Method to verify slack messages

message_verification.js

const crypto = require('crypto');

const signSecret = process.env.SLACK_SIGN_SECRET;

const validateRequest = (requestSignature, requestTime, rawBody, validFor = 300) => {
  const requestValidFrom = Math.floor(Date.now() / 1000) - validFor;
  if (requestTime < requestValidFrom) {
    throw new Error(`Request outdated: !(${requestTime} < ${requestValidFrom})`);
  }

  const hmac = crypto.createHmac('sha256', signSecret);
  const [version, hash] = requestSignature.split('=');
  hmac.update(`${version}:${requestTime}:${rawBody}`);
  const digest = hmac.digest('hex');
  if (hash !== digest) {
    throw new Error(`Request signature mismatch: !('${hash}' === '${digest}')`);
  }
}