Function wrapKeyImpl

lib/internal/crypto/webcrypto.js:1029–1078

(format, key, wrappingKey, wrapAlgorithm)

}

function wrapKeyImpl(format, key, wrappingKey, wrapAlgorithm) {
  const prefix = prepareSubtleMethod(this, 'wrapKey', arguments.length, 4);
  let i = 0;
  format = convertSubtleArgument(prefix, 'KeyFormat', format, i++);
  key = convertSubtleArgument(prefix, 'CryptoKey', key, i++);
  wrappingKey = convertSubtleArgument(prefix, 'CryptoKey', wrappingKey, i++);
  const algorithm = convertSubtleArgument(
    prefix, 'AlgorithmIdentifier', wrapAlgorithm, i++);
  let normalizedAlgorithm;
  try {
    normalizedAlgorithm = normalizeAlgorithm(algorithm, 'wrapKey');
  } catch {
    normalizedAlgorithm = normalizeAlgorithm(algorithm, 'encrypt');
  }

  if (normalizedAlgorithm.name !== getCryptoKeyAlgorithm(wrappingKey).name)
    throw lazyDOMException('Key algorithm mismatch', 'InvalidAccessError');

  if (!hasCryptoKeyUsage(wrappingKey, 'wrapKey'))
    throw lazyDOMException(
      'Unable to use this key to wrapKey', 'InvalidAccessError');

  const exportedKey = exportKeySync(format, key);
  let bytes = exportedKey;

  if (format === 'jwk') {
    // The WebCrypto spec stringifies JWKs in a new global object. Rather
    // than create a new realm here, detach this internally generated JWK from
    // user-mutated prototypes so JSON.stringify cannot read inherited toJSON
    // hooks from the current global.
    detachFromUserPrototypes(exportedKey);
    const json = JSONStringify(exportedKey);
    // As per the NOTE in step 13 https://w3c.github.io/webcrypto/#SubtleCrypto-method-wrapKey
    // we're padding AES-KW wrapped JWK to make sure it is always a multiple of 8 bytes
    // in length
    // The spec then UTF-8 encodes json.
    if (normalizedAlgorithm.name === 'AES-KW' && json.length % 8 !== 0) {
      bytes = encodeUtf8String(
        json + StringPrototypeRepeat(' ', 8 - (json.length % 8)));
    } else {
      bytes = encodeUtf8String(json);
    }
  }

  return cipherOrWrap(
    kWebCryptoCipherEncrypt,
    normalizedAlgorithm,
    wrappingKey,
    bytes);
}

// subtle.unwrapKey() is essentially a subtle.decrypt() followed
// by a subtle.importKey().