Webhooks

import { createHmac, timingSafeEqual } from "node:crypto";

// Header shapes ReasonOS sends: a Unix timestamp in seconds, and
// "sha256=" followed by 64 lowercase hex digits. Checking the shape first
// means a malformed or hostile header is a clean refusal, never an exception:
// timingSafeEqual throws when the two buffers differ in byte length, which a
// non-ASCII signature of the right character count would cause.
const TIMESTAMP = /^[0-9]{1,15}$/;
const SIGNATURE = /^sha256=[0-9a-f]{64}$/;

// rawBody is the request body as received (a Buffer), before any JSON parsing.
export function verifyReasonOSDelivery(headers, rawBody, secret) {
  const timestamp = headers["x-reasonos-timestamp"];
  const signature = headers["x-reasonos-signature-256"];
  if (typeof timestamp !== "string" || !TIMESTAMP.test(timestamp)) return false;
  if (typeof signature !== "string" || !SIGNATURE.test(signature)) return false;
  if (Math.abs(Date.now() / 1000 - Number(timestamp)) > 300) return false;
  const expected =
    "sha256=" +
    createHmac("sha256", secret).update(`${timestamp}.`).update(rawBody).digest("hex");
  // Both strings are now ASCII of the same length, so the byte lengths match.
  return timingSafeEqual(Buffer.from(expected, "ascii"), Buffer.from(signature, "ascii"));
}

import hashlib, hmac, re, time

# Header shapes ReasonOS sends: a Unix timestamp in seconds, and
# "sha256=" followed by 64 lowercase hex digits. Checking the shape first
# means a malformed or hostile header is a clean refusal, never an exception:
# str.isdigit() accepts characters such as "²" that int() cannot parse, and
# hmac.compare_digest() raises on a str that is not ASCII.
TIMESTAMP = re.compile(r"[0-9]{1,15}")
SIGNATURE = re.compile(r"sha256=[0-9a-f]{64}")

def verify_reasonos_delivery(headers, raw_body: bytes, secret: str) -> bool:
    timestamp = headers.get("X-ReasonOS-Timestamp")
    signature = headers.get("X-ReasonOS-Signature-256")
    if not isinstance(timestamp, str) or not TIMESTAMP.fullmatch(timestamp):
        return False
    if not isinstance(signature, str) or not SIGNATURE.fullmatch(signature):
        return False
    if abs(time.time() - int(timestamp)) > 300:
        return False
    expected = "sha256=" + hmac.new(
        secret.encode(), f"{timestamp}.".encode() + raw_body, hashlib.sha256
    ).hexdigest()
    return hmac.compare_digest(expected.encode("ascii"), signature.encode("ascii"))