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| # Securing Traffic using Let's Encrypt and Cert-Manager | ||
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| Securing client server communication is a crucial part of modern application architectures. One of the most important | ||
| steps in this process is implementing HTTPS (HTTP over TLS/SSL) for all communications. This encrypts the data | ||
| transmitted between the client and server, preventing eavesdropping and tampering. To do this, you need an SSL/TLS | ||
| certificate from a trusted Certificate Authority (CA). However, issuing and managing certificates can be a complicated | ||
| manual process. Luckily, there are many services and tools available to simplify and automate certificate issuance and | ||
| management. | ||
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| This guide will demonstrate how to: | ||
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| - Configure HTTPS for your application using a [Gateway](https://gateway-api.sigs.k8s.io/api-types/gateway/). | ||
| - Use [Let’s Encrypt](https://letsencrypt.org) as the Certificate Authority (CA) issuing the TLS certificate. | ||
| - Use [cert-manager](https://cert-manager.io) to automate the provisioning and management of the certificate. | ||
|
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| ## Prerequisities | ||
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| 1. Administrator access to a Kubernetes cluster. | ||
| 2. [Helm](https://helm.sh) and [kubectl](https://kubernetes.io/docs/tasks/tools/#kubectl) must be installed locally. | ||
| 3. Deploy NGINX Kubernetes Gateway (NKG) following the [deployment instructions](/docs/installation.md). | ||
| 4. A DNS resolvable domain name is required. It must resolve to the public endpoint of the NKG deployment, and this | ||
| public endpoint must be an external IP address or alias accessible over the internet. The process here will depend | ||
| on your DNS provider. This DNS name will need to be resolvable from the Let’s Encrypt servers, which may require | ||
| that you wait for the record to propagate before it will work. | ||
|
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| ## Overview | ||
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|  | ||
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| The diagram above shows a simplified representation of the cert-manager ACME Challenge and certificate issuance process | ||
| using Gateway API. Please note that not all of the Kubernetes objects created in this process are represented in | ||
| this diagram. | ||
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| At a high level, the process looks like this: | ||
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| 1. We deploy cert-manager and create a ClusterIssuer which specifies Let’s Encrypt as our CA and Gateway as our ACME | ||
| HTTP01 Challenge solver. | ||
| 2. We create a Gateway resource for our domain (cafe.example.com) and configure cert-manager integration using an | ||
| annotation. | ||
| 3. This kicks off the certificate issuance process – cert-manager contacts Let’s Encrypt to obtain a certificate, and | ||
| Let’s Encrypt starts the ACME challenge. As part of this challenge, a temporary HTTPRoute resource is created by | ||
| cert-manager which directs the traffic through NKG to verify we control the domain name in the certificate request. | ||
| 4. Once the domain has been verified, the certificate is issued. Cert-manager stores the keypair in a Kubernetes secret | ||
| that is referenced by the Gateway resource. As a result, NGINX is configured to terminate HTTPS traffic from clients | ||
| using this signed keypair. | ||
| 5. We deploy our application and our HTTPRoute which defines our routing rules. The routing rules defined configure | ||
| NGINX to direct requests to https://cafe.example.com/coffee to our coffee-app application, and to use the https | ||
| Listener defined in our Gateway resource. | ||
| 6. When the client connects to https://cafe.example.com/coffee, the request is routed to the coffee-app application | ||
| and the communication is secured using the signed keypair contained in the cafe-secret Secret. | ||
| 7. The certificate will be automatically renewed when it is close to expiry, the Secret will be updated using the new | ||
| Certificate, and NKG will dynamically update the keypair on the filesystem used by NGINX for HTTPS termination once | ||
| the Secret is updated. | ||
|
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| ## Details | ||
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| ### Step 1 – Deploy cert-manager | ||
