public ContainerWriter(Stream writeStream, string fileName, X509Certificate2 certificate)
{
this.writeStream = writeStream ?? throw new ArgumentNullException(nameof(writeStream));
this.fileName = fileName ?? throw new ArgumentNullException(nameof(writeStream));
FileNameHelper.CheckFileName(fileName, nameof(fileName));
this.aes = new AesManaged();
this.aes.Mode = CipherMode.CBC;
this.aes.Padding = PaddingMode.PKCS7;
this.aes.KeySize = 256;
this.aes.BlockSize = 128;
this.randomSource = new Random(Guid.NewGuid().GetHashCode());
this.aes.GenerateKey();
this.aes.GenerateIV();
this.header = new ContainerHeader();
this.header.CertificateThumbprint = certificate.Thumbprint;
this.header.EncryptedDataSize = 0L;
this.header.KeyType = this.GetKeyType(certificate.GetRSAPublicKey());
this.header.EncryptedKey = certificate.GetRSAPublicKey().Encrypt(this.aes.Key, RSAEncryptionPadding.Pkcs1); //RSA Padding
this.header.InitializeVector = this.aes.IV;
this.encryptor = this.aes.CreateEncryptor();
this.headerWrited = false;
this.AdditionalPadingSize = (uint)this.randomSource.Next(512, 2048);
}
public async Task <string> ReadFileName()
{
if (this.fileName != null)
{
return(this.fileName);
}
ContainerHeader header = await ContainerHeader.ReadFromStream(this.readerStream);
byte[]? aesKey = null;
try
{
aesKey = await this.cryptoAccessor.AsymetricDecrypt(header.CertificateThumbprint, header.EncryptedKey, RSAEncryptionPadding.Pkcs1); //RSA Padding
this.aesDecryptor = this.aes.CreateDecryptor(aesKey, header.InitializeVector);
this.cryptoStream = new CryptoStream(this.readerStream, this.aesDecryptor, CryptoStreamMode.Read);
using (BinaryDataStream bds = new BinaryDataStream(this.cryptoStream, false))
{
//TODO: Optimalization
for (uint i = 0; i < 16; i++)
{
bds.ReadByte();
}
uint randomDataSize = await bds.Read4BitNumber();
uint stringLen = await bds.Read4BitNumber();
//TODO: Optimalization
for (uint i = 0; i < randomDataSize; i++)
{
bds.ReadByte();
}
string fileName = await bds.ReadConstatntString((int)stringLen, Encoding.UTF8);
FileNameHelper.CheckFileName(fileName, nameof(fileName));
this.fileName = fileName;
return(fileName);
}
}
finally
{
if (aesKey != null)
{
for (int i = 0; i < aesKey.Length; i++)
{
aesKey[i] = 0x00;
aesKey[i] = 0xFF;
}
}
}
}
public static async Task <ContainerHeader> ReadFromStream(Stream stream)
{
using (BinaryDataStream dataStream = new BinaryDataStream(stream, false))
{
await CheckPrefix(dataStream);
ContainerHeader header = new ContainerHeader();
header.Version = await dataStream.Read2BitNumber();
if (header.Version != DefaultVersion)
{
throw new InvalidOperationException($"Encryption file version {header.Version} is not supported.");
}
header.Reserved = await dataStream.Read4BitNumber();
header.KeyType = (ContainerKeyType)await dataStream.Read4BitNumber();
int encryptedKeySize = header.KeyType switch
{
ContainerKeyType.Rsa2048 => 256,
ContainerKeyType.Rsa3072 => 384,
ContainerKeyType.Rsa4096 => 512,
_ => throw new NotSupportedException($"Not support key type {header.KeyType}")
};
header.EncryptedDataSize = await dataStream.Read8BitNumber();
header.CertificateThumbprint = await dataStream.ReadConstatntString(40, Encoding.ASCII);
header.EncryptedKey = new byte[encryptedKeySize];
header.InitializeVector = new byte[16];
await dataStream.ReadAsync(header.EncryptedKey, 0, header.EncryptedKey.Length);
await dataStream.ReadAsync(header.InitializeVector, 0, header.InitializeVector.Length);
return(header);
}
}