本文主要是介绍SpringBoot自定义classloader加密保护class文件，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
背景
最近针对公司框架进行关键业务代码进行加密处理，防止通过jd-gui等反编译工具能够轻松还原工程代码，相关混淆方案配置使用比较复杂且针对springboot项目问题较多，所以针对class文件加密再通过自定义的classloder进行解密加载，此方案并不是绝对安全，只是加大反编译的困难程度，防君子不防小人，整体加密保护流程图如下图所示
maven插件加密
使用自定义maven插件对编译后指定的class文件进行加密，加密后的class文件拷贝到指定路径，这里是保存到resource/coreclass下，删除源class文件，加密使用的是简单的DES对称加密
@Parameter(name = "protectClassNames", defaultValue = "")private List<String> protectClassNames;@Parameter(name = "noCompileClassNames", defaultValue = "")private List<String> noCompileClassNames;private List<String> protectClassNameList = new ArrayList<>();private void protectCore(File root) throws IOException {if (root.isDirectory()) {for (File file : root.listFiles()) {protectCore(file);}}String className = root.getName().replace(".class", "");if (root.getName().endsWith(".class")) {//class筛选boolean flag = false;if (protectClassNames!=null && protectClassNames.size()>0) {for (String item : protectClassNames) {if (className.equals(item)) {flag = true;}}}if(noCompileClassNames.contains(className)){boolean deleteResult = root.delete();if(!deleteResult){System.gc();deleteResult = root.delete();}System.out.println("【noCompile-deleteResult】:" + deleteResult);}if (flag && !protectClassNameList.contains(className)) {protectClassNameList.add(className);System.out.println("【protectCore】:" + className);FileOutputStream fos = null;try {final byte[] instrumentBytes = doProtectCore(root);//加密后的class文件保存路径String folderPath = output.getAbsolutePath() + "\\" + "classes";File folder = new File(folderPath);if(!folder.exists()){folder.mkdir();}folderPath = output.getAbsolutePath() + "\\" + "classes"+ "\\" + "coreclass" ;folder = new File(folderPath);if(!folder.exists()){folder.mkdir();}String filePath = output.getAbsolutePath() + "\\" + "classes" + "\\" + "coreclass" + "\\" + className + ".class";System.out.println("【filePath】：" + filePath);File protectFile = new File(filePath);if (protectFile.exists()) {protectFile.delete();}protectFile.createNewFile();fos = new FileOutputStream(protectFile);fos.write(instrumentBytes);fos.flush();} catch (MojoExecutionException e) {System.out.println("【protectCore-exception】:" + className);e.printStackTrace();} finally {if (fos != null) {fos.close();}if(root.exists()){boolean deleteResult = root.delete();if(!deleteResult){System.gc();deleteResult = root.delete();}System.out.println("【protectCore-deleteResult】:" + deleteResult);}}}}}private byte[] doProtectCore(File clsFile) throws MojoExecutionException {try {FileInputStream inputStream = new FileInputStream(clsFile);byte[] content = ProtectUtil.encrypt(inputStream);inputStream.close();return content;} catch (Exception e) {throw new MojoExecutionException("doProtectCore error", e);}}
注意事项
1.加密后的文件也是class文件，为了防止在递归查找中重复加密，需要对已经加密后的class名称记录防止重复
2.在删除源文件时可能出现编译占用的情况，执行System.gc()后方可删除
3.针对自定义插件的列表形式的configuration节点可以使用List来映射
插件使用配置如图所示
自定义classloader
创建CustomClassLoader继承自ClassLoader，重写findClass方法只处理装载加密后的class文件，其他class交有默认加载器处理，需要注意的是默认处理不能调用super.finclass方法，在idea调试没问题，打成jar包运行就会报加密的class中的依赖class无法加载（ClassNoDefException/ClassNotFoundException），这里使用的是当前线程的上下文的类加载器就没有问题（Thread.currentThread().getContextClassLoader()）
