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

sftpd/sftpd.go

@@ -29,6 +29,8 @@ const (
 	mkdirLogSender    = "Mkdir"
 	symlinkLogSender  = "Symlink"
 	removeLogSender   = "Remove"
+	chownLogSender    = "Chown"
+	chmodLogSender    = "Chmod"
 	operationDownload = "download"
 	operationUpload   = "upload"
 	operationDelete   = "delete"
@@ -54,6 +56,7 @@ var (
 	dataProvider         dataprovider.Provider
 	actions              Actions
 	uploadMode           int
+	setstatMode          int
 )
 
 type connectionTransfer struct {
@@ -103,6 +106,10 @@ type ConnectionStatus struct {
 	Transfers []connectionTransfer `json:"active_transfers"`
 }
 
+type sshSubsystemExitStatus struct {
+	Status uint32
+}
+
 func init() {
 	openConnections = make(map[string]Connection)
 	idleConnectionTicker = time.NewTicker(5 * time.Minute)