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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.

TLS usage is controlled by the tls.mode Custom Resource option, which can be set to allowTLS, preferTLS (default choice), requireTLS, or disabled:

...
spec:
  ...
  tls:
    mode: preferTLS

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.

Note

The tls.allowInvalidCertificates Custom Resource option is set to true by default to allow certificates automatically generated by the Operator. It can be set to false with other variants, such as certificates generated by cert-manager.

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/v1.14.5/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

Warning

Using manually generated certificates doesn’t work in the Operator version 1.16.0. Check the bug K8SPSMDB-1101 for updates.

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

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.

Modify certificates generation

There may be reasons to tweak the certificates generation, making it better fit some needs. Of course, maximum flexibility can be obtained with manual certificates generation, but sometimes slight tweaking the already automated job may be enough.

The following example shows how to increase CA duration with cert-manager for a cluster named cluster1:

  1. Delete the psmdb Custom Resource in the proper namespace (this will cause deletion of all Pods of the cluster, but later you will recreate the cluster using the same deploy/cr.yaml flie from which it was originally created).

    Note

    you may need to make sure that finalizers.delete-psmdb-pvc is not set if you want to preserver Persistent Volumes with the data.

    Deletion command should look as follows:

    ``` {.bash data-prompt=”$” } $ kubectl -n delete psmdb cluster1

  2. Deletion takes time. Check that all Pods disappear with kubectl -n <namespace_name> get pods command, and delete certificate related resources:

    {.bash data-prompt="$" } $ kubectl -n <namespace_name> delete issuer.cert-manager.io/cluster1-psmdb-ca-issuer issuer.cert-manager.io/cluster1-psmdb-issuer certificate.cert-manager.io/cluster1-ssl-internal certificate.cert-manager.io/cluster1-ssl certificate.cert-manager.io/cluster1-ca-cert secret/cluster1-ca-cert secret/cluster1-ssl secret/cluster1-ssl-internal

  3. Create your own custom CA:

    my_new_ca.yml
    apiVersion: cert-manager.io/v1
    kind: Issuer
    metadata:
      name: cluster1-psmdb-ca-issuer
    spec:
      selfSigned: {}
    ---
    apiVersion: cert-manager.io/v1
    kind: Certificate
    metadata:
      name: cluster1-ca-cert
    spec:
      commonName: cluster1-ca
      duration: 10000h0m0s
      isCA: true
      issuerRef:
        kind: Issuer
        name: cluster1-psmdb-ca-issuer
      renewBefore: 730h0m0s
      secretName: cluster1-ca-cert
    

    Apply it as usual, with the kubectl -n <namespace_name> apply -f my_new_ca.yml command.

  4. Recreate the cluster from the original deploy/cr.yaml configuration file:

    $ kubectl -n <namespace_name> apply -f deploy/cr.yaml
    
  5. Verify certificate duration in usual way.

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 tls.mode key to disabled and set unsafeFlags.tls to true in the deploy/cr.yaml: file.

...
spec:
  ...
  unsafeFlags
    tls: true
    ...
  tls:
    mode: disabled

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Last update: 2024-06-24