Configuration Suggestions on CCE Secret Security

Currently, CCE has configured static encryption for secret resources. The secrets created by users will be encrypted and stored in etcd of the CCE cluster. Secrets can be used in two modes: environment variable and file mounting. No matter which mode is used, CCE still transfers the configured data to users. Therefore, it is recommended that:

Do not record sensitive information in logs.
For the secret that uses the file mounting mode, the default file permission mapped in the container is 0644. Configure stricter permissions for the file. For example:
```
apiversion: v1
kind: Pod
metadata:
  name: mypod
spec:
  containers:
  - name: mypod
    image: redis
    volumeMounts:
    - name: foo
      mountPath: "/etc/foo"
  volumes:
  - name: foo
    secret:
      secretName: mysecret
      defaultMode: 256
```
In defaultMode: 256, 256 is a decimal number, which corresponds to the octal number 0400.

When the file mounting mode is used, configure the secret file name to hide the file in the container.

apiVersion: v1
kind: Secret
metadata:
  name: dotfile-secret
data:
  .secret-file: dmFsdWUtMg0KDQo=
---
apiVersion: v1
kind: Pod
metadata:
  name: secret-dotfiles-pod
spec:
  volumes:
  - name: secret-volume
    secret:
      secretName: dotfile-secret
  containers:
  - name: dotfile-test-container
    image: k8s.gcr.io/busybox
    command:
    - ls
    - "-1"
    - "/etc/secret-volume"
    volumeMounts:
    - name: secret-volume
      readOnly: true
      mountPath: "/etc/secret-volume"

In this way, .secret-file cannot be seen by running ls -l in the /etc/secret-volume/ directory, but can be viewed by running ls -al.

Encrypt sensitive information before creating a secret and decrypt the information when using it.

Using a Bound ServiceAccount Token to Access a Cluster

The secret-based ServiceAccount token does not support expiration time or auto update. In addition, after the mounting pod is deleted, the token is still stored in the secret. Token leakage may incur security risks. A bound ServiceAccount token is recommended for CCE clusters of version 1.23 or later. In this mode, the expiration time can be set and is the same as the pod lifecycle, reducing token leakage risks. Example:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: security-token-example
  namespace: security-example
spec:
  replicas: 1
  selector:
    matchLabels:
      app: security-token-example
      label: security-token-example
  template:
    metadata:
      annotations:
        seccomp.security.alpha.kubernetes.io/pod: runtime/default
      labels:
        app: security-token-example
        label: security-token-example
    spec:
      serviceAccountName: test-sa
      containers:
        - image: ...
          imagePullPolicy: Always
          name: security-token-example
      volumes:
        - name: test-projected
          projected:
            defaultMode: 420
            sources:
              - serviceAccountToken:
                  expirationSeconds: 1800
                  path: token
              - configMap:
                  items:
                    - key: ca.crt
                      path: ca.crt
                  name: kube-root-ca.crt
              - downwardAPI:
                  items:
                    - fieldRef:
                        apiVersion: v1
                        fieldPath: metadata.namespace
                      path: namespace