Certificate Management

mTLS and Certificate Issuance

FSM uses mTLS for encryption of data between pods as well as Pipy and service identity. Certificates are created and distributed to each Pipy proxy by the FSM control plane.

Types of Certificates

There are a few kinds of certificates used in FSM:

Root Certificate

The root certificate for the service mesh is stored in an Opaque Kubernetes Secret named fsm-ca-bundle in the namespace where fsm is installed (by default fsm-system). The secret YAML has the following shape:

apiVersion: v1
kind: Secret
type: Opaque
metadata:
      name: fsm-ca-bundle
      namespace: fsm-system
data:
  ca.crt: <base64 encoded root cert>
  private.key: <base64 encoded private key>

To read the root certificate (with the exception of Hashicorp Vault), you can retrieve the corresponding secret and decode it:

kubectl get secret -n $fsm_namespace $fsm_ca_bundle -o jsonpath='{.data.ca\.crt}' |
    base64 -d |
    openssl x509 -text -noout

Note: By default, the CA bundle is named fsm-ca-bundle.

This will provide valuable certificate information, such as the expiration date and the issuer.

Root Certificate Rotation

Tresor

WARNING: Rotating root certificates will incur downtime between any services as they transition their mTLS certs from one issuer to the next.

We are currently working on a zero-downtime root cert rotation mechanism that we expect to announce in one of our upcoming releases.

The self-signed root certificate, which is created via the Tresor package within FSM, will expire in a decade. To rotate the root cert, the following steps should be followed:

1. Delete the fsm-ca-bundle certificate in the fsm namespace

   export fsm_namespace=fsm-system # Replace fsm-system with the namespace where FSM is installed
   kubectl delete secret fsm-ca-bundle -n $fsm_namespace
   

2. Restart the control plane components

   kubectl rollout restart deploy fsm-controller -n $fsm_namespace
   kubectl rollout restart deploy fsm-injector -n $fsm_namespace
   kubectl rollout restart deploy fsm-bootstrap -n $fsm_namespace
   

When the components gets re-deployed, you should be able to eventually see the new fsm-ca-bundle secret in $fsm_namespace:

kubectl get secrets -n $fsm_namespace

NAME                           TYPE                                  DATA   AGE
fsm-ca-bundle                  Opaque                                3      74m

The new expiration date can be found with the following command:

kubectl get secret -n $fsm_namespace $fsm_ca_bundle -o jsonpath='{.data.ca\.crt}' |
    base64 -d |
    openssl x509 -noout -dates

For the Sidecar service and validation certificates to be rotated the data plane components must restarted.

Hashicorp Vault and Certmanager

For certificate providers other than Tresor, the process of rotating the root certificate will be different. For Hashicorp Vault and cert-manager.io, users will need to rotate the root certificate themselves outside of FSM.

Issuing Certificates

Open Service Mesh supports 3 methods of issuing certificates:

• using an internal FSM package, called Tresor. This is the default for a first time installation.
• using Hashicorp Vault
• using cert-manager

Using FSM’s Tresor certificate issuer

FSM includes a package, tresor. This is a minimal implementation of the certificate.Manager interface. It issues certificates leveraging the crypto Go library, and stores these certificates as Kubernetes secrets.

• To use the tresor package during development set export CERT_MANAGER=tresor in the .env file of this repo.

• To use this package in your Kubernetes cluster set the CERT_MANAGER=tresor variable in the Helm chart prior to deployment.

Additionally:

• fsm.caBundleSecretName - this string is the name of the Kubernetes secret, where the CA root certificate and private key will be saved.

Using Hashicorp Vault

Service Mesh operators, who consider storing their service mesh’s CA root key in Kubernetes insecure have the option to integrate with a Hashicorp Vault installation. In such scenarios a pre-configured Hashi Vault is required. Open Service Mesh’s control plane connects to the URL of the Vault, authenticates, and begins requesting certificates. This setup shifts the responsibility of correctly and securely configuring Vault to the operator.

