[Bug]: Impossible to rename or delete files with invalid characters in their names

⚠️ 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

With the latest stable29, after setting some forbidden characters for file names, the existing files/directories that have those characters in their names can't be renamed at all anymore.
Sabre complains that there is at least one invalid char in the name even if there is no invalid char in the target name but only in the current name.

Steps to reproduce

1. Create a file named a%b.txt
2. Add 'forbidden_chars' => ['%'], to config.php
3. Try to rename the file to ab.txt
4. The MOVE request fails.
   MOVE /remote.php/dav/files/admin/specialchars/a%25b.md
   with the Destination header being /remote.php/dav/files/admin/specialchars/ab.md

<?xml version="1.0" encoding="utf-8"?>
<d:error xmlns:d="DAV:" xmlns:s="http://sabredav.org/ns">
	<s:exception>Internal Server Error</s:exception>
	<s:message>
		The server was unable to complete your request.		If this happens again, please send the technical details below to the server administrator.		More details can be found in the server log.			</s:message>

	<s:technical-details>
		<s:remote-address>192.168.21.3</s:remote-address>
		<s:request-id>tEi9t7j2C4ZKeEsBblSc</s:request-id>

			<s:type>OCA\DAV\Connector\Sabre\Exception\InvalidPath</s:type>
		<s:code>0</s:code>
		<s:message>File name contains at least one invalid character</s:message>
		<s:file>/var/www/html/apps/dav/lib/Connector/Sabre/Directory.php</s:file>
		<s:line>219</s:line>

		<s:stacktrace>
			#0 /var/www/html/3rdparty/sabre/dav/lib/DAV/Tree.php(95): OCA\DAV\Connector\Sabre\Directory-&gt;getChild(&#039;a%b.md&#039;)
#1 /var/www/html/apps/dav/lib/DAV/ViewOnlyPlugin.php(76): Sabre\DAV\Tree-&gt;getNodeForPath(&#039;files/admin/spe...&#039;)
#2 /var/www/html/3rdparty/sabre/event/lib/WildcardEmitterTrait.php(89): OCA\DAV\DAV\ViewOnlyPlugin-&gt;checkViewOnly(Object(Sabre\HTTP\Request), Object(Sabre\HTTP\Response))
#3 /var/www/html/3rdparty/sabre/dav/lib/DAV/Server.php(472): Sabre\DAV\Server-&gt;emit(&#039;method:MOVE&#039;, Array)
#4 /var/www/html/apps/dav/lib/Connector/Sabre/Server.php(61): Sabre\DAV\Server-&gt;invokeMethod(Object(Sabre\HTTP\Request), Object(Sabre\HTTP\Response))
#5 /var/www/html/3rdparty/sabre/dav/lib/DAV/Server.php(321): OCA\DAV\Connector\Sabre\Server-&gt;start()
#6 /var/www/html/apps/dav/lib/Server.php(393): Sabre\DAV\Server-&gt;exec()
#7 /var/www/html/apps/dav/appinfo/v2/remote.php(35): OCA\DAV\Server-&gt;exec()
#8 /var/www/html/remote.php(172): require_once(&#039;/var/www/html/a...&#039;)
#9 {main}		</s:stacktrace>
		</s:technical-details>
</d:error>

Expected behavior

In NC >= 30, those files can be renamed to a valid name even if the current name is invalid.

Nextcloud Server version

29

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

List of activated Apps

Nextcloud Signing status

Nextcloud Logs

Additional info

No response

Start in apps/dav/lib/Connector/Sabre/Directory.php around line 219 and trace the MOVE request shown in the stack trace. Reproduce the configured forbidden character case, then verify that an existing file with an invalid current name can be renamed to a valid target name without triggering InvalidPath.