#Requires -Version 5.1
<#
    JbTecWiz Support Centre -- generated fix script

    Fault : Remote Desktop Gateway refuses connections -- event 4, 23003 and 23005
    Fix   : Fix the resource authorisation policy
    Source: https://jbtecwiz.com/support/srv-app-rdgateway

    Run as     : Elevated PowerShell
    Expect     : 30 minutes
    Risk       : medium
    Reversible : yes

    WHEN THIS IS THE RIGHT FIX
    Event 23005 -- the user is allowed in but not to that machine.

    HOW TO UNDO IT
    Remove the added computer group entry.

    This script walks the fix one step at a time and asks before each
    one. Steps with no command are things you do yourself -- it prints
    those and waits. Run with -DryRun to print without executing.

    --------------------------------------------------------------------
    NO WARRANTY - USE AT YOUR OWN RISK

    This script is provided by JbTecWiz as-is and with no warranty of any
    kind, express or implied. You run it entirely at your own risk.

    JbTecWiz accepts no liability for any loss or damage arising from its
    use, including but not limited to data loss, downtime, or configuration
    changes that turn out to be wrong for your system.

    You are responsible for reading this script before running it, for
    satisfying yourself that it suits the machine in front of you, and for
    having a working backup first. Some steps cannot be undone.
    --------------------------------------------------------------------
#>

[CmdletBinding()]
param(
    # Print every step and command without running anything.
    [switch]$DryRun,
    # Do not ask before each step. Read the script first if you use this.
    [switch]$Unattended
)

$ErrorActionPreference = 'Stop'
$script:Failed = 0

function Write-Rule { param([string]$Text)
    Write-Host ''
    Write-Host ('-' * 70) -ForegroundColor DarkGray
    if ($Text) { Write-Host $Text -ForegroundColor Cyan }
}

function Show-Prose { param([string]$Text, [string]$Colour = "Gray")
    if (-not $Text) { return }
    $words = $Text -split "\s+"; $line = "  "
    foreach ($w in $words) {
        if (($line.Length + $w.Length) -gt 74) { Write-Host $line -ForegroundColor $Colour; $line = "  " }
        $line += "$w "
    }
    if ($line.Trim()) { Write-Host $line -ForegroundColor $Colour }
}

function Invoke-Step {
    param(
        [int]$Number, [string]$Do, [string]$Why,
        [scriptblock]$Command, [switch]$Manual, [string]$Shell = "powershell"
    )
    Write-Rule "  Step $Number of 5"
    Show-Prose $Do "White"
    if ($Why) { Write-Host ""; Show-Prose $Why "DarkGray" }

    if ($Manual) {
        Write-Host ''
        Write-Host '  -> Do this yourself, then press Enter to carry on.' -ForegroundColor Yellow
        if (-not $Unattended -and -not $DryRun) { [void](Read-Host) }
        return
    }

    Write-Host ''
    foreach ($l in ($Command.ToString().Trim() -split "`n")) {
        Write-Host ("    " + $l.Trim()) -ForegroundColor Green
    }
    Write-Host ''

    if ($DryRun) { Write-Host "  (dry run -- not executed)" -ForegroundColor DarkGray; return }
    if (-not $Unattended) {
        $a = Read-Host "  Run this step? [Y]es / [S]kip / [Q]uit"
        if ($a -match "^[Qq]") { Write-Host "  Stopped at your request."; exit 0 }
        if ($a -match "^[Ss]") { Write-Host "  Skipped." -ForegroundColor DarkGray; return }
    }
    try { & $Command }
    catch {
        $script:Failed++
        Write-Host ("  Step $Number failed: " + $_.Exception.Message) -ForegroundColor Red
        Show-Prose "The rest of the fix may depend on this. Read the write-up before carrying on." "Red"
        if (-not $Unattended) {
            $c = Read-Host "  Carry on anyway? [y/N]"
            if ($c -notmatch "^[Yy]") { exit 1 }
        }
    }
}

Write-Rule
Write-Host '  Remote Desktop Gateway refuses connections -- event 4, 23003 and 23005' -ForegroundColor White
Write-Host '  Fix the resource authorisation policy' -ForegroundColor Cyan
Write-Host ''
Write-Host '  Risk: medium   Reversible   30 minutes'
Write-Host ''
Show-Prose 'No warranty. Use at your own risk - JbTecWiz accepts no liability. Read it before you run it, and have a backup.' 'DarkYellow'
Write-Rule

if (-not $Unattended -and -not $DryRun) {
    $go = Read-Host '  Ready? [y/N]'
    if ($go -notmatch "^[Yy]") { Write-Host "  Nothing was changed."; exit 0 }
}

Invoke-Step -Number 1 -Do 'List the resource policies and the computer groups they allow.' -Command {
    Get-ChildItem RDS:\GatewayServer\RAP | Format-Table Name
    Get-ChildItem 'RDS:\GatewayServer\RAP\Default RAP\ComputerGroupType'
}

Invoke-Step -Number 2 -Do 'The computer must be named exactly as the client asks for it. A policy listing the NetBIOS name rejects a client that connects by fully qualified name.' -Why 'This is the most common resource policy fault and it is invisible unless you compare the two strings directly. The gateway does no name resolution to match them.' -Manual

Invoke-Step -Number 3 -Do 'Add the target to the allowed group, or use an Active Directory group of computers for maintainability.' -Command {
    Set-Item 'RDS:\GatewayServer\RAP\Default RAP\ComputerGroupType' -Value 1
    New-Item -Path 'RDS:\GatewayServer\RAP\Default RAP\ComputerGroup' -Name 'EXAMPLE\RDS-Hosts' -ItemType String
}

Invoke-Step -Number 4 -Do 'Check the allowed ports -- a policy restricted to 3389 blocks anything on a custom port.' -Command {
    Get-ChildItem 'RDS:\GatewayServer\RAP\Default RAP' | Format-Table Name,CurrentValue
}

Invoke-Step -Number 5 -Do 'Restart the service and re-test.' -Command {
    Restart-Service TSGateway
}

Write-Rule "  Confirm it worked"
Show-Prose 'The connection to the intended host succeeds through the gateway.' 'White'

Write-Rule
if ($script:Failed -gt 0) {
    Write-Host ("  Finished with " + $script:Failed + " failed step(s).") -ForegroundColor Yellow
    Show-Prose 'Read the full write-up at https://jbtecwiz.com/support/srv-app-rdgateway' 'Yellow'
} else {
    Write-Host '  Finished.' -ForegroundColor Green
}
Write-Host ''
Show-Prose 'To undo: Remove the added computer group entry.' 'DarkGray'
Write-Rule