[Bug]: 24.0.4: HEAD on nonexistent paths logs warning to Nextcloud log

[AlvaroBrey]

⚠️ 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

The Nextcloud Android app uses the DAV api to check for existence of a file at several points. For this it does a HEAD request on the file path (/remote.php/dav/files/<user>/<file path>) and reads the HTTP response code.

Prior to Nextcloud 24.0.4, this worked as expected. However, in 24.0.4 a warning is logged to nextcloud.log every time a file is checked in this way and does not exist. This is a problem for server admins as it can create tremendous amounts of logspam: for example this will happen every time a user uploads a file as we check if it exists first. See nextcloud/android#10663 for details and more server logs.

Steps to reproduce

1. Install Nextcloud 24.0.4
2. Setup admin account
3. curl --head -u admin:<pass> <server IP>/remote.php/dav/files/admin/<random non-existing filename>

Expected behavior

No logs.

Installation method

Community Docker image

Operating system

Debian/Ubuntu

PHP engine version

No response

Web server

No response

Database engine version

SQlite

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

Fresh Nextcloud Server install

Are you using the Nextcloud Server Encryption module?

No response

What user-backends are you using?

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

Configuration report

No response

List of activated Apps

Enabled:
  - accessibility: 1.10.0
  - activity: 2.16.0
  - bruteforcesettings: 2.4.0
  - circles: 24.0.0
  - cloud_federation_api: 1.7.0
  - comments: 1.14.0
  - contactsinteraction: 1.5.0
  - dashboard: 7.4.0
  - dav: 1.22.0
  - federatedfilesharing: 1.14.0
  - federation: 1.14.0
  - files: 1.19.0
  - files_pdfviewer: 2.5.0
  - files_rightclick: 1.3.0
  - files_sharing: 1.16.2
  - files_trashbin: 1.14.0
  - files_versions: 1.17.0
  - files_videoplayer: 1.13.0
  - firstrunwizard: 2.13.0
  - logreader: 2.9.0
  - lookup_server_connector: 1.12.0
  - nextcloud_announcements: 1.13.0
  - notifications: 2.12.0
  - oauth2: 1.12.0
  - password_policy: 1.14.0
  - photos: 1.6.0
  - privacy: 1.8.0
  - provisioning_api: 1.14.0
  - recommendations: 1.3.0
  - serverinfo: 1.14.0
  - settings: 1.6.0
  - sharebymail: 1.14.0
  - support: 1.7.0
  - survey_client: 1.12.0
  - systemtags: 1.14.0
  - text: 3.5.1
  - theming: 1.15.0
  - twofactor_backupcodes: 1.13.0
  - updatenotification: 1.14.0
  - user_status: 1.4.0
  - viewer: 1.8.0
  - weather_status: 1.4.0
  - workflowengine: 2.6.0
Disabled:
  - admin_audit
  - encryption
  - files_external
  - user_ldap

Nextcloud Signing status

No response

Nextcloud Logs

{"reqId":"DmcdTsWS0sZzedqSNC19","level":2,"time":"2022-09-05T09:56:40+00:00","remoteAddr":"172.17.0.1","user":"admin","app":"no app in context","method":"HEAD","url":"/remote.php/dav/files/admin/asdsad","message":"File with name //asdsad could not be located","userAgent":"curl/7.84.0","version":"24.0.4.1","exception":{"Exception":"Sabre\\DAV\\Exception\\NotFound","Message":"File with name //asdsad could not be located","Code":0,"Trace":[{"file":"/var/www/html/3rdparty/sabre/dav/lib/DAV/Tree.php","line":78,"function":"getChild","class":"OCA\\DAV\\Connector\\Sabre\\Directory","type":"->","args":["asdsad"]},{"file":"/var/www/html/apps/dav/lib/DAV/ViewOnlyPlugin.php","line":74,"function":"getNodeForPath","class":"Sabre\\DAV\\Tree","type":"->","args":["files/admin/asdsad"]},{"file":"/var/www/html/3rdparty/sabre/event/lib/WildcardEmitterTrait.php","line":89,"function":"checkViewOnly","class":"OCA\\DAV\\DAV\\ViewOnlyPlugin","type":"->","args":[{"__class__":"Sabre\\HTTP\\Request"},{"__class__":"Sabre\\HTTP\\Response"}]},{"file":"/var/www/html/3rdparty/sabre/dav/lib/DAV/Server.php","line":472,"function":"emit","class":"Sabre\\DAV\\Server","type":"->","args":["method:GET",[{"__class__":"Sabre\\HTTP\\Request"},{"__class__":"Sabre\\HTTP\\Response"}]]},{"file":"/var/www/html/3rdparty/sabre/dav/lib/DAV/CorePlugin.php","line":251,"function":"invokeMethod","class":"Sabre\\DAV\\Server","type":"->","args":[{"__class__":"Sabre\\HTTP\\Request"},{"__class__":"Sabre\\HTTP\\Response"},false]},{"file":"/var/www/html/3rdparty/sabre/event/lib/WildcardEmitterTrait.php","line":89,"function":"httpHead","class":"Sabre\\DAV\\CorePlugin","type":"->","args":[{"__class__":"Sabre\\HTTP\\Request"},{"__class__":"Sabre\\HTTP\\Response"}]},{"file":"/var/www/html/3rdparty/sabre/dav/lib/DAV/Server.php","line":472,"function":"emit","class":"Sabre\\DAV\\Server","type":"->","args":["method:HEAD",[{"__class__":"Sabre\\HTTP\\Request"},{"__class__":"Sabre\\HTTP\\Response"}]]},{"file":"/var/www/html/3rdparty/sabre/dav/lib/DAV/Server.php","line":253,"function":"invokeMethod","class":"Sabre\\DAV\\Server","type":"->","args":[{"__class__":"Sabre\\HTTP\\Request"},{"__class__":"Sabre\\HTTP\\Response"}]},{"file":"/var/www/html/3rdparty/sabre/dav/lib/DAV/Server.php","line":321,"function":"start","class":"Sabre\\DAV\\Server","type":"->","args":[]},{"file":"/var/www/html/apps/dav/lib/Server.php","line":358,"function":"exec","class":"Sabre\\DAV\\Server","type":"->","args":[]},{"file":"/var/www/html/apps/dav/appinfo/v2/remote.php","line":35,"function":"exec","class":"OCA\\DAV\\Server","type":"->","args":[]},{"file":"/var/www/html/remote.php","line":166,"args":["/var/www/html/apps/dav/appinfo/v2/remote.php"],"function":"require_once"}],"File":"/var/www/html/apps/dav/lib/Connector/Sabre/Directory.php","Line":242,"message":"File with name //asdsad could not be located","exception":{},"CustomMessage":"File with name //asdsad could not be located"}}

Additional info

If there's a better way to check for file existence, please let us know.

cc @tobiasKaminsky

[szaimen]

cc @nextcloud/server-backend

[come-nc]

The logging comes from #32482 that adds the ViewOnlyPlugin class, I think.