Configuration Suggestions on CCE 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.

To achieve strong isolation, like in logical multi-tenancy situations, it is important to have system add-ons run on separate nodes or node pools. This helps keep them separated from service pods and reduces the risk of privilege escalation within a cluster. To do this, you can set the node affinity policy to either Node Affinity or Specified Node Pool Scheduling on the add-on installation page.

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 Service Containers to the Management Plane

To avoid unnecessary service interruption when restricting the service containers on a node from accessing the Kubernetes management plane, consider the following:

Check whether any containers on the node require access to the cluster management plane.
Once you have restricted the service containers on the node from accessing the management plane, all containers on that node will be unable to access the kube-apiserver of the cluster. Before making the configuration, make sure that none of the containers on the node need to access the kube-apiserver of the cluster.

Keep in mind that certain CCE add-ons, like CCE Advanced HPA, still require access to kube-apiserver. It is not recommended that you configure the access restriction on a node where such add-ons are running.
Configure taints and affinity for the node.
If the service containers on the node do not need to access kube-apiserver, it is recommended that you configure labels and taints for the node. Additionally, configure taints, tolerations, and node affinity for the containers on the node. This will prevent other containers from being scheduled to that node, thus avoiding service exceptions.

To restrict the service containers on a node from accessing the management plane, take the following steps:

Obtain 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.
Configure access rules.
- CCE cluster: Log in to each node in the 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, write the command to the /etc/rc.local script.
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
```