Parses signature data from the pk, kek, db, and dbx UEFI variables.

Check-Dbx.ps1

Write-Host "Checking for Administrator permission..."
if (-NOT ([Security.Principal.WindowsPrincipal] [Security.Principal.WindowsIdentity]::GetCurrent()).IsInRole([Security.Principal.WindowsBuiltInRole] "Administrator")) {
  Write-Warning "Insufficient permissions to run this script. Open the PowerShell console as administrator and run this script again."
  Break
} else {
  Write-Host "Running as administrator: continuing execution..." -ForegroundColor Green
}

 $patchfile  = $args[0]

 if ($patchfile -eq  $null) {
   $patchfile = ".\dbx-2021-April.bin"
   Write-Host "Patchfile not specified, using latest $patchfile`n"
 }
 $patchfile = (gci $patchfile).FullName

 Import-Module -Force .\Get-UEFIDatabaseSignatures.ps1

 # Print computer info
 $computer = gwmi Win32_ComputerSystem
 $bios = gwmi Win32_BIOS
 "Manufacturer: " + $computer.Manufacturer
 "Model: " + $computer.Model
 $biosinfo = $bios.Manufacturer , $bios.Name , $bios.SMBIOSBIOSVersion , $bios.Version -join ", "
 "BIOS: " + $biosinfo + "`n"

 $DbxRaw = Get-SecureBootUEFI dbx
 $DbxFound = $DbxRaw | Get-UEFIDatabaseSignatures

 $DbxBytesRequired = [IO.File]::ReadAllBytes($patchfile)
 $DbxRequired = Get-UEFIDatabaseSignatures -BytesIn $DbxBytesRequired

 # Flatten into an array of required EfiSignatureData data objects
 $RequiredArray = foreach ($EfiSignatureList in $DbxRequired) {
     Write-Verbose $EfiSignatureList
     foreach ($RequiredSignatureData in $EfiSignatureList.SignatureList) {
         Write-Verbose  $RequiredSignatureData
         $RequiredSignatureData.SignatureData
     }
 }
 Write-Information "Required `n" $RequiredArray

 # Flatten into an array of EfiSignatureData data objects (read from dbx)
 $FoundArray = foreach ($EfiSignatureList in $DbxFound) {
     Write-Verbose $EfiSignatureList
     foreach ($FoundSignatureData in $EfiSignatureList.SignatureList) {
         Write-Verbose  $FoundSignatureData
         $FoundSignatureData.SignatureData
     }
 }
 Write-Information "Found `n" $FoundArray

 $successes = 0
 $failures = 0
 $requiredCount = $RequiredArray.Count
 foreach ($RequiredSig in $RequiredArray) {
    if ($FoundArray -contains $RequiredSig) {
        Write-Information "FOUND: $RequiredSig"
        $successes++
    } else {
        Write-Error "!!! NOT FOUND`n$RequiredSig`n!!!`n"
        $failures++
    }
    $i = $successes + $failures
    Write-Progress -Activity 'Checking if all patches applied' -Status "Checking element $i of $requiredCount" -PercentComplete ($i/$requiredCount *100)
 }

 if ($failures -ne 0) {
     Write-Error "!!! FAIL:  $failures failures detected!"
     exit 4
     # $DbxRaw.Bytes | sc -encoding Byte dbx_found.bin
 } elseif ($successes -ne $RequiredArray.Count) {
     Write-Error "!!! Unexpected: $successes != $requiredCount expected successes!"
     exit 5
 } elseif ($successes -eq 0) {
     Write-Error "!!! Unexpected failure:  no successes detected, check command-line usage."
     exit 6
 } else {
     Write-Host "SUCCESS:  dbx.bin patch appears to be successfully applied"
 }

dbx-2020-July.bin

dbx-2020-October.bin

dbx-2021-April.bin

Get-UEFIDatabaseSignatures.ps1

function Get-UefiDatabaseSignatures {
<#
.SYNOPSIS

Parses UEFI Signature Databases into logical Powershell objects

.DESCRIPTION

Original Author: Matthew Graeber (@mattifestation)
Modified By: Jeremiah Cox (@int0x6)
Additional Source:  https://gist.github.com/mattifestation/991a0bea355ec1dc19402cef1b0e3b6f
License: BSD 3-Clause

.PARAMETER Variable

Specifies a UEFI variable, an instance of which is returned by calling the Get-SecureBootUEFI cmdlet. Only 'db' and 'dbx' are supported.

