Secure Kubernetes Secrets: A Complete Guide

Every Kubernetes application relies on sensitive data, from database credentials to API keys. Protecting this information is paramount, and Kubernetes Secrets provide a dedicated mechanism. However, effectively managing and securing these secrets requires a deep understanding of best practices and potential pitfalls.

This guide comprehensively explores Kubernetes secrets, covering their creation, management, and secure integration with your applications. We'll also explore how Plural simplifies Kubernetes complexity beyond Kubernetes secrets management. Whether you're a beginner or an experienced Kubernetes user, this guide will equip you with the knowledge to handle Kubernetes secrets securely and confidently.

Key Takeaways

• Secrets require active protection: Kubernetes Secrets are not secure by default. Encrypting secrets at rest, using strong RBAC, and limiting access are crucial for protecting sensitive data.
• External secret stores enhance security: Integrating Kubernetes with external secret management solutions like HashiCorp Vault or AWS Secrets Manager provides stronger security and simplifies complex secret management tasks.
• Simplifying Kubernetes Complexity with Plural: Beyond Kubernetes Secrets, teams often grapple with the complexity of managing multiple clusters, automating upgrades, enforcing security, and maintaining visibility across environments. Plural offers a comprehensive Kubernetes management platform to simplify and centralize these tasks.

What are Kubernetes Secrets?

Kubernetes Secrets are objects that store sensitive data, such as passwords, API keys, and certificates, within a Kubernetes cluster. Using Kubernetes Secrets is much safer than embedding this data directly into application code or configuration files. They provide a centralized and secure mechanism for managing credentials and other confidential information required by applications running in your cluster.

Why Kubernetes Secrets Matter

Protecting sensitive data is paramount. While Kubernetes Secrets offer a way to store this information, understanding their limitations is crucial. By default, Secrets are stored unencrypted in etcd, Kubernetes's data store. Anyone with direct access to the etcd data store can read all data stored in etcd, including Secrets, in plain text if encryption at rest is not enabled. Improper secret management is a significant security risk. Challenges like secret rotation and access control necessitate a comprehensive approach.

Create and Manage Kubernetes Secrets

This section details how to create and manage Kubernetes Secrets using kubectl and YAML manifests.

Use kubectl

The kubectl create secret generic command offers flexibility for defining Secrets. You can specify data directly using the --from-literal flag. For example, to create a secret named mysecret with a username and password:

kubectl create secret generic mysecret \
    --from-literal=username=admin \
    --from-literal=password=password123

This creates a Secret with base64 encoded values. To use plain text, use stringData:

kubectl create secret generic mysecret \
    --from-literal=username=admin \
    --from-literal=password=password123 --type=stringData

You can manage existing Secrets with kubectl commands as well, using kubectl get secret, kubectl edit secret, and kubectl delete secret.

Use YAML Manifests

Defining Secrets in YAML manifests provides a declarative approach to managing them. This allows you to store and version control your Secret definitions alongside your other Kubernetes configurations.

NOTE: The secret is base64 encoded, so pushing it directly to version control is not recommended; ensure it is encrypted using a tool like SOPS.

A basic YAML manifest for a Secret looks like this:

apiVersion: v1
kind: Secret
metadata:
  name: mysecret
type: Opaque
stringData:
  username: admin
  password: password123

Apply the manifest using kubectl apply -f <filename>.yaml. This method is generally preferred for managing Secrets, as it promotes Infrastructure-as-Code (IaC) best practices. Discover infrastructure management tools for Kubernetes in this comprehensive guide by Plural.

Kubernetes Secret Types and Use Cases

Kubernetes offers several types of secrets, each designed for specific use cases.

Opaque Secrets

Opaque secrets are the most basic type and store sensitive data in an unstructured key-value format. These secrets hold small amounts of sensitive data such as passwords, API keys, or database connection strings.

apiVersion: v1
kind: Secret
metadata:
  name: mysecret
type: Opaque
stringData:
  username: admin
  password: password123

TLS Secrets

Transport Layer Security (TLS) secrets store X.509 certificates and their corresponding private keys, essential for securing communication between services. These secrets use the kubernetes.io/tls type and are automatically understood by Kubernetes components like Ingress controllers and service meshes. When creating a TLS secret, ensure the certificate and key are correctly formatted and match each other to avoid connectivity issues.

