/// <summary>
/// The constructor.
/// </summary>
/// <param name="s">The underlying stream</param>
/// <param name="mode">To either encrypt or decrypt.</param>
/// <param name="cryptoParams">The pre-initialized WinZipAesCrypto object.</param>
/// <param name="length">The maximum number of bytes to read from the stream.</param>
internal WinZipAesCipherStream(System.IO.Stream s, WinZipAesCrypto cryptoParams, long length, CryptoMode mode)
: this(s, cryptoParams, mode)
{
// don't read beyond this limit!
_length = length;
//Console.WriteLine("max length of AES stream: {0}", _length);
}
internal WinZipAesCipherStream(System.IO.Stream s, WinZipAesCrypto cryptoParams, CryptoMode mode)
: base()
{
TraceOutput("-------------------------------------------------------");
TraceOutput("Create {0:X8}", this.GetHashCode());
_params = cryptoParams;
_s = s;
_mode = mode;
_nonce = 1;
if (_params == null)
{
throw new Exception("Supply a password to use AES encryption.");
}
int keySizeInBits = _params.KeyBytes.Length * 8;
if (keySizeInBits != 256 && keySizeInBits != 128 && keySizeInBits != 192)
{
throw new ArgumentOutOfRangeException("keysize",
"size of key must be 128, 192, or 256");
}
_mac = new HMACSHA1(_params.MacIv);
_aesCipher = new System.Security.Cryptography.RijndaelManaged();
_aesCipher.BlockSize = 128;
_aesCipher.KeySize = keySizeInBits; // 128, 192, 256
_aesCipher.Mode = CipherMode.ECB;
_aesCipher.Padding = PaddingMode.None;
byte[] iv = new byte[BLOCK_SIZE_IN_BYTES]; // all zeroes
// Create an ENCRYPTOR, regardless whether doing decryption or encryption.
// It is reflexive.
_xform = _aesCipher.CreateEncryptor(_params.KeyBytes, iv);
if (_mode == CryptoMode.Encrypt)
{
_iobuf = new byte[2048];
_PendingWriteBlock = new byte[BLOCK_SIZE_IN_BYTES];
}
#if WANT_TRACE
traceFileUntransformed = "unpack\\WinZipAesCipherStream.trace.untransformed.out";
traceFileTransformed = "unpack\\WinZipAesCipherStream.trace.transformed.out";
untransformed = System.IO.File.Create(traceFileUntransformed);
transformed = System.IO.File.Create(traceFileTransformed);
#endif
}
public static WinZipAesCrypto Generate(string password, int KeyStrengthInBits)
{
WinZipAesCrypto c = new WinZipAesCrypto(password, KeyStrengthInBits);
int saltSizeInBytes = c._KeyStrengthInBytes / 2;
c._Salt = new byte[saltSizeInBytes];
Random rnd = new Random();
rnd.NextBytes(c._Salt);
return(c);
}
public static WinZipAesCrypto ReadFromStream(string password, int KeyStrengthInBits, Stream s)
{
// from http://www.winzip.com/aes_info.htm
//
// Size(bytes) Content
// -----------------------------------
// Variable Salt value
// 2 Password verification value
// Variable Encrypted file data
// 10 Authentication code
//
// ZipEntry.CompressedSize represents the size of all of those elements.
// salt size varies with key length:
// 128 bit key => 8 bytes salt
// 192 bits => 12 bytes salt
// 256 bits => 16 bytes salt
WinZipAesCrypto c = new WinZipAesCrypto(password, KeyStrengthInBits);
int saltSizeInBytes = c._KeyStrengthInBytes / 2;
c._Salt = new byte[saltSizeInBytes];
c._providedPv = new byte[2];
s.Read(c._Salt, 0, c._Salt.Length);
s.Read(c._providedPv, 0, c._providedPv.Length);
c.PasswordVerificationStored = (Int16)(c._providedPv[0] + c._providedPv[1] * 256);
if (password != null)
{
c.PasswordVerificationGenerated = (Int16)(c.GeneratedPV[0] + c.GeneratedPV[1] * 256);
if (c.PasswordVerificationGenerated != c.PasswordVerificationStored)
{
throw new Exception("bad password");
}
}
return(c);
}