Ios 安装VPN时不保存密码

我正在尝试在我的应用程序上安装VPN，问题是安装后，IOS会提示我输入VPN密码，即使代码中指定了密码

我的代码有什么问题

 @IBAction func Install(_ sender: Any) {


        NEVPNManager.shared().loadFromPreferences { error in
            // setup the config:
            let password = "vpnpass"
            let vpnhost = "us-west.windscribe.com"
            let p = NEVPNProtocolIKEv2()
            p.username = "vpnuser"
            p.serverAddress = vpnhost
            p.remoteIdentifier = vpnhost
            p.authenticationMethod = .none
            p.passwordReference = password.data(using: .utf8)!
            p.useExtendedAuthentication = true
            p.serverCertificateIssuerCommonName = vpnhost
            p.disconnectOnSleep = false


            print("Password:")
            print(password.data(using: .utf8)!)


            var rules = [NEOnDemandRule]()
            let rule = NEOnDemandRuleConnect()
            rule.interfaceTypeMatch = .any
            rules.append(rule)

            NEVPNManager.shared().localizedDescription = "My VPN"
            NEVPNManager.shared().protocolConfiguration = p
            NEVPNManager.shared().onDemandRules = rules
            NEVPNManager.shared().isOnDemandEnabled = true
            NEVPNManager.shared().isEnabled = true
            NEVPNManager.shared().saveToPreferences { error in
                guard error == nil else {
                    print("NEVPNManager.saveToPreferencesWithCompletionHandler failed: \(error!.localizedDescription)")
                    return
                }
               VPNManager.sharedManager.startVPNTunnel()
            }
        }

此外，我无法在应用程序中自动启动它，因为无法识别

VPNManager.sharedManager.startVPNTunnel（）

此外，日志中还会出现以下内容：

2017-06-04 13:02:40.143478-0400 VPN[1212:157220] [] (null): SecItemCopyMatching failed: -50

---

p、 authenticationMethod=.none将其更改为NevpnikeAuthenticationMethodsSharedSecret，则不再询问密码

谢谢你的问候