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158 lines
4.3 KiB
158 lines
4.3 KiB
import 'dart:convert';
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import 'dart:typed_data';
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import 'package:pointycastle/export.dart';
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Uint8List createUint8ListFromString(String s) {
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var ret = Uint8List(s.length);
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for (var i = 0; i < s.length; i++) {
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ret[i] = s.codeUnitAt(i);
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}
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return ret;
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}
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// AES key size
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const keySize = 32; // 32 byte key for AES-256
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const iterationCount = 1000;
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class AesHelper {
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static const cbcMode = 'CBC';
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static const cfbMode = 'CFB';
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static Uint8List deriveKey(dynamic password,
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{String salt = '',
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int iterationCount = iterationCount,
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int derivedKeyLength = keySize}) {
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if (password == null || password.isEmpty) {
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throw ArgumentError('password must not be empty');
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}
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if (password is String) {
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password = createUint8ListFromString(password);
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}
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Uint8List saltBytes = createUint8ListFromString(salt);
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Pbkdf2Parameters params = Pbkdf2Parameters(saltBytes, iterationCount, derivedKeyLength);
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KeyDerivator keyDerivator = PBKDF2KeyDerivator(HMac(SHA256Digest(), 64));
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keyDerivator.init(params);
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return keyDerivator.process(password);
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}
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static Uint8List pad(Uint8List src, int blockSize) {
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var pad = PKCS7Padding();
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pad.init(null);
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int padLength = blockSize - (src.length % blockSize);
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var out = Uint8List(src.length + padLength)..setAll(0, src);
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pad.addPadding(out, src.length);
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return out;
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}
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static Uint8List unpad(Uint8List src) {
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var pad = PKCS7Padding();
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pad.init(null);
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int padLength = pad.padCount(src);
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int len = src.length - padLength;
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return Uint8List(len)..setRange(0, len, src);
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}
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static String aesEncrypt(dynamic password, Uint8List plaintext,
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{String mode = cbcMode}) {
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Uint8List derivedKey;
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if (password is String) {
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derivedKey = deriveKey(password);
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} else {
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derivedKey = password;
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}
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KeyParameter keyParam = KeyParameter(derivedKey);
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BlockCipher aes = AESEngine();
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var rnd = FortunaRandom();
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rnd.seed(keyParam);
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Uint8List iv = rnd.nextBytes(aes.blockSize);
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BlockCipher cipher;
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ParametersWithIV params = ParametersWithIV(keyParam, iv);
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switch (mode) {
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case cbcMode:
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cipher = CBCBlockCipher(aes);
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break;
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case cfbMode:
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cipher = CFBBlockCipher(aes, aes.blockSize);
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break;
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default:
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throw ArgumentError('incorrect value of the "mode" parameter');
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}
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cipher.init(true, params);
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Uint8List paddedText = pad(plaintext, aes.blockSize);
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Uint8List cipherBytes = _processBlocks(cipher, paddedText);
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Uint8List cipherIvBytes = Uint8List(cipherBytes.length + iv.length)
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..setAll(0, iv)
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..setAll(iv.length, cipherBytes);
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return base64.encode(cipherIvBytes);
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}
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static Uint8List aesDecryptBytes(dynamic password, Uint8List ciphertext,
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{String mode = cbcMode}) {
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Uint8List derivedKey;
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if (password is String) {
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derivedKey = deriveKey(password);
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} else {
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derivedKey = password;
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}
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KeyParameter keyParam = KeyParameter(derivedKey);
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BlockCipher aes = AESEngine();
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Uint8List iv = Uint8List(aes.blockSize)
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..setRange(0, aes.blockSize, ciphertext);
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BlockCipher cipher;
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ParametersWithIV params = ParametersWithIV(keyParam, iv);
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switch (mode) {
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case cbcMode:
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cipher = CBCBlockCipher(aes);
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break;
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case cfbMode:
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cipher = CFBBlockCipher(aes, aes.blockSize);
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break;
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default:
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throw ArgumentError('incorrect value of the "mode" parameter');
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}
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cipher.init(false, params);
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int cipherLen = ciphertext.length - aes.blockSize;
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Uint8List cipherBytes = Uint8List(cipherLen)
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..setRange(0, cipherLen, ciphertext, aes.blockSize);
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Uint8List paddedText = _processBlocks(cipher, cipherBytes);
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Uint8List textBytes = unpad(paddedText);
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return textBytes;
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}
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static String aesDecrypt(dynamic password, Uint8List ciphertext,
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{String mode = cbcMode}) {
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return String.fromCharCodes(aesDecryptBytes(password, ciphertext, mode: mode));
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}
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static Uint8List _processBlocks(BlockCipher cipher, Uint8List inp) {
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var out = Uint8List(inp.lengthInBytes);
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for (var offset = 0; offset < inp.lengthInBytes;) {
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var len = cipher.processBlock(inp, offset, out, offset);
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offset += len;
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}
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return out;
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}
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}
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