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using System;
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)
{
RijndaelManaged cipher = new RijndaelManaged();
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 NotImplementedException(); }
}
public override long Position
{
get { throw new NotImplementedException(); }
set { throw new NotImplementedException(); }
}
protected override void Dispose(bool disposing)
{
if (isDisposed)
{
return;
}
isDisposed = true;
if (disposing)
{
//read out last 10 auth bytes
var ten = new byte[10];
stream.Read(ten, 0, 10);
stream.Dispose();
}
}
public override void Flush()
{
throw new NotImplementedException();
}
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
Array.Copy(BitConverter.GetBytes(nonce++), 0, counter, 0, 4);
// 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 NotImplementedException();
}
public override void SetLength(long value)
{
throw new NotImplementedException();
}
public override void Write(byte[] buffer, int offset, int count)
{
throw new NotImplementedException();
}
}
}
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