How HubSpot signs webhooks

const crypto = require('node:crypto');

const TOLERANCE_SECONDS = 300;

/**
 * Verify a HubSpot webhook. rawBody: the request body as a Buffer, exactly as received
 * (before any JSON parsing); headers: lower-case names, as in req.headers.
 */
function verifyWebhook(rawBody, headers, secret, url = '', method = 'POST') {
  rawBody = Buffer.from(rawBody);
  const header = headers['x-hubspot-signature-v3'] || '';
  const signatures = [header.trim()];
  const ts = headers['x-hubspot-request-timestamp'] || '';
  url = url.replace(/%(3A|2F|3F|40|21|24|27|28|29|2A|2C|3B)/gi, (e) => decodeURIComponent(e));
  const signed = Buffer.concat([Buffer.from(method.toUpperCase() + url), rawBody, Buffer.from(ts)]);
  const key = secret;
  const expected = crypto.createHmac('sha256', key).update(signed).digest('base64');
  const valid = signatures.some((sig) => {
    const a = Buffer.from(sig);
    const b = Buffer.from(expected);
    return a.length === b.length && crypto.timingSafeEqual(a, b);
  });
  if (!valid) return false;
  const signedAt = Number(ts) / 1000;
  return Number.isFinite(signedAt) && Math.abs(Date.now() / 1000 - signedAt) <= TOLERANCE_SECONDS;
}

// Express: keep the raw body for this route
// app.post('/webhooks/hubspot', express.raw({ type: '*/*' }), (req, res) => {
//   if (!verifyWebhook(req.body, req.headers, process.env.HUBSPOT_WEBHOOK_SECRET, `https://${req.headers.host}${req.originalUrl}`, req.method)) return res.sendStatus(401);
//   res.sendStatus(200); // then process the event asynchronously
// });

import base64
import hashlib
import hmac
import re
import time

TOLERANCE_SECONDS = 300


def verify_webhook(raw_body: bytes, headers, secret: str, url: str = '', method: str = 'POST') -> bool:
    """Verify a HubSpot webhook. raw_body: the request body exactly as received (bytes);
    headers: a mapping with lower-case names (Flask and Django headers are case-insensitive)."""
    header = headers.get('x-hubspot-signature-v3', '')
    signatures = [header.strip()]
    ts = headers.get('x-hubspot-request-timestamp', '')
    url = re.sub(r'%(3A|2F|3F|40|21|24|27|28|29|2A|2C|3B)', lambda m: bytes.fromhex(m.group(1)).decode(), url, flags=re.I)
    signed = (method.upper() + url).encode() + raw_body + (ts).encode()
    key = secret.encode()
    digest = hmac.new(key, signed, hashlib.sha256).digest()
    expected = base64.b64encode(digest).decode()
    if not any(hmac.compare_digest(sig, expected) for sig in signatures):
        return False
    try:
        signed_at = int(ts) / 1000
    except ValueError:
        return False
    return abs(time.time() - signed_at) <= TOLERANCE_SECONDS


# Flask: verify_webhook(request.get_data(), request.headers, SECRET, request.url, request.method)

<?php

const TOLERANCE_SECONDS = 300;

/**
 * Verify a HubSpot webhook. $rawBody: file_get_contents('php://input'), before any decoding;
 * $headers: lower-case names, e.g. array_change_key_case(getallheaders()).
 */
function verify_webhook(string $rawBody, array $headers, string $secret, string $url = '', string $method = 'POST'): bool
{
    $header = (string) ($headers['x-hubspot-signature-v3'] ?? '');
    $signatures = [trim($header)];
    $ts = (string) ($headers['x-hubspot-request-timestamp'] ?? '');
    $url = preg_replace_callback('/%(3A|2F|3F|40|21|24|27|28|29|2A|2C|3B)/i', fn ($m) => rawurldecode($m[0]), $url);
    $signed = strtoupper($method) . $url . $rawBody . $ts;
    $key = $secret;
    $expected = base64_encode(hash_hmac('sha256', $signed, $key, true));
    $valid = false;
    foreach ($signatures as $sig) {
        $valid = $valid || hash_equals($expected, $sig);
    }
    if (! $valid) {
        return false;
    }
    $signedAt = (int) $ts / 1000;

    return $signedAt > 0 && abs(time() - $signedAt) <= TOLERANCE_SECONDS;
}

package webhooks

import (
	"crypto/hmac"
	"crypto/sha256"
	"encoding/base64"
	"math"
	"net/http"
	neturl "net/url"
	"regexp"
	"strconv"
	"strings"
	"time"
)

const toleranceSeconds = 300

// VerifyWebhook checks a HubSpot webhook. rawBody is the request body exactly as received
// (io.ReadAll(r.Body) before any decoding).
func VerifyWebhook(rawBody []byte, h http.Header, secret, url, method string) bool {
	header := h.Get("X-HubSpot-Signature-v3")
	signatures := []string{strings.TrimSpace(header)}
	ts := h.Get("x-hubspot-request-timestamp")
	url = regexp.MustCompile(`(?i)%(3A|2F|3F|40|21|24|27|28|29|2A|2C|3B)`).ReplaceAllStringFunc(url, func(e string) string { s, _ := neturl.PathUnescape(e); return s })
	signed := []byte{}
	signed = append(signed, strings.ToUpper(method)...)
	signed = append(signed, url...)
	signed = append(signed, rawBody...)
	signed = append(signed, ts...)
	key := []byte(secret)
	mac := hmac.New(sha256.New, key)
	mac.Write(signed)
	expected := base64.StdEncoding.EncodeToString(mac.Sum(nil))
	valid := false
	for _, sig := range signatures {
		if hmac.Equal([]byte(sig), []byte(expected)) {
			valid = true
		}
	}
	if !valid {
		return false
	}
	n, err := strconv.ParseFloat(ts, 64)
	if err != nil {
		return false
	}
	signedAt := n / 1000
	return math.Abs(float64(time.Now().Unix())-signedAt) <= toleranceSeconds
}