# Pause/unpause a process. Just provide a PID or a PID from the pipeline
# by Mick Douglas @BetterSafetyNet

# License: Creative Commons Attribution
# https://creativecommons.org/licenses/by/4.0/

# Warning:
# This script will pause (and unpause) running programs.
# Obviously, this can cause system stability issues.
# The author and contributors of this script assume NO liability for the use of this script.
# Users of this script are **stridently** urged to test in a non-production environment first.

# todos:
# Easy
# create better error logics
# make better help messages 

# Mid-level
# add logics to detect if debugger is attached
# add input validation checks
# - is ID an int?

# HARD!!
# - re-introduce the -Duration option & use ScheduledJob instead of sleep

# Credits:
# Shout out to Dave Kennedy for pointing me to this StackOverflow article.
# https://stackoverflow.com/questions/11010165/how-to-suspend-resume-a-process-in-windows

# Reference links:
# calling Windows API from PowerShell
# https://blog.dantup.com/2013/10/easily-calling-windows-apis-from-powershell/

# https://blogs.technet.microsoft.com/heyscriptingguy/2013/06/25/use-powershell-to-interact-with-the-windows-api-part-1/

# https://msdn.microsoft.com/en-us/library/windows/desktop/ms679295(v=vs.85).aspx

# Highly interesting article on how to use specific methods in a dll in PowerShell
#https://social.technet.microsoft.com/Forums/ie/en-US/660c36b5-205c-47b6-8b98-aaa97d69a582/use-powershell-to-automate-powerpoint-document-repair-message-response?forum=winserverpowershell



<#

.SYNOPSIS
This is a PowerShell script which allows one to Pause-Process or 
UnPause-Process.

.DESCRIPTION
This script will allow users to pause and unpause running commands.  This is 
accomplished by attaching a debugger to the selected process.  Removing the
debugger allows the program to resume normal operation.  

Note: not all programs can be paused in this manner.

.EXAMPLE
Import-Module .\pause-process.ps1

.EXAMPLE
Pause-Process -ID [PID]

.EXAMPLE
UnPause-Process -ID [PID]

.NOTES
This script is under active development.  
Until you are comfortable with how this works... DO NOT USE IN PRODUCTION!

.LINK
https://infosecinnovations.com/Alpha-Testing

#>



$script:nativeMethods = @();
function Register-NativeMethod([string]$dll, [string]$methodSignature)
{
    $script:nativeMethods += [PSCustomObject]@{ Dll = $dll; Signature = $methodSignature; }
}

function Add-NativeMethods()
{
    $nativeMethodsCode = $script:nativeMethods | % { "
        [DllImport(`"$($_.Dll)`")]
        public static extern $($_.Signature);
    " }

    Add-Type @"
        using System;
        using System.Runtime.InteropServices;
        public static class NativeMethods {
            $nativeMethodsCode
        }
"@
}


# Add methods here
Register-NativeMethod "kernel32.dll" "int DebugActiveProcess(int PID)"
Register-NativeMethod "kernel32.dll" "int DebugActiveProcessStop(int PID)"

# This builds the class and registers them (you can only do this one-per-session, as the type cannot be unloaded?)
Add-NativeMethods


function Pause-Process {

[CmdletBinding()]

    Param (
        [parameter(Mandatory=$True, ValueFromPipelineByPropertyName=$True)]
        [alias("OwningProcess")]
        [int]$ID
    )


    Begin {
        # Test to see if this is a running process
        # Future feature: Do checks to see if we can pause this process.
        write-verbose ("you entered an ID of: $ID")
    }


    Process {
        $PauseResult = [NativeMethods]::DebugActiveProcess($ID)
    }


    End {
        if ($PauseResult -eq $False) {
            Write-Error ("Unable to pause process: $ID")

        } else {
            Write-Verbose ("Process $ID was paused")
        }

    } 
}


function UnPause-Process {

[CmdletBinding()]

    Param (
	    [parameter(Mandatory=$True, ValueFromPipelineByPropertyName=$True)]
        [alias("OwningProcess")]
        [int]$ID
    )

    Begin{
        Write-Verbose ("Attempting to unpause PID: $ID")
    }


    Process {
        # Attempt the unpause
        $UnPauseResult = [NativeMethods]::DebugActiveProcessStop($ID)
    }

    End {
        if ($UnPauseResult -eq $False) {
            Write-Error ("unable to unpause process $ID. Is it running or gone?")
    
        } else {
            Write-Verbose ("$ID was resumed")
        }
    }
}