To create a TLS secret, use the dedicated kubectl create secret tls command with your certificate and key files.

kubectl create secret tls my-tls-secret --cert=path/to/tls.crt --key=path/to/tls.key

Docker Registry Secrets

Docker registry secrets store credentials for accessing private container registries. These secrets allow your Pods to pull images from registries requiring authentication. While kubernetes.io/dockercfg and kubernetes.io/dockerconfigjson are traditional types, using imagePullSecrets in your pod specifications is now the preferred method for managing registry credentials. This approach offers better security and flexibility.

Configure the secret with your registry's server address, username, password, and email:

kubectl create secret docker-registry my-registry-secret --docker-server=REGISTRY_SERVER --docker-username=USER --docker-password=PASSWORD --docker-email=EMAIL

Service Account Token Secrets

Service account token secrets store tokens used for authentication within the Kubernetes cluster. Kubernetes automatically creates these secrets for each service account and mounts them into pods running under that service account. For more granular control over service account authentication, consider using the TokenRequest API, which provides short-lived tokens and enhances security. You can get a time-limited API token for that ServiceAccount using kubectl:

kubectl create token build-robot

Use Kubernetes Secrets in Pods

Once you've created your Kubernetes Secrets, the next step is to integrate them into your Pods. There are two primary methods: environment variables and volume mounts. The best approach depends on your application's needs and how it handles configuration.

Environment Variables

Injecting Secrets as environment variables is the simplest approach. Kubernetes maps the key-value pairs from your Secret to environment variables within the Pod. This works well for applications designed to read configuration this way. However, all processes inside the container can access these variables, so this isn't ideal for highly sensitive data.

apiVersion: v1
kind: Pod
metadata:
  name: env-single-secret
spec:
  containers:
  - name: envars-test-container
    image: nginx
    env:
    - name: SECRET_USERNAME
      valueFrom:
        secretKeyRef:
          name: backend-user
          key: backend-username

Volume Mounts

For tighter control over access, mounting Secrets as volumes offers a more secure solution. Kubernetes creates a directory in the Pod and mounts the Secret data as files within it. You control the mount path, dictating which parts of your application can access the Secret. Kubernetes automatically updates these files when the Secret changes, keeping your application up-to-date without restarts (except for subPath mounts).

apiVersion: v1
kind: Pod
metadata:
  name: secret-test-pod
spec:
  containers:
    - name: test-container
      image: nginx
      volumeMounts:
        # name must match the volume name below
        - name: secret-volume
          mountPath: /etc/secret-volume
          readOnly: true
  # The secret data is exposed to Containers in the Pod through a Volume.
  volumes:
    - name: secret-volume
      secret:
        secretName: test-secret

Access Secrets in Applications

Whether you use environment variables or volume mounts, accessing the Secret data within your application is simple. For environment variables, use your programming language's standard methods. For volume mounts, read the data from the files in the mounted directory. Kubernetes'

Secure Your Kubernetes Secrets

While Kubernetes provides the Secret resource for storing confidential information, simply using Secrets isn't enough. This section outlines essential practices to keep your Kubernetes secrets safe.

Encrypt Secrets at Rest

Kubernetes Secrets are, by default, base64-encoded but stored as plaintext within etcd. This means if an attacker gains access to your etcd data, they can easily decode your secrets using the etcdctl command-line tool.

etcdctl get /registry/secrets/<namespace>/<secret-name>

The kube-apiserver process accepts an argument --encryption-provider-config that specifies a path to a configuration file. The contents of that file, if you specify one, control how Kubernetes API data is encrypted in etcd. For details on enabling this, see the Kubernetes documentation on encrypting data at rest.

Use Role-Based Access Control (RBAC)

Implementing Role-Based Access Control (RBAC) is fundamental to Kubernetes' security. RBAC lets you define role-based access control, who can access resources, and what actions they can perform. Never grant blanket access to secrets. Adhere to the principle of least privilege, granting only necessary permissions to specific users, groups, or service accounts.

