Kubernetes Secrets: How It Works & 7 Critical Best Practices

What Are Kubernetes Secrets?

Secrets store sensitive information, such as passwords, OAuth tokens, and SSH keys, securely inside a Kubernetes cluster. Kubernetes provides an object called Secret that lets you manage secrets separately from the application code, ensuring that they remain confidential and protected against unauthorized access.

The Kubernetes Secrets mechanism enables the secure deployment of applications within a Kubernetes cluster. Secrets can be accessed by authorized pods, which can retrieve them when needed without embedding the sensitive data in the application itself. Kubernetes provides mechanisms for ongoing maintenance of these secrets, enhancing the security and integrity of sensitive data.
This is part of a series of articles about Kubernetes management

How the Kubernetes Secrets Mechanism Works

The Kubernetes Secrets mechanism stores and retrieves sensitive data securely within clusters. The secrets are implemented as API objects, allowing Kubernetes administrators to create, manage, and consume them without direct interaction with sensitive values. This capability supports integration with existing Kubernetes workflows.

Storage and Retrieval Mechanisms

Kubernetes Secrets are stored in the etcd database, which underpins the Kubernetes API server. This database can encrypt secrets at rest, thus preventing unauthorized viewing of sensitive information, but it’s important to realize this is not the default behavior. In production environments, administrators configure encryption at rest for etcd, adding an extra layer of protection for the critical data secrets represent.

For retrieval, secrets must be accessed by authorized entities, primarily through pod specification files. Each pod can request access to a secret by referencing it in its configuration. These requests are validated against Kubernetes RBAC policies, ensuring only the correct pods can access the allocated secrets securely. This setup ensures integration between application deployments and sensitive data management.

Secret Lifecycle in Kubernetes

The lifecycle of a Kubernetes Secret begins with its creation and initialization within a cluster. Administrators typically generate secrets using kubectl or define them in configuration files before deploying them. Once established, these secrets are bound to relevant workloads within the Kubernetes environment, becoming a critical part of the application’s operational security model.

Managing the lifecycle involves monitoring and updating secrets as necessary, ensuring they remain current and secure. Kubernetes facilitates these updates without requiring service downtime. When secrets need modification (e.g., due to key rotation policies), Kubernetes supports altering these configurations dynamically, reflecting updates in consuming applications to preserve service integrity.

Types of Kubernetes Secrets

Kubernetes supports various types of secrets to accommodate different requirements for securing sensitive data:

Opaque Secrets

Opaque Secrets in Kubernetes offer a mechanism for storing arbitrary key-value pairs. These secrets allow developers to define sensitive data requirements specific to their applications without adhering to predefined formats. Because they are not restricted to a particular structure or type, opaque secrets provide versatility, applicable for various use cases, including API keys, passwords, or other custom credentials.

Creating an opaque secret requires developers to encode sensitive values in base64 format. This step ensures that the input data maintains confidentiality during the transfer and storage processes. Upon retrieval, the encoded secret values can be decoded and used by applications, maintaining data privacy and integrity throughout their lifecycle.

TLS Secrets

TLS Secrets handle the management of transport layer security credentials within Kubernetes environments. These secrets house SSL certificates and private keys essential for establishing secure HTTP connections. Serving as a mechanism for authenticating and encrypting data exchanges, TLS secrets are vital for securing communications between clients and services hosted on Kubernetes clusters.

By storing certificates and private key pairs, TLS Secrets streamline handling of secured web services. This capability ensures that sensitive certificate data remains hidden from unauthorized access. Deployment of TLS secrets also involves configuration within the service’s pod definition, allowing integration with SSL/TLS-enabled applications.

Docker Registry Secrets

Docker Registry Secrets manage authentication credentials required for accessing private container registries. These secrets facilitate pulling images from private repositories, thereby ensuring that only authorized clusters can deploy the application’s containerized components. Configuring Docker registry secrets mitigates unauthorized access, preserving integrity and confidentiality when leveraging private image repositories.

