[Bug]: mimetype inconsistency between Detection.detectPath and Loader.updateFilecache

[tacruc]

⚠️ 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

For files named like .ext e.g. ".gpx", ".ext" or ".maps" get different mimetypes by

server/lib/private/Files/Type/Detection.php

Line 195 in ce1dddc

public function detectPath($path): string {

or

server/lib/private/Files/Type/Loader.php

Line 164 in ce1dddc

public function updateFilecache($ext, $mimeTypeId) {

.

To clearify its about files which start with a . and then just have the extension.
Therefore existing files get different mime-types then new file.

Steps to reproduce

1. Create ".ext" file
2. Run Loader->updateFilecache("ext", mimeTypeId)
3. Create corresponding Mimetype mapping
4. Uploade a file called ".ext" to a different folder
5. See that it gets a different Mimetype

Expected behavior

• Get the same Mimetype
• It would be nice if it would be the Mimetype in the mapping, then mimetypes can be used to find .noindex and .nomedia files, or in maps a .maps file. Searching the file over the mimetype is faster as there is a db index.

Installation method

None

Operating system

None

PHP engine version

None

Web server

None

Database engine version

MySQL

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

[]

Nextcloud Signing status

No response

Nextcloud Logs

No response

Additional info

No response

[tacruc]

Possible fixes:

	public function detectPath($path): string {
		$this->loadMappings();

		$fileName = basename($path);


		// remove versioning extension: name.v1508946057 and transfer extension: name.ocTransferId2057600214.part
		$fileName = preg_replace('!((\.v\d+)|((\.ocTransferId\d+)?\.part))$!', '', $fileName);

		//try to guess the type by the file extension
		$extension = strrchr($fileName, '.');
		if ($extension !== false) {
			$extension = strtolower($extension);
			$extension = substr($extension, 1); //remove leading .
			return $this->mimetypes[$extension][0] ?? 'application/octet-stream';
		}

		return 'application/octet-stream';
	}

Pros:

• Minimal change
• Consistent with 'updateFilecache'

Cons:

• Won't fix MIME-type detector cannot detect double-extensions like .tar.gz by path. #35104

	/**
	 * detect mimetype only based on filename, content of file is not used
	 *
	 * @param string $path
	 * @return string
	 */
	public function detectPath($path): string {
		$this->loadMappings();
		$extensions = array_keys($this->mimetypes);
		$fileName = basename($path);
		// remove versioning extension: name.v1508946057 and transfer extension: name.ocTransferId2057600214.part
		$fileName = preg_replace('!((\.v\d+)|((\.ocTransferId\d+)?\.part))$!', '', $fileName);
		$fileExtensions = [];
		foreach ($extensions as $ext) {
			if (str_ends_with('.'.$fileName, '.'.$ext)) $fileExtensions[]=$ext;
		}

		usort($fileExtensions, function($a, $b) {
			return strlen($b) - strlen($a);
		});

		$extension = array_shift($fileExtensions);
		return $this->mimetypes[$extension][0] ?? 'application/octet-stream';
	}

Pros:

• Will additionally fix MIME-type detector cannot detect double-extensions like .tar.gz by path. #35104

Cons:

• Performance?
• Again not consistent with 'updateFilecache()'

	/**
	 * detect mimetype only based on filename, content of file is not used
	 *
	 * @param string $path
	 * @return string
	 */
	public function detectPath($path): string {
		$this->loadMappings();

		$fileName = preg_replace('!((\.v\d+)|((\.ocTransferId\d+)?\.part))$!', '', basename($path));

		if (preg_match(
			'!(^\.(?<ext1>[^\.]+))|(^\.?[^\.]+\.(?<ext2>.+))$!',
			$fileName,
			$matches)){
			$extension = $matches['ext1'] ?? $matches['ext2'];
			return $this->mimetypes[$extension][0] ?? 'application/octet-stream';
		}

		return 'application/octet-stream';
	}

Pros:

• Will additionally fix MIME-type detector cannot detect double-extensions like .tar.gz by path. #35104

Cons:

• but create error on something like text.old.txt as it recoginzes old.txt as extension
• Again not consistent with 'updateFilecache()'

[szaimen]

cc @nextcloud/server for input/feedback on this :)

[tacruc]

Different fix from @nickvergessen would be:
$update->createNamedParameter('%_' . $this->dbConnection->escapeLikeParameter('.' . $ext))