sftpd: add support for chmod/chown

added matching permissions too and a new setting "setstat_mode".
Setting setstat_mode to 1 you can keep the previous behaviour that
silently ignore setstat requests

dataprovider/dataprovider.go

@@ -65,7 +65,7 @@ var (
 		BoltDataProviderName, MemoryDataProviderName}
 	// ValidPerms list that contains all the valid permissions for an user
 	ValidPerms = []string{PermAny, PermListItems, PermDownload, PermUpload, PermOverwrite, PermRename, PermDelete,
-		PermCreateDirs, PermCreateSymlinks}
+		PermCreateDirs, PermCreateSymlinks, PermChmod, PermChown}
 	config          Config
 	provider        Provider
 	sqlPlaceholders []string

dataprovider/user.go

@@ -30,6 +30,10 @@ const (
 	PermCreateDirs = "create_dirs"
 	// create symbolic links is allowed
 	PermCreateSymlinks = "create_symlinks"
+	// changing file or directory permissions is allowed
+	PermChmod = "chmod"
+	// changing file or directory owner is allowed
+	PermChown = "chown"
 )
 
 // User defines an SFTP user