lib/macs/cbc_block_cipher_mac.dart

// See file LICENSE for more information.

library impl.mac.cbc_block_cipher_mac;

import 'dart:typed_data';

import 'package:pointycastle/api.dart';
import 'package:pointycastle/src/registry/registry.dart';
import 'package:pointycastle/src/impl/base_mac.dart';
import 'package:pointycastle/block/modes/cbc.dart';

/// standard CBC Block Cipher MAC - if no padding is specified the default of
/// pad of zeroes is used.
class CBCBlockCipherMac extends BaseMac {
  static final FactoryConfig factoryConfig = DynamicFactoryConfig.regex(
    Mac,
    r'^(.+)/CBC_CMAC(/(.+))?$',
    (_, final Match match) => () {
      var cipher = BlockCipher(match.group(1)!);
      var padding = match.groupCount >= 3 &&
              match.group(3) != null &&
              match.group(3)!.isNotEmpty
          ? Padding(match.group(3)!)
          : null;
      return CBCBlockCipherMac.fromCipherAndPadding(cipher, padding);
    },
  );

  late Uint8List _mac;

  late Uint8List _buf;
  late int _bufOff;
  final BlockCipher _cipher;
  final Padding? _padding;

  final int _macSize;

  ParametersWithIV? _params;

  ///
  /// create a standard MAC based on a CBC block cipher. This will produce an
  /// authentication code half the length of the block size of the cipher.
  ///
  /// * [cipher] the cipher to be used as the basis of the MAC generation.
  CBCBlockCipherMac.fromCipher(BlockCipher cipher)
      : this(cipher, (cipher.blockSize * 8) ~/ 2, null);

  ///
  /// create a standard MAC based on a CBC block cipher. This will produce an
  /// authentication code half the length of the block size of the cipher.
  ///
  /// * [cipher] the cipher to be used as the basis of the MAC generation.
  /// * [padding] the padding to be used to complete the last block.
  CBCBlockCipherMac.fromCipherAndPadding(BlockCipher cipher, Padding? padding)
      : this(cipher, (cipher.blockSize * 8) ~/ 2, padding);

  ///
  /// create a standard MAC based on a block cipher with the size of the
  /// MAC been given in bits. This class uses CBC mode as the basis for the
  /// MAC generation.
  ///
  /// Note: the size of the MAC must be at least 24 bits (FIPS Publication 81),
  /// or 16 bits if being used as a data authenticator (FIPS Publication 113),
  /// and in general should be less than the size of the block cipher as it
  /// reduces the chance of an exhaustive attack (see Handbook of Applied
  /// Cryptography).
  ///
  /// * [cipher] the cipher to be used as the basis of the MAC generation.
  /// * [macSizeInBits] the size of the MAC in bits, must be a multiple of 8.
  CBCBlockCipherMac.fromCipherAndMacSize(BlockCipher cipher, int macSizeInBits)
      : this(cipher, macSizeInBits, null);

  ///
  /// create a standard MAC based on a block cipher with the size of the
  /// MAC been given in bits. This class uses CBC mode as the basis for the
  /// MAC generation.
  ///
  /// Note: the size of the MAC must be at least 24 bits (FIPS Publication 81),
  /// or 16 bits if being used as a data authenticator (FIPS Publication 113),
  /// and in general should be less than the size of the block cipher as it
  /// reduces the chance of an exhaustive attack (see Handbook of Applied
  /// Cryptography).
  ///
  /// * [cipher] the cipher to be used as the basis of the MAC generation.
  /// * [macSizeInBits] the size of the MAC in bits, must be a multiple of 8.
  /// * [padding] the padding to be used to complete the last block.
  CBCBlockCipherMac(BlockCipher cipher, int macSizeInBits, Padding? padding)
      : _cipher = CBCBlockCipher(cipher),
        _macSize = macSizeInBits ~/ 8,
        _padding = padding {
    if ((macSizeInBits % 8) != 0) {
      throw ArgumentError('MAC size must be multiple of 8');
    }

    _mac = Uint8List(cipher.blockSize);

    _buf = Uint8List(cipher.blockSize);
    _bufOff = 0;
  }

  @override
  String get algorithmName {
    var paddingName = _padding != null ? '/${_padding.algorithmName}' : '';
    return '${_cipher.algorithmName}_CMAC$paddingName';
  }

  @override
  void init(CipherParameters params) {
    if (params is ParametersWithIV) {
      _params = params;
    } else if (params is KeyParameter) {
      final zeroIV = Uint8List(params.key.length);
      _params = ParametersWithIV(params, zeroIV);
    }

    reset();

    _cipher.init(true, _params);
  }

  @override
  int get macSize => _macSize;

  @override
  void updateByte(int inp) {
    if (_bufOff == _buf.length) {
      _cipher.processBlock(_buf, 0, _mac, 0);
      _bufOff = 0;
    }

    _buf[_bufOff++] = inp;
  }

  @override
  void update(Uint8List inp, int inOff, int len) {
    if (len < 0) {
      throw ArgumentError('Can\'t have a negative input length!');
    }

    var blockSize = _cipher.blockSize;
    var gapLen = blockSize - _bufOff;

    if (len > gapLen) {
      _buf.setRange(_bufOff, _bufOff + gapLen, inp.sublist(inOff));

      _cipher.processBlock(_buf, 0, _mac, 0);

      _bufOff = 0;
      len -= gapLen;
      inOff += gapLen;

      while (len > blockSize) {
        _cipher.processBlock(inp, inOff, _mac, 0);

        len -= blockSize;
        inOff += blockSize;
      }
    }

    _buf.setRange(_bufOff, _bufOff + len, inp.sublist(inOff));

    _bufOff += len;
  }

  /// Reset the mac generator.
  @override
  void reset() {
    // clean the buffer.
    for (var i = 0; i < _buf.length; i++) {
      _buf[i] = 0;
    }

    _bufOff = 0;

    // reset the underlying cipher.
    _cipher.reset();

    _cipher.init(true, _params);

    if (_params != null) {
      _cipher.init(true, _params);
    }
  }

  @override
  int doFinal(Uint8List out, int outOff) {
    var blockSize = _cipher.blockSize;

    if (_padding == null) {
      //
      // pad with zeroes
      //
      while (_bufOff < blockSize) {
        _buf[_bufOff] = 0;
        _bufOff++;
      }
    } else {
      if (_bufOff == blockSize) {
        _cipher.processBlock(_buf, 0, _mac, 0);
        _bufOff = 0;
      }

      _padding.addPadding(_buf, _bufOff);
    }

    _cipher.processBlock(_buf, 0, _mac, 0);

    out.setRange(outOff, outOff + _macSize, _mac);

    reset();

    return _macSize;
  }
}