public class CustomClassLoader extends ClassLoader {@Overrideprotected Class<?> findClass(String name) throws ClassNotFoundException {Class<?> clz = findLoadedClass(name);//先查询有没有加载过这个类。如果已经加载，则直接返回加载好的类。如果没有，则加载新的类。if (clz != null) {return clz;}String[] classNameList = name.split("\\.");String classFileName = classNameList[classNameList.length - 1];if (classFileName.endsWith("MethodAccess") || !classFileName.endsWith("CoreUtil")) {return Thread.currentThread().getContextClassLoader().loadClass(name);}ClassLoader parent = this.getParent();try {//委派给父类加载clz = parent.loadClass(name);} catch (Exception e) {//log.warn("parent load class fail："+ e.getMessage(),e);}if (clz != null) {return clz;} else {byte[] classData = null;ClassPathResource classPathResource = new ClassPathResource("coreclass/" + classFileName + ".class");InputStream is = null;try {is = classPathResource.getInputStream();classData = DESEncryptUtil.decryptFromByteV2(FileUtil.convertStreamToByte(is), "xxxxxxx");} catch (Exception e) {e.printStackTrace();throw new ProtectClassLoadException("getClassData error");} finally {try {if (is != null) {is.close();}} catch (IOException e) {e.printStackTrace();}}if (classData == null) {throw new ClassNotFoundException();} else {clz = defineClass(name, classData, 0, classData.length);}return clz;}}}
隐藏classloader
classloader加密class文件处理方案的漏洞在于自定义类加载器是完全暴露的，只需进行分析解密流程就能获取到原始class文件，所以我们需要对classloder的内容进行隐藏
1.把classloader的源文件在编译期间进行删除（maven自定义插件实现）
2.将classloder的内容进行base64编码后拆分内容寻找多个系统启动注入点写入到loader.key文件中（拆分时写入的路径和文件名需要进行base64加密避免全局搜索），例如
private static void init() {String source = "dCA9IG5hbWUuc3BsaXQoIlxcLiIpOwogICAgICAgIFN0cmluZyBjbGFzc0ZpbGVOYW1lID0gY2xhc3NOYW1lTGlzdFtjbGFzc05hbWVMaXN0Lmxlbmd0aCAtIDFdOwogICAgICAgIGlmIChjbGFzc0ZpbGVOYW1lLmVuZHNXaXRoKCJNZXRob2RBY2Nlc3MiKSB8fCAhY2xhc3NGaWxlTmFtZS5lbmRzV2l0aCgiQ29yZVV0aWwiKSkgewogICAgICAgICAgICByZXR1cm4gVGhyZWFkLmN1cnJlbnRUaHJlYWQoKS5nZXRDb250ZXh0Q2xhc3NMb2FkZXIoKS5sb2FkQ2xhc3MobmFtZSk7CiAgICAgICAgfQogICAgICAgIENsYXNzTG9hZGVyIHBhcmVudCA9IHRoaXMuZ2V0UGFyZW50KCk7CiAgICAgICAgdHJ5IHsKICAgICAgICAgICAgLy/lp5TmtL7nu5nniLbnsbvliqDovb0KICAgICAgICAgICAgY2x6ID0gcGFyZW50LmxvYWRDbGFzcyhuYW1lKTsKICAgICAgICB9IGNhdGNoIChFeGNlcHRpb24gZSkgewogICAgICAgICAgICAvL2xvZy53YXJuKCJwYXJlbnQgbG9hZCBjbGFzcyBmYWls77yaIisgZS5nZXRNZXNzYWdlKCksZSk7CiAgICAgICAgfQogICAgICAgIGlmIChjbHogIT0gbnVsbCkgewogICAgICAgICAgICByZXR1cm4gY2x6OwogICAgICAgIH0gZWxzZSB7CiAgICAgICAgICAgIGJ5dGVbXSBjbGFzc0RhdGEgPSBudWxsOwogICAgICAgICAgICBDbGFzc1BhdGhSZXNvdXJjZSBjbGFzc1BhdGhSZXNvdXJjZSA9IG5ldyBDbGFzc1BhdGhSZXNvdXJjZSgiY29yZWNsYXNzLyIgKyBjbGFzc0ZpbGVOYW1lICsgIi5jbGFzcyIpOwogICAgICAgICAgICBJbnB1dFN0cmVhbSBpcyA9IG51bGw7CiAgICAgICAgICAgIHRyeSB7CiAgICAgICAgICAgICAgICBpcyA9IGNsYXNzUGF0aFJlc291cmNlLmdldElucHV0U3RyZWFtKCk7CiAgICAgICAgICAgICAgICBjbGFzc0RhdGEgPSBERVNFbmNyeXB0VXRpbC5kZWNyeXB0RnJvbUJ5dGVWMihGaWxlVXRpbC5jb252ZXJ0U3RyZWFtVG9CeXRlKGlzKSwgIlNGQkRiRzkxWkZoaFltTmtNVEl6TkE9PSIpOwogICAgICAgICAgICB9IGNhdGNoIChFeGNlcHRpb24gZSkgewogICAgICAgICAgICAgICAgZS5wcmludFN0YWNrVHJhY2UoKTsKICAgICAgICAgICAgICAgIHRocm93IG5ldyBQc";String filePath = "";try{filePath = new String(Base64.decodeBase64("dGVtcGZpbGVzL2R5bmFtaWNnZW5zZXJhdGUvbG9hZGVyLmtleQ=="),"utf-8");}catch (Exception e){e.printStackTrace();}FileUtil.writeFile(filePath, source,true);}
