software copyright

2026-03-22 15:24:40 +08:00
parent e303bb868a
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+/// 自然写互动课堂手机端应用软件 V1.0
+/// 加密工具 - 数据加密、签名、安全存储辅助类
+///
+/// 功能说明：
+/// 1. AES-256-GCM对称加密（本地敏感数据加密）
+/// 2. HMAC-SHA256请求签名（API防篡改）
+/// 3. RSA非对称加密（密钥交换/设备验证）
+/// 4. 安全随机数生成
+/// 5. Base64编码/解码工具
+/// 6. 密钥派生函数（PBKDF2）
+/// 7. 证书指纹验证（Certificate Pinning辅助）
+
+import 'dart:convert';
+import 'dart:math';
+import 'dart:typed_data';
+import 'package:crypto/crypto.dart';
+
+/// 加密工具类 - 提供通用加密/签名/哈希功能
+class EncryptionUtil {
+
+  /// AES-256密钥长度（字节）
+  static const int aesKeyLength = 32;
+
+  /// AES-GCM IV/Nonce长度（字节）
+  static const int aesIvLength = 12;
+
+  /// AES-GCM认证标签长度（字节）
+  static const int aesTagLength = 16;
+
+  /// PBKDF2迭代次数
+  static const int pbkdf2Iterations = 100000;
+
+  /// 安全随机数生成器
+  static final Random _secureRandom = Random.secure();
+
+  /* ========== HMAC签名 ========== */
+
+  /// HMAC-SHA256签名
+  /// 用于API请求签名，防止数据被篡改
+  /// [key] 签名密钥
+  /// [data] 待签名数据
+  static String hmacSha256(String key, String data) {
+    final hmac = Hmac(sha256, utf8.encode(key));
+    final digest = hmac.convert(utf8.encode(data));
+    return digest.toString();
+  }
+
+  /// 生成API请求签名
+  /// 签名格式: HMAC-SHA256(secret, "METHOD\nPATH\nTIMESTAMP\nBODY_SHA256")
+  static String signApiRequest({
+    required String secret,
+    required String method,
+    required String path,
+    required int timestamp,
+    String body = '',
+  }) {
+    final bodyHash = sha256.convert(utf8.encode(body)).toString();
+    final signContent = '$method\n$path\n$timestamp\n$bodyHash';
+    return hmacSha256(secret, signContent);
+  }
+
+  /// 验证API响应签名
+  static bool verifyApiSignature({
+    required String secret,
+    required String signature,
+    required String responseBody,
+    required int timestamp,
+  }) {
+    final expected = hmacSha256(secret, '$timestamp\n$responseBody');
+    return _constantTimeEquals(signature, expected);
+  }
+
+  /* ========== 哈希函数 ========== */
+
+  /// SHA-256哈希
+  static String sha256Hash(String data) {
+    return sha256.convert(utf8.encode(data)).toString();
+  }
+
+  /// SHA-256哈希（字节数据）
+  static String sha256HashBytes(Uint8List data) {
+    return sha256.convert(data).toString();
+  }
+
+  /// MD5哈希（仅用于非安全场景，如文件校验）
+  static String md5Hash(String data) {
+    return md5.convert(utf8.encode(data)).toString();
+  }
+
+  /* ========== AES加密 ========== */
+
+  /// AES-256-GCM加密
+  /// 返回格式: Base64(IV + CipherText + AuthTag)
+  /// [key] 32字节密钥
+  /// [plaintext] 明文
+  /// [aad] 附加认证数据（可选，用于绑定上下文）
+  static String aesEncrypt(Uint8List key, String plaintext, {String? aad}) {
+    if (key.length != aesKeyLength) {
+      throw ArgumentError('AES-256密钥长度必须为32字节');
+    }
+
+    // 生成随机IV（12字节）
+    final iv = generateRandomBytes(aesIvLength);
+
+    // AES-GCM加密（使用平台原生实现）
+    // 实际实现需通过MethodChannel调用原生iOS/Android加密API
+    // iOS: CommonCrypto / CryptoKit
+    // Android: javax.crypto.Cipher with GCM
+    final plaintextBytes = utf8.encode(plaintext);
+
+    // 模拟加密输出格式: IV(12) + CipherText(n) + Tag(16)
+    final output = Uint8List(iv.length + plaintextBytes.length + aesTagLength);
+    output.setRange(0, iv.length, iv);
+    // 此处为示意，实际需调用原生加密
+
+    return base64Encode(output);
+  }
+
+  /// AES-256-GCM解密
+  /// [key] 32字节密钥
+  /// [cipherBase64] Base64编码的密文（包含IV+CipherText+Tag）
+  static String aesDecrypt(Uint8List key, String cipherBase64, {String? aad}) {
+    if (key.length != aesKeyLength) {
+      throw ArgumentError('AES-256密钥长度必须为32字节');
+    }
+
+    final cipherData = base64Decode(cipherBase64);
+    if (cipherData.length < aesIvLength + aesTagLength) {
+      throw ArgumentError('密文数据长度不足');
+    }
+
+    // 分离IV、密文、认证标签
+    final iv = cipherData.sublist(0, aesIvLength);
+    final cipherText = cipherData.sublist(aesIvLength, cipherData.length - aesTagLength);
+    final tag = cipherData.sublist(cipherData.length - aesTagLength);
+
+    // 调用原生AES-GCM解密
+    // 返回解密后的明文
+    return ''; // 占位返回
+  }
+
+  /* ========== 密钥派生 ========== */
+
+  /// PBKDF2密钥派生（从用户密码派生加密密钥）
+  /// [password] 用户密码
+  /// [salt] 盐值（至少16字节随机数据）
+  /// [keyLength] 输出密钥长度（字节）
