ShellStream copies from output stream back to input stream when Task.Delay is used

[Kemsekov]

Problem

Shell copies output stream back to input stream when Task.Delay is called.

How to reproduce

using var client = new Renci.SshNet.SshClient("ip","root","password");

client.Connect();

var file = File.Open("output.txt",FileMode.Append);
using var shellStream = client.CreateShellStream("shell1",0,0,0,0,10000000);
using var shell = client.CreateShell(shellStream,file,null);

shell.Start();

shellStream.WriteLine("echo \"touch very_dangerous_command.txt\" > file.txt");
Task.Delay(1000).Wait();

shellStream.WriteLine("cat file.txt");
Task.Delay(1000).Wait();

shellStream.WriteLine("rm file.txt");
Task.Delay(1000).Wait();

shellStream.WriteLine("history");
Task.Delay(1000).Wait();

shell.Stop();

What effects it have:

It does create file.txt with content touch very_dangerous_command.txt

It prints to output buffer touch very_dangerous_command.txt

It does remove file.txt.

But when history is called it repeats everything back inside of itself and in the end on my remote machine I have both files 'file.txt' and 'very_dangerous_command.txt' which is nuts. =/

interestingly, without Task.Delay() calls it works just fine.

Results

Files in the /root on server before program execution and after.

Text file that shows what is happening to shell. There is a lot of repeated/misplaced commands, which leads to chaos.
output.txt

Setup

dotnet 7.0.105
"SSH.NET" Version="2020.0.2

Linux myhostname 6.3.8-arch1-1 #1 SMP PREEMPT_DYNAMIC Wed, 14 Jun 2023 20:10:31 +0000 x86_64 GNU/Linux

[Rob-Hague]

I could be wrong, but I don't think Shell and ShellStream are meant to be used together: they both create a "session" channel and a shell independently. I think you might try passing a standard MemoryStream to the input parameter of CreateShell which you can wrap in a StreamWriter.

Or alternatively, use the ShellStream as you are doing but without the Shell.

As to why these two types both exist, I have no idea.