E2EEChat/lib/model/message.dart

import 'dart:convert';

import 'package:crypto/crypto.dart';
import 'package:e2ee_chat/common/cipher.dart';
import 'package:json_annotation/json_annotation.dart';
import 'package:dash_chat/dash_chat.dart';
import 'package:encrypt/encrypt.dart';
import 'package:pointycastle/asymmetric/api.dart';
import 'package:crypto/crypto.dart';

part 'message.g.dart';

@JsonSerializable()
class Message {
  Message(
      {required this.from,
      required this.to,
      required this.encKey64,
      required this.cipherText64,
      required this.publicKeyJson,
      required this.sign64,
      required this.iv64});

  factory Message.fromJson(Map<String, dynamic> json) => _$MessageFromJson(json);
  Map<String, dynamic> toJson() => _$MessageToJson(this);

  String from;
  String to;
  String encKey64;
  String cipherText64;
  String publicKeyJson;
  String sign64;
  String iv64;

  static Future<Message> encrypt(String from, String to, String plaintext, RSAPublicKeyStore publicKey) async {
    final key = Key.fromSecureRandom(1024); // aes 密钥

    final keyEnc = Encrypter(RSA(publicKey: publicKey));
    final encKey = keyEnc.encrypt(key.base64); // rsa 加密 aes 密钥

    final iv = IV.fromLength(64);
    final textEnc = Encrypter(AES(key));
    final cipherText = textEnc.encrypt(plaintext, iv: iv); // 密文

    final pair = await getRSAKeyPair(from);
    final signEnc = Encrypter(RSA(privateKey: pair.privateKey));
    final digest = sha512.convert(utf8.encode(plaintext)); // hash
    final sign = signEnc.encrypt(digest.toString()); // hex  签名

    return Message(
        from: from,
        to: to,
        encKey64: encKey.base64,
        cipherText64: cipherText.base64,
        publicKeyJson: jsonEncode(pair.publicKey.toJson()),
        sign64: sign.base64,
        iv64: iv.base64);
  }

  Future<ChatMessage?> get chatMessage async {
    ChatMessage? _message;
    final pair = await getRSAKeyPair(from);
    final keyEnc = Encrypter(RSA(privateKey: pair.privateKey));
    final keyBase64 = keyEnc.decrypt64(encKey64);
    final key = Key.fromBase64(keyBase64); // 获取key

    final iv = IV.fromBase64(iv64);
    final textEnc = Encrypter(AES(key));
    final plaintext = textEnc.decrypt64(cipherText64, iv: iv);

    final publicKey = RSAPublicKeyStore.fromJson(jsonDecode(publicKeyJson));
    final signEnc = Encrypter(RSA(publicKey: publicKey));
    final digestHex = signEnc.decrypt64(sign64);
    final digest = sha512.convert(utf8.encode(plaintext));

    if (digest.toString() == digestHex) {
      _message = ChatMessage.fromJson(jsonDecode(plaintext));
    }
    return _message;
  }
}

/*
class GroupMessage {
  int id = 0;
  String plaintext = "";
  final user = ToOne<User>();
  final group = ToOne<Group>();

  @Transient()
  ChatMessage get chatMessage => ChatMessage.fromJson(jsonDecode(plaintext));
}
*/