Creating Docker registry secrets requires encoding your registry credentials (such as username and password) in a specific format. The resulting secret allows Kubernetes to authenticate transparently when fetching container images. When properly configured, Docker registry secrets streamline the handling of sensitive authentication data, enabling efficient image management and deployment strategies within Kubernetes clusters.

Service Account Tokens

Service Account Tokens are dedicated secrets providing authentication credentials to access Kubernetes API resources. These tokens facilitate secure pod communication with the Kubernetes API server, allowing operations including defining roles, accessing cluster resources, and managing deployments. By using service account tokens, Kubernetes ensures controlled access to critical system components.

Kubernetes generates a service account token for each service account upon creation and stores it as a secret. Pods can mount this token, enabling authenticated interactions with the API server. Leveraging service account tokens maintains fine-grained access control within the Kubernetes environment while ensuring interaction between application components and Kubernetes API functionalities.

SSH Authentication Secrets

SSH Authentication Secrets manage SSH private keys and related credentials required for establishing secure SSH connections between services and infrastructure components. These secrets allow Kubernetes deployments to manage SSH credentials, enabling secure management and operation across distributed environments.

Creating SSH authentication secrets involves transferring encrypted SSH keys into a Kubernetes Secret object. Pods can then access these keys as needed, aligning with Kubernetes’ access control policies. Using SSH secrets facilitates protected data transmission between distributed systems and remote services, safeguarding sensitive information and reducing unauthorized access risks within the Kubernetes cluster.

Creating and Managing Secrets

Kubernetes offers multiple methods for creating and managing Secrets, ensuring that sensitive data such as credentials remains secure and easily accessible to authorized pods. One straightforward approach involves using raw data directly in the kubectl command. 

For example, to store a database username and password as a secret, you can run:

kubectl create secret generic db-user-pass \
    --from-literal=username=admin \
    --from-literal=password='S!B\*d$zDsb=’

In this command, the --from-literal flag allows you to input the sensitive data directly. Be sure to use single quotes to escape special characters like $, \, *, and =, which would otherwise be interpreted by the shell.

Another option is to store credentials in files and pass the file paths to kubectl. For instance, you can first save the credentials in text files:

echo -n 'admin' > ./username.txt
echo -n 'S!B\*d$zDsb=' > ./password.txt

The -n flag prevents the addition of a newline character, which ensures the credentials are stored correctly. Then, create the secret using:

kubectl create secret generic db-user-pass \
    --from-file=username=./username.txt \
    --from-file=password=./password.txt

The default key names in the secret will match the file names unless explicitly specified.

Once a secret is created, you can verify it using:

kubectl get secrets

To view detailed information about a specific secret, including the size of the stored data, run:

kubectl describe secret db-user-pass

However, the contents of the secret will not be shown by default to protect against accidental exposure.

You can also decode the secret values for verification by retrieving them in base64 format and decoding them:

kubectl get secret db-user-pass -o jsonpath='{.data.password}' | base64 --decode

Finally, if needed, you can update an existing secret using the kubectl edit secrets <secret-name> command, which opens the secret in your default editor for modification. Kubernetes supports secret updates without requiring downtime, ensuring seamless integration into dynamic environments.

Best Practices for Managing Secrets in Kubernetes

1. Implementing RBAC Policies

Role-based access control (RBAC) streamlines permission management in Kubernetes, defining who can access secrets and what operations they can perform. By assigning roles and permissions explicitly, RBAC enforces minimal privilege principles, preventing unauthorized access to secret data within Kubernetes environments. This framework supports fine-grained access capabilities.

Kubernetes’ RBAC policies are flexible, allowing organizations to tailor control levels across different teams and workloads. Administrators configure these roles using precise rulesets, aligning operational access permissions with predefined security requirements. Implementing RBAC policies as a cornerstone practice helps safeguard sensitive data throughout Kubernetes clusters.

2. Regularly Rotating Secrets

Regularly rotating secrets is essential for maintaining a secure Kubernetes environment, preventing prolonged exposure of sensitive credentials. Rotation involves updating secret data periodically, minimizing the damage potential from compromised information. This practice supports proactive security management by reducing window vulnerabilities.

