Security

This section addresses the certificate generation in Kuma across the following use-cases:

1. Security between our services, via the mTLS policy.
2. Security between the Kuma control plane and its data plane proxies, via the data plane proxy token.
3. Security when accessing the control plane.
4. Security when external system access the control plane.

This section is not to be confused with the mTLS policy that we can apply to a Mesh to secure service-to-service traffic.

Data plane proxy to control plane communication

A data plane connects to the control plane for its configuration, including mTLS certificates described in the following sections.

Encrypted communication

Because the data plane proxy and the control plane exchange sensitive information, the communication needs to be encrypted by TLS. By default, the control plane's server that is consumed by the data plane proxy is secured by TLS with autogenerated certificates.

For security purposes, the data plane proxy must verify the identity of the control plane. To do so, data planes need to obtain the CA that was used to generate the certificate by which the control plane's server is secured. Note, this CA is not the same CA for data plane proxy to data plane proxy communication.

To override autogenerated certificates:

1. Create a secret in the namespace in which Control Plane is installed

kubectl create secret generic general-tls-certs -n kuma-system \
  --from-file=tls.crt=/path/to/cert \
  --from-file=tls.key=/path/to/key \
  --from-file=ca.crt=/path/to/key

2. Point to this secret when installing Kuma

• kumactl install control-plane --tls-general-secret=general-tls-certs --tls-general-ca-bundle=<BASE64 content of ca.crt> via kumactl
• Set controlPlane.tls.general.secretName to general-tls-certs and controlPlane.tls.general.caBundle to <BASE64 content of ca.crt> via HELM

The Data plane Injector builtin in the control plane automatically provides the CA to the Kuma DP sidecar.

To override autogenerated certificates set the following configuration

• KUMA_DP_SERVER_TLS_CERT_FILE - path to a certificate
• KUMA_DP_SERVER_TLS_KEY_FILE - path to a key

Provide the CA that was used to sign certs above by using --ca-cert-file=/path/ca-cert.pem or via environment variable KUMA_CONTROL_PLANE_CA_CERT when starting the kuma-dp process.

Data plane proxy authentication

In order to obtain an mTLS certificate from the server (SDS (opens new window) built-in in the control plane), a data plane proxy must authenticate itself.

On Kubernetes, a data plane proxy proves its identity by leveraging ServiceAccountToken (opens new window) that is mounted in every pod.

On Universal, a data plane proxy must be explicitly configured with a unique security token (data plane proxy token) that will be used to prove its identity. The data plane proxy token is a signed JWT token (opens new window) that carries the data plane proxy name and name of the mesh that it belongs to.

It is signed by an RSA key auto-generated by the control plane when Mesh is created. Tokens are never stored in the control plane, the only thing that is stored is a signing key that is used to verify if a token is valid.

You can generate token either by REST API

curl -XPOST \ 
  -H "Content-Type: application/json" \
  --data '{"name": "dp-echo-1", "mesh": "default", "tags": {"kuma.io/service": ["backend", "backend-admin"]}}' \
  http://localhost:5681/tokens

or by using kumactl

kumactl generate dataplane-token \
  --name dp-echo-1 \
  --mesh default \
  --tag kuma.io/service=backend,backend-admin > /tmp/kuma-dp-echo1-token

The token should be stored in a file and then used when starting kuma-dp

$ kuma-dp run \
  --name=dp-echo-1 \
  --mesh=default \
  --cp-address=https://127.0.0.1:5678 \
  --dataplane-token-file=/tmp/kuma-dp-echo-1-token

You can also pass Dataplane Token as KUMA_DATAPLANE_RUNTIME_TOKEN Environment Variable.

Data Plane Proxy Token boundary

As we can see in the example above, we can generate a token by passing a name, mesh, and a list of tags. The control plane will then verify the data plane proxy resources that are connecting to it against the token. This means we can generate a token by specifying:

• Only mesh. By doing so we can reuse the token for all dataplanes in a given mesh.
• mesh + tag (ex. kuma.io/service). This way we can use one token across all instances/replicas of the given service. Please keep in mind that we have to specify to include all the services that a data plane proxy is in charge of. For example, if we have a Dataplane with two inbounds, one valued with kuma.io/service: backend and one with kuma.io/service: backend-admin, we need to specify both values (--tag kuma.io/service=backend,backend-admin).
• mesh + name + tag (ex. kuma.io/service). This way we can use one token for one instance/replicate of the given service.
• type. The type can be either dataplane (default if not specified) or ingress. An ingress data plane proxy in a multi-zone deployment requires an ingress token.

We can turn off the authentication by setting KUMA_DP_SERVER_AUTH_TYPE to none.

If we disable the authentication between the control plane and the data plane proxies, any data plane proxy will be able to impersonate any service, therefore this is not recommended in production.

Multizone

When running in multizone, mode we can generate data plane proxy token both on Global and Remote Control Plane. If the deployment pipeline is configured to generate data plane proxy token before running a data plane, it can rely on the Remote CP. This way Global CP is not a single point of failure.

Data plane to data plane communication

Kuma helps us to secure the existing infrastructure with mTLS.

Mutual TLS

Once a data plane has proved its identity to the control plane, it will be allowed to fetch its own identity certificate and a root CA certificate of the mesh. When establishing a connection between two data planes, each side validates the other data plane's certificate using the root CA of the mesh, which then confirms their identity.

mTLS is not enabled by default. To enable it, we must apply proper settings in Mesh policy. Additionally, when running on Universal we have to ensure that every data plane in the mesh has been configured with a dataplane proxy token.