.PARAMETER BytesIn

Specifies a byte array consisting of the PK, KEK, db, or dbx UEFI vairable contents.

.EXAMPLE

$DbxBytes = [IO.File]::ReadAllBytes('.\dbx.bin')

Get-UEFIDatabaseSignatures -BytesIn $DbxBytes

.EXAMPLE

Get-SecureBootUEFI -Name db | Get-UEFIDatabaseSignatures

.EXAMPLE

Get-SecureBootUEFI -Name dbx | Get-UEFIDatabaseSignatures

.EXAMPLE

Get-SecureBootUEFI -Name pk | Get-UEFIDatabaseSignatures

.EXAMPLE

Get-SecureBootUEFI -Name kek | Get-UEFIDatabaseSignatures

.INPUTS

Microsoft.SecureBoot.Commands.UEFIEnvironmentVariable

Accepts the output of Get-SecureBootUEFI over the pipeline.

.OUTPUTS

UefiSignatureDatabase

Outputs an array of custom powershell objects describing a UEFI Signature Database. "77fa9abd-0359-4d32-bd60-28f4e78f784b" refers to Microsoft as the owner.
#>

    [CmdletBinding()]
    param (
        [Parameter(Mandatory, ValueFromPipeline, ParameterSetName = 'UEFIVariable')]
        [ValidateScript({ ($_.GetType().Fullname -eq 'Microsoft.SecureBoot.Commands.UEFIEnvironmentVariable') -and (($_.Name -eq 'kek') -or ($_.Name -eq 'pk') -or ($_.Name -eq 'db') -or ($_.Name -eq 'dbx')) })]
        $Variable,

        [Parameter(Mandatory, ParameterSetName = 'ByteArray')]
        [Byte[]]
        [ValidateNotNullOrEmpty()]
        $BytesIn
    )

    $SignatureTypeMapping = @{
        'C1C41626-504C-4092-ACA9-41F936934328' = 'EFI_CERT_SHA256_GUID' # Most often used for dbx
        'A5C059A1-94E4-4AA7-87B5-AB155C2BF072' = 'EFI_CERT_X509_GUID'   # Most often used for db
    }

    $Bytes = $null

    if ($Variable) {
        $Bytes = $Variable.Bytes
    } else {
        $Bytes = $BytesIn
    }

    try {
        $MemoryStream = New-Object -TypeName IO.MemoryStream -ArgumentList @(,$Bytes)
        $BinaryReader = New-Object -TypeName IO.BinaryReader -ArgumentList $MemoryStream, ([Text.Encoding]::Unicode)
    } catch {
        throw $_
        return
    }

    # What follows will be an array of EFI_SIGNATURE_LIST structs

    while ($BinaryReader.PeekChar() -ne -1) {
        $SignatureType = $SignatureTypeMapping[([Guid][Byte[]] $BinaryReader.ReadBytes(16)).Guid]
        $SignatureListSize = $BinaryReader.ReadUInt32()
        $SignatureHeaderSize = $BinaryReader.ReadUInt32()
        $SignatureSize = $BinaryReader.ReadUInt32()

        $SignatureHeader = $BinaryReader.ReadBytes($SignatureHeaderSize)

        # 0x1C is the size of the EFI_SIGNATURE_LIST header
        $SignatureCount = ($SignatureListSize - 0x1C) / $SignatureSize

        $SignatureList = 1..$SignatureCount | ForEach-Object {
            $SignatureDataBytes = $BinaryReader.ReadBytes($SignatureSize)

            $SignatureOwner = [Guid][Byte[]] $SignatureDataBytes[0..15]

            switch ($SignatureType) {
                'EFI_CERT_SHA256_GUID' {
                    $SignatureData = ([Byte[]] $SignatureDataBytes[0x10..0x2F] | ForEach-Object { $_.ToString('X2') }) -join ''
                }

                'EFI_CERT_X509_GUID' {
                    $SignatureData = New-Object Security.Cryptography.X509Certificates.X509Certificate2 -ArgumentList @(,([Byte[]] $SignatureDataBytes[16..($SignatureDataBytes.Count - 1)]))
                }
            }

            [PSCustomObject] @{
                PSTypeName = 'EFI.SignatureData'
                SignatureOwner = $SignatureOwner
                SignatureData = $SignatureData
            }
        }

        [PSCustomObject] @{
            PSTypeName = 'EFI.SignatureList'
            SignatureType = $SignatureType
            SignatureList = $SignatureList
        }
    }
}