.netshellsshsftpssh.net

Respond interactive shell prompts using SSH.NET

I want to create an SFTP account via ASP.NET app. For defining its password I need to type it twice

root@localhost:~# passwd fadwa
Enter new password:
Retype new password:
passwd: password updated successfully

To do so via C# code, I've tried the following after consulting a lot of solutions here, but it doesn't work.

using (var client = new SshClient("xx.xxx.xxx.xxx", 22, "root", "********"))
{
    client.Connect();
    ShellStream shellStream = client.CreateShellStream(string.Empty, 0, 0, 0, 0, 0);
    StreamWriter stream = new StreamWriter(shellStream);
    StreamReader reader = new StreamReader(shellStream);
    stream.WriteLine("passwd fadwa"); // It displays -1
    stream.WriteLine("fadwa");
    stream.WriteLine("fadwa");
    Console.WriteLine(reader.Read());    // It displays -1     
    client.Disconnect();
}

I've tried it even without using the StreamWriter but directly :

shellStream.WriteLine("passwd fadwa\n" + "fadwa\n" + "fadwa\n");
while (true) Console.WriteLine(shellStream.Read());

also

shellStream.WriteLine("passwd fadwa");
shellStream.WriteLine("fadwa");
shellStream.WriteLine("fadwa"); 
while (true) Console.WriteLine(shellStream.Read());

And I got this, It stuck there!! Screenshot for the output displayed on the console

Any suggestions why it didn't work or other solution? I think I ve tried already the second solution and It worked, but not now.

Solution

  • You probably have to send the input only after the prompts appear. If you send the input too early, it gets ignored.

    A lame solution would be like:

    shellStream.WriteLine("passwd fadwa");
Thread.Sleep(100);
shellStream.WriteLine("fadwa");
Thread.Sleep(100);
shellStream.WriteLine("fadwa");

    Better solution would be to wait for the prompt, before sending the password – expect-like:

    shellStream.WriteLine("passwd fadwa");
shellStream.Expect("Enter new password:");
shellStream.WriteLine("fadwa");
shellStream.Expect("Retype new password:");
shellStream.WriteLine("fadwa");

    In general, automating a shell is always error-prone and should be avoided.