The following configuration parameters will be required for FSM to integrate with an existing Vault installation:

• Vault address
• Vault token
• Validity period for certificates

fsm install set flag control how FSM integrates with Vault. The following fsm install set options must be configured to issue certificates with Vault:

• --set fsm.certificateProvider.kind=vault - set this to vault
• --set fsm.vault.host - host name of the Vault server (example: vault.contoso.com)
• --set fsm.vault.protocol - protocol for Vault connection (http or https)
• --set fsm.vault.role - role created on Vault server and dedicated to Flomesh Service Mesh (example: fsm)
• --set fsm.certificateProvider.serviceCertValidityDuration - period for which each new certificate issued for service-to-service communication will be valid. It is represented as a sequence of decimal numbers each with optional fraction and a unit suffix, ex: 1h to represent 1 hour, 30m to represent 30 minutes, 1.5h or 1h30m to represent 1 hour and 30 minutes.

The Vault token must be provided to FSM so it can connect to Vault. The token can be configured as a set option or stored in a Kubernetes secret in the namespace of the FSM installation. If the fsm.vault.token option is not set, the fsm.vault.secret.name and fsm.vault.secret.key options must be configured.

• --set fsm.vault.token - token to be used by FSM to connect to Vault (this is issued on the Vault server for the particular role)
• --set fsm.vault.secret.name - the string name of the Kubernetes secret storing the Vault token
• --set fsm.vault.secret.key - the key of the Vault token in the Kubernetes secret

Additionally:

• fsm.caBundleSecretName - this string is the name of the Kubernetes secret where the service mesh root certificate will be stored. When using Vault (unlike Tresor) the root key will not be exported to this secret.

Installing Hashi Vault

Installation of Hashi Vault is out of scope for the Open Service Mesh project. Typically this is the responsibility of dedicated security teams. Documentation on how to deploy Vault securely and make it highly available is available on Vault’s website.

This repository does contain a script (deploy-vault.sh), which is used to automate the deployment of Hashi Vault for continuous integration. This is strictly for development purposes only. Running the script will deploy Vault in a Kubernetes namespace defined by the $K8S_NAMESPACE environment variable in your .env file. This script can be used for demonstration purposes. It requires the following environment variables:

export K8S_NAMESPACE=fsm-system-ns
export VAULT_TOKEN=xyz

Running the ./demo/deploy-vault.sh script will result in a dev Vault installation:

NAMESPACE         NAME                                    READY   STATUS    RESTARTS   AGE
fsm-system-ns     vault-5f678c4cc5-9wchj                  1/1     Running   0          28s

Fetching the logs of the pod will show details on the Vault installation:

==> Vault server configuration:

             Api Address: http://0.0.0.0:8200
                     Cgo: disabled
         Cluster Address: https://0.0.0.0:8201
              Listener 1: tcp (addr: "0.0.0.0:8200", cluster address: "0.0.0.0:8201", max_request_duration: "1m30s", max_request_size: "33554432", tls: "disabled")
               Log Level: info
                   Mlock: supported: true, enabled: false
           Recovery Mode: false
                 Storage: inmem
                 Version: Vault v1.4.0

WARNING! dev mode is enabled! In this mode, Vault runs entirely in-memory
and starts unsealed with a single unseal key. The root token is already
authenticated to the CLI, so you can immediately begin using Vault.

You may need to set the following environment variable:

    $ export VAULT_ADDR='http://0.0.0.0:8200'

The unseal key and root token are displayed below in case you want to
seal/unseal the Vault or re-authenticate.

Unseal Key: cZzYxUaJaN10sa2UrPu7akLoyU6rKSXMcRt5dbIKlZ0=
Root Token: xyz

Development mode should NOT be used in production installations!

==> Vault server started! Log data will stream in below:
...

The outcome of deploying Vault in your system is a URL and a token. For instance the URL of Vault could be http://vault.<fsm-namespace>.svc.cluster.local and the token xxx.

Note: <fsm-namespace> refers to the namespace where the fsm control plane is installed.

Configure FSM with Vault

After Vault installation and before we use Helm to deploy FSM, the following parameters must be provided provided in the Helm chart:

CERT_MANAGER=vault
VAULT_HOST="vault.${K8S_NAMESPACE}.svc.cluster.local"
VAULT_PROTOCOL=http
VAULT_TOKEN=xyz
VAULT_ROLE=fsm

When running FSM on your local workstation, use the following fsm install set options:

--set fsm.certificateProvider.kind="vault"
--set fsm.vault.host="localhost"  # or the host where Vault is installed
--set fsm.vault.protocol="http"
--set fsm.vault.token="xyz"
--set fsm.vault.role="fsm'
--set fsm.serviceCertValidityDuration=24h