Kubernetes simplifies secret rotation through automation, allowing changes to propagate without interrupting ongoing services. Integrating rotation into CI/CD pipelines enables consistent updates across deployment stages. Regular secret rotation is a preventive measure that enhances data security and curtails unauthorized access risks in Kubernetes applications.

3. Avoiding Hardcoding Secrets

Hardcoding secrets poses significant risks by exposing sensitive data in application code, making it accessible in source control and runtime environments. To mitigate this risk, developers should externalize secrets by storing them in Kubernetes Secrets, preventing exposure. This practice separates configuration data from code.

Using Kubernetes-mapped environment variables and volumes ensures secrets remain concealed and accessed securely by applications. Installing access controls further secures secrets, diminishing threats associated with accidental exposure or unauthorized access. Avoiding hardcoded secrets is pivotal for safeguarding sensitive information.

4. Auditing and Monitoring Access

Auditing and monitoring access to Kubernetes Secrets is essential for tracking their usage and identifying unauthorized activities. Implementing logging mechanisms allows visibility into who accessed secrets and when these events occurred. This capability aids in detecting anomalies or breaches, facilitating rapid response to potential security incidents within the Kubernetes environment.

Monitoring tools integrated with Kubernetes can assess secret access patterns, correlating data against expected behaviors. Administrators use these insights to fine-tune security policies and ensure only authorized personnel interact with sensitive data. Keeping well-documented audit trails and executing continuous monitoring are fundamental practices that enhance secret management efficacy.

5. Using External Secret Management Tools

External secret management tools augment Kubernetes’ native capabilities, offering enhanced security and compliance features. Integrations with systems like HashiCorp Vault, Azure Key Vault, or AWS Secrets Manager provide centralized management, sophisticated encryption strategies, and comprehensive audit logs. They also support high-standard compliance requirements.

By leveraging external tools, organizations can separate secret management from Kubernetes, granting administrators an interface for policy enforcement and access monitoring. These tools streamline lifecycle management, enabling secure rotations and enforcing decryption policies across diverse environments. Incorporating external secret management systems elevates Kubernetes’ security posture.

6. Implementing Immutable Secrets

Immutable secrets represent a security practice where secret data remains unmodifiable once created. This principle ensures that secrets maintain their original integrity over time, mitigating risks associated with accidental changes or unauthorized updates. Immutable secrets are particularly valuable in high-compliance contexts requiring strict data control.

Ensuring secrets’ immutability requires strategic planning at the deployment stage, with applications configured to handle immutable data without disruption. Kubernetes can implement these practices by restricting secret modifications through controlled mechanisms or specifying annotations preventing updates. The immutability model enhances data integrity in Kubernetes.

7. Automating Secret Updates With Operators

Operators are Kubernetes extensions that enhance application management, including automatic secret updates. By encapsulating application-specific logic, operators streamline secret updates through programmed actions, ensuring seamless data refreshes across managing deployments. Automated secret management reduces manual oversight, leading to fewer errors and consistent updates.

Adopting operators for secret management aligns secret lifecycle strategies with agile practices, enabling prompt updates and maintaining current security standards. This framework supports dynamic environments, where rapid deployments necessitate frequent secret rotations. Leveraging operators underscores Kubernetes’ adaptability, elevating operational efficiency while upholding security measures for sensitive data.

Related content: Read our guide to Kubernetes tools

CI/CD Security with Codefresh

Codefresh can help with CI/CD security in a number of ways

1. It provides out of the box integrations for several code scanning tools
2. It supports running security analysis tools before, during and after each deployment
3. It will work with any software supply security solution to monitor and assess risks in any part of the software lifecycle
4. It includes a built-in facility for storing secrets but also integrates with popular secret solutions (such as Hashicorp Vault or the secret facilities of major cloud providers)
5. It allows organizations to run pipelines and deploy application with a zero trust model where confidential information never leaves the customer premises

Most importantly because GitOps is the central paradigm behind all aspects of the Codefresh platform, with Codefresh organizations get auditing and tracing facilities out of the box using standard Git tools. Every action in Codefresh (even from the UI) is backed by a Git commit. Simply looking at Git history provides an audit log for everything that happened in the platform.