content: /*
  * Copyright 2010 Srikanth Reddy Lingala  
  * 
  * Licensed under the Apache License, Version 2.0 (the "License"); 
  * you may not use this file except in compliance with the License. 
  * You may obtain a copy of the License at 
  * 
  * https://www.apache.org/licenses/LICENSE-2.0
  * 
  * Unless required by applicable law or agreed to in writing, 
  * software distributed under the License is distributed on an "AS IS" BASIS, 
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
  * See the License for the specific language governing permissions and 
  * limitations under the License. 
  */
  
  package net.lingala.zip4j.crypto;
  
  import java.util.Arrays;
  
  import net.lingala.zip4j.crypto.PBKDF2.MacBasedPRF;
  import net.lingala.zip4j.crypto.PBKDF2.PBKDF2Engine;
  import net.lingala.zip4j.crypto.PBKDF2.PBKDF2Parameters;
  import net.lingala.zip4j.crypto.engine.AESEngine;
  import net.lingala.zip4j.exception.ZipException;
  import net.lingala.zip4j.exception.ZipExceptionConstants;
  import net.lingala.zip4j.model.AESExtraDataRecord;
  import net.lingala.zip4j.model.LocalFileHeader;
  import net.lingala.zip4j.util.InternalZipConstants;
  import net.lingala.zip4j.util.Raw;
  import net.lingala.zip4j.util.Zip4jConstants;
  
  public class AESDecrypter implements IDecrypter {
  	
  	private LocalFileHeader localFileHeader;
  	private AESEngine aesEngine;
  	private MacBasedPRF mac;
  	
  	private final int PASSWORD_VERIFIER_LENGTH = 2;
  	private int KEY_LENGTH;
  	private int MAC_LENGTH;
  	private int SALT_LENGTH;
  	
  	private byte[] aesKey;
  	private byte[] macKey;
  	private byte[] derivedPasswordVerifier;
  	private byte[] storedMac;
  	
  	private int nonce = 1;
  	private byte[] iv;
  	private byte[] counterBlock;
  	private int loopCount = 0;
  	
  	public AESDecrypter(LocalFileHeader localFileHeader, 
  			byte[] salt, byte[] passwordVerifier) throws ZipException {
  		
  		if (localFileHeader == null) {
  			throw new ZipException("one of the input parameters is null in AESDecryptor Constructor");
  		}
  		
  		this.localFileHeader = localFileHeader;
  		this.storedMac = null;
  		iv = new byte[InternalZipConstants.AES_BLOCK_SIZE];
  		counterBlock = new byte[InternalZipConstants.AES_BLOCK_SIZE];
  		init(salt, passwordVerifier);
  	}
  	
  	private void init(byte[] salt, byte[] passwordVerifier) throws ZipException {
  		if (localFileHeader == null) {
  			throw new ZipException("invalid file header in init method of AESDecryptor");
  		}
  		
  		AESExtraDataRecord aesExtraDataRecord = localFileHeader.getAesExtraDataRecord();
  		if (aesExtraDataRecord == null) {
  			throw new ZipException("invalid aes extra data record - in init method of AESDecryptor");
  		}
  		
  		switch (aesExtraDataRecord.getAesStrength()) {
  		case Zip4jConstants.AES_STRENGTH_128:
  			KEY_LENGTH = 16;
  			MAC_LENGTH = 16;
  			SALT_LENGTH = 8;
  			break;
  		case Zip4jConstants.AES_STRENGTH_192:
  			KEY_LENGTH = 24;
  			MAC_LENGTH = 24;
  			SALT_LENGTH = 12;
  			break;
  		case Zip4jConstants.AES_STRENGTH_256:
  			KEY_LENGTH = 32;
  			MAC_LENGTH = 32;
  			SALT_LENGTH = 16;
  			break;
  		default:
  			throw new ZipException("invalid aes key strength for file: " + localFileHeader.getFileName());
  		}
  		
  		if (localFileHeader.getPassword() == null || localFileHeader.getPassword().length <= 0) {
  			throw new ZipException("empty or null password provided for AES Decryptor");
  		}
  		
  		byte[] derivedKey = deriveKey(salt, localFileHeader.getPassword());
  		if (derivedKey == null || 
  				derivedKey.length != (KEY_LENGTH + MAC_LENGTH + PASSWORD_VERIFIER_LENGTH)) {
  			throw new ZipException("invalid derived key");
  		}
  		
  		aesKey = new byte[KEY_LENGTH];
  		macKey = new byte[MAC_LENGTH];
  		derivedPasswordVerifier = new byte[PASSWORD_VERIFIER_LENGTH];
  		
