public static void XTSEncrypt(SymmetricAlgorithm algorithm, byte[] key1, byte[] key2, ulong dataUnitIndex, byte[] inputBuffer, int inputOffset, int inputCount, byte[] outputBuffer, int outputOffset)
{
byte[] initializationVector = new byte[16];
ICryptoTransform encryptor1 = algorithm.CreateEncryptor(key1, initializationVector);
ICryptoTransform encryptor2 = algorithm.CreateEncryptor(key2, initializationVector);
XtsCryptoTransform transform = new XtsCryptoTransform(encryptor1, encryptor2, false);
transform.TransformBlock(inputBuffer, inputOffset, inputCount, outputBuffer, outputOffset, dataUnitIndex);
}
public override void Write(byte[] buffer, int offset, int count)
{
ValidateSize(count);
if (count == 0)
{
return;
}
var currentSector = CurrentSector;
if (_encryptor == null)
{
_encryptor = _xts.CreateEncryptor();
}
int transformedCount = _encryptor.TransformBlock(buffer, offset, count, _tempBuffer, 0, currentSector);
base.Write(_tempBuffer, 0, transformedCount);
}
public override int Read(byte[] buffer, int offset, int count)
{
ValidateSize(count);
var currentSector = CurrentSector;
var ret = base.Read(_tempBuffer, 0, count);
if (ret == 0)
{
return(0);
}
if (_decryptor == null)
{
_decryptor = _xts.CreateDecryptor();
}
var retV = _decryptor.TransformBlock(_tempBuffer, 0, ret, buffer, offset, currentSector);
return(retV);
}
protected override void TransformSectorImpl(Memory <byte> dest, ReadOnlyMemory <byte> src, long sectorNumber, bool logicalToPhysical)
{
checked
{
if (dest.Length != src.Length)
{
throw new ArgumentOutOfRangeException("dest.Length != src.Length");
}
if (dest.Length != SectorSize)
{
throw new ArgumentOutOfRangeException("dest.Length != SectorSize");
}
var destSeg = dest._AsSegment();
var srcSeg = src._AsSegment();
XtsCryptoTransform transform = logicalToPhysical ? this.CurrentDescrypter : this.CurrentEncrypter;
transform.TransformBlock(srcSeg.Array !, srcSeg.Offset, srcSeg.Count, destSeg.Array !, destSeg.Offset, (ulong)sectorNumber);
}
}
protected override async Task InitMetadataImplAsync(CancellationToken cancel = default)
{
Memory <byte> firstSectorData = new byte[XtsAesMetaDataSize];
// ヘッダの読み込みを試行する
int readSize = await this.PhysicalReadAsync(0, firstSectorData, cancel);
if (readSize == XtsAesMetaDataSize)
{
var metaDataParseResult = TryParseMetaData(firstSectorData);
metaDataParseResult.ThrowIfException();
var metaData = metaDataParseResult.Value !;
// パスワード検査
if (Secure.VeritySaltedPassword(metaData.SaltedPassword, this.CurrentPassword) == false)
{
throw new CoresException("XtsAesRandomAccess: Incorrect password.");
}
// 秘密鍵解読
var decrypted = ChaChaPoly.EasyDecryptWithPassword(metaData.MasterKeyEncryptedByPassword._GetHexBytes(), this.CurrentPassword);
decrypted.ThrowIfException();
// 秘密鍵サイズ検査
if (decrypted.Value.Length != XtsAesKeySize)
{
throw new CoresException("XtsAesRandomAccess: decrypted.Value.Length != XtsAesKeySize");
}
this.CurrentMasterKey = decrypted.Value;
this.CurrentMetaData = metaData;
}
else if (readSize == 0)
{
// ファイルの内容が存在しない
// マスターキーを新規作成する
this.CurrentMasterKey = Secure.Rand(XtsAesKeySize);
// メタデータを新規作成する
var metaData = new XtsAesRandomAccessMetaData
{
Version = 1,
VirtualSize = 0,
SaltedPassword = Secure.SaltPassword(this.CurrentPassword),
MasterKeyEncryptedByPassword = ChaChaPoly.EasyEncryptWithPassword(this.CurrentMasterKey, this.CurrentPassword)._GetHexString(),
};
this.CurrentMetaData = metaData;
// メタデータを書き込みする
await WriteMetaDataAsync(cancel);
}
else
{
// 不正 ここには来ないはず
throw new CoresException($"XtsAesRandomAccess: Invalid readSize: {readSize}");
}
// XTS を作成
this.CurrentXts = XtsAes256.Create(this.CurrentMasterKey.ToArray());
this.CurrentEncrypter = this.CurrentXts.CreateEncryptor();
this.CurrentDescrypter = this.CurrentXts.CreateDecryptor();
}
