Starting .ps1 Script from PowerShell with Parameters and Credentials and getting output using variable

Question

Hello Stack Community :)

I have a simple goal. I\'d like to start some PowerShell Script from an another Powershell Script, but there are 3 conditions:

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Answer 1

Start-Process would be my last resort choice for invoking PowerShell from PowerShell - especially because all I/O becomes strings and not (deserialized) objects.

Two alternatives:

1. If the user is a local admin and PSRemoting is configured

If a remote session against the local machine (unfortunately restricted to local admins) is a option, I'd definitely go with Invoke-Command:

$strings = Invoke-Command -FilePath C:\...\script1.ps1 -ComputerName localhost -Credential $credential

$strings will contain the results.

---

2. If the user is not an admin on the target system

You can write your own "local-only Invoke-Command" by spinning up an out-of-process runspace by:

1. Creating a PowerShellProcessInstance, under a different login
2. Creating a runspace in said process
3. Execute your code in said out-of-process runspace

I put together such a function below, see inline comments for a walk-through:

function Invoke-RunAs
{
    [CmdletBinding()]
    param(
        [Alias('PSPath')]
        [ValidateScript({Test-Path $_ -PathType Leaf})]
        [Parameter(Position = 0, Mandatory = $true, ValueFromPipeline = $true, ValueFromPipelineByPropertyName = $true)]
        [string]
        ${FilePath},

        [Parameter(Mandatory = $true)]
        [pscredential]
        [System.Management.Automation.CredentialAttribute()]
        ${Credential},

        [Alias('Args')]
        [Parameter(ValueFromRemainingArguments = $true)]
        [System.Object[]]
        ${ArgumentList},

        [Parameter(Position = 1)]
        [System.Collections.IDictionary]
        $NamedArguments
    )

    begin
    {
        # First we set up a separate managed powershell process
        Write-Verbose "Creating PowerShellProcessInstance and runspace"
        $ProcessInstance = [System.Management.Automation.Runspaces.PowerShellProcessInstance]::new($PSVersionTable.PSVersion, $Credential, $null, $false)

        # And then we create a new runspace in said process
        $Runspace = [runspacefactory]::CreateOutOfProcessRunspace($null, $ProcessInstance)
        $Runspace.Open()
        Write-Verbose "Runspace state is $($Runspace.RunspaceStateInfo)"
    }

    process
    {
        foreach($path in $FilePath){
            Write-Verbose "In process block, Path:'$path'"
            try{
                # Add script file to the code we'll be running
                $powershell = [powershell]::Create([initialsessionstate]::CreateDefault2()).AddCommand((Resolve-Path $path).ProviderPath, $true)

                # Add named param args, if any
                if($PSBoundParameters.ContainsKey('NamedArguments')){
                    Write-Verbose "Adding named arguments to script"
                    $powershell = $powershell.AddParameters($NamedArguments)
                }

                # Add argument list values if present
                if($PSBoundParameters.ContainsKey('ArgumentList')){
                    Write-Verbose "Adding unnamed arguments to script"
                    foreach($arg in $ArgumentList){
                        $powershell = $powershell.AddArgument($arg)
                    }
                }

                # Attach to out-of-process runspace
                $powershell.Runspace = $Runspace

                # Invoke, let output bubble up to caller
                $powershell.Invoke()

                if($powershell.HadErrors){
                    foreach($e in $powershell.Streams.Error){
                        Write-Error $e
                    }
                }
            }
            finally{
                # clean up
                if($powershell -is [IDisposable]){
                    $powershell.Dispose()
                }
            }
        }
    }

    end
    {
        foreach($target in $ProcessInstance,$Runspace){
            # clean up
            if($target -is [IDisposable]){
                $target.Dispose()
            }
        }
    }
}

Then use like so:

$output = Invoke-RunAs -FilePath C:\path\to\script1.ps1 -Credential $targetUser -NamedArguments @{ClientDevice = "ClientName"}