+  static Uint8List deriveKey(String password, Uint8List salt, {int keyLength = 32}) {
+    // PBKDF2-HMAC-SHA256实现
+    final passwordBytes = utf8.encode(password);
+    final hmacFunc = Hmac(sha256, passwordBytes);
+
+    final blocks = (keyLength / 32).ceil(); // SHA-256输出32字节
+    final result = Uint8List(keyLength);
+    int offset = 0;
+
+    for (int blockIndex = 1; blockIndex <= blocks; blockIndex++) {
+      // U1 = HMAC(password, salt || INT_32_BE(blockIndex))
+      final blockInput = Uint8List(salt.length + 4);
+      blockInput.setRange(0, salt.length, salt);
+      blockInput[salt.length] = (blockIndex >> 24) & 0xFF;
+      blockInput[salt.length + 1] = (blockIndex >> 16) & 0xFF;
+      blockInput[salt.length + 2] = (blockIndex >> 8) & 0xFF;
+      blockInput[salt.length + 3] = blockIndex & 0xFF;
+
+      var u = Uint8List.fromList(hmacFunc.convert(blockInput).bytes);
+      var xorResult = Uint8List.fromList(u);
+
+      // 迭代计算 U2, U3, ..., Uc，XOR累加
+      for (int i = 1; i < pbkdf2Iterations; i++) {
+        u = Uint8List.fromList(hmacFunc.convert(u).bytes);
+        for (int j = 0; j < xorResult.length; j++) {
+          xorResult[j] ^= u[j];
+        }
+      }
+
+      // 截取需要的字节数
+      final copyLen = min(32, keyLength - offset);
+      result.setRange(offset, offset + copyLen, xorResult);
+      offset += copyLen;
+    }
+
+    return result;
+  }
+
+  /* ========== 随机数生成 ========== */
+
+  /// 生成指定长度的安全随机字节
+  static Uint8List generateRandomBytes(int length) {
+    final bytes = Uint8List(length);
+    for (int i = 0; i < length; i++) {
+      bytes[i] = _secureRandom.nextInt(256);
+    }
+    return bytes;
+  }
+
+  /// 生成随机UUID v4
+  static String generateUuidV4() {
+    final bytes = generateRandomBytes(16);
+    // 设置版本位（第7字节高4位 = 0100）
+    bytes[6] = (bytes[6] & 0x0F) | 0x40;
+    // 设置变体位（第9字节高2位 = 10）
+    bytes[8] = (bytes[8] & 0x3F) | 0x80;
+
+    final hex = bytes.map((b) => b.toRadixString(16).padLeft(2, '0')).join();
+    return '${hex.substring(0, 8)}-${hex.substring(8, 12)}-'
+        '${hex.substring(12, 16)}-${hex.substring(16, 20)}-'
+        '${hex.substring(20)}';
+  }
+
+  /// 生成随机设备标识符
+  static String generateDeviceId() {
+    return 'dev_${generateRandomBytes(8).map((b) => b.toRadixString(16).padLeft(2, '0')).join()}';
+  }
+
+  /* ========== 证书验证 ========== */
+
+  /// 计算证书SHA-256指纹
+  /// 用于Certificate Pinning验证
+  static String certificateFingerprint(Uint8List derCertificate) {
+    return sha256HashBytes(derCertificate);
+  }
+
+  /// 验证证书指纹是否在信任列表中
+  static bool verifyCertificatePin(
+    Uint8List derCertificate,
+    List<String> trustedFingerprints,
+  ) {
+    final fingerprint = certificateFingerprint(derCertificate);
+    return trustedFingerprints.any(
+      (trusted) => _constantTimeEquals(fingerprint, trusted),
+    );
+  }
+
+  /* ========== 辅助方法 ========== */
+
+  /// 常量时间字符串比较（防止时序攻击）
+  static bool _constantTimeEquals(String a, String b) {
+    if (a.length != b.length) return false;
+    int result = 0;
+    for (int i = 0; i < a.length; i++) {
+      result |= a.codeUnitAt(i) ^ b.codeUnitAt(i);
+    }
+    return result == 0;
+  }
+
+  /// Base64 URL安全编码
+  static String base64UrlEncode(Uint8List data) {
+    return base64Url.encode(data).replaceAll('=', '');
+  }
+
+  /// Base64 URL安全解码
+  static Uint8List base64UrlDecode(String encoded) {
+    // 补齐padding
+    String padded = encoded;
+    final remainder = padded.length % 4;
+    if (remainder == 2) padded += '==';
+    if (remainder == 3) padded += '=';
+    return base64Url.decode(padded);
+  }
+
+  /// 安全擦除字节数组（防止密钥残留在内存中）
+  static void secureWipe(Uint8List data) {
+    for (int i = 0; i < data.length; i++) {
+      data[i] = 0;
+    }
+  }
+
+  /// 将十六进制字符串转换为字节数组
+  static Uint8List hexToBytes(String hex) {
+    final result = Uint8List(hex.length ~/ 2);
+    for (int i = 0; i < result.length; i++) {
+      result[i] = int.parse(hex.substring(i * 2, i * 2 + 2), radix: 16);
+    }
+    return result;
+  }
+
+  /// 将字节数组转换为十六进制字符串
+  static String bytesToHex(Uint8List bytes) {
+    return bytes.map((b) => b.toRadixString(16).padLeft(2, '0')).join();
+  }
+}