How FSM Integrates with Vault

When the FSM control plane starts, a new certificate issuer is instantiated. The kind of cert issuer is determined by the fsm.certificateProvider.kind set option. When this is set to vault FSM uses a Vault cert issuer. This is a Hashicorp Vault client, which satisfies the certificate.Manager interface. It provides the following methods:

  - IssueCertificate - issues new certificates
  - GetCertificate - retrieves a certificate given its Common Name (CN)
  - RotateCertificate - rotates expiring certificates
  - GetAnnouncementsChannel - returns a channel, which is used to announce when certificates have been issued or rotated

FSM assumes that a CA has already been created on the Vault server. FSM also requires a dedicated Vault role (for instance pki/roles/fsm). The Vault role created by the ./demo/deploy-vault.sh script applies the following configuration, which is only appropriate for development purposes:

• allow_any_name: true
• allow_subdomains: true
• allow_baredomains: true
• allow_localhost: true
• max_ttl: 24h

Hashi Vault’s site has excellent documentation on how to create a new CA. The ./demo/deploy-vault.sh script uses the following commands to setup the dev environment:

export VAULT_TOKEN="xyz"
export VAULT_ADDR="http://localhost:8200"
export VAULT_ROLE="fsm"

# Launch the Vault server in dev mode
vault server -dev -dev-listen-address=0.0.0.0:8200 -dev-root-token-id=${VAULT_TOKEN}

# Also save the token locally so this is available
echo $VAULT_TOKEN>~/.vault-token;

# Enable the PKI secrets engine (See: https://www.vaultproject.io/docs/secrets/pki#pki-secrets-engine)
vault secrets enable pki;

# Set the max lease TTL to a decade
vault secrets tune -max-lease-ttl=87600h pki;

# Set URL configuration (See: https://www.vaultproject.io/docs/secrets/pki#set-url-configuration)
vault write pki/config/urls issuing_certificates='http://127.0.0.1:8200/v1/pki/ca' crl_distribution_points='http://127.0.0.1:8200/v1/pki/crl';

# Configure a role named "fsm" (See: https://www.vaultproject.io/docs/secrets/pki#configure-a-role)
vault write pki/roles/${VAULT_ROLE} allow_any_name=true allow_subdomains=true;

# Create a root certificate named "fsm.root" (See: https://www.vaultproject.io/docs/secrets/pki#setup)
vault write pki/root/generate/internal common_name='fsm.root' ttl='87600h'

The FSM control plane provides verbose logs on operations done with the Vault installations.

Using cert-manager

cert-manager is another provider for issuing signed certificates to the FSM service mesh, without the need for storing private keys in Kubernetes. cert-manager has support for multiple issuer backends core to cert-manager, as well as pluggable external issuers.

Note that ACME certificates are not supported as an issuer for service mesh certificates.

When FSM requests certificates, it will create cert-manager CertificateRequest resources that are signed by the configured issuer.

Configure cert-manger for FSM signing

cert-manager must first be installed, with an issuer ready, before FSM can be installed using cert-manager as the certificate provider. You can find the installation documentation for cert-manager here.

Once cert-manager is installed, configure an issuer resource to serve certificate requests. It is recommended to use an Issuer resource kind (rather than a ClusterIssuer) which should live in the FSM namespace (fsm-system by default).

Once ready, it is required to store the root CA certificate of your issuer as a Kubernetes secret in the FSM namespace (fsm-system by default) at the ca.crt key. The target CA secret name can be configured on FSM using fsm install --set fsm.caBundleSecretName=my-secret-name (typically fsm-ca-bundle).

kubectl create secret -n fsm-system generic fsm-ca-bundle --from-file ca.crt

Refer to the cert-manager demo to learn more.

Configure FSM with cert-manager

In order for FSM to use cert-manager with the configured issuer, set the following CLI arguments on the fsm install command:

• --set fsm.certificateProvider.kind="cert-manager" - Required to use cert-manager as the provider.
• --set fsm.certmanager.issuerName - The name of the [Cluster]Issuer resource (defaulted to fsm-ca).
• --set fsm.certmanager.issuerKind - The kind of issuer (either Issuer or ClusterIssuer, defaulted to Issuer).
• --set fsm.certmanager.issuerGroup - The group that the issuer belongs to (defaulted to cert-manager.io which is all core issuer types).