Do not create local world-readable files and directories per default

Starting with e5dc1a8 ("Set umask before operations that create
local files") Nextcloud would create local files and directories with
their permission set to world readable. While you can protect access
to nextcloud's data/ directory by -x'ing it, when it comes to
permissions and security, a defensive approach is always
preferable. Hence this changes the used umask from 022 to 027.

This partly addresses #29041.

Signed-off-by: Florian Schmaus <flo@geekplace.eu>

lib/private/Files/Storage/Local.php

@@ -87,8 +87,8 @@ public function getId() {
 
 	public function mkdir($path) {
 		$sourcePath = $this->getSourcePath($path);
-		$oldMask = umask(022);
-		$result = @mkdir($sourcePath, 0777, true);
+		$oldMask = umask(027);
+		$result = @mkdir($sourcePath, 0770, true);
 		umask($oldMask);
 		return $result;
 	}
@@ -259,7 +259,7 @@ public function touch($path, $mtime = null) {
 		if ($this->file_exists($path) and !$this->isUpdatable($path)) {
 			return false;
 		}
-		$oldMask = umask(022);
+		$oldMask = umask(027);
 		if (!is_null($mtime)) {
 			$result = @touch($this->getSourcePath($path), $mtime);
 		} else {
@@ -278,7 +278,7 @@ public function file_get_contents($path) {
 	}
 
 	public function file_put_contents($path, $data) {
-		$oldMask = umask(022);
+		$oldMask = umask(027);
 		$result = file_put_contents($this->getSourcePath($path), $data);
 		umask($oldMask);
 		return $result;
@@ -351,15 +351,15 @@ public function copy($path1, $path2) {
 		if ($this->is_dir($path1)) {
 			return parent::copy($path1, $path2);
 		} else {
-			$oldMask = umask(022);
+			$oldMask = umask(027);
 			$result = copy($this->getSourcePath($path1), $this->getSourcePath($path2));
 			umask($oldMask);
 			return $result;
 		}
 	}
 
 	public function fopen($path, $mode) {
-		$oldMask = umask(022);
+		$oldMask = umask(027);
 		$result = fopen($this->getSourcePath($path), $mode);
 		umask($oldMask);
 		return $result;