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

    Fault : VPN errors 809, 789 and 691 -- the tunnel will not come up
    Fix   : Work out which side is refusing the credentials
    Source: https://jbtecwiz.com/support/win-net-vpn-809

    Run as     : Elevated PowerShell on the NPS or RRAS server
    Expect     : 25 minutes
    Risk       : low
    Reversible : yes

    WHEN THIS IS THE RIGHT FIX
    Error 691. The tunnel is fine; the account is being turned away.

    HOW TO UNDO IT
    Any group or dial-in change can be reversed directly. Note the original
    value before changing it.

    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 '  VPN errors 809, 789 and 691 -- the tunnel will not come up' -ForegroundColor White
Write-Host '  Work out which side is refusing the credentials' -ForegroundColor Cyan
Write-Host ''
Write-Host '  Risk: low   Reversible   25 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 'Look for the rejection on the NPS server. It states the reason code and the policy that matched, which is the whole answer.' -Command {
    Get-WinEvent -LogName Security -MaxEvents 60 | Where-Object Id -in 6273,6274,6278 | Format-List TimeCreated,Message
}

Invoke-Step -Number 2 -Do 'Reason code 65 is "the connection was rejected by a policy", 16 is bad credentials, 48 is "no policy matched". Match the code to what to change.' -Manual

Invoke-Step -Number 3 -Do 'Check the account is in the group the network policy requires, and that dial-in access is not set to Deny.' -Why 'msNPAllowDialin set to False overrides group membership and policy entirely, and nothing in the client error hints at it.' -Command {
    Get-ADUser jbloggs -Properties MemberOf,msNPAllowDialin | Format-List Name,msNPAllowDialin,MemberOf
}

Invoke-Step -Number 4 -Do 'Confirm the authentication method the policy allows matches what the client offers -- a client set to MS-CHAPv2 against a policy that only permits EAP fails as 691.' -Manual

Write-Rule "  Confirm it worked"
Show-Prose 'Event 6272 (access granted) appears on the NPS server for the account and the tunnel comes up.' '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-vpn-809' 'Yellow'
} else {
    Write-Host '  Finished.' -ForegroundColor Green
}
Write-Host ''
Show-Prose 'To undo: Any group or dial-in change can be reversed directly. Note the original value before changing it.' 'DarkGray'
Write-Rule