param(
    [string]$certStore = "LocalMachineTrustedPeople",
    [string]$filename = "sp.pfx",
    [string]$password = "password",
    [string]$username = "$Env:COMPUTERNAMEWebSiteUser"
)

function getKeyFilePath($cert) {
    return "$ENV:ProgramDataMicrosoftCryptoRSAMachineKeys" + $cert.PrivateKey.CspKeyContainerInfo.UniqueKeyContainerName
}

$certFromFile = New-Object System.Security.Cryptography.X509Certificates.X509Certificate2($filename, $password)
$certFromStore = Get-ChildItem "Cert:$certStore" | Where-Object {$_.Thumbprint -eq $certFromFile.Thumbprint}
$certExistsInStore = $certFromStore.Count -gt 0
$keyExists = $certExistsInStore -and ($certFromStore.PrivateKey -ne $null) -and (Test-Path(getKeyFilePath($certFromStore)))

if ((!$certExistsInStore) -or (!$keyExists)) {

    $keyFlags = [System.Security.Cryptography.X509Certificates.X509KeyStorageFlags]::MachineKeySet
    $keyFlags = $keyFlags -bor [System.Security.Cryptography.X509Certificates.X509KeyStorageFlags]::PersistKeySet
    $certFromFile.Import($filename, $password, $keyFlags)

    $store = Get-Item "Cert:$certStore"
    $store.Open("ReadWrite")

    if ($certExistsInStore) {
        #Cert is in the store, but we have no persisted private key
        #Remove it so we can add the one we just imported with the key file
        $store.Remove($certFromStore)
    }

    $store.Add($certFromFile)
    $store.Close()

    $certFromStore = $certFromFile
    "Installed x509 certificate"
}

$pkFile = Get-Item(getKeyFilePath($certFromStore))
$pkAcl = $pkFile.GetAccessControl("Access")
$readPermission = $username,"Read","Allow"
$readAccessRule = new-object System.Security.AccessControl.FileSystemAccessRule $readPermission
$pkAcl.AddAccessRule($readAccessRule)
Set-Acl $pkFile.FullName $pkAcl
"Granted read permission on private key to web user"