fix(files_external): on case insensitive system, block case change

When a file/directory is renamed to the same name with only case change,
the rename fail. We block this kind of rename.
The user will have to rename to another name first.

Signed-off-by: Benjamin Gaussorgues <benjamin.gaussorgues@nextcloud.com>

apps/files_external/lib/Lib/Backend/SMB.php

@@ -59,6 +59,11 @@ public function __construct(IL10N $l, Password $legacyAuth) {
 				(new DefinitionParameter('show_hidden', $l->t('Show hidden files')))
 					->setType(DefinitionParameter::VALUE_BOOLEAN)
 					->setFlag(DefinitionParameter::FLAG_OPTIONAL),
+				(new DefinitionParameter('case_sensitive', $l->t('Case sensitive file system')))
+					->setType(DefinitionParameter::VALUE_BOOLEAN)
+					->setFlag(DefinitionParameter::FLAG_OPTIONAL)
+					->setDefaultValue(true)
+					->setTooltip($l->t('Disabling it will allow to use a case insentive file system, but comes with a performance penalty')),
 				(new DefinitionParameter('check_acl', $l->t('Verify ACL access when listing files')))
 					->setType(DefinitionParameter::VALUE_BOOLEAN)
 					->setFlag(DefinitionParameter::FLAG_OPTIONAL)

apps/files_external/lib/Lib/Storage/SMB.php

@@ -93,6 +93,8 @@ class SMB extends Common implements INotifyStorage {
 	/** @var bool */
 	protected $showHidden;
 
+	private bool $caseSensitive;
+
 	/** @var bool */
 	protected $checkAcl;
 
@@ -139,6 +141,7 @@ public function __construct($params) {
 		$this->root = rtrim($this->root, '/') . '/';
 
 		$this->showHidden = isset($params['show_hidden']) && $params['show_hidden'];
+		$this->caseSensitive = (bool) ($params['case_sensitive'] ?? true);
 		$this->checkAcl = isset($params['check_acl']) && $params['check_acl'];
 
 		$this->statCache = new CappedMemoryCache();
@@ -325,6 +328,12 @@ public function rename($source, $target, $retry = true): bool {
 		if ($this->isRootDir($source) || $this->isRootDir($target)) {
 			return false;
 		}
+		if ($this->caseSensitive === false
+			&& mb_strtolower($target) === mb_strtolower($source)
+		) {
+			// Forbid changing case only on case-insensitive file system
+			return false;
+		}
 
 		$absoluteSource = $this->buildPath($source);
 		$absoluteTarget = $this->buildPath($target);
@@ -674,6 +683,16 @@ public function mkdir($path) {
 
 	public function file_exists($path) {
 		try {
+			if ($this->caseSensitive === false) {
+				$filename = basename($path);
+				$siblings = $this->getDirectoryContent(dirname($this->buildPath($path)));
+				foreach ($siblings as $sibling) {
+					if ($sibling['name'] === $filename) {
+						return true;
+					}
+				}
+				return false;
+			}
 			$this->getFileInfo($path);
 			return true;
 		} catch (\OCP\Files\NotFoundException $e) {