/// <summary>
/// Constructor
/// </summary>
/// <param name="stream">The stream on which to perform the cryptographic transformation.</param>
/// <param name="transform">Instance of ZipAESTransform</param>
/// <param name="mode">Read or Write</param>
public ZipAESStream(Stream stream, ZipAESTransform transform, CryptoStreamMode mode)
: base(stream, transform, mode) {
_stream = stream;
_transform = transform;
_slideBuffer = new byte[1024];
_blockAndAuth = CRYPTO_BLOCK_SIZE + AUTH_CODE_LENGTH;
// mode:
// CryptoStreamMode.Read means we read from "stream" and pass decrypted to our Read() method.
// Write bypasses this stream and uses the Transform directly.
if (mode != CryptoStreamMode.Read) {
throw new Exception("ZipAESStream only for read");
}
}
Stream CreateAndInitDecryptionStream(Stream baseStream, ZipEntry entry)
{
CryptoStream result = null;
if ( (entry.Version < ZipConstants.VersionStrongEncryption)
|| (entry.Flags & (int)GeneralBitFlags.StrongEncryption) == 0) {
var classicManaged = new PkzipClassicManaged();
OnKeysRequired(entry.Name);
if (HaveKeys == false) {
throw new ZipException("No password available for encrypted stream");
}
result = new CryptoStream(baseStream, classicManaged.CreateDecryptor(key, null), CryptoStreamMode.Read);
CheckClassicPassword(result, entry);
}
else {
#if !NET_1_1 && !NETCF_2_0
if (entry.Version == ZipConstants.VERSION_AES) {
//
OnKeysRequired(entry.Name);
if (HaveKeys == false) {
throw new ZipException("No password available for AES encrypted stream");
}
var saltLen = entry.AESSaltLen;
var saltBytes = new byte[saltLen];
var saltIn = baseStream.Read(saltBytes, 0, saltLen);
if (saltIn != saltLen)
throw new ZipException("AES Salt expected " + saltLen + " got " + saltIn);
//
var pwdVerifyRead = new byte[2];
baseStream.Read(pwdVerifyRead, 0, 2);
var blockSize = entry.AESKeySize / 8; // bits to bytes
var decryptor = new ZipAESTransform(rawPassword_, saltBytes, blockSize, false);
var pwdVerifyCalc = decryptor.PwdVerifier;
if (pwdVerifyCalc[0] != pwdVerifyRead[0] || pwdVerifyCalc[1] != pwdVerifyRead[1])
throw new Exception("Invalid password for AES");
result = new ZipAESStream(baseStream, decryptor, CryptoStreamMode.Read);
}
else
#endif
{
throw new ZipException("Decryption method not supported");
}
}
return result;
}