first commit

lib/utils/aes_decrypt.dart

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+import 'dart:convert';
+import 'dart:typed_data';
+
+import 'package:pointycastle/export.dart';
+
+class AesDecrypt {
+  static const String _cn = 'i0.a';
+
+  static const List<int> _obf = <int>[
+    0xED,
+    0x7A,
+    0x7F,
+    0x3F,
+    0x9E,
+    0x6E,
+    0xE7,
+    0xF9,
+    0x06,
+    0xA0,
+    0xA8,
+    0xE4,
+    0x16,
+    0xE5,
+    0x69,
+    0x70,
+  ];
+
+  /// Java String.hashCode() 等价实现（32-bit signed）
+  static int javaStringHashCode(String str) {
+    int h = 0;
+    for (int i = 0; i < str.length; i++) {
+      h = _toSigned32(h * 31 + str.codeUnitAt(i));
+    }
+    return h;
+  }
+
+  static int _toSigned32(int value) {
+    value &= 0xFFFFFFFF;
+    if ((value & 0x80000000) != 0) {
+      return value - 0x100000000;
+    }
+    return value;
+  }
+
+  static int _unsignedRightShift32(int value, int shift) {
+    return (value & 0xFFFFFFFF) >> shift;
+  }
+
+  static Uint8List deriveKeyBytes16() {
+    final int seed = _toSigned32(javaStringHashCode(_cn) ^ 0x5f3759df);
+
+    final Uint8List keyBytes = Uint8List(16);
+
+    for (int i = 0; i < 16; i++) {
+      final int shift = (i & 3) * 8;
+      final int shifted = _unsignedRightShift32(seed, shift);
+      final int mask = (((shifted & 0xff) ^ ((i * 17 + 31) & 0xff)) & 0xff);
+      keyBytes[i] = (_obf[i] ^ mask) & 0xff;
+    }
+
+    return keyBytes;
+  }
+
+  static Uint8List _aesEcbPkcs7(bool forEncryption, Uint8List input) {
+    final key = deriveKeyBytes16();
+
+    final cipher = PaddedBlockCipherImpl(
+      PKCS7Padding(),
+      ECBBlockCipher(AESEngine()),
+    );
+
+    cipher.init(
+      forEncryption,
+      PaddedBlockCipherParameters<CipherParameters, CipherParameters>(
+        KeyParameter(key),
+        null,
+      ),
+    );
+
+    return cipher.process(input);
+  }
+
+  /// 对应 JS / Java encrypt(String) -> Base64.NO_WRAP
+  static String encrypt(String plainText) {
+    try {
+      final Uint8List input = Uint8List.fromList(utf8.encode(plainText));
+      final Uint8List encrypted = _aesEcbPkcs7(true, input);
+      return base64.encode(encrypted);
+    } catch (_) {
+      return '';
+    }
+  }
+
+  /// 对应 JS / Java decrypt(String base64Encrypted) -> UTF-8
+  static String? decrypt(String base64Encrypted) {
+    try {
+      final Uint8List encrypted = Uint8List.fromList(
+        base64.decode(base64Encrypted),
+      );
+      final Uint8List decrypted = _aesEcbPkcs7(false, encrypted);
+      final String text = utf8.decode(decrypted, allowMalformed: false);
+      return text.isNotEmpty ? text : null;
+    } catch (_) {
+      return null;
+    }
+  }
+}