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

    Fault : A document will not open -- Protected View, "file format is not valid", or a corrupt file
    Fix   : Check the File Block policy
    Source: https://jbtecwiz.com/support/win-office-file-wont-open

    Run as     : PowerShell as the affected user
    Expect     : 20 minutes
    Risk       : medium
    Reversible : yes

    WHEN THIS IS THE RIGHT FIX
    Old formats fail across the board -- every .xls or every .doc -- rather
    than one particular file. These blocks exist because the legacy binary
    formats have a long history of parser vulnerabilities: unblock the
    narrowest format that solves the problem, convert the file, and put the
    block back.

    HOW TO UNDO IT
    Set the value back to 2, or delete the value you added, to restore the
    block.

    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.
#>

[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 '  A document will not open -- Protected View, "file format is not valid", or a corrupt file' -ForegroundColor White
Write-Host '  Check the File Block policy' -ForegroundColor Cyan
Write-Host ''
Write-Host '  Risk: medium   Reversible   20 minutes'
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 'Read the current File Block settings for the application.' -Why 'A value of 2 blocks the format outright. 1 opens it in Protected View. 0 permits it. Baselines such as the Microsoft security baseline set several of these to 2, which is a deliberate hardening choice someone made, not a defect.' -Command {
    Get-ItemProperty 'HKCU:\Software\Microsoft\Office\16.0\Excel\Security\FileBlock' -ErrorAction SilentlyContinue
}

Invoke-Step -Number 2 -Do 'Also check the policy hive, which overrides the user one and cannot be changed by the user.' -Command {
    Get-ItemProperty 'HKCU:\Software\Policies\Microsoft\Office\16.0\Excel\Security\FileBlock' -ErrorAction SilentlyContinue
}

Invoke-Step -Number 3 -Do 'Decide whether the format should be permitted at all. The right answer for a one-off archive file is usually to convert it on a controlled machine, not to unblock the format for everyone.' -Manual

Invoke-Step -Number 4 -Do 'If it is to be permitted, set the specific format to open in Protected View rather than fully trusting it.' -Command {
    Set-ItemProperty -Path 'HKCU:\Software\Microsoft\Office\16.0\Excel\Security\FileBlock' -Name 'Excel95Workbooks' -Type DWord -Value 1
}

Invoke-Step -Number 5 -Do 'Once the file is open, save it to a current format so the problem does not recur.' -Manual

Write-Rule "  Confirm it worked"
Show-Prose 'The file opens, in Protected View if that is what you set, and re-saves cleanly as .xlsx or .docx.' '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-office-file-wont-open' 'Yellow'
} else {
    Write-Host '  Finished.' -ForegroundColor Green
}
Write-Host ''
Show-Prose 'To undo: Set the value back to 2, or delete the value you added, to restore the block.' 'DarkGray'
Write-Rule