PowerShell QZ Tray Session Stealer (for Windows fast user switching)

README.MD

PowerShell QZ Tray Session Stealer

Custom session stealer for Windows fast user switching

For a pure Batch solution, see here instead: https://gist.github.com/tresf/ff91bd29f1f6846c13bf6f8bc255ab55

Problem

• QZ Tray is a singleton application, so only one instance can run at a time.
• Windows fast-user switching feature leaves applications running when a new user signs onto a shared workstation
• QZ Tray can "steal" the instance, however this is retroactive and places a burden on the user

Solution

• A solution is to detect that a user switch has occured and start QZ Tray on the new desktop automatically

Limitations

• This should ONLY be run on shared workstations with one user at a time. Terminal Server environments should instead leverage a dedicated print-server solution.

Steps

1. Copy start_if_active.ps1 to C:\Program Files\QZ Tray\
2. Import Steal QZ Tray At Login.xml to Task Scheduler
3. Test fast-user switching

start_if_active.ps1

<# 
.SYNOPSIS
    Starts .\qz-tray.exe but only if the user is actively logged in
#>

$hidden = $True
if($host.Name -match 'consolehost') {
	$hidden = $False
}

if($hidden) {
	# Attempt to actually hide this window
	$ShowWindow = Add-Type -Name ShowWindow -Member '[DllImport("user32.dll")] public static extern bool ShowWindow(int handle, int state);' -NameSpace Native
	$ShowWindow::ShowWindow(([System.Diagnostics.Process]::GetCurrentProcess() | Get-Process).MainWindowHandle, 0)
}

$activeUser = Get-CimInstance –ClassName Win32_ComputerSystem | Select-Object -ExpandProperty UserName -First 1
$currentUser = [System.Security.Principal.WindowsIdentity]::GetCurrent().Name

$qz = "$(split-path -parent $MyInvocation.MyCommand.Definition)\qz-tray.exe"
$message = "[$($MyInvocation.MyCommand.Name)] $(Get-Date -f "yyyy-MM-dd HH:mm:ss")"
$foregroundColor = "yellow"
if ( $activeUser -ieq $currentUser ) {
	$foregroundColor = "green"
	$message += " SUCCESS: `"$currentUser`" is active, starting $qz"
	Start-Process $qz -ArgumentList "--steal"
} else {
	$message += " SKIPPED: `"$currentUser`" is NOT active, skipping $qz"
}

$message >> "$env:APPDATA\qz\task-scheduler.log"
Write-Host -ForegroundColor $foregroundColor $message
Write-Host
if(-Not $hidden) {
	pause
}

Steal QZ Tray At Login.xml

<?xml version="1.0" encoding="UTF-16"?>
<Task version="1.2" xmlns="http://schemas.microsoft.com/windows/2004/02/mit/task">
  <RegistrationInfo>
    <Date>2022-12-13T12:29:01.6615572</Date>
    <Author>tres@qz.io</Author>
    <URI>\Steal QZ Tray At Login</URI>
  </RegistrationInfo>
  <Triggers>
    <EventTrigger>
      <Enabled>true</Enabled>
      <Subscription>&lt;QueryList&gt;&lt;Query Id="0" Path="Security"&gt;&lt;Select Path="Security"&gt;*[EventData[ (Data[@Name='LogonType']=2) and (Data[@Name='ElevatedToken']='%%1843')]] and *[System[(EventID=4624)]]&lt;/Select&gt;&lt;/Query&gt;&lt;/QueryList&gt;</Subscription>
    </EventTrigger>
  </Triggers>
  <Principals>
    <Principal id="Author">
      <GroupId>S-1-5-32-545</GroupId>
      <RunLevel>LeastPrivilege</RunLevel>
    </Principal>
  </Principals>
  <Settings>
    <MultipleInstancesPolicy>StopExisting</MultipleInstancesPolicy>
    <DisallowStartIfOnBatteries>false</DisallowStartIfOnBatteries>
    <StopIfGoingOnBatteries>false</StopIfGoingOnBatteries>
    <AllowHardTerminate>true</AllowHardTerminate>
    <StartWhenAvailable>false</StartWhenAvailable>
    <RunOnlyIfNetworkAvailable>false</RunOnlyIfNetworkAvailable>
    <IdleSettings>
      <StopOnIdleEnd>false</StopOnIdleEnd>
      <RestartOnIdle>false</RestartOnIdle>
    </IdleSettings>
    <AllowStartOnDemand>true</AllowStartOnDemand>
    <Enabled>true</Enabled>
    <Hidden>false</Hidden>
    <RunOnlyIfIdle>false</RunOnlyIfIdle>
    <WakeToRun>false</WakeToRun>
    <ExecutionTimeLimit>PT0S</ExecutionTimeLimit>
    <Priority>7</Priority>
  </Settings>
  <Actions Context="Author">
    <Exec>
      <Command>powershell.exe</Command>
      <Arguments>-WindowStyle Hidden -File start_if_active.ps1</Arguments>
      <WorkingDirectory>%PROGRAMFILES%\QZ Tray\</WorkingDirectory>
    </Exec>
  </Actions>
</Task>