PowerShell, read/write to SSH.NET streams

Question

I would like to connect to a server via SSH, with PowerShell, and then change to a different user.

In order to accomplish connecting to a server with PowerShell via SSH, I used SSH from PowerShell using the SSH.NET library and How to connect via SSH from powershell. That was great and gave me simple commandlets such as new-sshsession and invoke-sshcommand to work with.

Next, I wanted to su to a different user. When I tried to do that via the commandlets, I got the error: standard in must be a tty.

I understand that I can edit the security settings on the server to let me su to a user without being in interactive mode. However, I can't change that setting on all the servers I want to connect to.

Working off of a C# example I found at https://sshnet.codeplex.com/discussions/285853, I put together:

$server = "server1"
$port = 22
$username = "user1"
$password = "password1"

$ssh = new-object Renci.SshNet.SshClient($server, $port, $username, $password)
$ssh.Connect()

$inputstream = new-object System.IO.MemoryStream
$streamwriter = new-object System.IO.StreamWriter($inputstream)
$outputstream = new-object System.IO.MemoryStream
$streamreader = new-object System.IO.StreamReader($outputstream)

$shell = $ssh.CreateShell($inputstream, $outputstream, $outputstream)
$shell.Start()
$streamwriter.WriteLine("echo hello > tempfile.txt")
$streamwriter.Flush()
$streamreader.ReadToEnd()

$shell.Stop()

Running, that I get output such as:

Last login: Fri Nov  8 11:37:45 2013 from 10.XXX.XXX.XXX
[user1@server1 /users/user1]

However, /users/user1/tempfile.txt never gets written and I do not get any further output.

Do you see what I'm doing wrong?

Answer 1

Using an example from https://sshnet.codeplex.com/discussions/439210, I was able to solve my problem with the below code. The main issue was that I was creating two different streams for input/output and I needed to just use one stream.

$server = "server1"
$port = 22
$username = "user1"
$password = "password1"

###############################################################

function ReadStream($reader)
{
    $line = $reader.ReadLine();
    while ($line -ne $null)
    {
        $line
        $line = $reader.ReadLine()
    }
}

function WriteStream($cmd, $writer, $stream)
{
    $writer.WriteLine($cmd)
    while ($stream.Length -eq 0)
    {
        start-sleep -milliseconds 500
    }
}

###############################################################

$ssh = new-object Renci.SshNet.SshClient($server, $port, $username, $password)
$ssh.Connect()

$stream = $ssh.CreateShellStream("dumb", 80, 24, 800, 600, 1024)

$reader = new-object System.IO.StreamReader($stream)
$writer = new-object System.IO.StreamWriter($stream)
$writer.AutoFlush = $true

while ($stream.Length -eq 0)
{
    start-sleep -milliseconds 500
}
ReadStream $reader

WriteStream "su - root" $writer $stream
ReadStream $reader

WriteStream "password" $writer $stream
ReadStream $reader

WriteStream "pwd" $writer $stream
ReadStream $reader

$stream.Dispose()
$ssh.Disconnect()
$ssh.Dispose()