/// <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>
int InitialRead(byte[] destination, int offset, int count)
{
if ( !CanDecompressEntry ) {
throw new ZipException("Library cannot extract this entry. Version required is (" + entry.Version.ToString() + ")");
}
// Handle encryption if required.
if (entry.IsCrypted) {
#if NETCF_1_0
throw new ZipException("Encryption not supported for Compact Framework 1.0");
#else
if (password == null) {
throw new ZipException("No password set.");
}
// Generate and set crypto transform...
PkzipClassicManaged managed = new PkzipClassicManaged();
byte[] key = PkzipClassic.GenerateKeys(ZipConstants.ConvertToArray(password));
inputBuffer.CryptoTransform = managed.CreateDecryptor(key, null);
byte[] 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));
}
#endif
} else {
#if !NETCF_1_0
inputBuffer.CryptoTransform = null;
#endif
}
if ((csize > 0) || ((flags & (int)GeneralBitFlags.Descriptor) != 0)) {
if ((method == (int)CompressionMethod.Deflated) && (inputBuffer.Available > 0)) {
inputBuffer.SetInflaterInput(inf);
}
internalReader = new ReadDataHandler(BodyRead);
return BodyRead(destination, offset, count);
}
else {
internalReader = new ReadDataHandler(ReadingNotAvailable);
return 0;
}
}
Stream CreateAndInitDecryptionStream(Stream baseStream, ZipEntry entry)
{
CryptoStream result = null;
if ( (entry.Version < ZipConstants.VersionStrongEncryption)
|| (entry.Flags & (int)GeneralBitFlags.StrongEncryption) == 0) {
PkzipClassicManaged 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");
}
int saltLen = entry.AESSaltLen;
byte[] saltBytes = new byte[saltLen];
int saltIn = baseStream.Read(saltBytes, 0, saltLen);
if (saltIn != saltLen)
throw new ZipException("AES Salt expected " + saltLen + " got " + saltIn);
//
byte[] pwdVerifyRead = new byte[2];
baseStream.Read(pwdVerifyRead, 0, 2);
int blockSize = entry.AESKeySize / 8; // bits to bytes
ZipAESTransform decryptor = new ZipAESTransform(rawPassword_, saltBytes, blockSize, false);
byte[] 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;
}