verify-github-webhook.ts

const crypto = require("crypto")

export function verifyGithubWebhook(payload: string, signature: string, secret: string) {
  const hmac = crypto.createHmac("sha1", secret)
  hmac.update(JSON.stringify(payload))
  const calculatedSignature = "sha1=" + hmac.digest("hex")
  const valid = crypto.timingSafeEqual(Buffer.from(calculatedSignature), Buffer.from(signature))
  if (!valid) {
    throw new Error("Invalid github webhook call")
  }
}