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Transport Layer Security (TLS)

The Percona Operator for MongoDB uses Transport Layer Security (TLS) cryptographic protocol for the following types of communication:

  • Internal - communication between Percona Server for MongoDB instances in the cluster
  • External - communication between the client application and the cluster

The internal certificate is also used as an authorization method.

Certificates for TLS security can be generated in several ways. By default, the Operator generates long-term certificates automatically if there are no certificate secrets available. Other options are the following ones:

  • the Operator can use a specifically installed cert-manager, which will automatically generate and renew short-term TLS certificates,
  • certificates can be generated manually.

You can also use pre-generated certificates available in the deploy/ssl-secrets.yaml file for test purposes, but we strongly recommend avoiding their usage on any production system!

The following subsections explain how to configure TLS security with the Operator yourself, as well as how to temporarily disable it if needed.

Install and use the cert-manager

About the cert-manager

The cert-manager is a Kubernetes certificate management controller which widely used to automate the management and issuance of TLS certificates. It is community-driven, and open source.

When you have already installed cert-manager and deploy the operator, the operator requests a certificate from the cert-manager. The cert-manager acts as a self-signed issuer and generates certificates. The Percona Operator self-signed issuer is local to the operator namespace. This self-signed issuer is created because Percona Server for MongoDB requires all certificates issued by the same CA (Certificate authority).

Self-signed issuer allows you to deploy and use the Percona Operator without creating a cluster issuer separately.

Installation of the cert-manager

The steps to install the cert-manager are the following:

  • create a namespace,
  • disable resource validations on the cert-manager namespace,
  • install the cert-manager.

The following commands perform all the needed actions:

$ kubectl apply -f https://github.com/jetstack/cert-manager/releases/download/v1.12.4/cert-manager.yaml --validate=false

After the installation, you can verify the cert-manager by running the following command:

$ kubectl get pods -n cert-manager

The result should display the cert-manager and webhook active and running:

NAME                                       READY   STATUS    RESTARTS   AGE
cert-manager-7d59dd4888-tmjqq              1/1     Running   0          3m8s
cert-manager-cainjector-85899d45d9-8ncw9   1/1     Running   0          3m8s
cert-manager-webhook-84fcdcd5d-697k4       1/1     Running   0          3m8s

Once you create the database with the Operator, it will automatically trigger cert-manager to create certificates. Whenever you check certificates for expiration, you will find that they are valid and short-term.

Generate certificates manually

To generate certificates manually, follow these steps:

  1. Provision a Certificate Authority (CA) to generate TLS certificates,
  2. Generate a CA key and certificate file with the server details,
  3. Create the server TLS certificates using the CA keys, certs, and server details.

The set of commands generate certificates with the following attributes:

  • Server-pem - Certificate
  • Server-key.pem - the private key
  • ca.pem - Certificate Authority

You should generate certificates twice: one set is for external communications, and another set is for internal ones. A secret created for the external use must be added to the spec.secrets.ssl key of the deploy/cr.yaml file. A certificate generated for internal communications must be added to the spec.secrets.sslInternal key of the deploy/cr.yaml file.

Note

If you only create the external certificate, then the Operator will not generate the internal one, but instead use certificate you have provided for both external and internal communications.

Supposing that your cluster name is my-cluster-name, the instructions to generate certificates manually are as follows:

$ CLUSTER_NAME=my-cluster-name
$ NAMESPACE=default
$ cat <<EOF | cfssl gencert -initca - | cfssljson -bare ca
  {
    "CN": "Root CA",
    "names": [
      {
        "O": "PSMDB"
      }
    ],
    "key": {
      "algo": "rsa",
      "size": 2048
    }
  }
EOF

$ cat <<EOF > ca-config.json
  {
    "signing": {
      "default": {
        "expiry": "87600h",
        "usages": ["signing", "key encipherment", "server auth", "client auth"]
      }
    }
  }
EOF

$ cat <<EOF | cfssl gencert -ca=ca.pem  -ca-key=ca-key.pem -config=./ca-config.json - | cfssljson -bare server
  {
    "hosts": [
      "localhost",
      "${CLUSTER_NAME}-rs0",
      "${CLUSTER_NAME}-rs0.${NAMESPACE}",
      "${CLUSTER_NAME}-rs0.${NAMESPACE}.svc.cluster.local",
      "*.${CLUSTER_NAME}-rs0",
      "*.${CLUSTER_NAME}-rs0.${NAMESPACE}",
      "*.${CLUSTER_NAME}-rs0.${NAMESPACE}.svc.cluster.local"
    ],
    "names": [
      {
        "O": "PSMDB"
      }
    ],
    "CN": "${CLUSTER_NAME/-rs0}",
    "key": {
      "algo": "rsa",
      "size": 2048
    }
  }
EOF
$ cfssl bundle -ca-bundle=ca.pem -cert=server.pem | cfssljson -bare server

