SubtleCrypto.verify()

const encoder = new TextEncoder();
const data = encoder.encode('Bestellung #4711: 3 Artikel');

const { privateKey, publicKey } = await crypto.subtle.generateKey(
  { name: 'ECDSA', namedCurve: 'P-256' },
  true,
  ['sign', 'verify']
);

const algo = { name: 'ECDSA', hash: 'SHA-256' };
const signature = await crypto.subtle.sign(algo, privateKey, data);

const ok = await crypto.subtle.verify(algo, publicKey, signature, data);
console.log('Gültig:', ok);

// Manipulierte Daten
const tampered = encoder.encode('Bestellung #4711: 30 Artikel');
console.log('Manipuliert gültig:', await crypto.subtle.verify(algo, publicKey, signature, tampered));

const hexToBytes = (hex) =>
  new Uint8Array(hex.match(/.{2}/g).map((b) => parseInt(b, 16)));

const verifyWebhook = async (secret, body, signatureHex) => {
  const enc = new TextEncoder();
  const key = await crypto.subtle.importKey(
    'raw',
    enc.encode(secret),
    { name: 'HMAC', hash: 'SHA-256' },
    false,
    ['verify']
  );
  return crypto.subtle.verify('HMAC', key, hexToBytes(signatureHex), enc.encode(body));
};

// Zum Testen: Signatur zuerst selbst erzeugen
const enc = new TextEncoder();
const signKey = await crypto.subtle.importKey(
  'raw', enc.encode('geheim'), { name: 'HMAC', hash: 'SHA-256' }, false, ['sign']
);
const body = '{"event":"payment.succeeded"}';
const sig = new Uint8Array(await crypto.subtle.sign('HMAC', signKey, enc.encode(body)));
const sigHex = [...sig].map((b) => b.toString(16).padStart(2, '0')).join('');

console.log(await verifyWebhook('geheim', body, sigHex));
console.log(await verifyWebhook('falsch', body, sigHex));

const b64urlToBytes = (s) => {
  const b64 = s.replace(/-/g, '+').replace(/_/g, '/').padEnd(Math.ceil(s.length / 4) * 4, '=');
  return Uint8Array.from(atob(b64), (c) => c.charCodeAt(0));
};

const verifyJwtRS256 = async (token, publicJwk) => {
  const [header, payload, sig] = token.split('.');
  const key = await crypto.subtle.importKey(
    'jwk',
    publicJwk,
    { name: 'RSASSA-PKCS1-v1_5', hash: 'SHA-256' },
    false,
    ['verify']
  );
  const valid = await crypto.subtle.verify(
    'RSASSA-PKCS1-v1_5',
    key,
    b64urlToBytes(sig),
    new TextEncoder().encode(`${header}.${payload}`)
  );
  if (!valid) throw new Error('Ungültige Signatur');
  return JSON.parse(new TextDecoder().decode(b64urlToBytes(payload)));
};

// Aufruf: const claims = await verifyJwtRS256(token, jwkVomServer);