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| The first step is to deploy cert-manager onto the cluster. | ||
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| - Add the Helm repository. | ||
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| ```shell | ||
| helm repo add jetstack https://charts.jetstack.io | ||
| helm repo update | ||
| ``` | ||
|
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| - Install cert-manager, and enable the GatewayAPI feature gate: | ||
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| ```shell | ||
| helm install \ | ||
| cert-manager jetstack/cert-manager \ | ||
| --namespace cert-manager \ | ||
| --create-namespace \ | ||
| --version v1.12.0 \ | ||
| --set installCRDs=true \ | ||
| --set "extraArgs={--feature-gates=ExperimentalGatewayAPISupport=true}" | ||
| ``` | ||
|
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| ### Step 2 – Create a ClusterIssuer | ||
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| Next we need to create a [ClusterIssuer](https://cert-manager.io/docs/concepts/issuer/), a Kubernetes resource that | ||
| represents the certificate authority (CA) that will generate the signed certificates by honouring certificate signing | ||
| requests. | ||
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| We are using the ACME Issuer type, and Let's Encrypt as the CA server. In order for Let's Encypt to verify that we own | ||
| the domain a certificate is being requested for, we must complete "challenges". This is to ensure clients are | ||
| unable to request certificates for domains they do not own. We will configure the Issuer to use a HTTP01 challenge, and | ||
| our Gateway resource that we will create in the next step as the solver. To read more about HTTP01 challenges, see | ||
| [here](https://cert-manager.io/docs/configuration/acme/http01/). Use the following YAML definition to create the | ||
| resource, but please note the `email` field must be updated to your own email address. | ||
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| ```yaml | ||
| apiVersion: cert-manager.io/v1 | ||
| kind: ClusterIssuer | ||
| metadata: | ||
| name: letsencrypt-prod | ||
| spec: | ||
| acme: | ||
| # You must replace this email address with your own. | ||
| # Let's Encrypt will use this to contact you about expiring | ||
| # certificates, and issues related to your account. | ||
| email: my-name@example.com | ||
| server: https://acme-v02.api.letsencrypt.org/directory | ||
| privateKeySecretRef: | ||
| # Secret resource that will be used to store the account's private key. | ||
| name: issuer-account-key | ||
| # Add a single challenge solver, HTTP01 using NKG | ||
| solvers: | ||
| - http01: | ||
| gatewayHTTPRoute: | ||
| parentRefs: # This is the name of the Gateway that will be created in the next step | ||
| - name: gateway | ||
| namespace: default | ||
| kind: Gateway | ||
| ``` | ||
|
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| ### Step 3 – Deploy our Gateway with the cert-manager annotation | ||
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| Next we need to deploy our Gateway. Use can use the below YAML manifest, updating the `spec.listeners[1].hostname` | ||
| field to the required value for your environment. | ||
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| ```yaml | ||
| apiVersion: gateway.networking.k8s.io/v1beta1 | ||
| kind: Gateway | ||
| metadata: | ||
| name: gateway | ||
| annotations: # This is the name of the ClusterIssuer created in the previous step | ||
| cert-manager.io/cluster-issuer: letsencrypt-prod | ||
| spec: | ||
| gatewayClassName: nginx | ||
| listeners: | ||
| - name: http | ||
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| port: 80 | ||
| protocol: HTTP | ||
| - name: https | ||
| # Important: The hostname needs to be set to your domain | ||
| hostname: "cafe.example.com" | ||
| port: 443 | ||
| protocol: HTTPS | ||
| tls: | ||
| mode: Terminate | ||
| certificateRefs: | ||
| - kind: Secret | ||
| name: cafe-secret | ||
| ``` | ||
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| It's worth noting a couple of key details in this manifest: | ||
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| - The cert-manager annotation is present in the metadata – this enables the cert-manager integration, and tells | ||
| cert-manager which ClusterIssuer configuration it should use for the certificates. | ||
| - There are two Listeners configured, an HTTP Listener on port 80, and an HTTPS Listener on port 443. | ||
| - The http Listener on port 80 is required for the HTTP01 ACME challenge to work. This is because as part of the | ||
