": "no app in context",
  "method": "POST",
  "url": "/ocs/v2.php/apps/files/api/v1/templates/create",
  "message": "Could not create path \"/THE_USER/files/external/EXTERNAL_STORAGE_TARGET_FOLDER/New text file.md\"",
  "userAgent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36",
  "version": "28.0.2.4",
  "exception": {
    "Exception": "OCP\\Files\\NotPermittedException",
    "Message": "Could not create path \"/THE_USER/files/external/EXTERNAL_STORAGE_TARGET_FOLDER/New text file.md\"",
    "Code": 0,
    "Trace": [
      {
        "file": "/ServerMain/service/nextcloud/app/lib/private/Files/Template/TemplateManager.php",
        "line": 162,
        "function": "newFile",
        "class": "OC\\Files\\Node\\Folder",
        "type": "->"
      },
      {
        "file": "/ServerMain/service/nextcloud/app/apps/files/lib/Controller/TemplateController.php",
        "line": 80,
        "function": "createFromTemplate",
        "class": "OC\\Files\\Template\\TemplateManager",
        "type": "->",
        "args": [
          "*** sensitive parameters replaced ***"
        ]
      },
      {
        "file": "/ServerMain/service/nextcloud/app/lib/private/AppFramework/Http/Dispatcher.php",
        "line": 230,
        "function": "create",
        "class": "OCA\\Files\\Controller\\TemplateController",
        "type": "->",
        "args": [
          "*** sensitive parameters replaced ***"
        ]
      },
      {
        "file": "/ServerMain/service/nextcloud/app/lib/private/AppFramework/Http/Dispatcher.php",
        "line": 137,
        "function": "executeController",
        "class": "OC\\AppFramework\\Http\\Dispatcher",
        "type": "->"
      },
      {
        "file": "/ServerMain/service/nextcloud/app/lib/private/AppFramework/App.php",
        "line": 184,
        "function": "dispatch",
        "class": "OC\\AppFramework\\Http\\Dispatcher",
        "type": "->"
      },
      {
        "file": "/ServerMain/service/nextcloud/app/lib/private/Route/Router.php",
        "line": 315,
        "function": "main",
        "class": "OC\\AppFramework\\App",
        "type": "::"
      },
      {
        "file": "/ServerMain/service/nextcloud/app/ocs/v1.php",
        "line": 65,
        "function": "match",
        "class": "OC\\Route\\Router",
        "type": "->"
      },
      {
        "file": "/ServerMain/service/nextcloud/app/ocs/v2.php",
        "line": 23,
        "args": [
          "/ServerMain/service/nextcloud/app/ocs/v1.php"
        ],
        "function": "require_once"
      }
    ],
    "File": "/ServerMain/service/nextcloud/app/lib/private/Files/Node/Folder.php",
    "Line": 193,
    "message": "Could not create path \"/THE_USER/files/external/EXTERNAL_STORAGE_TARGET_FOLDER/New text file.md\"",
    "exception": [],
    "CustomMessage": "Could not create path \"/THE_USER/files/external/EXTERNAL_STORAGE_TARGET_FOLDER/New text file.md\""
  },
  "id": "65b8a095105cf"
}

Additional info

No response

nextcloud / server