$ kubectl create secret generic my-cluster-name-ssl-internal --from-file=tls.crt=server.pem --from-file=tls.key=server-key.pem --from-file=ca.crt=ca.pem --type=kubernetes.io/tls

$ cat <<EOF | cfssl gencert -ca=ca.pem  -ca-key=ca-key.pem -config=./ca-config.json - | cfssljson -bare client
  {
    "hosts": [
      "${CLUSTER_NAME}-rs0",
      "${CLUSTER_NAME}-rs0.${NAMESPACE}",
      "${CLUSTER_NAME}-rs0.${NAMESPACE}.svc.cluster.local",
      "*.${CLUSTER_NAME}-rs0",
      "*.${CLUSTER_NAME}-rs0.${NAMESPACE}",
      "*.${CLUSTER_NAME}-rs0.${NAMESPACE}.svc.cluster.local"
    ],
    "names": [
      {
        "O": "PSMDB"
      }
    ],
    "CN": "${CLUSTER_NAME/-rs0}",
    "key": {
      "algo": "rsa",
      "size": 2048
    }
  }
EOF

$ kubectl create secret generic my-cluster-name-ssl --from-file=tls.crt=client.pem --from-file=tls.key=client-key.pem --from-file=ca.crt=ca.pem --type=kubernetes.io/tls

Update certificates

If a cert-manager is used, it should take care of updating the certificates. If you generate certificates manually, you should take care of updating them in proper time.

TLS certificates issued by cert-manager are short-term ones, valid for 3 months. They are reissued automatically on schedule and without downtime.

image

Versions of the Operator prior 1.9.0 have used 3 month root certificate, which caused issues with the automatic TLS certificates update. If that’s your case, you can make the Operator update along with the official instruction.

Note

If you use the cert-manager version earlier than 1.9.0, and you would like to avoid downtime while updating the certificates after the Operator update to 1.9.0 or newer version, force the certificates regeneration by a cert-manager.

Check your certificates for expiration

  1. First, check the necessary secrets names (my-cluster-name-ssl and my-cluster-name-ssl-internal by default):

    $ kubectl get certificate
    

    You will have the following response:

    NAME                           READY   SECRET                         AGE
    my-cluster-name-ssl            True    my-cluster-name-ssl            49m
    my-cluster-name-ssl-internal   True    my-cluster-name-ssl-internal   49m
    
  2. Optionally you can also check that the certificates issuer is up and running:

    $ kubectl get issuer
    

    The response should be as follows:

    NAME                              READY   AGE
    my-cluster-name-psmdb-issuer      True    61m
    my-cluster-name-psmdb-ca-issuer   True    61m
    

    Note

    The presence of two issuers has the following meaning. The my-cluster-name-psmdb-ca-issuer issuer is used to create a self signed CA certificate (my-cluster-name-ca-cert), and then the my-cluster-name-psmdb-issuer issuer is used to create SSL certificates (my-cluster-name-ssl and my-cluster-name-ssl-internal) signed by the my-cluster-name-ca-cert CA certificate.

  3. Now use the following command to find out the certificates validity dates, substituting Secrets names if necessary:

    $ {
      kubectl get secret/my-cluster-name-ssl-internal -o jsonpath='{.data.tls\.crt}' | base64 --decode | openssl x509 -noout -dates
      kubectl get secret/my-cluster-name-ssl -o jsonpath='{.data.ca\.crt}' | base64 --decode | openssl x509 -noout -dates
      }
    

    The resulting output will be self-explanatory:

    notBefore=Apr 25 12:09:38 2022 GMT notAfter=Jul 24 12:09:38 2022 GMT
    notBefore=Apr 25 12:09:38 2022 GMT notAfter=Jul 24 12:09:38 2022 GMT
    

Update certificates without downtime

If you don’t use cert-manager and have created certificates manually, you can follow the next steps to perform a no-downtime update of these certificates if they are still valid.

Note

For already expired certificates, follow the alternative way.

Having non-expired certificates, you can roll out new certificates (both CA and TLS) with the Operator as follows.

