Container Engine for Kubernetes: Security Practices

Oracle University Podcast

In the season's final episode, hosts Lois Houston and Nikita Abraham interview senior OCI instructor Mahendra Mehra about the security practices that are vital for OKE clusters on OCI. Mahendra shares his expert insights on the importance of Kubernetes security, especially in today's digital landscape where the integrity of data and applications is paramount. OCI Container Engine for Kubernetes Specialist: https://mylearn.oracle.com/ou/course/oci-container-engine-for-kubernetes-specialist/134971/210836 Oracle University Learning Community: https://education.oracle.com/ou-community LinkedIn: https://www.linkedin.com/showcase/oracle-university/ X (formerly Twitter): https://twitter.com/Oracle_Edu Special thanks to Arijit Ghosh, David Wright, Radhika Banka, and the OU Studio Team for helping us create this episode. --------------------------------------------------------- Episode Transcript:

00:00

Welcome to the Oracle University Podcast, the first stop on your cloud journey. During this series of informative podcasts, we’ll bring you foundational training on the most popular Oracle technologies. Let’s get started!

00:26

Nikita: Welcome to the Oracle University Podcast! I’m Nikita Abraham, Principal Technical Editor with Oracle University, and with me is Lois Houston, Director of Innovation Programs.

Lois: Hi there! In our last episode, we spoke about self-managed nodes and how you can manage Kubernetes deployments.

Nikita: Today is the final episode of this series on OCI Container Engine for Kubernetes. We’re going to look at the security side of things and discuss how you can implement vital security practices for your OKE clusters on OCI, and safeguard your infrastructure and data.

00:59

Lois: That’s right, Niki! We can’t overstate the importance of Kubernetes security, especially in today's digital landscape, where the integrity of your data and applications is paramount. With us today is senior OCI instructor, Mahendra Mehra, who will take us through Kubernetes security and compliance practices. Hi Mahendra! It’s great to have you here. I want to jump right in and ask you, how can users add a service account authentication token to a kubeconfig file?

Mahendra: When you set up the kubeconfig file for a cluster, by default, it contains an Oracle Cloud Infrastructure CLI command to generate a short-lived, cluster-scoped, user-specific authentication token.

The authentication token generated by the CLI command is appropriate to authenticate individual users accessing the cluster using kubectl and the Kubernetes Dashboard. However, the generated authentication token is not appropriate to authenticate processes and tools accessing the cluster, such as continuous integration and continuous delivery tools. To ensure access to the cluster, such tools require long-lived non-user-specific authentication tokens. One solution is to use a Kubernetes service account. Having created a service account, you bind it to a cluster role binding that has cluster administration permissions.

You can create an authentication token for this service account, which is stored as a Kubernetes secret. You can then add the service account as a user definition in the kubeconfig file itself. Other tools can then use this service account authentication token when accessing the cluster.

02:47

Nikita: So, as I understand it, adding a service account authentication token to a kubeconfig file enhances security and enables automated tools to interact seamlessly with your Kubernetes cluster. So, let’s talk about the permissions users need to access clusters they have created using Container Engine for Kubernetes.

Mahendra: For most operations on Container Engine for Kubernetes clusters, IAM leverages the concept of groups. A user's permissions are determined by the IAM groups they belong to, including dynamic groups. The access rights for these groups are defined by policies.

IAM provides granular control over various cluster operations, such as the ability to create or delete clusters, add, remove, or modify node pool, and dictate the Kubernetes object create, delete, view operations a user can perform. All these controls are specified at the group and policy levels.

In addition to IAM, the Kubernetes role-based access control authorizer can enforce additional fine-grained access control for users on specific clusters via Kubernetes RBAC roles and ClusterRoles.

04:03

Nikita: What are Kubernetes RBAC roles and ClusterRoles, Mahendra?

Mahendra: Roles here defines permissions for resources within a specific namespace and ClusterRole is a global object that will provide access to global objects as well as non-resource URLs, such as API version and health endpoints on the API server. Kubernetes RBAC also includes RoleBindings and ClusterRoleBindings. RoleBinding grants permission to subjects, which can be a user, service, or group interacting with the Kubernetes API. It specified an allowed operation for a given subject in the cluster.

