Transition to different PKI modes

Google Distributed Cloud (GDC) air-gapped provides a public key infrastructure (PKI) API to get web certificates. This page provides instructions to transition from one PKI certificate mode to another. For more information about PKI mode configuration types, see Web TLS certificate configuration

Before you begin

To get the permissions you need to configure the PKI default certificate issuer, ask your Organization IAM Admin to grant you the Platform Admin Infra PKI Admin (pa-infra-pki-admin) role in the system namespace.

Transition to BYO subCA mode

This section provides a series of steps to transition to the bring your own (BYO) SubCA cert mode.

Create a BYO subCA

To create a BYO subCA, apply a custom resource to your Distributed Cloud instance.

Create a CertificateAuthority resource and save it as a YAML file. In the following example, you see a sample CertificateAuthority resource
```
apiVersion: pki.security.gdc.goog/v1
kind: CertificateAuthority
metadata:
  name: CA_NAME
  namespace: pki-system
spec:
  caProfile:
    commonName: COMMON_NAME
    duration: DURATION
    renewBefore: RENEW_BEFORE
  caCertificate:
    externalCA: {}
  certificateProfile:
    keyUsage:
    - digitalSignature
    - keyCertSign
    - crlSign
    extendedKeyUsage:
    - serverAuth
  secretConfig:
    secretName: SECRET_NAME
```
Replace the following variables:
- CA_NAME: the name of the subCA.
- COMMON_NAME: the common name of the CA certificate.
- DURATION: the requested lifetime of the CA certificate.
- RENEW_BEFORE: the rotation time before the CA certificate expires.
- SECRET_NAME: the name of the Kubernetes Secret that will hold the private key and signed CA certificate.
Apply the custom resource to your Distributed Cloud instance.
```
kubectl apply -f byo-subca.yaml --kubeconfig ADMIN_CLUSTER_KUBECONFIG
```
Replace ADMIN_CLUSTER_KUBECONFIG with the org admin cluster's kubeconfig path.

A CSR for Sub CA generates and waits for you to sign it. To sign the CSR, follow the instructions in the section Sign the BYO subCA certificate.

Sign the BYO subCA certificate

Get the certificate signing requests (CSR) from your GDC environment:
```
kubectl get certificateauthorities CA_NAME -n pki-system -ojson | jq -j '"echo ",
.status.externalCA.csr, " | base64 -d > ","sub_ca.csr\n"' | bash
```
The command generates the file sub_ca.csr in the current directory. This file contains a CSR for an X.509 CA certificate.
Use the customer's root CA's protocol to request signed CA certificates for the sub_ca.csr file.
For an approved certificate signing request, you will obtain a CA certificate signed by the customer's root CA. Store the certificate to the sub_ca.crt file in the current directory. In addition, obtain the customer's root CA certificate and store it to the ca.crt file in the current directory. Reach out to PMO for exact instructions.

Verify the Subject Alternative Name (SAN) extensions in the certificate:

openssl x509 -text -noout -in sub_ca.crt | grep -A 1 "Subject Alternative Name"

If the CA certificate has Common Name (CN) rather than SAN, then verify the CN in the certificate:
```
openssl x509 -text -noout -in sub_ca.crt | grep -A 1 "Subject: CN"
```

Generate the spec to patch the CertificateAuthority resource:

 echo "spec:
caCertificate:
  externalCA:
    signedCertificate:
      certificate: $(base64 -w0 sub_ca.crt)
      ca: $(base64 -w0 ca.crt)" > patch.txt

The content in the patch.txt file looks similar to the following snippet:

 spec:
  caCertificate:
   externalCA:
    signedCertificate:
     certificate: LS0tLS1CRUdJTiBDRVJUSUZJQ0FURS0tLS0tCk1JSURSekNDQ…
     ca: LS0tLS1CRUdJTiBDRVJUSUZJQ0FURS0tLS0tCk1JSURRVENDQ…

Edit the spec of the CertificateAuthority resource:

kubectl patch certificateauthority CA_NAME -n pki-system --patch-file patch.txt --type='merge'

Verify the readiness of the BYO subCA:

kubectl get certificateauthority CA_NAME -n pki-system -ojson | jq -r ' .status.conditions[] | select( .type as $id | "Ready" | index($id))'

You see output similar to the following:

{
  "lastTransitionTime": "2024-04-30T22:10:50Z",
  "message": "Certificate authority is ready for use",
  "observedGeneration": 3,
  "reason": "Ready",
  "status": "True",
  "type": "Ready"
}

Verify the expiration of the signed CA certificates:

kubectl -n pki-system get secret SECRET_NAME -ojson | jq -j '"echo ",
.metadata.name, " $(echo ", .data["tls.crt"], "| base64 -d | openssl x509 -enddate -noout)\n"' | bash

Create a CertificateIssuer resource YAML file and save the file. For example, byo-subca-issuer.yaml:

apiVersion: pki.security.gdc.goog/v1
kind: CertificateIssuer
metadata:
  name: BYO_SUBCA_ISSUER
  namespace: pki-system
spec:
  caaasConfig:
    certificateAuthorityRef:
      namespace: pki-system
      name: CA_NAME

Replace BYO_SUBCA_ISSUER with the name of the byo subCA issuer.

