private void WriteHeaderInCurrentPositionIfNotReadonly(EncryptedFile.Header fileHeader)
{
if (isReadonly)
{
return;
}
var headerBytes = StructConverter.ConvertStructToBits(fileHeader);
stream.Write(headerBytes, 0, EncryptedFile.Header.HeaderSize);
}
private void WriteHeaderInCurrentPositionIfNotReadonly(EncryptedFile.Header fileHeader, ulong magicNumber)
{
if (isReadonly)
{
return;
}
var headerSize = GetHeaderSizeByMagicNumber(magicNumber);
var headerBytes = StructConverter.ConvertStructToBits(fileHeader, headerSize);
stream.Write(headerBytes, 0, headerSize);
}
private EncryptedFile.Header ReadOrWriteHeader(int defaultBlockSize)
{
lock (locker)
{
stream.Position = 0;
if (stream.Length >= EncryptedFile.Header.HeaderSize)
{
// Read header
var headerBytes = stream.ReadEntireBlock(EncryptedFile.Header.HeaderSize);
var header = StructConverter.ConvertBitsToStruct <EncryptedFile.Header>(headerBytes);
if (header.MagicNumber != EncryptedFile.DefaultMagicNumber)
{
throw new InvalidDataException("The magic number in the file doesn't match the expected magic number for encypted files. Perhaps this file isn't encrypted?");
}
return(header);
}
else
{
// Write header
var sizeTest = settings.Codec.EncodeBlock("Dummy key", new byte[defaultBlockSize]);
var header = new EncryptedFile.Header
{
MagicNumber = EncryptedFile.DefaultMagicNumber,
DecryptedBlockSize = defaultBlockSize,
IVSize = sizeTest.IV.Length,
EncryptedBlockSize = sizeTest.Data.Length
};
var headerBytes = StructConverter.ConvertStructToBits(header);
if (!isReadonly)
{
stream.Write(headerBytes, 0, EncryptedFile.Header.HeaderSize);
}
return(header);
}
}
}
private EncryptedFile.Header ReadOrWriteEmptyHeader(int defaultBlockSize)
{
lock (locker)
{
stream.Position = 0;
if (stream.Length >= EncryptedFile.Header.HeaderSize)
{
// Read header
var magicNumber = stream.ReadUInt64();
var headerSize = GetHeaderSizeByMagicNumber(magicNumber);
stream.Position = 0;
var headerBytes = stream.ReadEntireBlock(headerSize);
var fileHeader = StructConverter.ConvertBitsToStruct <EncryptedFile.Header>(headerBytes, headerSize);
if (fileHeader.MagicNumber != EncryptedFile.DefaultMagicNumber && fileHeader.MagicNumber != EncryptedFile.WithTotalSizeMagicNumber)
{
throw new InvalidDataException("The magic number in the file doesn't match the expected magic number for encrypted files. Perhaps this file isn't encrypted?");
}
return(fileHeader);
}
else
{
// Write empty header
var sizeTest = settings.Codec.EncodeBlock("Dummy key", new byte[defaultBlockSize]);
var fileHeader = new EncryptedFile.Header
{
MagicNumber = EncryptedFile.WithTotalSizeMagicNumber,
DecryptedBlockSize = defaultBlockSize,
IVSize = sizeTest.IV.Length,
EncryptedBlockSize = sizeTest.Data.Length,
TotalUnencryptedSize = 0
};
WriteHeaderInCurrentPositionIfNotReadonly(fileHeader, fileHeader.MagicNumber);
return(fileHeader);
}
}
}
