As part of a writing a decommission server PowerShell script at work, I had a requirement for a quick and easy SSH function to connect to our NetBackup server at work and remove the server from the backup system (Symantec if you’re reading this, please can we have a PowerShell module? *wishful thinking*…). Not quite needing the entire functionality provided by this module (based on the SSH.NET Library), I came across a function on PS Fab. One fantastic thing about this function is that supports the automatic acceptance of an SSH key when you connect to a host for the first time.

I made a few changes to the code, amended comments that referenced plist rather than plink and put it into a more standard function form with examples (that you might be able to add to an existing library). This is the result:

Function Invoke-SSH 
{
	<#
	.SYNOPSIS 
	Uses Plink.exe to SSH to a host and execute a list of commands.
	.DESCRIPTION
	Uses Plink.exe to SSH to a host and execute a list of commands.
	.PARAMETER hostname
	The host you wish to connect to.
	.PARAMETER username
	Username to connect with.
	.PARAMETER password
	Password for the specified user account.
	.PARAMETER commandArray
	A single, or list of commands stored in an array object.
	.PARAMETER plinkAndPath
	The location of the plink.exe including the executable (e.g. F:\tools\plink.exe)
	.PARAMETER connectOnceToAcceptHostKey
	If set to true, it will accept the remote host key (use when connecting for the first time)
	.EXAMPLE
	Invoke-SSH -username root -hostname centos-server -password Abzy4321! -plinkAndPath "F:\tools\plink.exe" -commandArray $commands -connectOnceToAcceptHostKey $true
	.EXAMPLE
	Invoke-SSH -username root -hostname centos-server -password Abzy4321! -plinkAndPath "F:\tools\plink.exe" -commandArray ifconfig -connectOnceToAcceptHostKey $true
	.NOTES
	Author: Robin Malik
	Source: Modified from: http://www.zerrouki.com/invoke-ssh/
	#>
	
	Param(
		[Parameter(Mandatory=$true,HelpMessage="Enter a host to connect to.")]
		[string]
		$hostname,
		
		[Parameter(Mandatory=$true,HelpMessage="Enter a username.")]
		[string]
		$username,
		
		[Parameter(Mandatory=$true,HelpMessage="Enter the password.")]
		[string]
		$password,
		
		[Parameter(Mandatory=$true,HelpMessage="Provide a command or comma separated list of commands")]
		[array]
		$commandArray,
		
		[Parameter(Mandatory=$true,HelpMessage="Path to plink (e.g. F:\tools\plink.exe).")]
		[string]
		$plinkAndPath,
		
		[Parameter(HelpMessage="Accept host key if connecting for the first time (the default is `$false)")]
		[string]
		$connectOnceToAcceptHostKey = $false
	)
	
	$target = $username + '@' + $hostname
	$plinkoptions = "-ssh $target -pw $password"
	 
	# On first connect to a host, plink will prompt you to accept the remote host key. 
	# This section will login and accept the host key then logout:
	if($ConnectOnceToAcceptHostKey)
	{
		$plinkCommand  = [string]::Format('echo y | & "{0}" {1} exit', $plinkAndPath, $plinkoptions )
		$msg = Invoke-Expression $plinkCommand
	}
	
	# Build the SSH Command by looping through the passed value(s). Append exit in order to logout:
	$commandArray += "exit"
	$commandArray | % { $remoteCommand += [string]::Format('{0}; ', $_) }
	
	# Format the command to pass to plink:
	$plinkCommand = [string]::Format('& "{0}" {1} "{2}"', $plinkAndPath, $plinkoptions , $remoteCommand)
	 
	# Execute the command and display the output:
	$msg = Invoke-Expression $plinkCommand
	Write-Output $msg
}

Copy and paste this function into a PowerShell window, and then test it with the below code (changing where appropriate of course):

$plinkAndPath = "F:\tools\plink\plink.exe"
$username = "root"
$password = "Adk3453#5341!"
$hostname = "centos-server"
# Commands to execute:
$Commands = @()
$Commands += "ifconfig"
$Commands += "ls"
Invoke-SSH -username $username -hostname $hostname -password $password -plinkAndPath $plinkAndPath -commandArray $Commands -connectOnceToAcceptHostKey $true