Genesys Cloud webhook signature validation failing in PowerShell

NICE CXone API & Integrations
1

Trying to understand why my signature check fails. I am using PowerShell to verify Genesys Cloud webhooks.

  1. Get header X-GC-Webhook-Signature
  2. Decode base64
  3. Compare HMAC SHA256 of body

It always mismatches. Here is the code:

$sign = [Convert]::FromBase64String($webhook.Headers['X-GC-Webhook-Signature'])
$expected = [System.Security.Cryptography.HMACSHA256]::new($secret)
$calc = $expected.ComputeHash([System.Text.Encoding]::UTF8.GetBytes($body))
if ($sign -ne $calc) { Write-Host "Invalid" }

Is the body encoding different?