vendor: change goftp/server url

Closing #3674

vendor/goftp.io/server/auth.go

@@ -0,0 +1,33 @@
+// Copyright 2018 The goftp Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package server
+
+import (
+	"crypto/subtle"
+)
+
+// Auth is an interface to auth your ftp user login.
+type Auth interface {
+	CheckPasswd(string, string) (bool, error)
+}
+
+var (
+	_ Auth = &SimpleAuth{}
+)
+
+// SimpleAuth implements Auth interface to provide a memory user login auth
+type SimpleAuth struct {
+	Name     string
+	Password string
+}
+
+// CheckPasswd will check user's password
+func (a *SimpleAuth) CheckPasswd(name, pass string) (bool, error) {
+	return constantTimeEquals(name, a.Name) && constantTimeEquals(pass, a.Password), nil
+}
+
+func constantTimeEquals(a, b string) bool {
+	return len(a) == len(b) && subtle.ConstantTimeCompare([]byte(a), []byte(b)) == 1
+}