How to Secure Kubernetes Secrets and Sensitive Data

Kubernetes secrets are objects within the Kubernetes system that store sensitive data such as user credentials, OAuth tokens, SSH keys, and other confidential information. This resource type is intended to secure sensitive content from exposure in scripts or application code. In other words, their primary function is to facilitate the secure usage of this data by applications running within the Kubernetes ecosystem without exposing it in pod specifications, command-line arguments, or application code.

Secrets allow for a separation of duties, where the deployment and management of the application code are distinct from the management of its sensitive configuration details. This decoupling enables better security practices and reduces the risk of sensitive data being exposed during the development process or in source code repositories.

To use a secret, an application or a pod references it. Kubernetes provides the data stored in the secret to the pod as either environment variables or as files in a volume mounted within the pod's filesystem. This method ensures that sensitive data is only held in memory or in transient, Kubernetes-controlled filesystems, rather than being written to disk where it might be less secure.

Kubernetes secrets are namespaced objects, meaning they’re only accessible to pods within the same namespace, which is a method of isolating group resources within a cluster. The data within a secret is stored as base64-encoded strings, but it should be noted that this is not a method of encryption and doesn’t provide reliable security against unauthorized access from within the cluster.

To enhance the security of secrets, organizations should carefully control access to them using Kubernetes RBAC. Whenever possible, the etcd datastore should be encrypted at rest. These secrets should be managed and rotated regularly to minimize the risks associated with potential Secret leakage or compromise.

Importance of Securing Kubernetes Secrets

Failure to secure Kubernetes secrets impacts an organization's security posture and operational integrity. Sensitive data in containerized environments is put at risk, and IT infrastructure can be exposed to threats when secrets aren't adequately secured. 

The risks associated with mismanaged Kubernetes secrets are many. Poorly configured access controls can allow unauthorized users or applications to access secret data. Inadequate encryption practices can expose data at rest to potential theft or manipulation. And, the lack of secret object rotation and management policies can leave old, unused, or compromised secrets accessible, increasing the risk of their misuse over time.

Inadequate security for Kubernetes secrets also runs the risk of noncompliance with data protection regulations. Many regulations like GDPR, CCPA, and HIPAA have stringent requirements for data security to protect sensitive information. Mismanaged secrets can lead to a security breach that exposes sensitive data and results in penalties ranging from fines to legal actions. 

Related Article: Kubernetes Security Posture Management (KSPM)

How Kubernetes Secrets Work

A secret is a key-value pair that includes a secret ID and authenticates information. Kubelet uses the secret ID to identify the credentials that must be provided to an application container when creating a pod. Kubelet runs on each node in a cluster and manages pods and their containers. Secrets are only accessible by pods if they're explicitly part of a mounted volume or, at the moment, kubelet pulls an image for use in a pod.

The Kubernetes API server stores Kubernetes secrets, which can be accessed by only specific users with permission to access the server. As the Kubernetes API server is a single point of failure for the application, we must ensure that our data is kept safe and secure.

Kubernetes secrets provide a secure way to share configuration data between a controller and its workers, such as between a kubelet and a pod. They also offer an alternative way to store sensitive data in the Kubernetes cluster, such as credentials to access external applications. Additionally, they provide a convenient way to create new resources on our Kubernetes cluster, such as new deployments or namespaces.

Secrets can be created manually or through automated processes, and they're stored within the Kubernetes cluster in etcd, the cluster's key-value store. Still, they're stored in a base64-encoded format, not encrypted. As a result, they're considered obfuscated rather than fully secure. But Kubernetes allows fine-grained access control through RBAC. This means you can define who can access and manipulate secrets within the cluster based on roles and permissions.

Pods can access secrets by mounting them as files or environment variables, which allows applications running within the pod to utilize sensitive information securely. Kubernetes supports updating secrets, allowing for seamless changes to sensitive data without disrupting running applications. Best practices recommend regular rotation of secrets to reduce the risk of compromise, and Kubernetes supports automated rotation through controllers or external tools.

While Kubernetes secrets provide a convenient way to manage sensitive data, they're not encrypted within the cluster. Additional measures — encryption at rest and using external secret management systems, for example — may be required. Additionally, Kubernetes secrets are scoped to a single namespace, limiting their availability to pods within that namespace. Cross-namespace access requires specific configurations or external solutions.

