We’re trying to handle NICE Cognigy webhook events using a TypeScript Express handler running on Node 18. The signature verification keeps failing with a 401. I copied the middleware setup from the integration guide.
const crypto = require('crypto');
const signature = req.headers['x-cognigy-signature'];
const expected = crypto.createHmac('sha256', process.env.WEBHOOK_SECRET)
.update(JSON.stringify(req.body))
.digest('hex');
if (!crypto.timingSafeEqual(Buffer.from(signature), Buffer.from(expected))) {
return res.status(401).send('Invalid signature');
}
Docs state: “Ensure the HMAC-SHA256 hash is calculated on the raw request body string before any JSON parsing occurs.” I’m using JSON.stringify on the parsed body object. Why does not work? The hash doesn’t match the header value.
Also the Zod validation throws on the sessionId field.
const WebhookSchema = z.object({
sessionId: z.string().uuid(),
botId: z.string()
});
The payload has sessionId as a standard string. Docs say: “Session identifiers follow standard v4 UUID conventions without hyphens for high throughput.” But the incoming JSON has hyphens. z.string().uuid() rejects it.
Redis lock also times out on concurrent sessions. We’ve set the TTL to 5 seconds but the async queue worker takes 8 seconds. The lock releases and we get duplicate CRM updates.
The latency tracking middleware logs 400ms average but error rate is 12%. Audit logs write to stdout but never flush to the file buffer during high load.
Why does the signature check fail when the body matches the doc example?
- Intercept the raw HTTP request stream before Express mutates it. Cognigy signs the original payload, not the parsed
req.body object. When the runtime executes express.json(), it strips whitespace and ructures the JSON tree, which breaks the crypto.createHmac('sha256') calculation. You’ll need to capture the buffer before the body parser touches it.
- Decode the base64 webhook secret before feeding it into the cipher. The platform console often stores
process.env.WEBHOOK_SECRET as an encoded string. Running Buffer.from(secret, 'base64').toString('utf8') prevents immediate hash divergence.
- Replace strict equality checks with
crypto.timingSafeEqual. Standard === comparisons throw false positives under load and leave the endpoint vulnerable to timing side channels. Buffer length mismatches also crash the middleware if you don’t pad the inputs.
- Deploy this middleware pattern to handle the verification and context routing. It captures the raw payload, computes the SHA256 HMAC, and validates the
req.headers['x-cognigy-signature'] header. I’ve wired it to check the agent context against /api/v2/users/me via the PureCloudPlatformClientV2 instance before processing the Cognigy intent payload.
import crypto from 'crypto';
import { Request, Response, NextFunction } from 'express';
import { PureCloudPlatformClientV2 } from 'genesyscloud';
export function verifyCognigySignature(req: Request, res: Response, next: NextFunction) {
const rawPayload = req.rawBody || JSON.stringify(req.body);
const signatureHeader = req.headers['x-cognigy-signature'] as string;
const secret = Buffer.from(process.env.WEBHOOK_SECRET || '', 'base64').toString('utf8');
const hmac = crypto.createHmac('sha256', secret).update(rawPayload).digest('base64');
const expected = `sha256=${hmac}`;
if (!crypto.timingSafeEqual(Buffer.from(signatureHeader), Buffer.from(expected))) {
return res.status(401).json({ error: 'signature mismatch' });
}
// Validate GC context before routing
const platformClient = new PureCloudPlatformClientV2();
platformClient.auth.loginOAuthClientCredentials({
clientId: process.env.GC_CLIENT_ID!,
clientSecret: process.env.GC_CLIENT_SECRET!
}).then(() => {
return platformClient.Users.getUsersUser({ userId: process.env.GC_AGENT_ID! });
}).then(() => next()).catch(() => res.status(503).send('GC unreachable'));
}
- Hook up the body parser verification callback to preserve the raw stream. Configure
app.use(express.json({ verify: (req, res, buf) => { req.rawBody = buf.toString(); } })) so the buffer stays accessible downstream. The client_app_sdk wrapper in our Playwright suite hits this exact pattern when mocking desktop webhook callbacks. Honestly, the body parser eats the original whitespace faster than you can blink. Miss the raw buffer capture and the hash always drifts. Make sure your oauth:client:read scope is attached to the credentials used in the platformClient auth flow, otherwise the /api/v2/users/me call fails before the middleware even finishes.
Cause: express.json() mutates the incoming data before the crypto check runs, so it’s like grading a rewritten essay instead of the original draft.
Solution: step one is grabbing the raw buffer, step two is skipping the body parser for this route, and step three is decoding the secret so the hmac matches the exact bytes Cognigy signed.
saw this exact setup in a recent community post and the raw buffer fix cleared the 401s right away, just paste the middleware before the json parser runs.
Problem
The suggestion above resolved the 401s immediately. Implementation confirmed. The signature verification kept rejecting valid payloads because Express was parsing the JSON before the crypto check ran, which altered the exact string being hashed. It’s a common trap when setting up external integrations. The ADMIN_UI routing rules were completely fine, but the backend middleware needed adjustment to catch the raw stream. Payload structure gets mangled during standard parsing.
Code
app.post('/webhook/cognigy', (req, res) => {
let rawBody = '';
req.on('data', chunk => { rawBody += chunk.toString(); });
req.on('end', () => {
const signature = req.headers['x-cognigy-signature'];
const secret = Buffer.from(process.env.WEBHOOK_SECRET, 'base64').toString('utf-8');
const expected = crypto.createHmac('sha256', secret).update(rawBody).digest('hex');
if (signature === expected) {
res.status(200).json({ status: 'verified' });
} else {
res.status(401).json({ error: 'signature mismatch' });
}
});
});
Error
The 401 Unauthorized responses stopped completely once the EXPRESS_JSON parser was bypassed for this endpoint. The HMAC_VERIFICATION calculation now matches the exact byte sequence Cognigy signs. Queue analytics dashboards are finally pulling the event data without throwing validation exceptions. You’ll notice the payload arrives intact. The ROUTE_HANDLER now processes the buffer correctly. Standard parsers really complicate things.
Question
Does the platform documentation need an update to explicitly warn about body parser interference, or is this standard behavior for most NODE_RUNTIME environments. The ADMIN_UI configuration panel doesn’t show any webhook signing toggles anyway.
The API docs specify the signature validation requires the exact raw buffer. Your DEPLOY_PIPELINE shouldn’t trigger express.json() here. Messes up the byte count. The ROUTE_CONFIG stays clean when the middleware checks the unaltered stream.
app.post('/webhook', express.raw({type:'application/json'}), (req, res) => {
const sig = crypto.createHmac('sha256', process.env.WEBHOOK_SECRET).update(req.body).digest('hex');
res.status(sig === req.headers['x-cognigy-signature'] ? 200 : 401).end();
});