Powershell Helpers

This includes examples for how to configure powershell startup scripts for a useful configuration.

• Requires:
  • Windows Subsystem for Linux (installed and working) e.g.: wsl --install Debian
  • Linux (under wsl) should be upto date, and have desired packages installed e.g.:

   bash
   apt update; apt upgrade
   apt install dnsutils tmux man ssh bash-completion
   umask 077; mkdir ~/.ssh; #for ssh-copy-id to have a place to work from

# Place this file in our $profile location and restart powershell.
#  e.g.:   copy Downloads\example.ps1 $profile
#     $profile defaults to $HOME\Documents\PowerShell\Microsoft.PowerShell_profile.ps1
#     aka: c:\Users\username\Documents\PowerShell\Microsoft.PowerShell_profile.ps1
# If you want to sign it see function `user-sign-psscript` below for signing
# This enables the use of: 
#    set-executionPolicy -ExecutionPolicy AllSigned -Scope CurrentUser
# Or if you don't care about security on Powershell locally, you can ignore local signing, and just use:
#    set-executionPolicy -ExecutionPolicy RemoteSigned -Scope CurrentUser

$debugpreference = "SilentlyContinue"

set-alias -Name npp "C:\Program Files\Notepad++\notepad++.exe"
set-alias -Name notepad++ npp


function setup-wslinterop ($bash_function_name_array) {
	<#
	.SYNOPSIS
	Perform initial configuration of the Windows SubSystem for Linux (WSL) function aliases.
	
		`set-wslinterop vim`  		- create a new virtual powershell function named `vim` and call the WSL/bash provided `vim` command when invoked.
		`set-wslinterop $array`     - create a new set of virtual powershell functions based on $array
		
	.DESCRIPTION
	- See https://github.com/mikebattista/PowerShell-WSL-Interop for more information and available customization options.
	- Invocation of this function will attempt to perform basic sanity checking and initial configuration including:
		- Verify modern Powershell is available
		- Verify WSL is available
		- Download, Install, Import `WSLInterop` module from PSGallery
		- Check if signing is enforced, and attempt to self-sign PSGallery module and add trust if needed
	- Configure hardcoded values for user preferences for environment or default arguments (customize this file or other variables as desired)
	- Specifically setup virtual functions for every element in the $array passed into this function that map into WSL/Linux/Bash functions
		
	#>
	# https://github.com/mikebattista/PowerShell-WSL-Interop
	if (-not ($psversiontable.PSEdition -like "Core")) {
		Write-Warning "Requires a modern version of Powershell Core."
		Write-Warning "See https://aka.ms/powershell-release?tag=stable or https://learn.microsoft.com/en-us/powershell/scripting/install/installing-powershell-on-windows for more information"
	}
	if (-not (Invoke-Expression "wsl.exe --status")) { 
		# Windows Subsystem for Linux error check using wsl --status
		return $false 
	} else
	{ 
		if ( -not (get-module WslInterop -ListAvailable) ) {
			Write-Warning "Performing initial install of Powershell Gallery module: WslInterop..."
			Install-Module WslInterop
			$current_policy = get-executionpolicy
			if ( $current_policy -ilike "*allsigned*" ) {
				$mod_path = (get-installedmodule wslinterop).InstalledLocation + "\wslinterop.psm1"
				Write-Warning "Signing WslInterop module to allow execution.  If prompted to trust a new certificate, click yes."
				user-sign-psscript "$mod_path"
			}
			Import-Module WslInterop
			#bash -ic "sudo apt install bash-completion dnsutils tmux -y"
		}
		# Dynamically create powershell functions that map to wsl commands (bash commands or native linux utils, etc.)
		Import-WslCommand $bash_function_name_array
		# Default prefixed arguments for invoked functions
		$global:WslDefaultParameterValues = new-object([System.Collections.Hashtable])
		$global:WslDefaultParameterValues["ls"] = "-alF --group-directories-first --color"
		$global:WslEnvironmentVariables = new-object([System.Collections.Hashtable])
		#WSL environment variables for the invoked functions
		$global:WslEnvironmentVariables["PAGER"] = "/usr/bin/less -X"
		Write-Host -Foregroundcolor Green -NoNewLine 'The following wsl bash functions were imported : '
		Write-Host -Foregroundcolor yellow	$bash_function_name_array	
	}
}


function user-sign-psscript ($File){
	<#
	.SYNOPSIS
	Perform lightweight automatic authenticode sign and trust operations on powershell scripts to enable more secure defaults.
	
		`user-sign-psscript example.ps1`  <Sign and trust the file named example.ps1>
		`user-sign-psscript`			  <Sign and trust the $profile file>
		
	.DESCRIPTION
	- If there is a code signing certificate and key in the Windows certificate store under Personal\Certificates (aka CurrentUser\My), use it for the next step.
	- If there is no applicable certificate, create a new self-signed certificate using the current username/domain in the CN field.
	- Copy Certificate to the Trusted Root store for the Current User (does not require admin)
	- Copy Certificate to the Trusted Publisher store for the Current User (does not require admin)
	- Perform Set-AuthenticodeSignature on the passed in file name with the applicable certificate.	
	#>
	
[DateTime] $ValidThrough = (Get-Date)
# Check to see if there is one in the cert store and use it
$cert = Get-ChildItem Cert:\CurrentUser\My -CodeSigningCert | Where-Object { $_.NotAfter -gt $ValidThrough } | Select-Object -First 1
if ( -not $cert ) {
    #Create self-signed cert
    $params = @{
        Subject = "CN=$env:USERNAME@$env:USERDOMAIN PowerShell CodeSigning"
        Type = 'CodeSigning'
        CertStoreLocation = 'Cert:\CurrentUser\My'
        HashAlgorithm = 'sha256'
        }
    $cert = New-SelfSignedCertificate @params
    # You can change these to LocalMachine instead of CurrentUser, but requires admin.  For portability, leaving as user.
    $RootcertStore = New-Object System.Security.Cryptography.X509Certificates.X509Store("Root", "CurrentUser")
    $RootcertStore.Open("ReadWrite")
    # Will cause a dialog to appear for confirmation.
    $RootcertStore.Add($cert)
    $RootcertStore.Close()
    $PubcertStore = New-Object System.Security.Cryptography.X509Certificates.X509Store("TrustedPublisher", "CurrentUser")
    $PubcertStore.Open("ReadWrite")
    $PubcertStore.Add($cert)
    $PubcertStore.Close()
    }
if ( -not $File) { $File = $profile }
if ( Test-Connection timestamp.digicert.com -tcpport 80 -ErrorAction SilentlyContinue ) {
	Set-AuthenticodeSignature $File $cert -TimestampServer 'http://timestamp.digicert.com' | select-object Status, StatusMessage, Path
	}
else {
	Write-Warning "No connectivity to timestamp server at http://timestamp.digicert.com, falling back to no timestamp counter-signature"
	Set-AuthenticodeSignature $File $cert | select-object Status, StatusMessage, Path
	}
}

$bash_function_name_array = "vi", "ssh-copy-id", "grep", "sed", "cut", "ls", "uname", "tmux", "dig", "host", "man", "openssl", "tail", "find", "head", "less", "which", "env"
setup-wslinterop $bash_function_name_array