Null check error in web worker when using `RsaOaepPrivateKey.importPkcs8Key` for RSA decryption

[chaudharydeepanshu]

Description

I'm using this package for RSA decryption in both isolates and web workers. While it works fine in isolates, I encounter a null check error when running in a web worker.

Code

This is the function that runs for decryption:

import 'dart:convert';
import 'package:encrypt/encrypt.dart';
import 'package:webcrypto/webcrypto.dart';
import 'package:pem/pem.dart';
import 'package:basic_utils/basic_utils.dart';

Future<String> decryptDEKWeb({
  required String encryptedDek,
  required String rsaPrivateKeyPKCS1,
}) async {
  // Get RSAPrivateKey from the rsaPrivateKeyPKCS1
  final rSAPrivateKey =
  RSAKeyParser().parse(rsaPrivateKeyPKCS1) as RSAPrivateKey;

  // Get PKCS#8 from RSAPrivateKey
  String pkcs8 = CryptoUtils.encodeRSAPrivateKeyToPem(rSAPrivateKey);

  // Decode PKCS#8 key to get key data
  List<int> keyData = PemCodec(PemLabel.privateKey).decode(pkcs8);

  // Import key data as a private key
  final privateKey = await RsaOaepPrivateKey.importPkcs8Key(keyData, Hash.sha1);

  if (encryptedDek.startsWith('encRsa_')) {
    final encryptedData = base64.decode(encryptedDek.substring(7));

    // Decrypt the encrypted data
    final decryptedBytes = await privateKey.decryptBytes(encryptedData);

    return base64.encode(decryptedBytes);
  } else {
    throw ('Invalid encrypted dek');
  }
}

Error

This is the error I get in the web worker:

[   +1 ms] RethrownDartError: Null check operator used on a null value

           dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/errors.dart 329:10  createErrorWithStack
           dart-sdk/lib/_internal/js_dev_runtime/patch/core_patch.dart 265:28            _throw
           dart-sdk/lib/core/errors.dart 120:5                                           throwWithStackTrace
           dart-sdk/lib/async/zone.dart 1386:11                                          callback
           dart-sdk/lib/async/schedule_microtask.dart 40:11                              _microtaskLoop
           dart-sdk/lib/async/schedule_microtask.dart 49:5                               _startMicrotaskLoop
           dart-sdk/lib/_internal/js_dev_runtime/patch/async_patch.dart 181:7            <fn>

From what I can tell, the error is being thrown on this line:

final privateKey = await RsaOaepPrivateKey.importPkcs8Key(keyData, Hash.sha1);

Environment

• The code runs fine in isolates, but throws this error when used in a web worker.
• The web worker code is generated using isolate_manager with the following command:

  dart run isolate_manager:generate
  

Steps to Reproduce

1. Run the provided decryptDEKWeb function inside a web worker environment.
2. Observe the null check error when calling RsaOaepPrivateKey.importPkcs8Key.

Expected Behavior

The function should successfully import the private key and decrypt the data, as it does in an isolate.

Additional Information

• The keyData passed to importPkcs8Key is valid, as confirmed by logging it before the function call.
• This issue seems specific to web workers, as the same code works without issues outside of web worker.

Let me know if any further details are required for debugging.