package com.zwl.util.zip.impl;
import java.util.zip.ZipException;
import org.bouncycastle.crypto.CipherParameters;
import org.bouncycastle.crypto.PBEParametersGenerator;
import org.bouncycastle.crypto.digests.SHA1Digest;
import org.bouncycastle.crypto.engines.AESEngine;
import org.bouncycastle.crypto.generators.PKCS5S2ParametersGenerator;
import org.bouncycastle.crypto.macs.HMac;
import org.bouncycastle.crypto.modes.SICBlockCipher;
import org.bouncycastle.crypto.params.KeyParameter;
import org.bouncycastle.crypto.params.ParametersWithIV;
/**
* Adapter for bouncy castle crypto implementation (decryption).
*
* @author olaf@merkert.de
*/
public class AESDecrypterBC extends AESCryptoBase implements AESDecrypter {
public AESDecrypterBC( byte[] pwBytes, byte[] salt, byte[] pwVerification ) throws ZipException {
super.saltBytes = salt;
PBEParametersGenerator generator = new PKCS5S2ParametersGenerator();
generator.init( pwBytes, salt, ITERATION_COUNT );
cipherParameters = generator.generateDerivedParameters(KEY_SIZE_BIT*2 + 16);
byte[] keyBytes = ((KeyParameter)cipherParameters).getKey();
this.cryptoKeyBytes = new byte[ KEY_SIZE_BYTE ];
System.arraycopy( keyBytes, 0, cryptoKeyBytes, 0, KEY_SIZE_BYTE );
this.authenticationCodeBytes = new byte[ KEY_SIZE_BYTE ];
System.arraycopy( keyBytes, KEY_SIZE_BYTE, authenticationCodeBytes, 0, KEY_SIZE_BYTE );
// based on SALT + PASSWORD (password is probably correct)
this.pwVerificationBytes = new byte[ 2 ];
System.arraycopy( keyBytes, KEY_SIZE_BYTE*2, this.pwVerificationBytes, 0, 2 );
if( !ByteArrayHelper.isEqual( this.pwVerificationBytes, pwVerification ) ) {
throw new ZipException("wrong password - " + ByteArrayHelper.toString(this.pwVerificationBytes) + "/ " + ByteArrayHelper.toString(pwVerification));
}
// create the first 16 bytes of the key sequence again (using pw+salt)
generator.init( pwBytes, salt, ITERATION_COUNT );
cipherParameters = generator.generateDerivedParameters(KEY_SIZE_BIT);
// checksum added to the end of the encrypted data, update on each encryption call
this.mac = new HMac( new SHA1Digest() );
mac.init( new KeyParameter(authenticationCodeBytes) );
this.aesCipher = new SICBlockCipher(new AESEngine());
this.blockSize = aesCipher.getBlockSize();
// incremented on each 16 byte block and used as encryption NONCE (ivBytes)
nonce = 1;
}
// --------------------------------------------------------------------------
protected CipherParameters cipherParameters;
protected SICBlockCipher aesCipher;
protected HMac mac;
/**
* perform pseudo "in-place" encryption
*/
public void decrypt( byte[] in, int length ) {
int pos = 0;
while( pos<in.length && pos<length ) {
decryptBlock( in, pos, length );
pos += blockSize;
}
}
/**
* encrypt 16 bytes (AES standard block size) or less
* starting at "pos" within "in" byte[]
*/
protected void decryptBlock( byte[] in, int pos, int length ) {
byte[] decryptedIn = new byte[blockSize];
byte[] ivBytes = ByteArrayHelper.toByteArray( nonce++, 16 );
ParametersWithIV ivParams = new ParametersWithIV(cipherParameters, ivBytes);
aesCipher.init( false, ivParams );
int remainingCount = length-pos;
if( remainingCount>=blockSize ) {
mac.update( in, pos, blockSize );
aesCipher.processBlock( in, pos, decryptedIn, 0 );
System.arraycopy( decryptedIn, 0, in, pos, blockSize );
} else {
mac.update( in, pos, remainingCount );
byte[] extendedIn = new byte[blockSize];
System.arraycopy( in, pos, extendedIn, 0, remainingCount );
aesCipher.processBlock( extendedIn, 0, decryptedIn, 0 );
System.arraycopy( decryptedIn, 0, in, pos, remainingCount );
}
}
public byte[] getFinalAuthentication() {
byte[] macBytes = new byte[ mac.getMacSize() ];
mac.doFinal( macBytes, 0 );
byte[] macBytes10 = new byte[10];
System.arraycopy( macBytes, 0, macBytes10, 0, 10 );
return macBytes10;
}
}