We’ve got a Node.js endpoint listening for .queue.member.added events. The goal is to verify the X-Genesys-Signature header to stop replay attacks. The docs say to base64-decode the header and compare it to an HMAC-SHA256 of the raw body using our client secret. It’s failing every time. The signature length looks right, but the comparison always returns false. Here’s the verification logic we’re using:
const crypto = require('crypto');
const sigHeader = req.headers['x-genesys-signature'];
const body = req.body;
const secret = process.env.GENESYS_CLIENT_SECRET;
const decodedSig = Buffer.from(sigHeader, 'base64').toString('utf8');
const calculatedSig = crypto.createHmac('sha256', secret).update(body).digest('base64');
console.log('Header:', decodedSig);
console.log('Calc: ', calculatedSig);
The console logs show completely different strings. The header decodes to something that looks like raw binary garbage, while the calculated signature is a clean base64 string. Are we supposed to hash the body before base64 encoding it again? Or is the header already hex-encoded? The documentation is vague on the exact byte format expected in the header versus what createHmac spits out.
Are you stripping newlines from the raw body before hashing? Node.js stream parsing often adds a trailing \n. That single character breaks the HMAC match. Try logging body.length vs the expected payload size. If it’s off by one, trim it.
const cleanBody = req.body.replace(/\n$/, '');
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The base64 issue is likely a red herring. The real problem is usually how you’re handling the request body stream in Node.js before it hits your crypto function. If you’re logging or parsing req.body before signing, the stream might be consumed or modified. The docs state: “The signature is calculated over the raw request body.” You need to capture the raw buffer first. Also, check your client secret. Are you using the one from the Webhook definition or the App credentials? They are different. Here’s a safer pattern using express middleware to capture the raw body without mutation:
app.use(express.json({
verify: (req, res, buf) => {
req.rawBody = buf.toString();
}
}));
// Then in your route
const crypto = require('crypto');
const hmac = crypto.createHmac('sha256', process.env.GENESYS_CLIENT_SECRET)
.update(req.rawBody)
.digest('base64');
if (hmac !== req.headers['x-genesys-signature']) {
return res.status(403).send('Invalid signature');
}
Don’t forget to URL decode the signature header if it contains special characters. The .NET SDK handles this automatically, but raw HTTP requires manual care.
1 Like
Don’t use the App Client Secret. That’s the trap. The webhook signature is generated using the secret stored specifically in the Webhook definition within Genesys Cloud, not your OAuth app credentials. Mixing them up guarantees a mismatch.
Also, Node.js req.body is often a string by the time you access it. Crypto functions need a Buffer. If you’re passing a string to crypto.createHmac, the byte representation might differ from what Genesys hashed. Force it to a buffer.
const crypto = require('crypto');
// Use the secret from the Webhook definition, NOT the App
const webhookSecret = 'your_webhook_specific_secret';
const signature = req.headers['x-genesys-signature'];
const expected = crypto.createHmac('sha256', webhookSecret)
.update(req.rawBody || req.body) // Ensure you have the raw buffer
.digest('base64');
if (signature !== expected) {
return res.status(401).send('Invalid signature');
}
Check the Webhook config page. Copy the secret directly from there. Paste it into your code. Test again.
1 Like
The point regarding the webhook definition secret is accurate. We encountered the identical mismatch during our migration of notification handlers to Tokio. Genesys Cloud computes the HMAC-SHA256 signature over the exact raw bytes received. The base64 decode failure typically stems from the header omitting padding characters. Strict decoders will reject this. While it’s a minor oversight on their side, it’s a common pattern in high-throughput event streams.
You’ll need to normalize unpadded base64 manually before passing it to your cryptographic routine. Additionally, retrieve the secret directly from the webhook configuration endpoint rather than hardcoding it. The /api/v2/webhooks/{id} response exposes the secret field, which requires the webhook:read scope for programmatic access. If you’re leveraging the PureCloudPlatformClientV2 SDK, simply invoke webhooks_api.get_webhook(id).await and extract the secret string.
Here’s how we structure it in our Rust service. We remove the padding expectation, normalize the body buffer, and execute the HMAC verification within the async task.
use base64::{engine::general_purpose::STANDARD, Engine};
use hmac::{Hmac, Mac};
use sha2::Sha256;
type HmacSha256 = Hmac<Sha256>;
async fn verify_genesys_signature(raw_body: &[u8], header_sig: &str, secret: &str) -> bool {
let mut padded_sig = header_sig.to_string();
let pad_len = (4 - (header_sig.len() % 4)) % 4;
padded_sig.push_str(&"=".repeat(pad_len));
let decoded_sig = match STANDARD.decode(&padded_sig) {
Ok(sig) => sig,
Err(_) => return false,
};
let mut mac = HmacSha256::new_from_slice(secret.as_bytes()).expect("HMAC key valid");
mac.update(raw_body);
let computed_sig = mac.finalize().into_bytes();
decoded_sig == computed_sig.as_slice()
}
The primary pitfall here is buffering. If you’re routing through Express or Fastify, the middleware pipeline may UTF-8 decode the buffer into a string before your verification hook executes. This alters the byte representation entirely. Preserve the raw Buffer until the HMAC validation completes. Once verified, we pipe the payload directly into our event queue. The notification stream throughput is high enough that blocking on string conversions becomes a bottleneck.
Review your base64 engine configuration. Most Node.js crypto wrappers enforce strict padding by default. Switching to a lenient decoder or manually appending padding resolves the decode failure. Additionally, monitor for URL-safe base64 variants if reverse proxies modify the header. Genesys utilizes the standard alphabet, so ensure the secret aligns precisely with the webhook definition.