自定义classloader加密java程序

大概想法是这样的：
1. 生成密钥用于在des算法中加密。
2. classloader类中动态的解密class，并且通过反射机制执行main方法。
3. 对classloader类进行高质量的混淆。

首先需要生成des算法中的key：

import java.io.File;
import java.io.FileOutputStream;
import java.security.SecureRandom;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;

class Key {

	private String keyName;

	public Key() {

	}

	public Key(String keyName) {
		this.keyName = keyName;
	}

	public void createKey(String keyName) throws Exception {

		SecureRandom sr = new SecureRandom();
		KeyGenerator kg = KeyGenerator.getInstance("DES");
		kg.init(sr);
		SecretKey key = kg.generateKey();
		System.out.println(key.toString());
		byte rawKeyData[] = key.getEncoded();
		FileOutputStream fo = new FileOutputStream(new File(keyName));
		fo.write(rawKeyData);
		fo.close();
	}

	public static void main(String args[]) {
		try {
			new Key("").createKey("d:/key.txt");

		} catch (Exception e) {
			e.printStackTrace();
		}

	}
}

有了key之后就可以对class进行加密了：

package com.hitachi.crypt;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.security.SecureRandom;

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.DESKeySpec;

public class Crypt {

    public static void main(String[] args) throws Exception {

        SecureRandom sr = new SecureRandom();
        FileInputStream fi = new FileInputStream(new File("d:/key.txt"));
        byte rawKeyData[] = new byte[fi.available()];
        fi.read(rawKeyData);
        fi.close();
        DESKeySpec dks = new DESKeySpec(rawKeyData);
        SecretKey key = SecretKeyFactory.getInstance("DES").generateSecret(dks);
        Cipher cipher = Cipher.getInstance("DES");
        cipher.init(Cipher.ENCRYPT_MODE, key, sr);
        FileInputStream fi2 = new FileInputStream(new File("d:/HelloWorld.class"));
        byte data[] = new byte[fi2.available()];
        fi2.read(data);
        fi2.close();
        byte encryptedData[] = cipher.doFinal(data);
        FileOutputStream fo = new FileOutputStream(new File("d:/HelloWorld.class"));
        fo.write(encryptedData);
        fo.close();
    }
}

然后还是关键的classloader类：

package com.hitachi.classloader;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.util.Hashtable;
import java.util.jar.JarEntry;
import java.util.jar.JarInputStream;

public class MyClassLoader extends ClassLoader {

	private static String myClasspath = new String("");
	private static Hashtable<String, Class<?>> loadClassHashTable = new Hashtable<String, Class<?>>();
	private static Hashtable<String, Long> loadClassTime = new Hashtable<String, Long>();

	public MyClassLoader() {

	}

	/** */
	/**
	 * create a classloader and specify a classpath.
	 * 
	 * @param myClasspath
	 *            the specified classpath name.
	 */
	public MyClassLoader(String myClasspath) {
		if (!myClasspath.endsWith("\\")) {
			myClasspath = myClasspath + "\\";
		}
		MyClassLoader.myClasspath = myClasspath;
	}

	/** */
	/**
	 * set the classpath
	 * 
	 * @param myClasspath
	 *            the specified classpath name
	 */
	public void SetmyClasspath(String myClasspath) {
		if (!myClasspath.endsWith("\\")) {
			myClasspath = myClasspath + "\\";
		}
		MyClassLoader.myClasspath = myClasspath;
	}

	/** */
	/**
	 * Loads the class with the specified binary name. This method searches for
	 * classes in the same manner as the loadClass(String, boolean) method.
	 * Invoking this method is equivalent to invoking {loadClass(name,false)}.
	 * 
	 * @param className
	 *            The binary name of the class.
	 * 
	 * @return The resulting <tt>Class</tt> object.
	 * 
	 * @throws ClassNotFoundException
	 *             If the class was not found.
	 */
	@SuppressWarnings("unchecked")
	public Class loadClass(String className) throws ClassNotFoundException {
		return loadClass(className, false);
	}

	/** */
	/**
	 * Loads the class with the specified binary name. The default
	 * implementation of this method searches for classes in the following
	 * order:
	 * 
	 * Invoke {findLoadedClass(String)} to check if the class has already been
	 * loaded.
	 * 
	 * Invoke {findSystemClass(String)} to load the system class.
	 * 
	 * Invoke the {findClass(String)} method to find the class.
	 * 
	 * If the class was found using the above steps, and the resolve flag is
	 * true, this method will then invoke the {resolveClass(Class)} method on
	 * the resulting Class object.
	 * 
	 * @param name
	 *            The binary name of the class.
	 * 
	 * @param resolve
	 *            If true then resolve the class.
	 * 
	 * @return The resulting Class object.
	 * 
	 * @throws ClassNotFoundException
	 *             If the class could not be found.
	 */
	@SuppressWarnings("unchecked")
	protected Class loadClass(String name, boolean resolve)
			throws ClassNotFoundException {

		try {
			Class foundClass = findLoadedClass(name);