Apply the custom resource to your Distributed Cloud instance in the admin cluster using the kubectl CLI:
```
kubectl apply -f byo-subca-issuer.yaml --kubeconfig ADMIN_CLUSTER_KUBECONFIG
```

Verify the readiness of the new issuer:

kubectl -n pki-system get certificateissuer.pki.security.gdc.goog/BYO_SUBCA_ISSUER -ojson | jq -r ' .status.conditions[] | select( .type as $id | "Ready" | index($id))'

Transition to BYO Certificate mode

This section provides a series of steps to transition to the BYO-cert mode.

Create a BYO CertificateIssuer

Create a CertificateIssuer resource and save it as a YAML file, for example, byo-cert-issuer.yaml. This BYO cert issuer uses the managed default-tls-ca as the fallback CA:

apiVersion: pki.security.gdc.goog/v1
kind: CertificateIssuer
metadata:
  name: BYO_CERT_ISSUER_NAME
  namespace: pki-system
spec:
  byoCertConfig:
    fallbackCertificateAuthority:
      name: default-tls-ca
      namespace: pki-system

Replace BYO_CERT_ISSUER_NAME with the name of the BYO-cert issuer.

Apply the custom resource to your Distributed Cloud instance in the admin cluster:
```
kubectl apply -f byo-cert-issuer.yaml –kubeconfig ADMIN_CLUSTER_KUBECONFIG
```

Verify the readiness of the new issuer.

kubectl -n pki-system get certificateissuer.pki.security.gdc.goog/BYO_CERT_ISSUER_NAME -ojson | jq -r ' .status.conditions[] | select( .type as $id | "Ready" | index($id))'

The output looks similar to the following:

{
  "lastTransitionTime": "2024-05-01T22:25:20Z",
  "message": "",
  "observedGeneration": 1,
  "reason": "FallbackCAReady",
  "status": "True",
  "type": "Ready"
}

Sign the BYO Certificate

When waiting for the CSR to be externally signed, a BYO-cert can be temporarily issued by a fallback CA specified in the BYO-cert issuer. Get the current BYO-cert default-wildcard-cert status:

kubectl get certificate.pki.security.gdc.goog/default-wildcard-cert -n istio-system -o json | jq -r ' .status.conditions[] | select( .type as $id | "Ready" | index($id))'

The output looks similar to the following:

{
  "lastTransitionTime": "2024-05-03T08:42:10Z",
  "message": "Certificate is issued by a fallback CA",
  "observedGeneration": 1,
  "reason": "UsingFallbackCA",
  "status": "True",
  "type": "Ready"
}

The ready reason states UsingFallbackCA to indicate the fallback CA issues the certificate. It's then stored in the secret and ready for use.

Get the certificate secret name:

kubectl -n istio-system get certificate.pki.security.gdc.goog/default-wildcard-cert -ojson | jq -r '.spec.secretConfig.secretName'

The output looks similar to the following:

web-tls

Check the issuer from the secret:
```
kubectl get secret web-tls -n istio-system -o jsonpath='{.data.tls\.crt}' |
base64 -d | openssl x509 -text -noout | grep Issuer
```
The output looks similar to the following:
```
Issuer: CN = GDC Managed ORG TLS CA
```
A bring-your-own certificate (BYO-cert) can temporarily use a matched certificate while awaiting its own CSR signature. An example-service certificate with dnsName as example-service.org-1.zone1.google.gdch.test is matched by the default-wildcard-certwith DNSName *.org-1.zone1.google.gdch.test from the same certificate issuer. The example-service certificate can hold the following status while waiting for its CSR to be signed:
```
{
  "lastTransitionTime": "2024-05-03T22:30:51Z",
  "message": "Using a matched issued Certificate: default-wildcard-cert/istio-system",
  "observedGeneration": 1,
  "reason": "UsingMatchedCert",
  "status": "True",
  "type": "Ready"
}
```

Get the CSR from the certificate status:

kubectl -n istio-system get certificate.pki.security.gdc.goog/default-wildcard-cert -ojson | jq -r ' .status.byoCertStatus.csrStatus'

The output looks similar to the following:

{
  "conditions": [
    {
      "lastTransitionTime": "2024-05-03T18:14:19Z",
      "message": "",
      "observedGeneration": 1,
      "reason": "WaitingForSigning",
      "status": "False",
      "type": "Ready"
    }
  ],
  "csr": "LS0tLS1CRUdJTiBDRVJUSUZJQ0FURSB..."
}

