Verify webhook signatures

npm install standardwebhooks

import { Webhook } from 'standardwebhooks'
const wh = new Webhook(process.env.ORIGAMI_WEBHOOK_SECRET!) // whsec_…
const payload = wh.verify(req.rawBody, req.headers) // throws on failure

import crypto from 'crypto'

const PREFIX = 'whsec_'

function keyForSecret(secret: string): Buffer {
  const body = secret.startsWith(PREFIX) ? secret.slice(PREFIX.length) : secret
  return Buffer.from(body, 'base64')
}

export function verifyOrigamiWebhook({
  rawBody,
  webhookId,
  webhookTimestamp,
  webhookSignature,
  secret,
}: {
  rawBody: Buffer | string
  webhookId: string
  webhookTimestamp: string
  webhookSignature: string
  secret: string
}): boolean {
  const ts = Number(webhookTimestamp)
  if (!Number.isFinite(ts) || Math.abs(Date.now() / 1000 - ts) > 300) return false

  const body = typeof rawBody === 'string' ? rawBody : rawBody.toString('utf8')
  const signed = `${webhookId}.${webhookTimestamp}.${body}`
  const expected = crypto
    .createHmac('sha256', keyForSecret(secret))
    .update(signed, 'utf8')
    .digest('base64')

  for (const match of webhookSignature.matchAll(/v1,([^\s,]+)/g)) {
    const provided = match[1]
    if (provided.length !== expected.length) continue
    try {
      if (crypto.timingSafeEqual(Buffer.from(provided), Buffer.from(expected))) return true
    } catch {
      /* defensive */
    }
  }
  return false
}

import base64
import hmac
import time
from hashlib import sha256

PREFIX = "whsec_"

def key_for_secret(secret: str) -> bytes:
    body = secret[len(PREFIX):] if secret.startswith(PREFIX) else secret
    return base64.b64decode(body)

def verify_origami_webhook(*, raw_body: bytes, webhook_id: str,
                           webhook_timestamp: str, webhook_signature: str,
                           secret: str) -> bool:
    try:
        ts = int(webhook_timestamp)
    except ValueError:
        return False
    if abs(time.time() - ts) > 300:
        return False

    signed = f"{webhook_id}.{webhook_timestamp}.".encode("utf-8") + raw_body
    expected = base64.b64encode(
        hmac.new(key_for_secret(secret), signed, sha256).digest()
    ).decode("utf-8")

    import re
    for m in re.finditer(r"v1,([^\s,]+)", webhook_signature):
        provided = m.group(1)
        if hmac.compare_digest(provided, expected):
            return True
    return False

package origamiwebhook

import (
    "crypto/hmac"
    "crypto/sha256"
    "encoding/base64"
    "regexp"
    "strconv"
    "strings"
    "time"
)

const prefix = "whsec_"

func keyForSecret(secret string) ([]byte, error) {
    body := strings.TrimPrefix(secret, prefix)
    return base64.StdEncoding.DecodeString(body)
}

var v1Re = regexp.MustCompile(`v1,([^\s,]+)`)

func Verify(rawBody []byte, webhookID, webhookTimestamp, webhookSignature, secret string) bool {
    ts, err := strconv.ParseInt(webhookTimestamp, 10, 64)
    if err != nil {
        return false
    }
    if delta := time.Now().Unix() - ts; delta > 300 || delta < -300 {
        return false
    }

    key, err := keyForSecret(secret)
    if err != nil {
        return false
    }
    mac := hmac.New(sha256.New, key)
    mac.Write([]byte(webhookID + "." + webhookTimestamp + "."))
    mac.Write(rawBody)
    expected := base64.StdEncoding.EncodeToString(mac.Sum(nil))

    for _, m := range v1Re.FindAllStringSubmatch(webhookSignature, -1) {
        if hmac.Equal([]byte(m[1]), []byte(expected)) {
            return true
        }
    }
    return false
}

require "base64"
require "openssl"

PREFIX = "whsec_"

def key_for_secret(secret)
  body = secret.start_with?(PREFIX) ? secret[PREFIX.length..-1] : secret
  Base64.decode64(body)
end

def verify_origami_webhook(raw_body:, webhook_id:, webhook_timestamp:,
                           webhook_signature:, secret:)
  ts = Integer(webhook_timestamp) rescue (return false)
  return false if (Time.now.to_i - ts).abs > 300

  signed = "#{webhook_id}.#{webhook_timestamp}.#{raw_body}"
  expected = Base64.strict_encode64(
    OpenSSL::HMAC.digest("sha256", key_for_secret(secret), signed)
  )

  webhook_signature.scan(/v1,([^\s,]+)/).any? do |(provided)|
    next false if provided.bytesize != expected.bytesize
    # OpenSSL.fixed_length_secure_compare ships on Ruby 2.7+ and is
    # the constant-time byte comparator. Pre-2.7 receivers can use
    # the pure-Ruby loop in the standardwebhooks gem.
    OpenSSL.fixed_length_secure_compare(provided, expected)
  end
end

use base64::{engine::general_purpose, Engine};
use hmac::{Hmac, Mac};
use sha2::Sha256;
use std::time::{SystemTime, UNIX_EPOCH};

const PREFIX: &str = "whsec_";

fn key_for_secret(secret: &str) -> Option<Vec<u8>> {
    let body = secret.strip_prefix(PREFIX).unwrap_or(secret);
    general_purpose::STANDARD.decode(body).ok()
}

pub fn verify(
    raw_body: &[u8],
    webhook_id: &str,
    webhook_timestamp: &str,
    webhook_signature: &str,
    secret: &str,
) -> bool {
    let ts: i64 = match webhook_timestamp.parse() {
        Ok(t) => t,
        Err(_) => return false,
    };
    let now = SystemTime::now()
        .duration_since(UNIX_EPOCH)
        .map(|d| d.as_secs() as i64)
        .unwrap_or(0);
    if (now - ts).abs() > 300 {
        return false;
    }

    let key = match key_for_secret(secret) {
        Some(k) => k,
        None => return false,
    };
    let mut mac =
        Hmac::<Sha256>::new_from_slice(&key).expect("HMAC accepts any key size");
    mac.update(webhook_id.as_bytes());
    mac.update(b".");
    mac.update(webhook_timestamp.as_bytes());
    mac.update(b".");
    mac.update(raw_body);
    let expected = general_purpose::STANDARD.encode(mac.finalize().into_bytes());

    webhook_signature
        .split(|c: char| c == ' ' || c == ',')
        .filter_map(|piece| piece.strip_prefix("v1,"))
        // Constant-time compare: only equal-length byte slices may match.
        .any(|provided| {
            provided.len() == expected.len()
                && constant_time_eq::constant_time_eq(
                    provided.as_bytes(),
                    expected.as_bytes(),
                )
        })
}

WEBHOOK_ID=01J7C5K…
WEBHOOK_TIMESTAMP=1717800000
RAW_BODY='{"type":"sequence.email.sent", …}'
SECRET=whsec_XXXXXXXX
KEY=$(printf '%s' "$SECRET" | sed 's/^whsec_//' | base64 -d)
echo -n "${WEBHOOK_ID}.${WEBHOOK_TIMESTAMP}.${RAW_BODY}" \
  | openssl dgst -sha256 -binary -hmac "$KEY" \
  | base64
# Compare to one of the v1,<sig> entries in `webhook-signature`.