RoleBinding is always created in a specific namespace. When associated with a role, it provides users permission specified within that role related to the objects within that namespace. When associated with a ClusterRole, it provides access to namespaced objects only defined within that cluster rule and related to the roles namespace.

ClusterRoleBinding, on the other hand, is a global object. It associates cluster roles with users, groups, and service accounts. But it cannot be associated with a namespaced role. ClusterRoleBinding is used to provide access to global objects, non-namespaced objects, or to namespaced objects in all namespaces.

05:36

Lois: Mahendra, what’s IAM’s role in this? How do IAM and Kubernetes RBAC work together?

Mahendra: IAM provides broader permissions, while Kubernetes RBAC offers fine-grained control. Users authorized either by IAM or Kubernetes RBAC can perform Kubernetes operations. When a user attempts to perform any operation on a cluster, except for create role and create cluster role operations, IAM first determines whether a group or dynamic group to which the user belongs has the appropriate and sufficient permissions. If so, the operation succeeds. If the attempted operation also requires additional permissions granted via a Kubernetes RBAC role or cluster role, the Kubernetes RBAC authorizer then determines whether the user or group has been granted the appropriate Kubernetes role or Kubernetes ClusterRoles.

06:41

Lois: OK. What kind of permissions do users need to define custom Kubernetes RBAC rules and ClusterRoles?

Mahendra: It's common to define custom Kubernetes RBAC rules and ClusterRoles for precise control. To create these, a user must have existing roles or ClusterRoles with equal or higher privileges. By default, users don't have any RBAC roles assigned. But there are default roles like cluster admin or super user privileges.

07:12

Nikita: I want to ask you about securing and handling sensitive information within Kubernetes clusters, and ensuring a robust security posture. What can you tell us about this?

Mahendra: When creating Kubernetes clusters using OCI Container Engine for Kubernetes, there are two fundamental approaches to store application secrets. We can opt for storing and managing secrets in an external secrets store accessed seamlessly through the Kubernetes Secrets Store CSI driver. Alternatively, we have the option of storing Kubernetes secret objects directly in etcd.

07:53

Lois: OK, let’s tackle them one by one. What can you tell us about the first method, storing secrets in an external secret store?

Mahendra: This integration allows Kubernetes clusters to mount multiple secrets, keys, and certificates into pods as volumes. The Kubernetes Secrets Store CSI driver facilitates seamless integration between our Kubernetes clusters and external secret stores.

With the Secrets Store CSI driver, our Kubernetes clusters can mount and manage multiple secrets, keys, and certificates from external sources. These are accessible as volumes, making it easy to incorporate them into our application containers. OCI Vault is a notable external secrets store. And Oracle provides the Oracle Secrets Store CSI driver provider to enable Kubernetes clusters to seamlessly access secrets stored in Vault.

08:54

Nikita: And what about the second method? How can we store secrets as Kubernetes secret objects in etcd?

Mahendra: In this approach, we store and manage our application secrets using Kubernetes secret objects. These objects are directly managed within etcd, the distributed key value store used for Kubernetes cluster coordination and state management.

In OKE, etcd reads and writes data to and from block storage volumes in OCI block volume service. By default, OCI ensures security of our secrets and etcd data by encrypting it at rest. Oracle handles this encryption automatically, providing a secure environment for our secrets.

Oracle takes responsibility for managing the master encryption key for data at rest, including etcd and Kubernetes secrets. This ensures the integrity and security of our stored secrets. If needed, there are options for users to manage the master encryption key themselves.

10:06

Lois: OK. We understand that managing secrets is a critical aspect of maintaining a secure Kubernetes environment, and one that users should not take lightly. Can we talk about OKE Container Image Security? What essential characteristics should container images possess to fortify the security posture of a user’s applications?

Mahendra: In the dynamic landscape of containerized applications, ensuring the security of containerized images is paramount.

It is not uncommon for the operating system packages included in images to have vulnerabilities. Managing these vulnerabilities enables you to strengthen the security posture of your system and respond quickly when new vulnerabilities are discovered. You can set up Oracle Cloud Infrastructure Registry, also known as Container Registry, to scan images in a repository for security vulnerabilities published in the publicly available Common Vulnerabilities and Exposures Database.

11:10

Lois: And how is this done? Is it automatic?

