/// <summary>
/// Perform the initial read on an entry which may include
/// reading encryption headers and setting up inflation.
/// </summary>
/// <param name="destination">The destination to fill with data read.</param>
/// <param name="offset">The offset to start reading at.</param>
/// <param name="count">The maximum number of bytes to read.</param>
/// <returns>The actual number of bytes read.</returns>
private int InitialRead(byte[] destination, int offset, int count)
{
if (!CanDecompressEntry)
{
throw new ZipException("Library cannot extract this entry. Version required is (" + entry.Version + ")");
}
// Handle encryption if required.
if (entry.IsCrypted)
{
if (password == null)
{
throw new ZipException("No password set.");
}
// Generate and set crypto transform...
var managed = new PkzipClassicManaged();
var key = PkzipClassic.GenerateKeys(ZipConstants.ConvertToArray(password));
inputBuffer.CryptoTransform = managed.CreateDecryptor(key, null);
var cryptbuffer = new byte[ZipConstants.CryptoHeaderSize];
inputBuffer.ReadClearTextBuffer(cryptbuffer, 0, ZipConstants.CryptoHeaderSize);
if (cryptbuffer[ZipConstants.CryptoHeaderSize - 1] != entry.CryptoCheckValue)
{
throw new ZipException("Invalid password");
}
if (csize >= ZipConstants.CryptoHeaderSize)
{
csize -= ZipConstants.CryptoHeaderSize;
}
else if ((entry.Flags & (int) GeneralBitFlags.Descriptor) == 0)
{
throw new ZipException(string.Format("Entry compressed size {0} too small for encryption", csize));
}
}
else
{
inputBuffer.CryptoTransform = null;
}
if ((method == (int) CompressionMethod.Deflated) && (inputBuffer.Available > 0))
{
inputBuffer.SetInflaterInput(inf);
}
internalReader = BodyRead;
return BodyRead(destination, offset, count);
}
/// <summary>
/// Initializes encryption keys based on given password
/// </summary>
/// <param name="password">The password.</param>
protected void InitializePassword(string password)
{
var pkManaged = new PkzipClassicManaged();
var key = PkzipClassic.GenerateKeys(ZipConstants.ConvertToArray(password));
cryptoTransform_ = pkManaged.CreateEncryptor(key, null);
}