  		System.arraycopy(derivedKey, 0, aesKey, 0, KEY_LENGTH);
  		System.arraycopy(derivedKey, KEY_LENGTH, macKey, 0, MAC_LENGTH);
  		System.arraycopy(derivedKey, KEY_LENGTH + MAC_LENGTH, derivedPasswordVerifier, 0, PASSWORD_VERIFIER_LENGTH);
  		
  		if (derivedPasswordVerifier == null) {
  			throw new ZipException("invalid derived password verifier for AES");
  		}
  		
  		if (!Arrays.equals(passwordVerifier, derivedPasswordVerifier)) {
  			throw new ZipException("Wrong Password for file: " + localFileHeader.getFileName(), ZipExceptionConstants.WRONG_PASSWORD);
  		}
  		
  		aesEngine = new AESEngine(aesKey);
  		mac = new MacBasedPRF("HmacSHA1");
  		mac.init(macKey);
  	}
  	
  	public int decryptData(byte[] buff, int start, int len) throws ZipException {
  		
  		if (aesEngine == null) {
  			throw new ZipException("AES not initialized properly");
  		}
  		
  		try {
  			
  			for (int j = start; j < (start + len); j += InternalZipConstants.AES_BLOCK_SIZE) {
  				loopCount = (j + InternalZipConstants.AES_BLOCK_SIZE <= (start + len)) ? 
  						InternalZipConstants.AES_BLOCK_SIZE : ((start + len) - j);
  				
  				mac.update(buff, j, loopCount);
  				Raw.prepareBuffAESIVBytes(iv, nonce, InternalZipConstants.AES_BLOCK_SIZE);
  				aesEngine.processBlock(iv, counterBlock);
  				
  				for (int k = 0; k < loopCount; k++) {
  					buff[j + k] = (byte)(buff[j + k] ^ counterBlock[k]);
  				}
  				
  				nonce++;
  			}
  			
  			return len;
  			
  		} catch (ZipException e) {
  			throw e;
  		} catch (Exception e) {
  			throw new ZipException(e);
  		}
  	}
  	
  	public int decryptData(byte[] buff) throws ZipException {
  		return decryptData(buff, 0, buff.length);
  	}
  	
  	private byte[] deriveKey(byte[] salt, char[] password) throws ZipException {
  		try {
  			PBKDF2Parameters p = new PBKDF2Parameters("HmacSHA1", "ISO-8859-1",
  	                    salt, 1000);
  	        PBKDF2Engine e = new PBKDF2Engine(p);
  	        byte[] derivedKey = e.deriveKey(password, KEY_LENGTH + MAC_LENGTH + PASSWORD_VERIFIER_LENGTH);
  			return derivedKey;
  		} catch (Exception e) {
  			throw new ZipException(e);
  		}
  	}
  	
  	public int getPasswordVerifierLength() {
  		return PASSWORD_VERIFIER_LENGTH;
  	}
  	
  	public int getSaltLength() {
  		return SALT_LENGTH;
  	}
  	
  	public byte[] getCalculatedAuthenticationBytes() {
  		return mac.doFinal();
  	}
  	
  	public void setStoredMac(byte[] storedMac) {
  		this.storedMac = storedMac;
  	}
  
  	public byte[] getStoredMac() {
  		return storedMac;
  	}
  
  //	public byte[] getStoredMac() throws ZipException {
  //		if (raf == null) {
  //			throw new ZipException("attempting to read MAC on closed file handle");
  //		}
  //		
  //		try {
  //			byte[] storedMacBytes = new byte[InternalZipConstants.AES_AUTH_LENGTH];
  //			int bytesRead = raf.read(storedMacBytes);
  //			if (bytesRead != InternalZipConstants.AES_AUTH_LENGTH) {
  //				if (zipModel.isSplitArchive()) {
  ////					unzipEngine.startNextSplitFile();
  //					if (bytesRead == -1) bytesRead = 0;
  //					int newlyRead = raf.read(storedMacBytes, bytesRead, InternalZipConstants.AES_AUTH_LENGTH - bytesRead);
  //					bytesRead += newlyRead;
  //					if (bytesRead != InternalZipConstants.AES_AUTH_LENGTH) {
  //						throw new ZipException("invalid number of bytes read for stored MAC after starting split file");
  //					}
  //				} else {
  //					throw new ZipException("invalid number of bytes read for stored MAC");
  //				}
  //			}
  //			return storedMacBytes;
  //		} catch (IOException e) {
  //			throw new ZipException(e);
  //		} catch (Exception e) {
  //			throw new ZipException(e);
  //		}
  //		
  //	}
  }
  