| HTTP01 Challenge, a temporary HTTPRoute will be created by cert-manager to solve the ACME challenge, and this | ||
| HTTPRoute requires a Listener on port 80. See the [HTTP01 Gateway API solver documentation](https://cert-manager.io/docs/configuration/acme/http01/#configuring-the-http-01-gateway-api-solver) | ||
| for more information. | ||
| - The https Listener on port 443 is the Listener we will use in our HTTPRoute in the next step. Cert-manager will | ||
| create a Certificate for this Listener block. | ||
| - The hostname needs to set to the required value. A new certificate will be issued from the `letsencrypt-prod` | ||
| ClusterIssuer for the domain, e.g. "cafe.example.com", once the ACME challenge is successful. | ||
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| Once the certificate has been issued, cert-manager will create a Certificate resource on the cluster and the | ||
| `cafe-secret` Secret containing the signed keypair in the same Namespace as the Gateway. We can verify the Secret has | ||
| been created successfully using `kubectl`. Note it will take a little bit of time for the Challenge to complete and the | ||
| Secret to be created: | ||
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| ```shell | ||
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| kubectl get secret cafe-secret | ||
| ``` | ||
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| ```text | ||
| NAME TYPE DATA AGE | ||
| cafe-secret kubernetes.io/tls 2 20s | ||
| ``` | ||
|
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| ### Step 4 – Deploy our application and HTTPRoute | ||
| Now we can create our coffee Deployment and Service, and configure the routing rules. You can use the following manifest | ||
| to create the Deployment and Service: | ||
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| ```yaml | ||
| apiVersion: apps/v1 | ||
| kind: Deployment | ||
| metadata: | ||
| name: coffee | ||
| spec: | ||
| replicas: 1 | ||
| selector: | ||
| matchLabels: | ||
| app: coffee | ||
| template: | ||
| metadata: | ||
| labels: | ||
| app: coffee | ||
| spec: | ||
| containers: | ||
| - name: coffee | ||
| image: nginxdemos/nginx-hello:plain-text | ||
| ports: | ||
| - containerPort: 8080 | ||
| --- | ||
| apiVersion: v1 | ||
| kind: Service | ||
| metadata: | ||
| name: coffee | ||
| spec: | ||
| ports: | ||
| - port: 80 | ||
| targetPort: 8080 | ||
| protocol: TCP | ||
| name: http | ||
| selector: | ||
| app: coffee | ||
| ``` | ||
|
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| Deploy our HTTPRoute to configure our routing rules for the coffee application. Note the `parentRefs` section in the | ||
| spec refers to the Listener configured in the previous step. | ||
|
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| ```yaml | ||
| apiVersion: gateway.networking.k8s.io/v1beta1 | ||
| kind: HTTPRoute | ||
| metadata: | ||
| name: coffee | ||
| spec: | ||
| parentRefs: | ||
| - name: gateway | ||
| sectionName: https | ||
| hostnames: # Update the hostname to match what is configured in the Gateway resource | ||
| - "cafe.example.com" | ||
| rules: | ||
| - matches: | ||
| - path: | ||
| type: PathPrefix | ||
| value: /coffee | ||
| backendRefs: | ||
| - name: coffee | ||
| port: 80 | ||
| ``` | ||
|
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| ## Testing | ||
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| To test everything has worked correctly, we can use curl to the navigate to our endpoint, e.g. | ||
| https://cafe.example.com/coffee. To verify using curl, we can use the `-v` option to increase verbosity and inspect the | ||
| presented certificate. The output will look something like this: | ||
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| ```shell | ||
| curl https://cafe.example.com/coffee -v | ||
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| ``` | ||
|
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| ```text | ||
| * Trying 54.195.47.105:443... | ||
| * Connected to cafe.example.com (54.195.47.105) port 443 (#0) | ||
| * ALPN: offers h2,http/1.1 | ||
| * (304) (OUT), TLS handshake, Client hello (1): | ||
| * CAfile: /etc/ssl/cert.pem | ||
| * CApath: none | ||
| * (304) (IN), TLS handshake, Server hello (2): | ||
| * (304) (IN), TLS handshake, Unknown (8): | ||
| * (304) (IN), TLS handshake, Certificate (11): | ||
| * (304) (IN), TLS handshake, CERT verify (15): | ||
| * (304) (IN), TLS handshake, Finished (20): | ||
| * (304) (OUT), TLS handshake, Finished (20): | ||
| * SSL connection using TLSv1.3 / AEAD-CHACHA20-POLY1305-SHA256 | ||
| * ALPN: server accepted http/1.1 | ||