Certificates

In Kuma, any TLS certificate that is being issued by the control plane must have a CA (Certificate Authority) that can be either auto-generated by Kuma via a builtin backend, or can be initialized with a customer certificate and key via a provided backend.

Third-party extensions, cloud implementations or commercial offerings may be extending the CA backend support.

For both builtin and provided CA backends, on Kubernetes the root CA certificate is stored as a Kubernetes Secret (opens new window), while on Universal Kuma leverages the same underlying storage backend that is used for storing policies.

When the mTLS policy is enabled, data plane proxy certificates are ephemeral: thet are re-created on every data plane proxy restart and never persisted on disk.

Data plane proxy certificates generated by Kuma are X.509 certificates that are SPIFFE (opens new window) compliant. The SAN of the certificates is set to spiffe://<mesh name>/<service name>.

User to control plane communication

Users and automation tools can interact with the control plane via the API Server using tools like curl or kumactl. API Server is exposed by default on :5681 on HTTP and :5682 on HTTPS.

Encrypted communication

API Server HTTPS server is secured by default by autogenerated certificates. We can override those certificates.

To override autogenerated certificates:

1. Create a secret in the namespace in which Control Plane is installed

kubectl create secret tls api-server-tls -n kuma-system \
  --cert=/root/test-certs/cert.pem \
  --key=/root/test-certs/key.pem

2. Point to this secret when installing Kuma

• kumactl install control-plane --tls-api-server-secret=api-server-tls via kumactl
• Set controlPlane.tls.apiServer.secretName to api-server-tls via HELM

To override autogenerated certificates set the following configuration

• KUMA_API_SERVER_HTTPS_TLS_CERT_FILE - path to a certificate
• KUMA_API_SERVER_HTTPS_TLS_KEY_FILE - path to a key

We can then configure secure connection using kumactl CLI tool.

kumactl config control-planes add \
  --name <NAME> \
  --address https://<KUMA_CP_DNS_NAME>:5682 \
  --ca-cert-file <CA.PEM> \

We can also hide the HTTP version of API Server by binding it to localhost KUMA_API_SERVER_HTTP_INTERFACE: 127.0.0.1 or by disabling it altogether KUMA_API_SERVER_HTTP_ENABLED: false

Authentication

Some endpoints like managing Secrets or generating data plane proxy token require authentication. There are two ways to access those endpoints.

Request originating from localhost

For the simplicity of use, requests that are originating from the same machine as CP are authenticated. We can disable this behavior by setting KUMA_API_SERVER_AUTH_ALLOW_FROM_LOCALHOST to false

On Kubernetes, we can port-forward 5681 port and access the admin endpoints.

Client certificates

When accessing admin endpoints from a different machine we need to use client certificates.

1. Generate client certificates by using kumactl

$ kumactl generate tls-certificate --type=client \
  --cert-file=/path/to/cert \
  --key-file=/path/to/key

2. Configure the control plane with client certificates

1. Create a secret in the namespace in which Control Plane is installed

$ kubectl create secret generic api-server-client-certs -n kuma-system \
  --from-file=client1.pem=/path/to/cert/cert1.pem \
  --from-file=client2.pem=/path/to/cert/cert2.pem

We can provide as many client certificates as we want. Remember to only put there certificates without keys.

2. Point to this secret when installing Kuma

• kumactl install control-plane tls-api-server-client-certs-secret=api-server-client-certs via kumactl
• Set controlPlane.tls.apiServer.clientCertsSecretName to api-server-client-certs via HELM

1. Put all the certificates in one directory
2. Configure control plane by pointing to this directory KUMA_API_SERVER_AUTH_CLIENT_CERTS_DIR

3. Configure kumactl with valid client certificates

$ kumactl config control-planes add \
  --name <NAME> --address https://<KUMA_CP_DNS_NAME>:5682 \
  --client-cert-file <CERT.PEM> \
  --client-key-file <KEY.PEM> \
  --ca-cert-file <CA.PEM>

Control plane to Postgres communication

Since on Universal secrets such as provided CA's private key are stored in Postgres, a connection between Postgres and Kuma CP should be secured with TLS.

To secure the connection, we first need to pick the security mode using KUMA_STORE_POSTGRES_TLS_MODE. There are several modes:

• disable - is not secured with TLS (secrets will be transmitted over network in plain text).
• verifyNone - the connection is secured but neither hostname, nor by which CA the certificate is signed is checked.
• verifyCa - the connection is secured and the certificate presented by the server is verified using the provided CA.
• verifyFull - the connection is secured, certificate presented by the server is verified using the provided CA and server hostname must match the one in the certificate.

The CA used to verify the server's certificate can be set using the KUMA_STORE_POSTGRES_TLS_CA_PATH environment variable.

After configuring the above security settings in Kuma, we also have to configure Postgres' pg_hba.conf (opens new window) file to restrict unsecured connections.

Here is an example configuration that will allow only TLS connections and will require username and password:

# TYPE  DATABASE        USER            ADDRESS                 METHOD
hostssl all             all             0.0.0.0/0               password

We can also provide a client key and certificate for mTLS using the KUMA_STORE_POSTGRES_TLS_CERT_PATH and KUMA_STORE_POSTGRES_TLS_KEY_PATH variables. This pair can be used in conjunction with the cert auth-method described here (opens new window).