Master Kubernetes RBAC authorization with this practical guide by Plural, covering roles, permissions, and best practices for securing your Kubernetes environment.

Integrate with External Secret Stores

For enhanced security, integrate Kubernetes External Secrets Operator with secret management solutions. HashiCorp Vault and AWS Secrets Manager offer robust security features, including encryption, access control, and auditing. Kubernetes External Secrets sync secrets from these external stores into your Kubernetes cluster. This approach keeps sensitive information outside of your cluster's etcd, reducing the impact of a potential breach.

Beyond Kubernetes Secrets: Simplifying Kubernetes Complexity with Plural

As organizations scale their use of Kubernetes, managing secrets is just one of many operational challenges. Beyond secrets, teams often grapple with the complexity of managing multiple clusters, automating upgrades, enforcing security, and maintaining visibility across environments. This is where Plural steps in with a comprehensive Kubernetes management platform designed to simplify and centralize these tasks.

Key Features of Plural

• Centralized Management: Operations Console manages all your Kubernetes clusters across clouds and environments from one intuitive interface, eliminating the need for disparate tools and manual processes.
• GitOps-Based Continuous Deployment: Continuous Deployment automates application and infrastructure deployment using familiar tools like Helm, Kustomize, and Terraform, with built-in drift detection and PR automation.
• Advanced Monitoring and Security: Gain full visibility into your fleet, enforce cluster-wide security policies, and leverage enterprise-grade features like SSO integration and auditability.
• AI-Powered Troubleshooting: Plural's AI-driven Insights provide actionable insights, optimize cluster efficiency, and diagnose issues, reducing the time spent on troubleshooting and maintenance.
• Infrastructure as Code (IaC): Manage complex infrastructure using Kubernetes-native APIs supporting tools like Terraform, Ansible, and Pulumi, without the need for labor-intensive CI/CD pipelines.
• Self-Service and Automation: Empower teams to generate manifests and manage workflows through a user-friendly UI, reducing the need for specialized Kubernetes expertise.

Organizations implementing Plural have reported an 88% reduction in operational costs and a remarkable 95% decrease in day-2 operations, while engineering teams have experienced a 50% increase in available bandwidth.

Discover Plural Platform or schedule a demo to see it in action.

Related Articles

• Kubernetes Secrets: A Practical Guide
• Kubernetes Cluster Security: A Comprehensive Guide

Frequently Asked Questions

Why shouldn't I embed secrets directly into my application code?

Embedding secrets directly into your application code presents significant security risks. If your code is compromised, so are your secrets. Storing secrets separately, like in Kubernetes Secrets, and then referencing them in your application provides a more secure and manageable approach. This separation also makes it easier to rotate secrets without modifying your application code.

Are Kubernetes Secrets encrypted? How can I improve their security?

By default, Kubernetes Secrets are base64 encoded, not encrypted. While encoding offers a basic level of obfuscation, it's easily reversible. For true security, enable encryption at rest for your etcd data store, where Secrets are stored. Use Role-Based Access Control (RBAC) to restrict access to Secrets, ensuring only authorized users and services can view or modify them. Consider using external secret management solutions like HashiCorp Vault for even stronger security.

What are the different ways to use Secrets in my Pods?

You can use Secrets in your Pods through environment variables or volume mounts. Environment variables are simpler to implement but offer less control over access. All processes within the container can access environment variables. On the other hand, volume mounts allow you to mount Secrets as files within a specific directory in your Pod, providing more granular control over which parts of your application can access the secret data.

How do I manage Secrets across multiple Kubernetes clusters?

Managing Secrets across multiple clusters can be challenging. Using tools like Plural, you can centralize secret management and automate the distribution of secrets to all your clusters. This ensures consistency and simplifies the process of updating or rotating secrets. External secret stores, like HashiCorp Vault, also offer solutions for managing secrets across multiple environments.

What should I do if my Secret exceeds the size limit?

Kubernetes Secrets have a size limit. If your secret data exceeds this limit, you won't be able to create the Secret. Consider breaking down your secret data into smaller chunks and storing them as separate Secrets. Alternatively, explore using external secret stores, which often don't have the same size restrictions as Kubernetes Secrets, for managing larger sensitive data.