Request doesn't go through the middleware in express - node.js

Question

I am integrating a Twitch API for subs, and having issue with getting the webhook callback response to the middleware function that it should check the header and verify the signature.
I am receive the right response! however, it stops right there!
I check the order of the routes, and I am not sure what I am missing
I am following https://dev.twitch.tv/docs/eventsub
app.post('/createWebhook/:broadcasterId', (req, res) => {
const createWebHookParams = {
host: "api.twitch.tv",
path: "helix/eventsub/subscriptions",
method: 'POST',
headers: {
"Content-Type": "application/json",
"Client-ID": clientId,
"Authorization": "Bearer " + authToken
}
}
const createWebHookBody = {
"type": "channel.follow",
"version": "1",
"condition": {
"broadcaster_user_id": req.params.broadcasterId
},
"transport": {
"method": "webhook",
"callback": "ngrokURL/notification",
"secret": webhookSecret //
}
}
let responseData = ""
const webhookReq = https.request(createWebHookParams, (result) => {
result.setEncoding('utf8')
result.on('data', (d) => {
responseData = responseData + d
})
.on('end', (result) => {
const responseBody = JSON.parse(responseData) // json
console.log(responseBody)
res.send(responseBody)
})
})
webhookReq.on('error', (e) => {
console.log("Error")
})
webhookReq.write(JSON.stringify(createWebHookBody))
webhookReq.end()
});
// middlewsre ---> // not triggered!!!
app.use(express.json({
verify: verifyTwitchSignature
}));
// making post to receeive the notification.
app.post('/notification', (req, res) => {
console.log("incoming notificatin", req.body)
res.status(200).end();
})
// the middleware verifing the signature
const crypto = require("crypto");
const twitchSigningSecret = process.env.SECRET;
const verifyTwitchSignature = (req, res, buf, encoding)=>{
const messageId = req.header("Twitch-Eventsub-Message-Id");
const timeStamp = req.header("Twitch-Eventsub-Message-Timestamp")
const messageSignature = req.header("Twitch-Eventsub-Message-Signature")
console.log(`Message ${messageId} Signature: `,messageSignature)
if (!twitchSigningSecret){
console.log(`Twitch signing secret is empty`);
throw new Error ("Twitch signing secret is empty.");
}
const computedSignature = "sha256=" + crypto.createHmac("sha256", twitchSigningSecret).update(messageId + timeStamp + buf).digist("hex");
console.log(`Message ${messageId} Computed Signature: `, computedSignature)
if (messageSignature !== computedSignature) {
throw new Error("Invalid Signature.");
}else {
console.log("Verification Successful");
}
}
module.exports = verifyTwitchSignature

Answer 1

I believe in your verifyTwitchSignature function you need to pass next as one of the parameters and in the else-statement when it passes call next();.
That is my observation.
If you are working with middleware you always have to pass next together with req and res. next is what calls the next middleware or function in the queue.