| * Server certificate: | ||
| * subject: CN=cafe.example.com | ||
| * start date: Aug 11 08:22:11 2023 GMT | ||
| * expire date: Nov 9 08:22:10 2023 GMT | ||
| * subjectAltName: host "cafe.example.com" matched cert's "cafe.example.com" | ||
| * issuer: C=US; O=Let's Encrypt; CN=R3 | ||
| * SSL certificate verify ok. | ||
| * using HTTP/1.1 | ||
| > GET /coffee HTTP/1.1 | ||
| > Host: cafe.example.com | ||
| > User-Agent: curl/7.88.1 | ||
| > Accept: */* | ||
| > | ||
| < HTTP/1.1 200 OK | ||
| < Server: nginx/1.25.1 | ||
| < Date: Fri, 11 Aug 2023 10:03:21 GMT | ||
| < Content-Type: text/plain | ||
| < Content-Length: 163 | ||
| < Connection: keep-alive | ||
| < Expires: Fri, 11 Aug 2023 10:03:20 GMT | ||
| < Cache-Control: no-cache | ||
| < | ||
| Server address: 192.168.78.136:8080 | ||
| Server name: coffee-9bf875848-xvkqv | ||
| Date: 11/Aug/2023:10:03:21 +0000 | ||
| URI: /coffee | ||
| Request ID: e64c54a2ac253375ac085d48980f000a | ||
| * Connection #0 to host cafe.example.com left intact | ||
| ``` | ||
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| ## Troubleshooting | ||
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| - For troubeshooting anything related to the cert-manager installation or Issuer setup, see | ||
| [the cert-manager troubleshooting guide](https://cert-manager.io/docs/troubleshooting/). | ||
| - For troubleshooting the HTTP01 ACME Challenge, please see the cert-manager | ||
| [ACME troubleshooting guide](https://cert-manager.io/docs/troubleshooting/acme/). | ||
| - Note that for the HTTP01 Challenge to work using the Gateway resource, HTTPS redirect must not be configured. | ||
| - The temporary HTTPRoute created by cert-manager routes the traffic between cert-manager and the Let's Encrypt server | ||
| through NKG. If the Challenge is not successful, it may be useful to inspect the NGINX logs to see the ACME | ||
| Challenge requests. You should see something like the following: | ||
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| ```shell | ||
| kubectl logs <pod-name> -n nginx-gateway -c nginx | ||
| <...> | ||
| 52.208.162.19 - - [15/Aug/2023:13:18:12 +0000] "GET /.well-known/acme-challenge/bXQn27Lenax2AJKmOOS523T-MWOKeFhL0bvrouNkUc4 HTTP/1.1" 200 87 "-" "cert-manager-challenges/v1.12.0 (linux/amd64) cert-manager/bd192c4f76dd883f9ee908035b894ffb49002384" | ||
| 52.208.162.19 - - [15/Aug/2023:13:18:14 +0000] "GET /.well-known/acme-challenge/bXQn27Lenax2AJKmOOS523T-MWOKeFhL0bvrouNkUc4 HTTP/1.1" 200 87 "-" "cert-manager-challenges/v1.12.0 (linux/amd64) cert-manager/bd192c4f76dd883f9ee908035b894ffb49002384" | ||
| 52.208.162.19 - - [15/Aug/2023:13:18:16 +0000] "GET /.well-known/acme-challenge/bXQn27Lenax2AJKmOOS523T-MWOKeFhL0bvrouNkUc4 HTTP/1.1" 200 87 "-" "cert-manager-challenges/v1.12.0 (linux/amd64) cert-manager/bd192c4f76dd883f9ee908035b894ffb49002384" | ||
| 52.208.162.19 - - [15/Aug/2023:13:18:18 +0000] "GET /.well-known/acme-challenge/bXQn27Lenax2AJKmOOS523T-MWOKeFhL0bvrouNkUc4 HTTP/1.1" 200 87 "-" "cert-manager-challenges/v1.12.0 (linux/amd64) cert-manager/bd192c4f76dd883f9ee908035b894ffb49002384" | ||
| 52.208.162.19 - - [15/Aug/2023:13:18:20 +0000] "GET /.well-known/acme-challenge/bXQn27Lenax2AJKmOOS523T-MWOKeFhL0bvrouNkUc4 HTTP/1.1" 200 87 "-" "cert-manager-challenges/v1.12.0 (linux/amd64) cert-manager/bd192c4f76dd883f9ee908035b894ffb49002384" | ||
| 3.128.204.81 - - [15/Aug/2023:13:18:22 +0000] "GET /.well-known/acme-challenge/bXQn27Lenax2AJKmOOS523T-MWOKeFhL0bvrouNkUc4 HTTP/1.1" 200 87 "-" "Mozilla/5.0 (compatible; Let's Encrypt validation server; +https://www.letsencrypt.org)" | ||
| 23.178.112.204 - - [15/Aug/2023:13:18:22 +0000] "GET /.well-known/acme-challenge/bXQn27Lenax2AJKmOOS523T-MWOKeFhL0bvrouNkUc4 HTTP/1.1" 200 87 "-" "Mozilla/5.0 (compatible; Let's Encrypt validation server; +https://www.letsencrypt.org)" | ||
| 35.166.192.222 - - [15/Aug/2023:13:18:22 +0000] "GET /.well-known/acme-challenge/bXQn27Lenax2AJKmOOS523T-MWOKeFhL0bvrouNkUc4 HTTP/1.1" 200 87 "-" "Mozilla/5.0 (compatible; Let's Encrypt validation server; +https://www.letsencrypt.org)" | ||
| <...> | ||
| ``` | ||
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| ## Links | ||
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| - Gateway docs: https://gateway-api.sigs.k8s.io | ||
| - Cert-manager Gateway usage: https://cert-manager.io/docs/usage/gateway/ | ||
| - Cert-manager ACME: https://cert-manager.io/docs/configuration/acme/ | ||
| - Let’s Encrypt: https://letsencrypt.org | ||
| - NGINX HTTPS docs: https://docs.nginx.com/nginx/admin-guide/security-controls/terminating-ssl-http/ | ||
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