  1. Generate a new CA certificate (ca.pem). Optionally you can also generate a new TLS certificate and a key for it, but those can be generated later on step 6.

  2. Get the current CA (ca.pem.old) and TLS (tls.pem.old) certificates and the TLS certificate key (tls.key.old):

    $ kubectl get secret/my-cluster-name-ssl-internal -o jsonpath='{.data.ca\.crt}' | base64 --decode > ca.pem.old
    $ kubectl get secret/my-cluster-name-ssl-internal -o jsonpath='{.data.tls\.crt}' | base64 --decode > tls.pem.old
    $ kubectl get secret/my-cluster-name-ssl-internal -o jsonpath='{.data.tls\.key}' | base64 --decode > tls.key.old
    
  3. Combine new and current ca.pem into a ca.pem.combined file:

    $ cat ca.pem ca.pem.old >> ca.pem.combined
    
  4. Create a new Secrets object with old TLS certificate (tls.pem.old) and key (tls.key.old), but a new combined ca.pem (ca.pem.combined):

    $ kubectl delete secret/my-cluster-name-ssl-internal
    $ kubectl create secret generic my-cluster-name-ssl-internal --from-file=tls.crt=tls.pem.old --from-file=tls.key=tls.key.old --from-file=ca.crt=ca.pem.combined --type=kubernetes.io/tls
    
  5. The cluster will go through a rolling reconciliation, but it will do it without problems, as every node has old TLS certificate/key, and both new and old CA certificates.

  6. If new TLS certificate and key weren’t generated on step 1, do that now.

  7. Create a new Secrets object for the second time: use new TLS certificate (server.pem in the example) and its key (server-key.pem), and again the combined CA certificate (ca.pem.combined):

    $ kubectl delete secret/my-cluster-name-ssl-internal
    $ kubectl create secret generic my-cluster-name-ssl-internal --from-file=tls.crt=server.pem --from-file=tls.key=server-key.pem --from-file=ca.crt=ca.pem.combined --type=kubernetes.io/tls
    
  8. The cluster will go through a rolling reconciliation, but it will do it without problems, as every node already has a new CA certificate (as a part of the combined CA certificate), and can successfully allow joiners with new TLS certificate to join. Joiner node also has a combined CA certificate, so it can authenticate against older TLS certificate.

  9. Create a final Secrets object: use new TLS certificate (server.pmm) and its key (server-key.pem), and just the new CA certificate (ca.pem):

    $ kubectl delete secret/my-cluster-name-ssl-internal
    $ kubectl create secret generic my-cluster-name-ssl-internal --from-file=tls.crt=server.pem --from-file=tls.key=server-key.pem --from-file=ca.crt=ca.pem --type=kubernetes.io/tls
    
  10. The cluster will go through a rolling reconciliation, but it will do it without problems: the old CA certificate is removed, and every node is already using new TLS certificate and no nodes rely on the old CA certificate any more.

Update certificates with downtime

If your certificates have been already expired (or if you continue to use the Operator version prior to 1.9.0), you should move through the pause - update Secrets - unpause route as follows.

  1. Pause the cluster in a standard way, and make sure it has reached its paused state.

  2. If cert-manager is used, delete issuer and TLS certificates:

    $ {
      kubectl delete issuer/my-cluster-name-psmdb-ca-issuer issuer/my-cluster-name-psmdb-issuer 
      kubectl delete certificate/my-cluster-name-ssl certificate/my-cluster-name-ssl-internal
      }
    
  3. Delete Secrets to force the SSL reconciliation:

    $ kubectl delete secret/my-cluster-name-ssl secret/my-cluster-name-ssl-internal
    
  4. Check certificates to make sure reconciliation have succeeded.

  5. Unpause the cluster in a standard way, and make sure it has reached its running state.

Run Percona Server for MongoDB without TLS

Omitting TLS is also possible, but we recommend that you run your cluster with the TLS protocol enabled.

To disable TLS protocol (e.g. for demonstration purposes) set the spec.allowUnsafeConfigurations key to true in the deploy/cr.yaml file and and make sure that there are no certificate secrets available. This is the only condition under which the cluster will work without TLS.

Warning

Normally, the Operator prevents users from configuring a cluster with unsafe parameters (starting it with less than 3 replica set instances or without TLS, etc.), automatically changing such unsafe parameters to safe defaults. If you switch the cluster to the unsafe configurations permissive mode, you will not be able to switch it back by setting spec.allowUnsafeConfigurations key to false, the flag will be ignored.

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Last update: 2024-02-27