Verify Slack signature with Node.js (on Lambda)

slack_verify_request.js

const crypto = require('crypto');

const verifySlackSignature = (event) => {
    const rawString = `v0:${event.headers['X-Slack-Request-Timestamp']}:${event.body}`;
    const hmac = crypto.createHmac('sha256', process.env['SLACK_SIGNING_SECRET']);
    return `v0=${hmac.update(rawString).digest('hex')}` === event.headers['X-Slack-Signature'];
};