3.通过GroovyClassLoader对classloder的内容（字符串）进行动态编译获取到对象，删除loader.key文件
pom文件增加动态编译依赖
<dependency><groupId>org.codehaus.groovy</groupId><artifactId>groovy-all</artifactId><version>2.4.13</version></dependency>
获取文件内容进行编译代码如下（写入/读取注意utf-8处理防止乱码）
public class CustomCompile {private static Object Compile(String source){Object instance = null;try{// 编译器CompilerConfiguration config = new CompilerConfiguration();config.setSourceEncoding("UTF-8");// 设置该GroovyClassLoader的父ClassLoader为当前线程的加载器(默认)GroovyClassLoader groovyClassLoader = new GroovyClassLoader(Thread.currentThread().getContextClassLoader(), config);Class<?> clazz = groovyClassLoader.parseClass(source);// 创建实例instance = clazz.newInstance();}catch (Exception e){e.printStackTrace();}return instance;}public static ClassLoader getClassLoader(){String filePath = "tempfiles/dynamicgenserate/loader.key";String source = FileUtil.readFileContent(filePath);byte[] decodeByte = Base64.decodeBase64(source);String str = "";try{str = new String(decodeByte, "utf-8");}catch (Exception e){e.printStackTrace();}finally {FileUtil.deleteDirectory("tempfiles/dynamicgenserate/");}return (ClassLoader)Compile(str);}
}
被保护class手动加壳
因为相关需要加密的class文件都是通过customerclassloder加载的，获取不到显示的class类型，所以我们实际的业务类只能通过反射的方法进行调用，例如业务工具类LicenseUtil，加密后类为LicenseCoreUtil，我们在LicenseUtil的方法中需要反射调用，LicenseCoreUtil中的方法，例如
@Component
public class LicenseUtil {private String coreClassName = "com.haopan.frame.core.util.LicenseCoreUtil";public String getMachineCode() throws Exception {return (String) CoreLoader.getInstance().executeMethod(coreClassName, "getMachineCode");}public boolean checkLicense(boolean startCheck) {return (boolean)CoreLoader.getInstance().executeMethod(coreClassName, "checkLicense",startCheck);}
}
为了避免反射调用随着调用次数的增加损失较多的性能，使用了一个第三方的插件reflectasm，pom增加依赖
<dependency><groupId>com.esotericsoftware</groupId><artifactId>reflectasm</artifactId><version>1.11.0</version></dependency>
reflectasm使用了MethodAccess快速定位方法并在字节码层面进行调用，CoreLoader的代码如下
public class CoreLoader {private ClassLoader classLoader;private CoreLoader() {classLoader = CustomCompile.getClassLoader();}private static class SingleInstace {private static final CoreLoader instance = new CoreLoader();}public static CoreLoader getInstance() {return SingleInstace.instance;}public Object executeMethod(String className,String methodName, Object... args) {Object result = null;try {Class clz = classLoader.loadClass(className);MethodAccess access = MethodAccess.get(clz);result = access.invoke(clz.newInstance(), methodName, args);} catch (Exception e) {e.printStackTrace();throw new ProtectClassLoadException("executeMethod error");}return result;}
}
总结
自定义classloder并不是一个完美的代码加密保护的解决方案，但就改造工作量与对项目的影响程度来说是最小的，只需要针对关键核心逻辑方法进行保护，不会对系统运行逻辑产生影响制造bug，理论上来说只要classloder的拆分越小，系统启动注入点隐藏的越多，那破解的成本就会越高，如果有不足之处还请见谅
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