			// check if the class has already been loaded.
			if (foundClass != null) {
				System.out.println("Complete to load the class: " + name);
				return foundClass;
			}

			// if the class is systemClass, load the system class by system
			if (name.startsWith("java.")) {
				foundClass = findSystemClass(name);
				loadClassHashTable.put(name, foundClass);
				System.out.println("System is loading the class: " + name);
				return foundClass;
			}

			// invoke the findClass() method to load the class
			try {
				foundClass = findClass(name);
			} catch (Exception fnfe) {
			}

			if (resolve && (foundClass != null)) {
				resolveClass(foundClass);
			}
			return foundClass;
		} catch (Exception e) {
			throw new ClassNotFoundException(e.toString());
		}
	}

	/** */
	/**
	 * Finds the class with the specified binary name.The default implementation
	 * throws a ClassNotFoundException.
	 * 
	 * @param className
	 *            The binary name of the class.
	 * 
	 * @return The resulting Class object.
	 * 
	 * @throws ClassNotFoundException
	 *             If the class could not be found.
	 */
	@SuppressWarnings("unchecked")
	public Class findClass(String className) {

		byte[] classData = null;
		try {
			classData = loadClassData(className);
		} catch (IOException e) {
			e.printStackTrace();
		}
		if (classData == null) {
			return null;
		}

		System.out.println("MyClassLoader is loading : " + className + "");
		Class c = defineClass(className, classData, 0, classData.length);
		MyClassLoader.loadClassHashTable.put(className, c);
		System.out.println("Complete to load the class :" + className);
		return c;
	}

	/** */
	/**
	 * Loads the classData with the specified binary name. This method searches
	 * for classes in the specified classpath as
	 * searchFile(myClasspath,className) method.
	 * 
	 * @param name
	 *            The binary name of the class
	 * 
	 * @return The resulting the classData of the class object by byte[]
	 * 
	 * @throws IOException
	 *             if have some failed or interrupted I/O operations.
	 */
	private byte[] loadClassData(String className) throws IOException {

		String filePath = searchFile(myClasspath, className + ".class");

		if (!(filePath == null || filePath == "")) {

			System.out.println("It have found the file : " + className
					+ ".  Begin to read the data and load the class。");
			FileInputStream inFile = new FileInputStream(filePath);
			byte[] classData = new byte[inFile.available()];
			inFile.read(classData);
			inFile.close();
			loadClassTime.put(className, new File(filePath).lastModified());
			return classData;
		} else {

			filePath = searchFile(myClasspath, className + ".java");
			if (!(filePath == null || filePath == "")) {
				System.out.println("It have found the file : " + filePath
						+ ".  Begin to translate");
				Runtime.getRuntime().exec("javac " + filePath);
				try {
					Thread.sleep(1000);
				} catch (InterruptedException e) {
					e.printStackTrace();
				}
				System.out.println("Translate it over : " + filePath);
				return loadClassData(className);
			} else {
				System.out
						.println("Haven't found the file， and fail to read the classData！");
				return null;
			}
		}
	}

	/** */
	/**
	 * Loads the class with the specified binary name.The default implementation
	 * throws a ClassNotFoundException.
	 * 
	 * @param classData
	 *            The data of the class.
	 * @param className
	 *            The binary name of the class.
	 * 
	 * @return The resulting Class object.
	 * 
	 * @throws ClassNotFoundException
	 *             If the class could not be found.
	 */
	public Class loadClass(byte[] classData, String className)
			throws ClassNotFoundException {

		System.out.println("MyClassLoader is loading : " + className + "");
		Class c = defineClass(className, classData, 0, classData.length);
		loadClassHashTable.put(className, c);
		System.out.println("Complete to load the class :" + className);

		return c;
	}

	/** */
	/**
	 * Loads the class with the specified binary name.The default implementation
	 * throws a ClassNotFoundException.
	 * 
	 * @param className
	 *            The binary name of the class.
	 * @param jarName
	 *            The binary name of the jar that search the class from it.
	 * 
	 * @return The resulting Class object.
	 * 
	 * @throws ClassNotFoundException
	 *             If the class could not be found.
	 */
	protected Class loadClass(String className, String jarName)
			throws ClassNotFoundException {

		String jarPath = searchFile(myClasspath, jarName + ".jar");
		JarInputStream in = null;

		if (!(jarPath == null || jarPath == "")) {

			try {
				in = new JarInputStream(new FileInputStream(jarPath));
				JarEntry entry;
				while ((entry = in.getNextJarEntry()) != null) {
					String outFileName = entry.getName().substring(
							entry.getName().lastIndexOf("/") + 1,
							entry.getName().length());
					if (outFileName.equals(className + ".class")) {
						if (entry.getSize() == -1) {
							System.err.println("error ： can't read the file！");
							return null;
						}
						byte[] classData = new byte[(int) entry.getSize()];
						System.out
								.println("It have found the file : "
										+ className
										+ ".  Begin to read the data and load the class。");
						in.read(classData);
						return loadClass(classData, className);
					}
				}
				System.out.println("Haven't found the file " + className
						+ " in " + jarName + ".jar.");
			} catch (IOException e) {
				e.printStackTrace();
			} finally {
				try {
					in.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
		} else {
			System.out.println("Haven't found the jarFile: " + jarName
					+ ".jar.");
			return null;
		}
		return null;
	}

