E2EEChat/lib/common/cipher.dart

import 'dart:async';
import 'dart:convert';
import 'dart:io';
import 'dart:math';

import 'package:cookie_jar/cookie_jar.dart';
import 'package:crypto/crypto.dart';
import 'package:encrypt/encrypt.dart' as encrypt;
import 'package:encrypt/encrypt_io.dart';
import 'package:flutter_secure_storage/flutter_secure_storage.dart';
import 'package:path_provider/path_provider.dart';
import 'package:pointycastle/asymmetric/api.dart';
import 'package:pointycastle/export.dart';
import 'package:pointycastle/src/platform_check/platform_check.dart';

import 'api.dart';
import 'global.dart';


class RSAPublicKeyStore extends RSAPublicKey {
  RSAPublicKeyStore(BigInt modulus, BigInt exponent) : super(modulus, exponent);

  Map<String, dynamic> toJson() => {"modulus": modulus.toString(), "exponent": exponent.toString()};

  factory RSAPublicKeyStore.fromJson(Map<String, dynamic> map) {
    return RSAPublicKeyStore(BigInt.parse(map["modulus"]), BigInt.parse(map["exponent"]));
  }


  Future<void> save(String key) async {
    try {
      final storage = FlutterSecureStorage();
      storage.write(key: key, value: jsonEncode(toJson()));
    } catch (e) {
      debug('save $key error: $e');
    }
  }

  static Future<RSAPublicKeyStore?> load(String key) async {
    RSAPublicKeyStore? result;
    try {
      final storage = FlutterSecureStorage();
      final json = await storage.read(key: key);
      result = RSAPublicKeyStore.fromJson(jsonDecode(json!));
    } catch (e) {
      debug('load $key error: $e');
    }
    return result;
  }
}

class RSAPrivateKeyStore extends RSAPrivateKey {
  RSAPrivateKeyStore(BigInt modulus, BigInt privateExponent, BigInt p, BigInt q)
      : super(modulus, privateExponent, p, q);
  Map<String, dynamic> toJson() => {
        "modulus": modulus.toString(),
        "privateExponent": privateExponent.toString(),
        "p": p.toString(),
        "q": q.toString(),
      };
  factory RSAPrivateKeyStore.fromJson(Map<String, dynamic> map) {
    return RSAPrivateKeyStore(
      BigInt.parse(map["modulus"]),
      BigInt.parse(map["privateExponent"]),
      BigInt.parse(map["p"]),
      BigInt.parse(map["q"]),
    );
  }


  Future<void> save(String key) async {
    try {
      final storage = FlutterSecureStorage();
      storage.write(key: key, value: jsonEncode(toJson()));
    } catch (e) {
      debug('save $key error: $e');
    }
  }

  static Future<RSAPrivateKeyStore?> load(String key) async {
    RSAPrivateKeyStore? result;
    try {
      final storage = FlutterSecureStorage();
      final json = await storage.read(key: key);
      result = RSAPrivateKeyStore.fromJson(jsonDecode(json!));
    } catch (e) {
      debug('load $key error: $e');
    }
    return result;
  }
}

AsymmetricKeyPair<RSAPublicKeyStore, RSAPrivateKeyStore> generateRSAKeyPair({SecureRandom? secureRandom, int bitLength = 2048}) {
  // Create an RSA key generator and initialize it

  secureRandom ??= getSecureRandom();

  final keyGen = RSAKeyGenerator()
    ..init(ParametersWithRandom(RSAKeyGeneratorParameters(BigInt.parse('65537'), bitLength, 64), secureRandom));

  // Use the generator

  final pair = keyGen.generateKeyPair();

  // Cast the generated key pair into the RSA key types

  final myPublic = pair.publicKey as RSAPublicKeyStore;
  final myPrivate = pair.privateKey as RSAPrivateKeyStore;

  return AsymmetricKeyPair<RSAPublicKeyStore, RSAPrivateKeyStore>(myPublic, myPrivate);
}

SecureRandom getSecureRandom() {
  final secureRandom = SecureRandom('Fortuna')..seed(KeyParameter(encrypt.SecureRandom(32).bytes));
  return secureRandom;
}

Future<AsymmetricKeyPair<RSAPublicKeyStore, RSAPrivateKeyStore>> getRSAKeyPair(String username) async {
  final _privateKey = 'e2ee chat private key of $username';
  final _publicKey = 'e2ee chat public key of $username';
  try {
    final privateKey = await RSAPrivateKeyStore.load(_privateKey);
    final publicKey = await RSAPublicKeyStore.load(_publicKey);
    if (privateKey != null && publicKey != null) {
      return AsymmetricKeyPair<RSAPublicKeyStore, RSAPrivateKeyStore>(publicKey, privateKey);
    }
  } catch (e) {
    debug('get rsa Public key failed: $e');
  }
  final pair = generateRSAKeyPair();
  pair.publicKey.save(_publicKey);
  pair.privateKey.save(_privateKey);
  await Api().addPublicKey(jsonEncode(pair.publicKey.toJson()));
  return pair;
}