Introduction
When you are running applications in Kubernetes, security is key. One of the most important steps to secure your applications is using SSL/TLS certificates. These certificates ensure that the data exchanged between your users and your applications is encrypted, making it hard for bad actors to snoop on sensitive information.
Managing SSL certificates might sound tricky at first, but Kubernetes makes it easier with a tool called cert-manager. In this blog, we will explore how SSL certificates work in Kubernetes, the different ways to manage them, and why cert-manager is the best solution to simplify the process.
What Are SSL Certificates and Why Do You Need Them?
SSL certificates are used to encrypt communication between a user and a web server. When you visit a website with “https:” in the URL, that’s SSL at work. Without an SSL certificate, your website’s traffic is vulnerable to interception by attackers.
For public facing apps, having SSL certificates is essential. But what about internal services in your Kubernetes cluster? Even those need protection, especially if you are dealing with sensitive data. SSL certificates ensure that traffic within your cluster is encrypted, too.
Managing SSL Certificates Manually: The Old-School Way
Without cert-manager, you need to manage SSL certificates by hand. You would generate a certificate using a tool like OpenSSL, Let’s Encrypt or any other available tools which can help you to manage the certificates. Once certificate is created, store it in a Kubernetes Secret, and update it before it expired. It’s not impossible, but it’s a tedious process. You need to track expiration dates and make sure to renew certificates before they lapse.
Doing this manually for one or two services is manageable, but what if you have dozens of services? That’s where things get complicated. Luckily, cert-manager was created to solve this exact problem.
Cert-Manager: Automating SSL Certificate Management
cert-manager – a tool that automates the entire process of issuing, renewing, and managing SSL certificates in your Kubernetes cluster. With cert-manager, you define what kind of certificate you need in a simple configuration file, and it handles the rest!
It uses CRDs to define the desired state of certificates. It then interacts with external CAs, like Let’s Encrypt, to issue the certificate and automatically renew it when it’s about to expire. Cert-manager integrates with Kubernetes Ingress/GatewayAPI resources, ensuring your services are always secured.
Cert-manager supports multiple options for getting your certificates. Let’s explore a few of them I use most of the time:
Options for Managing Certificates with Cert-Manager
i. Let’s Encrypt(ACME Issuer)
Let’s Encrypt is one of the most popular choices for obtaining SSL certificates. It’s a free, automated service that provides SSL certificates. Cert-manager can talk to Let’s Encrypt using a protocol called ACME to automatically request certificates and renew them when needed.
Here is a quick overview of how cert-manager works with Let’s Encrypt:
- Cert-manager requests a certificate from Let’s Encrypt.
- Let’s Encrypt verifies that you own the domain by using a DNS challenge(adding a txt DNS record) or an HTTP challenge(placing a file on your server).
- Once verified, Let’s Encrypt issues the certificate, and cert-manager saves it in your Kubernetes cluster.
- Cert-manager then tracks when the certificate is about to expire and renews it automatically.
ii. Self-Signed Certificates
Sometimes, you don’t need to go through a public certificate authority like Let’s Encrypt. For example, when you are running services internally in your Kubernetes cluster(development or testing), you can use self-signed certificates. These are certificates that you generate yourself, and cert-manager can automate this process too!
Self-signed certificates are quick and easy to set up, but they don’t provide the same level of trust as certificates from a well-known authority like Let’s Encrypt.
iii. CA Issuer(Using Your Own Certificate Authority)
If your organization already has its own internal Certificate Authority(CA), cert-manager can issue certificates using this CA Issuer. This is useful if you need to have full control over your certificates and cant or dont want to rely on external services like Let’s Encrypt.
With a CA Issuer, you can use your own root certificates to sign SSL certificates for services in your Kubernetes cluster. This is common in enterprises that manage their own infrastructure and need tighter control over security.
You can also manage CA certificates using the self-signed issuer, which can be leveraged in the CA issuer to generate certificates.
iv. Vault
HashiCorp Vault is another popular tool for managing secrets and certificates. Cert-manager supports integration with Vault as a certificate issuer, allowing you to use Vault to sign and manage certificates within your Kubernetes cluster. Vault offers powerful secret management capabilities, and combining it with cert-manager adds flexibility to your certificate management process.
While I haven’t tried the Vault integration with cert-manager yet, it looks promising for organizations already using Vault for secret management, as it provides centralized control and robust security features. I will explore this integration in future setups!
Why Cert-Manager Is a Game-Changer?
Let’s recap why cert-manager is a fantastic tool for managing SSL certificates in Kubernetes:
- Automation: No more manual renewals! Cert-manager automatically handles the entire lifecycle of your SSL certificates.
- Multiple Issuer Options: Whether you want to use Let’s Encrypt for public websites, self-signed certificates for internal services, or your own internal CA, cert-manager supports them all.
- Kubernetes Native: Cert-manager integrates directly into your Kubernetes cluster, so you don’t have to worry about external systems or manual setups.
- Security: By automating certificate management, cert-manager helps ensure that your services are always protected with up-to-date SSL certificates, reducing the risk of human error.
- Version-Control: All cert-manager resources can be stored in version control, allowing you to use GitOps principles for easy deployment and management.
Conclusion
Cert-manager simplifies SSL certificate management in Kubernetes by automating the entire lifecycle-from issuance to renewal. Whether you need Let’s Encrypt for public apps, self-signed certificates for internal services, or your own CA, cert-manager has versatile options to suit your needs.
In the next blog, we will dive into the hands-on setup of cert-manager to help you secure your Kubernetes applications effortlessly. Stay tuned!
If you have any query related to this topic, please add a comment or ping me on LinkedIn.
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