	/** */
	/**
	 * Reloads the class with the specified binary name. Needn't have to restart
	 * JVM then reload the class.
	 * 
	 * @param className
	 *            The binary name of the class need to reload .
	 * 
	 * @return The resulting Class object.
	 * 
	 * @throws ClassNotFoundException
	 *             If the class was not found.
	 */
	public Class reload(String fileName) {

		String filePath = searchFile(myClasspath, fileName + ".class");
		Long a = new File(filePath).lastModified();

		if (!a.equals(loadClassTime.get(fileName))) {
			loadClassHashTable.remove(fileName);
			loadClassTime.remove(fileName);
			try {
				MyClassLoader mc2 = new MyClassLoader(myClasspath);
				mc2.loadClass(fileName);
			} catch (ClassNotFoundException e) {
				e.printStackTrace();
			}
		} else {
			System.out
					.println("The class is the newest version , needn't reloading.");
		}
		return null;
	}

	/** */
	/**
	 * search the file with the specified binary name. Needn't have to restart
	 * JVM then reload the class.
	 * 
	 * @param classpath
	 *            the specified path where we search.
	 * @param fileName
	 *            The binary name of the file that want to search.
	 * 
	 * @return The resulting file path.
	 */
	public String searchFile(String classpath, String fileName) {

		String cut = fileName.substring(fileName.lastIndexOf('.'), fileName
				.length());
		String path = fileName.substring(0, fileName.lastIndexOf('.')).replace(
				'.', '/')
				+ cut;

		File f = new File(classpath + path);
		if (f.isFile()) {
			return f.getPath();
		} else {
			String objects[] = new File(classpath).list();
			for (int i = 0; i < objects.length; i++) {
				if (new File(classpath + File.separator + objects[i])
						.isDirectory()) {
					String s = searchFile(classpath + objects[i]
							+ File.separator, fileName);
					if (s == null || s == "") {
						continue;
					} else {
						return s;
					}
				}
			}
		}
		return null;
	};

}

最后解密，并且通过反射机制执行：

package com.hitachi.crypt;

import java.io.File;
import java.io.FileInputStream;
import java.lang.reflect.Method;
import java.security.SecureRandom;

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.DESKeySpec;

import com.hitachi.classloader.MyClassLoader;
public class Decrypt {

	public static void main(String[] args) throws Exception {

		SecureRandom sr = new SecureRandom();
		FileInputStream fi = new FileInputStream(new File("d:/key.txt"));
		byte rawKeyData[] = new byte[fi.available()];
		fi.read(rawKeyData);
		fi.close();
		DESKeySpec dks = new DESKeySpec(rawKeyData);
		SecretKey key = SecretKeyFactory.getInstance("DES").generateSecret(dks);
		Cipher cipher = Cipher.getInstance("DES");
		cipher.init(Cipher.DECRYPT_MODE, key, sr);
		FileInputStream fi2 = new FileInputStream(new File(
				"D:/HelloWorld.class"));
		byte encryptedData[] = new byte[fi2.available()];
		fi2.read(encryptedData);
		fi2.close();
		byte decryptedData[] = cipher.doFinal(encryptedData);
		MyClassLoader mcl = new MyClassLoader("D:/");
		Class cl = mcl.loadClass(decryptedData, "HelloWorld");
		Method mainMethod = cl.getMethod("sayHello");
		mainMethod.invoke(null, null);
	}
}

其中源文件是这样的：

public class HelloWorld {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		System.out.println("Hello world");
	}

	public static void sayHello() {
		System.out.println("Hello");
	}

}

就可以了。

评论

4 楼 lzj0470 2011-12-24  

这种方式，带来的问题很大。如：返回一个对象，然后再调用一些办法

3 楼 qskm 2010-07-22  

这个怎么用呢？楼主没说清楚啊，
1、 加密的话该怎么加密？直接执行Crypt类，一个一个加密class文件还是怎么整？
2、 加载class的classloader类是放在哪里？需要配置还是如何调用的？
3、 基于ssh的系统能用不？
4、 ？？？

2 楼 thxg 2009-11-08  

博主好，请教一个classloader相关的问题，我用classloader加载了一个jar文件，用完之后希望可以跟据用户意愿删掉这个jar文件，但据说VM不退出，就不会释放，就无法删除，有什么好办法解决这个问题吗？参考问答模块的链接：
http://www.iteye.com/problems/28854

1 楼 雁行 2009-06-12  

好复杂啊
参考一下