public static Memory <byte> EasyDecrypt(ReadOnlyMemory <byte> src, string?password = null)
{
if (password._IsNullOrZeroLen())
{
password = Consts.Strings.EasyEncryptDefaultPassword;
}
return(ChaChaPoly.EasyDecryptWithPassword(src, password));
}
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();
}