What is the standard approach to validate the HMAC signature on incoming webhooks from Genesys Cloud Digital Channels when triggering ServiceNow Data Actions? The signature mismatch occurs consistently during peak UK business hours despite using the shared secret from the integration settings, suggesting a potential encoding issue with the payload body.
If you check the docs, they mention the HMAC signature calculation must use the exact raw request body, not a parsed or reformatted version. When ServiceNow receives the webhook, it often pretty-prints the JSON payload before passing it to the signature verification script. This reformatting changes the string being hashed, causing the mismatch. The fix is to ensure the signature is calculated against the raw body exactly as Genesys Cloud sends it.
Here is a standard JavaScript snippet for the ServiceNow script include that handles this correctly:
var crypto = require('crypto');
var secret = 'your_shared_secret_here';
var payload = request.body; // Ensure this is the raw string, not parsed JSON
// Calculate HMAC-SHA256
var hmac = crypto.createHmac('sha256', secret);
hmac.update(payload);
var calculatedSignature = hmac.digest('hex');
// Compare with the signature from the header
var receivedSignature = request.headers['x-genesys-signature'];
if (calculatedSignature === receivedSignature) {
// Signature is valid, proceed with data action
gs.info('Webhook signature verified successfully');
} else {
gs.error('Signature mismatch. Calculated: ' + calculatedSignature + ' vs Received: ' + receivedSignature);
}
As a scheduling coordinator, I see similar issues when sync jobs fail because the timestamp format in the payload doesn’t match what the scheduler expects. The key is consistency. Make sure the ServiceNow endpoint isn’t modifying the body before verification. If you are using a middleware or load balancer, check if it is buffering or altering the content. The raw body must remain intact from the moment Genesys Cloud sends it until the moment ServiceNow calculates the hash. This usually resolves the peak hour failures, which are often just timing-related buffer issues.
I normally fix this by bypassing the ServiceNow default JSON parser entirely and reading the raw buffer directly. When dealing with bulk export metadata or digital channel recordings, maintaining the exact byte sequence is critical for any chain of custody requirements. The reformatting issue mentioned is valid, but in ServiceNow, the GlideHTTPRequest object often converts the body to a string before you can inspect it. You need to access the raw input stream.
A more robust approach is to use a Script Include that captures the raw bytes before any transformation. Check this internal note on webhook ingestion: KB00482: Handling Raw HTTP Bodies in ServiceNow.
Ensure your integration settings in Genesys Cloud are sending the signature in the X-Genesys-Signature header. If the payload includes complex nested objects from digital channels, even whitespace changes can break the hash. Always verify the encoding is UTF-8. This prevents the silent failures we often see during peak hours in the London region.