<#
.SYNOPSIS
    Reports on SMBv1, turns on SMBv1 access auditing, or disables SMBv1 for good.
.DESCRIPTION
    Three modes:
      Report  (default) Shows whether the SMB1 server protocol is enabled, whether the SMB1
              feature is installed, whether auditing is on, and which clients have used
              SMB1 recently according to the audit log. Changes nothing.
      Audit   Turns on SMB1 access auditing (AuditSmb1Access). Windows then logs event 3000
              in Microsoft-Windows-SMBServer/Audit every time a client connects with SMB1.
              Leave it a couple of weeks, then run Report to see who'd break.
      Disable Turns off the SMB1 server protocol and removes the SMB1Protocol optional
              feature (client and server). Usually needs a restart to finish.
    Supports -WhatIf. Needs to run elevated.
.PARAMETER Mode
    Report, Audit or Disable.
.PARAMETER AuditDays
    How far back to look in the audit log in Report mode. Default: 14.
.EXAMPLE
    .\Set-Smb1Protocol.ps1
.EXAMPLE
    .\Set-Smb1Protocol.ps1 -Mode Audit
.EXAMPLE
    .\Set-Smb1Protocol.ps1 -Mode Disable -WhatIf
#>
[CmdletBinding(SupportsShouldProcess)]
param(
    [ValidateSet('Report', 'Audit', 'Disable')]
    [string]$Mode = 'Report',

    [ValidateRange(1, 365)]
    [int]$AuditDays = 14
)

$ErrorActionPreference = 'Stop'

function Get-Smb1Status {
    $server = Get-SmbServerConfiguration
    $feature = Get-WindowsOptionalFeature -Online -FeatureName SMB1Protocol -ErrorAction SilentlyContinue

    # Who has actually talked SMB1 to this machine lately?
    $clients = @()
    try {
        $events = Get-WinEvent -FilterHashtable @{
            LogName   = 'Microsoft-Windows-SMBServer/Audit'
            Id        = 3000
            StartTime = (Get-Date).AddDays(-$AuditDays)
        } -ErrorAction Stop
        $clients = @($events | ForEach-Object {
                if ($_.Message -match 'Client Address:\s*(\S+)') { $Matches[1] }
            } | Group-Object | Sort-Object Count -Descending |
            ForEach-Object { '{0} ({1}x)' -f $_.Name, $_.Count })
    }
    catch {
        Write-Verbose "No SMB1 audit events in the last $AuditDays days (or the log is empty)."
    }

    [pscustomobject]@{
        ComputerName       = $env:COMPUTERNAME
        Smb1ServerEnabled  = $server.EnableSMB1Protocol
        Smb1FeatureState   = if ($feature) { $feature.State.ToString() } else { 'NotPresent' }
        AuditingEnabled    = $server.AuditSmb1Access
        Smb1ClientsSeen    = $clients
        # A pending state means the change is staged and waiting on a reboot.
        RestartNeeded      = [bool]($feature -and "$($feature.State)" -like '*Pending')
    }
}

switch ($Mode) {
    'Report' {
        Get-Smb1Status
    }

    'Audit' {
        if ($PSCmdlet.ShouldProcess($env:COMPUTERNAME, 'Enable SMB1 access auditing')) {
            Set-SmbServerConfiguration -AuditSmb1Access $true -Force -Confirm:$false
            Write-Verbose 'Auditing on. SMB1 connections will show up as event 3000 in Microsoft-Windows-SMBServer/Audit.'
        }
        Get-Smb1Status
    }

    'Disable' {
        $restart = $false

        if ($PSCmdlet.ShouldProcess($env:COMPUTERNAME, 'Disable SMB1 server protocol')) {
            Set-SmbServerConfiguration -EnableSMB1Protocol $false -Force -Confirm:$false
        }

        $feature = Get-WindowsOptionalFeature -Online -FeatureName SMB1Protocol -ErrorAction SilentlyContinue
        if ($feature -and "$($feature.State)" -notin 'Disabled', 'DisabledWithPayloadRemoved', 'DisablePending') {
            if ($PSCmdlet.ShouldProcess($env:COMPUTERNAME, 'Remove SMB1Protocol optional feature')) {
                try {
                    $r = Disable-WindowsOptionalFeature -Online -FeatureName SMB1Protocol -NoRestart
                    $restart = [bool]$r.RestartNeeded
                }
                catch {
                    Write-Warning "Couldn't remove the SMB1Protocol feature: $($_.Exception.Message)"
                }
            }
        }
        else {
            Write-Verbose 'SMB1Protocol feature is already disabled, pending a restart, or not present.'
        }

        $status = Get-Smb1Status
        $status.RestartNeeded = $status.RestartNeeded -or $restart
        if ($status.RestartNeeded) { Write-Warning 'Restart required to finish removing SMB1.' }
        $status
    }
}