How Do You Store Sensitive Data in Kubernetes?

Storing sensitive data in Kubernetes is primarily done through Kubernetes secrets. This helps to avoid storing sensitive data in application code or container images, which can be insecure and lead to security vulnerabilities. The following is a brief overview of the process of creating, storing, and using secrets.

Create a Secret

Kubernetes secrets can be created directly via the Kubernetes API or using a YAML file. The data within a Secret uses base64 encode to offer a basic level of obfuscation. The kubectl create secret command can be used to create secrets, or a secret can be created using a YAML file and then applying the kubectl command.

Store Sensitive Data

When defining a Kubernetes secret, sensitive data can be included in key value pairs. Each key under the data field is a secret object to be stored, with the value being the sensitive data to secure.

Use Kubernetes Secrets 

Stored Kubernetes secrets can be accessed for a number of resources, including by pods, deployments, and services. In Kubernetes, apiVersion is used to define objects like pods, deployments, and services. Kubernetes APIs are versioned to ensure that the system is forward-compatible and backward-compatible, allowing developers to use different versions of API resources, such as secrets, within their clusters.

Combining volumeMounts with Kubernetes secrets makes it possible to inject sensitive information into pods securely without exposing that information in the application code or pod specification. This provides a secure way to use credentials, keys, and other sensitive data within applications. 

How Do You Secure Secrets in Kubernetes?

Kubernetes secrets are stored within Kubernetes’ API server, the underlying data store (etcd), a key value store used to hold the cluster’s data. In Kubernetes, base64 encode is used to store sensitive data such as passwords and tokens. It's important to understand that this is not for security, as base64 can be easily decoded. It simply ensures that binary data can be safely stored and transmitted in text formats. 

It's essential to encrypt Kubernetes secrets at rest to provide adequate security protections for cluster resources. Kubernetes supports this capability through the configuration of encryption at rest for the etcd datastore rather than requiring teams to build in this step manually. Kubernetes administrators can use keys managed by a key management service (KMS) provider to encrypt data in etcd.

Access to Kubernetes' secrets can also be tightly controlled using Kubernetes’ RBAC system. RBAC is used to define who can access and modify secrets. This allows fine-grained permission settings to ensure that only authorized pods and users can access the sensitive information contained within secrets. 

Challenges in Securing Kubernetes Secrets

Securing Kubernetes secrets presents several challenges due to the complexity of Kubernetes environments and the sensitive information that secrets contains, such as passwords, tokens, and keys. The following are several commonly cited vulnerabilities and challenges associated with securing secrets.

etcd Limitations

As noted above, Kubernetes stores secrets in etcd, which is not inherently secure storage. Unless it's explicitly configured to store data in an encrypted format, secrets can be easily accessed by anyone with access to the etcd cluster.

Misconfigured Access Controls 

If access controls aren't properly configured, unauthorized users or pods can allow unauthorized users or applications to access sensitive information and compromise the entire system. This is often the result of misconfigured RBAC policies granting overly permissive access to secrets.

Secrets in Logs and Debug Information

Secrets are at risk of exposure if they're accidentally logged or included in debugging output. Several reasons this happens are verbose logging levels, insufficient data sanitization, or oversight during the development and debugging phases. 

Secrets in Source Code

Developers sometimes inadvertently include secrets in source code repositories, especially when configuration files aren't properly managed or ignored. If the source code repository becomes publicly available, secrets will be exposed. 

Secrets Lifecycle Management

Managing the lifecycle of secrets, including creation, updates, and rotation, can be complex and error-prone. If stale or unused, secrets may not be adequately tracked or removed, and old or compromised secrets remain active.

What Are the Best Practices to Make Kubernetes Secrets More Secure?

The following are proven best practices for securing Kubernetes secrets.

Audit and Monitor Kubernetes Secret Access

Keep detailed logs of all interactions with secrets, including who accesses and modifies them and when. An audit trail is critical for identifying unauthorized access or potential breaches, allowing for timely remediation actions.

Avoid Hardcoding Kubernetes Secrets

Use environment variables or mount secrets as volumes rather than hardcoding them in application code or Docker images. Instead, use Kubernetes secrets or external secret management systems to inject sensitive data into applications at runtime.

