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WinzipAesCryptoStream.cs
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WinzipAesCryptoStream.cs
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using System;
using System.Buffers.Binary;
using System.IO;
using System.Security.Cryptography;
namespace SharpCompress.Common.Zip
{
internal class WinzipAesCryptoStream : Stream
{
private const int BLOCK_SIZE_IN_BYTES = 16;
private readonly SymmetricAlgorithm _cipher;
private readonly byte[] _counter = new byte[BLOCK_SIZE_IN_BYTES];
private readonly Stream _stream;
private readonly ICryptoTransform _transform;
private int _nonce = 1;
private byte[] _counterOut = new byte[BLOCK_SIZE_IN_BYTES];
private bool _isFinalBlock;
private long _totalBytesLeftToRead;
private bool _isDisposed;
internal WinzipAesCryptoStream(Stream stream, WinzipAesEncryptionData winzipAesEncryptionData, long length)
{
this._stream = stream;
_totalBytesLeftToRead = length;
_cipher = CreateCipher(winzipAesEncryptionData);
var iv = new byte[BLOCK_SIZE_IN_BYTES];
_transform = _cipher.CreateEncryptor(winzipAesEncryptionData.KeyBytes, iv);
}
private SymmetricAlgorithm CreateCipher(WinzipAesEncryptionData winzipAesEncryptionData)
{
var cipher = Aes.Create();
cipher.BlockSize = BLOCK_SIZE_IN_BYTES * 8;
cipher.KeySize = winzipAesEncryptionData.KeyBytes.Length * 8;
cipher.Mode = CipherMode.ECB;
cipher.Padding = PaddingMode.None;
return cipher;
}
public override bool CanRead
{
get { return true; }
}
public override bool CanSeek
{
get { return false; }
}
public override bool CanWrite
{
get { return false; }
}
public override long Length
{
get { throw new NotSupportedException(); }
}
public override long Position
{
get { throw new NotSupportedException(); }
set { throw new NotSupportedException(); }
}
protected override void Dispose(bool disposing)
{
if (_isDisposed)
{
return;
}
_isDisposed = true;
if (disposing)
{
//read out last 10 auth bytes
Span<byte> ten = stackalloc byte[10];
_stream.ReadFully(ten);
_stream.Dispose();
}
}
public override void Flush()
{
throw new NotSupportedException();
}
public override int Read(byte[] buffer, int offset, int count)
{
if (_totalBytesLeftToRead == 0)
{
return 0;
}
int bytesToRead = count;
if (count > _totalBytesLeftToRead)
{
bytesToRead = (int)_totalBytesLeftToRead;
}
int read = _stream.Read(buffer, offset, bytesToRead);
_totalBytesLeftToRead -= read;
ReadTransformBlocks(buffer, offset, read);
return read;
}
private int ReadTransformOneBlock(byte[] buffer, int offset, int last)
{
if (_isFinalBlock)
{
throw new InvalidOperationException();
}
int bytesRemaining = last - offset;
int bytesToRead = (bytesRemaining > BLOCK_SIZE_IN_BYTES)
? BLOCK_SIZE_IN_BYTES
: bytesRemaining;
// update the counter
BinaryPrimitives.WriteInt32LittleEndian(_counter, _nonce++);
// Determine if this is the final block
if ((bytesToRead == bytesRemaining) && (_totalBytesLeftToRead == 0))
{
_counterOut = _transform.TransformFinalBlock(_counter,
0,
BLOCK_SIZE_IN_BYTES);
_isFinalBlock = true;
}
else
{
_transform.TransformBlock(_counter,
0, // offset
BLOCK_SIZE_IN_BYTES,
_counterOut,
0); // offset
}
XorInPlace(buffer, offset, bytesToRead);
return bytesToRead;
}
private void XorInPlace(byte[] buffer, int offset, int count)
{
for (int i = 0; i < count; i++)
{
buffer[offset + i] = (byte)(_counterOut[i] ^ buffer[offset + i]);
}
}
private void ReadTransformBlocks(byte[] buffer, int offset, int count)
{
int posn = offset;
int last = count + offset;
while (posn < buffer.Length && posn < last)
{
int n = ReadTransformOneBlock(buffer, posn, last);
posn += n;
}
}
public override long Seek(long offset, SeekOrigin origin)
{
throw new NotSupportedException();
}
public override void SetLength(long value)
{
throw new NotSupportedException();
}
public override void Write(byte[] buffer, int offset, int count)
{
throw new NotSupportedException();
}
}
}