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MEM v ENNBEE - Battles with Modern Device Management

Enabling BitLocker and WinRE on failed Windows Devices

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Microsoft Intune Windows 10 and later BitLocker Security Encryption PowerShell
Author
Nick Benton
Principal Cloud Endpoint Consultant and Intune Blogger
Table of Contents

You may have enabled and configure BitLocker for silent encryption on your Windows 10 Autopilot joined devices, but have you had the headache of devices that don’t have a Windows Recovery Environment (WinRE) configured? Yep? Me too…

What you’ll see in either the BitLocker-API event log, or within the Encryption Readiness reporting in Microsoft Intune the following, glorious error:

The OS volume is unprotected | Windows Recovery Environment (WinRE) isn't configured

Configuration
#

So how do we go about enabling WinRE if it exists, setup BitLocker encryption, and grab the BitLocker recovery key and ping it to Azure AD?

Here’s how…

Updating the Script
#

This Microsoft script has been adapted to check for the WinRE configuration before it continues and attempts to enable BitLocker, the $HotToTrot variable is used to denote whether to continue or not.

The below is the added section to check and enable, or attempt to enable, WinRE:

$HotToTrot ="false"
#Checks Windows Recovery Environment and enables if disabled
if($WinREStatus -like '*Windows RE status:         Enabled*'){
    $HotToTrot = "True"
    Write-Verbose -Message "WinRE Partition Enabled and good to enable BitLocker $HotToTrot"
}
Else{
    Try{
        $WinREEnable = reagentc.exe /enable
        if($WinREEnable -like '*Operation Successful*'){
            $HotToTrot = "True"
            Write-Verbose -Message "WinRE Partition Enabled and good to enable BitLocker, HotToTrot set to $HotToTrot"
        }
        Else{
            $HotToTrot ="false"
            Write-Verbose -Message "Unable to enabled WinRE, HotToTrot set to $HotToTrot"
        }
    }
    Catch{
        $HotToTrot ="false"
        Write-Verbose -Message "Unable to enabled WinRE"
    }
}
if($HotToTrot -eq 'True')

Fixing the Script
#

The script has logic in place to escrow the recovery key to Azure AD, using either the BackupToAAD-BitLockerKeyProtector commandlet or, if this isn’t available, using a call to GraphAPI. The below sections needed to be updated due to where the Azure AD Join information is now stored in the registry:

# Check if we can use BackupToAAD-BitLockerKeyProtector commandlet
if (Get-Command -Name "BackupToAAD-BitLockerKeyProtector" -ErrorAction "SilentlyContinue") {

    # BackupToAAD-BitLockerKeyProtector commandlet exists
    Write-Verbose -Message "Saving Key to AAD using BackupToAAD-BitLockerKeyProtector"
    $BLV = Get-BitLockerVolume -MountPoint $OSDrive | Select-Object *
    If ($Null -ne $BLV.KeyProtector) {
        BackupToAAD-BitLockerKeyProtector -MountPoint $OSDrive -KeyProtectorId $BLV.KeyProtector[1].KeyProtectorId
    }
    Else {
        Write-Error "'Get-BitLockerVolume' failed to retrieve drive encryption details for $OSDrive"
    }
}
else {
    # BackupToAAD-BitLockerKeyProtector commandlet not available, using other mechanism
    Write-Verbose -Message "BackupToAAD-BitLockerKeyProtector not available"
    Write-Verbose -Message "Saving Key to AAD using Enterprise Registration API"

    # Get the AAD Machine Certificate
    $cert = Get-ChildItem -Path "Cert:\LocalMachine\My\" | Where-Object { $_.Issuer -match "CN=MS-Organization-Access" }

    # Obtain the AAD Device ID from the certificate
    $id = $cert.Subject.Replace("CN=", "")

    # Obtain the Tenant ID from the certificate thumbprint
    $tenantid = ($cert.Thumbprint).Replace("-","")

    # Get the tenant name from the registry
    $tenant = (Get-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Control\CloudDomainJoin\JoinInfo\$($tenantid)").UserEmail.Split('@')[1]

    # Create the URL to post the data to based on the tenant and device information
    $url = "https://enterpriseregistration.windows.net/manage/$tenant/device/$($id)?api-version=1.0"

    # Generate the body to send to AAD containing the recovery information
    Write-Verbose -Message "Saving key protector to AAD for self-service recovery by manually posting it to:"
    Write-Verbose -Message "`t$url"

    # Get the BitLocker key information from WMI
    (Get-BitLockerVolume -MountPoint $OSDrive).KeyProtector | Where-Object { $_.KeyProtectorType -eq 'RecoveryPassword' } | ForEach-Object {
        $key = $_
        $body = "{""key"":""$($key.RecoveryPassword)"",""kid"":""$($key.KeyProtectorId.replace('{','').Replace('}',''))"",""vol"":""OSV""}"
        Write-Verbose -Message "KeyProtectorId : $($key.KeyProtectorId) key: $($key.RecoveryPassword)"

        # Post the data to the URL and sign it with the AAD Machine Certificate
        $req = Invoke-WebRequest -Uri $url -Body $body -UseBasicParsing -Method "Post" -UseDefaultCredentials -Certificate $cert
        $req.RawContent
        Write-Verbose -Message " -- Key save web request sent to AAD - Self-Service Recovery should work"
    }
}

Putting it All Together
#

The full script can be found here, I would strongly advise testing this prior to pushing it out via Microsoft Intune.

Script Deployment
#

Save the above script and create a new PowerShell script deployment in Microsoft Intune using the following configuration settings, then deploy to a test group of devices.

BitLocker Script

Bingo! One battle won, onto the next.

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