Enable Encryption at Rest and in Transit

Encrypt Kubernetes secrets at rest and in transit. For encryption at rest, Kubernetes supports encrypting Secret data at the API server level before it's written to etcd. Use a Kubernetes secrets Management provider or comparable encryption to protect secrets while being stored. For data in transit, make sure communications between applications and the secrets management service are encrypted using TLS or other secure protocols.

Implement Role-Based Access Control

Use RBAC to manage users’ access to secrets in a cluster. Define roles with specific permissions (e.g., read only access to secrets) and assign these roles to users, groups, containers, pods, or service accounts to restrict access to secrets to authorized entities.

Isolate Kubernetes Secrets with Namespace and Anti-Affinity Rules

Leverage Kubernetes namespaces to isolate secrets and limit their access to specific parts of a cluster. Anti-affinity rules can also be used to minimize the number of secrets stored on a single node. These tactics reduce the impact of a potential node compromise.

Least Privilege Principle

Apply the principle of least privilege to all access controls. Every application or user should have access only to the secrets that are absolutely necessary for their functions.

Minimize Lifecycles for Kubernetes Secrets

Adopt practices for short-lived secrets wherever possible, expiring and renewing secrets frequently.

Rotate Kubernetes Secrets Regularly

Change and update secrets regularly to reduce the risks associated with static or long-lived credentials. Be sure to implement a process to apply changes in a way that does not disrupt applications’ operations. Automated rotation mechanisms can help manage this process to ensure that old secrets are replaced with new ones at predefined intervals without downtime or manual intervention.

Streamline Revocation Processes

Develop processes and implement mechanisms for revoking and replacing compromised secrets across all affected systems.

Use Dedicated Secrets Management Tools

Consider using an external secret management system that integrates with Kubernetes to provide enhanced security features, such as automated secret rotation, enhanced encryption, and fine-grained access controls.

What Tools Are Available to Secure Secrets in Kubernetes?

A variety of native and third-party tools and solutions are available to secure Kubernetes secrets

Built-In Kubernetes Secrets Management Features

• Kubernetes secrets object stores and manages sensitive information, such as passwords, OAuth tokens, and SSH keys.
• RBAC enables fine-grained control over who can access secrets within the Kubernetes cluster.
• Secrets in environment variables allows exposure of secrets to a container as environment variables without hardcoding them.
• Volume mounts mount secrets as files in a pod to share sensitive information with applications running within the pod.

Third-Party Solutions for Enhanced Kubernetes Secret Management

When managing secrets in Kubernetes environments, leveraging external tools and solutions can significantly enhance security beyond what is provided with Kubernetes' Native secrets Management capabilities. The following are several types of external tools and solutions and the functionality that they typically offer.

Secrets Vaults

Secrets vaults provide secure storage, access, and management of secrets with support for:

• Automatic generation of temporary secrets for services and applications
• Automated rotation of secrets
• Fine-grained access policies based on roles and responsibilities

Configuration Management Tools

Configuration management tools help manage secrets by automating the deployment and management of software with functionality including:

• Ability to dynamically insert secrets into application configurations at deployment time
• Environment separation (e.g., development, staging, production) to prevent leakage between environments

Container Security Platforms

Container security platforms, such as a CNAPP, offer comprehensive security solutions for containerized environments, including Kubernetes security posture management (KSPM) and secrets management features that include:

• Monitoring runtime environments to detect and respond to unauthorized access to secrets
• Scanning for hardcoded secrets in container images or configuration files

Cloud Provider Secrets Management Services

Cloud provider secrets management services offer secrets management services that integrate with their cloud environments and services to provide:

• Enforcement of the principle of least privilege for secrets access
• Centralized management of all secrets across various services and applications
• Integration with identity access management (IAM)

Encryption-as-a-Service

Encryption-as-a-service offers key management and encryption capabilities for data at rest and in transit, along with:

• Key Rotation and management tools
• Mechanisms to enforce security policies around encryption practices

Considerations When Implementing Third-Party Kubernetes Secrets Management Solutions

When implementing an external tool for Kubernetes Secrets management, consider the following:

• Compatibility: Integrates smoothly with the Kubernetes environment and workflow.
• Compliance: Supports compliance with relevant regulations.
• Scalability: Can scale with Kubernetes clusters without creating performance bottlenecks.

Kubernetes Secrets FAQ