There are different methods for signing a CSR based on the external CA configuration. When signing, use the SAN from the CSR. For example:

function signCert() {
   certName=$1
   ns=$2

   # Download the CSR from the certificate
   kubectl get certificate.pki.security.gdc.goog $certName -n $ns -o jsonpath='{.status.byoCertStatus.csrStatus.csr}' | base64 -d > $certName.csr

   # Get SAN from the csr
   san=$(openssl req -in $certName.csr -noout -text | grep 'DNS:' | sed -s 's/^[ ]*//')

   # Save SAN to extension config
   cat <<EOF >$certName-csr.ext
 keyUsage=digitalSignature,keyEncipherment
 extendedKeyUsage=serverAuth,clientAuth
 subjectAltName=${san}
 EOF

   # Sign the CSR with an external CA. You need to prepare the external CA cert and key
   openssl x509 -req -in $certName.csr -days 365 -CA ext-ca.crt -CAkey ext-ca.key -CAcreateserial -extfile $certName-csr.ext -out $certName-signed.crt
   openssl x509 -in $certName-signed.crt -text -noout

   # Upload the externally signed certificate by patching.
   echo "spec:
     byoCertificate:
        certificate: $(base64 -w0 $certName-signed.crt)
        ca: $(base64 -w0 ext-ca.crt)" > patch.txt

   kubectl patch certificate.pki.security.gdc.goog $certName -n $ns --patch-file patch.txt --type='merge'
 }

 # Use the function to sign the default-wildcard-cert in the istio-system namespace
 signCert default-wildcard-cert istio-system

Verify the following details:

The certificate's CSR status is Ready

kubectl -n istio-system get certificate.pki.security.gdc.goog/default-wildcard-cert -ojson | jq -r ' .status.byoCertStatus.csrStatus.conditions'

[
   {
      "lastTransitionTime": "2024-05-03T21:56:25Z",
      "message": "",
      "observedGeneration": 2,
      "reason": "Signed",
      "status": "True",
      "type": "Ready"
   }
]

The certificate is Ready with the reason Issued

kubectl get certificate.pki.security.gdc.goog/default-wildcard-cert -n istio-system -o json | jq -r ' .status.conditions[] | select( .type as $id | "Ready" | index($id))'

The output looks similar to the following:

{
  "lastTransitionTime": "2024-05-03T08:42:10Z",
  "message": "Certificate is issued",
  "observedGeneration": 2,
  "reason": "Issued",
  "status": "True",
  "type": "Ready"
}

The secret is updated:

kubectl get secret web-tls -n istio-system -o jsonpath='{.data.tls\.crt}' | base64 -d | openssl x509 -text -noout | grep Issuer

The output looks similar to the following:

        Issuer: CN = external-ca

Transition to a BYO Certificate with ACME mode

This section provides a series of steps to transition to a BYO-cert with ACME mode.

Create a CertificateIssuer with ACME config

Create a CertificateIssuer resource with ACME config and save it as a YAML file, such as acme-issuer.yaml.
```
apiVersion: pki.security.gdc.goog/v1
kind: CertificateIssuer
metadata:
  name: ACME_ISSUER_NAME
  namespace: pki-system
spec:
     acmeConfig:
       rootCACertificate: ROOT_CA_CERTIFICATE
       acme:
         server: ACME_SERVER_URL
         caBundle: CA_BUNDLE
         privateKeySecretRef:
           name: PRIVATE_KEY_SECRET_NAME
```
Replace the following variables:
- ACME_ISSUER_NAME: the name of the ACME issuer.
- ROOT_CA_CERTIFICATE: the root CA data of certificates issued by ACME server.
- ACME_SERVER_URL: the URL to access the ACME server's directory endpoint.
- CA_BUNDLE: the Base64-encoded bundle of PEM CAs that validates the certificate chain presented by the ACME server.
- PRIVATE_KEY_SECRET_NAME: the name of the secret that contains the ACME account private key.
To use an existing ACME account private key, ensure the secret holding it uses the name PRIVATE_KEY_SECRET_NAME within the same namespace as the ACME issuer. If you don't provide this secret, a new one with the same name generates automatically to store the ACME account private key.

Apply the custom resource to your Distributed Cloud instance:

kubectl apply -f acme-issuer.yaml --kubeconfig ADMIN_CLUSTER_KUBECONFIG

Verify the readiness of the new issuer:

kubectl --kubeconfig ADMIN_CLUSTER_KUBECONFIG -n pki-system get certificateissuer.pki.security.gdc.goog/ACME_ISSUER_NAME -ojson | jq -r ' .status.conditions[] | select( .type as $id | "Ready" | index($id))'

You see output similar to the following:

{
  "lastTransitionTime": "2024-05-01T18:32:17Z",
  "message": "",
  "observedGeneration": 1,
  "reason": "ACMEClientReady",
  "status": "True",
  "type": "Ready"
}

Certificate reissuance

To switch the default issuer to the new ACME issuer, see Change default certificate issuer

To immediately reissue certificates with the new default issuer, see Manually reissue PKI web certificates.