Mahendra: To perform image scanning, Container Registry makes use of the Oracle Cloud Infrastructure Vulnerability Scanning Service and Vulnerability Scanning REST API. When new vulnerabilities are added to the CVE database, the container registry initiates automatic rescanning of images in repositories that have scanning enabled.

11:41

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12:20

Nikita: Welcome back! Mahendra, what are the benefits of image scanning?

Mahendra: You can gain valuable insights into each image scan conducted over the past 13 months. This includes an overview of the number of vulnerabilities detected and an overall risk assessment for each scan. Additionally, you can delve into comprehensive details of each scan featuring descriptions of individual vulnerabilities, their associated risk levels, and direct links to the CVE database for more comprehensive information. This historical and detailed data empowers you to monitor, compare, and enhance image security over time. You can also disable image scanning on a particular repository by removing the image scanner.

13:11

Nikita: Another characteristic that container images should have is unaltered integrity, right?

Mahendra: For compliance and security reasons, system administrators often want to deploy software into a production system. Only when they are satisfied that the software has not been modified since it was published compromising its integrity. Ensuring the unaltered integrity of software is paramount for compliance and security in production environment.

13:41

Lois: Mahendra, what are the mechanisms that guarantee this integrity within the context of Oracle Cloud Infrastructure?

Mahendra: Image signatures play a pivotal role in not only verifying the source of an image but also ensuring its integrity. Oracle's Container Registry facilitates this process by allowing users or systems to push images and sign them using a master encryption key sourced from the OCI Vault.

It's worth noting that an image can have multiple signatures, each associated with a distinct master encryption key. These signatures are uniquely tied to an image OCID, providing granularity to the verification process. Furthermore, the process of image signing mandates the use of an RSA asymmetric key from the OCI Vault, ensuring a robust and secure validation of the image's unaltered integrity.

14:45

Nikita: In the context of container images, how can users ensure the use of trusted sources within OCI?

Mahendra: System administrators need the assurance that the software being deployed in a production system originates from a source they trust.

Signed images play a pivotal role, providing a means to verify both the source and the integrity of the image. To further strengthen this, administrators can create image verification policies for clusters, specifying which master encryption keys must have been used to sign images. This enhances security by configuring container engine for Kubernetes clusters to allow the deployment of images signed with specific encryption keys from Oracle Cloud Infrastructure Registry. Users or systems retrieving signed images from OCIR can trust the source and be confident in the image's integrity.

15:46

Lois: Why is it imperative for users to use signed images from Oracle Cloud Infrastructure Registry when deploying applications to a Container Engine for Kubernetes cluster? Mahendra: This practice is crucial for ensuring the integrity and authenticity of the deployed images.

To achieve this enforcement. It's important to note that an image in OCIR can have multiple signatures, each linked to a different master encryption key. This multikey association adds layers of security to the verification process.

A cluster's image verification policy comes into play, allowing administrators to specify up to five master encryption keys. This policy serves as a guideline for the cluster, dictating which keys are deemed valid for image signatures.

If a cluster's image verification policy doesn't explicitly specify encryption keys, any signed image can be pulled regardless of the key used. Any unsigned image can also be pulled potentially compromising the security measures.

16:56

Lois: Mahendra, can you break down the essential permissions required to bolster security measures within a user’s OKE clusters?

Mahendra: To enable clusters to include master encryption key in image verification policies, you must give clusters permission to use keys from OCI Vault. For example, to grant this permission to a particular cluster in the tenancy, we must use the policy—allow any user to use keys in tenancy where request.user.id is set to the cluster's OCID.

Additionally, for clusters to seamlessly pull signed images from Oracle Cloud Infrastructure Registry, it's vital to provide permissions for accessing repositories in OCIR.

17:43

Lois: I know this may sound like a lot, but OKE container image security is vital for safeguarding your containerized applications. Thank you so much, Mahendra, for being with us through the season and taking us through all of these important concepts.

Nikita: To learn more about the topics covered today, visit mylearn.oracle.com and search for the OCI Container Engine for Kubernetes Specialist course. Join us next week for another episode of the Oracle University Podcast. Until then, this is Nikita Abraham…

Lois Houston: And Lois Houston, signing off!

18:16

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