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

    Fault : Remote Desktop: "an internal error has occurred" -- 0x204, 0x1104, 0x3
    Fix   : Resolve the CredSSP encryption oracle mismatch at the right end
    Source: https://jbtecwiz.com/support/win-net-rdp-internal

    Run as     : Elevated PowerShell
    Expect     : 20 minutes
    Risk       : high
    Reversible : yes

    WHEN THIS IS THE RIGHT FIX
    The error names CredSSP or an encryption oracle remediation, usually
    0x80090326.

    HOW TO UNDO IT
    Remove the AllowEncryptionOracle value, as shown in the last step.

    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 4"
    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: "an internal error has occurred" -- 0x204, 0x1104, 0x3' -ForegroundColor White
Write-Host '  Resolve the CredSSP encryption oracle mismatch at the right end' -ForegroundColor Cyan
Write-Host ''
Write-Host '  Risk: high   Reversible   20 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 'Identify which end is unpatched. The correct fix is always to patch the server, not to weaken the client.' -Command {
    Get-HotFix | Sort-Object InstalledOn -Descending | Select-Object -First 10 HotFixID,InstalledOn
}

Invoke-Step -Number 2 -Do 'Bring the remote machine up to date. This removes the mismatch permanently and is the only fix that does not reduce security.' -Manual

Invoke-Step -Number 3 -Do 'If the remote machine genuinely cannot be patched right now and access is needed to do so, the client can be relaxed temporarily.' -Why 'Value 2 is Vulnerable -- it permits a downgraded session that an attacker on the path can exploit. It exists to get you in to patch the far end, and should be reverted the moment you have.' -Command {
    New-Item -Path 'HKLM:\Software\Microsoft\Windows\CurrentVersion\Policies\System\CredSSP\Parameters' -Force | Out-Null
    Set-ItemProperty 'HKLM:\Software\Microsoft\Windows\CurrentVersion\Policies\System\CredSSP\Parameters' -Name AllowEncryptionOracle -Type DWord -Value 2
}

Invoke-Step -Number 4 -Do 'Revert as soon as the server is patched.' -Command {
    Remove-ItemProperty 'HKLM:\Software\Microsoft\Windows\CurrentVersion\Policies\System\CredSSP\Parameters' -Name AllowEncryptionOracle
}

Write-Rule "  Confirm it worked"
Show-Prose 'With both ends patched and the client value removed, the session connects normally.' '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/win-net-rdp-internal' 'Yellow'
} else {
    Write-Host '  Finished.' -ForegroundColor Green
}
Write-Host ''
Show-Prose 'To undo: Remove the AllowEncryptionOracle value, as shown in the last step.' 'DarkGray'
Write-Rule