Container Security

Controlling the Pod Scheduling Scope

The nodeSelector or nodeAffinity is used to limit the range of nodes to which applications can be scheduled, preventing the entire cluster from being threatened due to the exceptions of a single application.

Suggestions on Container Security Configuration

• Set the computing resource limits (request and limit) of a container. This prevents the container from occupying too many resources and affecting the stability of the host and other containers on the same node.
• Unless necessary, do not mount sensitive host directories to containers, such as /, /boot, /dev, /etc, /lib, /proc, /sys, and /usr.
• Do not run the sshd process in containers unless necessary.
• Unless necessary, it is not recommended that containers and hosts share the network namespace.
• Unless necessary, it is not recommended that containers and hosts share the process namespace.
• Unless necessary, it is not recommended that containers and hosts share the IPC namespace.
• Unless necessary, it is not recommended that containers and hosts share the UTS namespace.
• Unless necessary, do not mount the sock file of Docker to any container.

Container Permission Access Control

When using a containerized application, comply with the minimum privilege principle and properly set securityContext of Deployments or StatefulSets.

• Configure runAsUser to specify a non-root user to run a container.
• Configure privileged to prevent containers being used in scenarios where privilege is not required.
• Configure capabilities to accurately control the privileged access permission of containers.
• Configure allowPrivilegeEscalation to disable privilege escape in scenarios where privilege escalation is not required for container processes.
• Configure seccomp to restrict the container syscalls. For details, see Restrict a Container's Syscalls with seccomp in the official Kubernetes documentation.
• Configure ReadOnlyRootFilesystem to protect the root file system of a container.

  Example YAML for a Deployment:

  apiVersion: apps/v1
  kind: Deployment
  metadata:
    name: security-context-example
    namespace: security-example
  spec:
    replicas: 1
    selector:
      matchLabels:
        app: security-context-example
        label: security-context-example
    strategy:
      rollingUpdate:
        maxSurge: 25%
        maxUnavailable: 25%
      type: RollingUpdate
    template:
      metadata:
        annotations:
          seccomp.security.alpha.kubernetes.io/pod: runtime/default
        labels:
          app: security-context-example
          label: security-context-example
      spec:
        containers:
          - image: ...
            imagePullPolicy: Always
            name: security-context-example
            securityContext:
              allowPrivilegeEscalation: false
              readOnlyRootFilesystem: true
              runAsUser: 1000
              capabilities:
                add:
                - NET_BIND_SERVICE
                drop:
                - all		
            volumeMounts:
              - mountPath: /etc/localtime
                name: localtime
                readOnly: true
              - mountPath: /opt/write-file-dir
                name: tmpfs-example-001
        securityContext:
          seccompProfile:
            type: RuntimeDefault
        volumes:
          - hostPath:
              path: /etc/localtime
              type: ""
            name: localtime
          - emptyDir: {}            
            name: tmpfs-example-001 

Restricting the Access of Containers to the Management Plane

If application containers on a node do not need to access Kubernetes, you can perform the following operations to disable containers from accessing kube-apiserver:

1. Query the container CIDR block and private API server address.

   On the Clusters page of the CCE console, click the name of the cluster to find the information on the details page.

2. Log in to each node in the CCE cluster as user root and run the following command:
   • VPC network:

     iptables -I OUTPUT -s {container_cidr} -d {Private API server IP} -j REJECT

   • Container tunnel network:

     iptables -I FORWARD -s {container_cidr} -d {Private API server IP} -j REJECT

   {container_cidr} indicates the container CIDR of the cluster, for example, 10.0.0.0/16.

   To ensure configuration persistence, you are advised to write the command to the /etc/rc.local script.

3. Run the following command in the container to access kube-apiserver and check whether the request is intercepted:

   curl -k https://{Private API server IP}:5443