StartTLS connection without auth

[biancapop]

Hello, I need to create a StartTLS conexion without authentification for my smtp server. I tried all the ways you explain in the examples and documentation, even in the issues but I had no luck. This is my actual code: VERSION 1: var options = new SmtpServerOptionsBuilder() .ServerName(listen) .Port(port) .Port(securePort, isSecure: true) .MessageStore(new MessageProcessor(Path.Combine(rootPath, dataFolderName), ini)) .Certificate(new X509Certificate(cert)) .Build(); server = new SmtpServer.SmtpServer(options);

VERSION 2: var options = new SmtpServerOptionsBuilder() .ServerName(listen) .Port(port) .Endpoint(builder => builder .Port(securePort, true) .AuthenticationRequired(false) .IsSecure(true) .AllowUnsecureAuthentication(true)) .MessageStore(new MessageProcessor(Path.Combine(rootPath, dataFolderName), ini)) .Certificate(new X509Certificate(cert)) .Build(); VERSION 3: This is from your sample app: var options = new SmtpServerOptionsBuilder() .ServerName(listen) .Port(port) .Endpoint(endpoint => endpoint .Port(27, true) .AllowUnsecureAuthentication(false) .AuthenticationRequired(false)) .Certificate(X509Certificate.CreateFromCertFile(cert)) .MessageStore(new MessageProcessor(Path.Combine(rootPath, dataFolderName), ini)) .Build();

So when I send an email it just keeps hangign untill I get a timeout message. How can I achive this?

[cosullivan]

Hi @biancapop,

In your configuration where you have .Port(..., true) or if you use .IsSecure(true) set those to false.

Setting those to true means the endpoint is secure by default and in which case it will try to update the connection to SSL when the client connects rather than waiting for the client to issue a STARTTLS command.

Thanks, Cain.

[biancapop]

Hello Cain, Thank you very much for your response. So I did what you said and I now can se the STARTLS command when connecting with telnet but when I try to send an email the connection ends. I used openssl to debug it and all I get this message:

openssl s_client -connect generico.stampymail.com:25 -starttls smtp

CONNECTED(00000003) 140249106454416:error:140790E5:SSL routines:ssl23_write:ssl handshake failure:s23_lib.c:177: --- no peer certificate available --- No client certificate CA names sent --- SSL handshake has read 178 bytes and written 324 bytes --- New, (NONE), Cipher is (NONE) Secure Renegotiation IS NOT supported Compression: NONE Expansion: NONE No ALPN negotiated SSL-Session: Protocol : TLSv1.2 Cipher : 0000 Session-ID: Session-ID-ctx: Master-Key: Key-Arg : None Krb5 Principal: None PSK identity: None PSK identity hint: None Start Time: 1583162027 Timeout : 300 (sec) Verify return code: 0 (ok) --- I have no idea what I am doing wrong.. Thank you very much!

[cosullivan]

Hi,

Two things to check, is your X509 certificate a self signed certificate or is it signed by a trusted CA Root?

Also, what environment are you running on? Are you running this on Windows or are you running under Linux?

Thanks, Cain.

[biancapop]

Hello Cain, I run this on Linux and I have a self signed certificate. Thank you! :)

[cosullivan]

Ok, then both of those could potentially be the cause.

Firstly, with the self signed certificate it will most likely be failing validation.

When using self signed certificates you have two choices, adding them as trusted roots to your computer or ignoring the validation errors;

See this in the samples; https://github.com/cosullivan/SmtpServer/blob/master/Src/SampleApp/Examples/SecureServerExample.cs#L17

If you are using .NET Core 3.1 on Linux then this also could be an issue, see this thread; https://github.com/cosullivan/SmtpServer/issues/119

If so I would suggest trying on .NET Core 3 and see if it works firstly on that.

Thanks, Cain.