how to use TLS 1.2 in FTP over SSL

Question

Hi, I am using below code to transfer file to mainframe server

Ftp fClient = new Ftp();

        try
        {
            //ftp over ssl -> secure ftp protocol for mainframe
            fClient.Settings.SslAcceptAllCertificates = true;
            fClient.Connect(ftpServerName, SslMode.Explicit);
            fClient.Login(ftpUserName, ftpPassword);
            fClient.TransferType = FtpTransferType.Ascii;
            fClient.Site("RECFM=FB LRECL=100 BLOCKSIZE=0");

            fClient.PutFile(sourceFilePath, ftpFilePath);
        }

It seems it is using TLS 1.0 to connect and it is failing to connect to server because now server is enforcing TLS 1.2.

How can I modify the code to use TLS 1.2 for connection?

Answer 1

TLS 1.2 is enabled by default and it should be negotiated as the first possible choice. You can ensure that TLS 1.2 is enabled like this:

fClient.Settings.SslAllowedVersions = TlsVersion.TLS12;

However, I think the problem is probably caused by something else. Please, create the communication log and post it here or send it to support@rebex.net for analysis. It can be created like this:

fClient.LogWriter = new Rebex.FileLogWriter(@"c:\data\ftp.log", Rebex.LogLevel.Debug);

Comments

Hi, I tried using fClient.Settings.SslAllowedVersions = TlsVersion.TLS12;
But it is giving error in TLS12. it is only showing TLS10 and TLS11. There is no option to select TLS12.

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Rebex dlls that we are using are of version "3.0.4700.0".

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Oh, it explains everything. Version 3.0.4700.0 is from 2012. We added support for TLS 1.2 in 2015 (see https://www.rebex.net/total-pack/history.aspx#5555).

Please, try the latest version. You can download free trial from https://www.rebex.net/total-pack/download.aspx