SSH.NET" Version=2020.0.0

[alona0610]

Hi
I have a problem with SSH.Net 2020.0.0 When trying to SFTP file to Linux Server.
I am using .Net Core 3.1 under IIS.

The error that I am getting randomly is that the server is timing out.
Renci.SshNet.Common.SshOperationTimeoutException: Connection failed to establish within 30000 milliseconds.

Below is my code.
var connectionInfo = new RenciSftp.ConnectionInfo(this.FileServerHost,
this.FileServerUsername,
new RenciSftp.PasswordAuthenticationMethod(this.FileServerUsername, this.FileServerPassword));

 using (var client = new RenciSftp.SftpClient(connectionInfo))
 {
 try
 {
 client.Connect();
 client.ChangeDirectory(remoteDir);
 client.BufferSize = 4 * 1024; // bypass Payload error large files
 using (var fileStream = fileStorage.GetFileStream(session))
 {
 client.UploadFile(fileStream, serverFilename);
 }
 }

 catch (Renci.SshNet.Common.SshConnectionException ex)
 {
 this.AddUploadError("ERROR","SshConnectionException", hostName + "; " + IP, ex.ToString());
 }
 catch (System.Net.Sockets.SocketException ex)
 {
 this.AddUploadError("ERROR", "SocketException", hostName + "; " + IP, ex.ToString());
 }

 catch (Renci.SshNet.Common.SshAuthenticationException ex)
 {
 this.AddUploadError("ERROR","SshAuthenticationException", hostName + "; " + IP, ex.ToString());
 }
 catch (Exception ex)
 {
 this.AddUploadError("ERROR","General Error", hostName + "; " + IP, ex.ToString());
 }

 client.Disconnect();
 client.Dispose();

}

[alona0610]

Any info on that error?

[vvvarunv]

With 2020.0.1 I am also seeing similar errors

connection time(ms) : 30013, exception : Renci.SshNet.Common.SshOperationTimeoutException: Session operation has timed out

I reverted to 2016.1.0 and things are fine now

This is when trying to SSH into a Cisco router.

[vvvarunv]

@drieseng : Any update on this?

[drieseng]

Can any of you give me (private) access to a server/device that I can use to reproduce this issue?

[Sparin]

Hi everyone!

We (on my job) recently met this error on connecting to Cisco Catalyst 9300-48UN-A Switch (Cisco IOS XE 16.12.2s). In our case, we unexpectedly stuck at awaiting SSH_MSG_KEXINIT from the Cisco switch after a few successful connections. It's just awaiting 30 seconds for timeout and drop the connection then.

During a sniffing session, we've concluded switch awaits SSH_MSG_KEXINIT from us for no reason. We tried to move sending SSH_MSG_KEXINIT from the KeyExchange.cs file/procedure just before the awaiting SSH_MSG_KEXINIT from the server at Session.cs. Looking to RFC 4253 Section 7 and source code of SSH.NET, I didn't find any reason to awaits SSH_MSG_KEXINIT from the server. So it looks like a race condition deadlock.

Our step to reproduce a little bit the same

1. Deploy any ASP.NET Core or .NET Core 3.1 server under IIS 10 deployment
2. Invoke your SSH.NET code to Cisco at anyways for multiple times
3. First attempts probably will be fine, but after some time you'll get a deadlock

Our code snippet which we are testing

public bool IsKeyValid(string userName, string privateKey)
{
 using var privateKeyStream = new MemoryStream(Encoding.ASCII.GetBytes(privateKey));
 using var sshClient = new SshClient(_address, _port ?? 22, userName, new PrivateKeyFile(privateKeyStream));
 sshClient.Connect();

 return sshClient.IsConnected;
}

Can any of you give me (private) access to a server/device that I can use to reproduce this issue?

@drieseng We don't have direct access to the switch and server with this problem, but maybe we can agree on a Zoom session with the owner. But probably they'll decline the request for NDA reasons

[WojciechNagorski]

It's done in #1274

[WojciechNagorski]

The 2023.0.1 version has been released to Nuget: https://www.nuget.org/packages/SSH.NET/2023.0.1