CODEWITHSUNDEEP
powershellsshputtyplink
leeand00
leeand00

Reputation: 26392

Using System.Diagnostics.Process to input a y to a Plink on standard input?

How do I pass a Y into a process started by a System.Diagnostic.Process in PowerShell?

function Start-NewPlinkProcess(
        [string]$pfile = 'plink.exe',
        [string]$arguments = 'somehost -l somelogin -pw somepasswd ping -c 12 someOtherHost > /home/homeie/mePingTestResults.txt'
    ){
    $p = New-Object System.Diagnostics.Process;
    $p.StartInfo.UseShellExecute = $false;
    $p.StartInfo.RedirectStandardOutput = $true;
    $p.StartInfo.RedirectStandardInput = $true;
    $p.StartInfo.FileName = $pfile;
    $p.StartInfo.Arguments = $arguments
    $p.StandardInput.WriteLine("Y") # Pass a Y to stdin ignore that...
    $pident = ($p.Start()).Id
    Write-Host("pid: $($pident)");
    #$p.WaitForExit();
    #$p.StandardOutput.ReadToEnd();
    return $p
}

When I call it I still get:

If you trust this host, enter "y" to add the key to
PuTTY's cache and carry on connecting.
If you want to carry on connecting just once, without
adding the key to the cache, enter "n".
If you do not trust this host, press Return to abandon the
connection.
Store key in cache? (y/n)

I've read elsewhere that it's possible to try something like echo y | plink ... and have it read it in piped from standard input, but I want to have more control over it then just that.

Upvotes: 1

Views: 981

Answers (2)

Martin Prikryl
Martin Prikryl

Reputation: 202262

Do not!

Verifying host key fingerprint is an integral part of securing your connection. Blindly accepting any host key will make you vulnerable to the man-in-the-middle attacks.

Instead, use the -hostkey switch to provide the fingerprint of the expected/known host key.

[string]$arguments = 'somehost -l somelogin -pw somepasswd ping -hostkey xx:xx:xx:xx:... -c 12 someOtherHost > /home/homeie/mePingTestResults.txt'

Upvotes: 1

Paul G
Paul G

Reputation: 1229

Just move your StandardInput line below where the process is started.

function Start-NewPlinkProcess(
        [string]$pfile = 'plink.exe',
        [string]$arguments = 'somehost -l somelogin -pw somepasswd ping -c 12 someOtherHost > /home/homeie/mePingTestResults.txt'
    ){
    $p = New-Object System.Diagnostics.Process;
    $p.StartInfo.UseShellExecute = $false;
    $p.StartInfo.RedirectStandardOutput = $true;
    $p.StartInfo.RedirectStandardInput = $true;
    $p.StartInfo.FileName = $pfile;
    $p.StartInfo.Arguments = $arguments
    $pident = ($p.Start()).Id
    Write-Host("pid: $($pident)");
    $p.StandardInput.WriteLine("Y") # Pass a Y to stdin ignore that...
    #$p.WaitForExit();
    #$p.StandardOutput.ReadToEnd();
    return $p
}

Upvotes: 0

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