[Bug]: Cannot upload files with mtime set to a small value

[felix-walter]

⚠️ 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 OR Nextcloud Community Forum (I've searched it).
• Nextcloud Server is up to date. See Maintenance and Release Schedule for supported versions.
• I agree to follow Nextcloud's Code of Conduct.

Bug description

When uploading files with a small modification timestamp such as 1, Nextcloud returns the following error:

X-OC-MTime header must be a valid positive integer

Sometimes, only a generic HTTP 500 error is shown by the web interface and the user needs to check the network requests in the dev. console to see the error message.

This prevents uploading files built with Nix without previously changing the modification time for any of those files: Nix sets the timestamp to 1 for ensuring reproducible builds.

The bug occurs due to the check in apps/dav/lib/Connector/Sabre/MtimeSanitizer.php introduced in 69b8044.

As small timestamps such as 1 are perfectly valid values for the modification timestamp, they should be allowed.

Steps to reproduce

1. Create a file with a low modification timestamp, e.g., via touch -m -t 197001010100.01 abc.txt; or build something with Nix and try to upload the result.
2. Try to upload the file, e.g., using the web interface.

Expected behavior

The files are uploaded successfully and the small timestamp value is preserved.

Installation method

Official All-in-One appliance

Nextcloud Server version

28

Operating system

None

PHP engine version

None

Web server

None

Database engine version

None

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

None

Are you using the Nextcloud Server Encryption module?

None

What user-backends are you using?

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

Configuration report

No response

List of activated Apps

No response

Nextcloud Signing status

No response

Nextcloud Logs

No response

Additional info

No response

[joshtrichards]

The original check for this predates that. It's from #30114. I believe it may have been originally driven by the mtime matter that arose in late 2021 (with the Desktop client). I don't recall the specifics, but we might be able to make the sanitize check more specific these days.

[skjnldsv]

This is a wontfix. This measure was taken to fix an important bug which invalid mtimes could trigger a massive file deletion

[felix-walter]

Maybe an option in this case would be to show a somewhat sensible error message in the web UI instead of just a HTTP 500? Something such as "The file you are trying to upload has an unsupported modification date, please change it before uploading."?

It took me quite some time to figure out the cause of the issue here.