Communication security with TLS

Table of contents

  1. Automated TLS certificate management using cert-manager
  2. Manual TLS certificate management

NFD supports mutual TLS authentication between the nfd-master and nfd-worker instances. That is, nfd-worker and nfd-master both verify that the other end presents a valid certificate.

TLS authentication is enabled by specifying -ca-file, -key-file and -cert-file args, on both the nfd-master and nfd-worker instances. The template specs provided with NFD contain (commented out) example configuration for enabling TLS authentication.

The Common Name (CN) of the nfd-master certificate must match the DNS name of the nfd-master Service of the cluster. By default, nfd-master only check that the nfd-worker has been signed by the specified root certificate (-ca-file).

Additional hardening can be enabled by specifying -verify-node-name in nfd-master args, in which case nfd-master verifies that the NodeName presented by nfd-worker matches the Common Name (CN) or a Subject Alternative Name (SAN) of its certificate. Note that -verify-node-name complicates certificate management and is not yet supported in the helm or kustomize deployment methods.

Automated TLS certificate management using cert-manager

cert-manager can be used to automate certificate management between nfd-master and the nfd-worker pods.

The NFD source code repository contains an example kustomize overlay and helm chart that can be used to deploy NFD with cert-manager supplied certificates enabled.

To install cert-manager itself can be done as easily as this, below, or you can refer to their documentation for other installation methods such as the helm chart they provide.

kubectl apply -f

To use the kustomize overlay to install node-feature-discovery with TLS enabled, you may use the following:

kubectl apply -k deployment/overlays/samples/cert-manager

To make use of the helm chart, override values.yaml to enable both the tls.enabled and tls.certManager options. Note that if you do not enable tls.certManager, helm will successfully install the application, but deployment will wait until certificates are manually created, as demonstrated below.

See the sample installation commands in the Helm Deployment and Configuration sections above for how to either override individual values, or provide a yaml file with which to override default values.

Manual TLS certificate management

If you do not with to make use of cert-manager, the certificates can be manually created and stored as secrets within the NFD namespace.

Create a CA certificate

openssl req -x509 -newkey rsa:4096 -keyout ca.key -nodes \
        -subj "/CN=nfd-ca" -days 10000 -out ca.crt

Create a common openssl config file.

cat <<EOF > nfd-common.conf
[ req ]
default_bits = 4096
prompt = no
default_md = sha256
req_extensions = req_ext
distinguished_name = dn

[ dn ]
C = XX
ST = some-state
L = some-city
O = some-company
OU = node-feature-discovery

[ req_ext ]
subjectAltName = @alt_names

[ v3_ext ]

Now, create the nfd-master certificate.

cat <<EOF > nfd-master.conf
.include nfd-common.conf

[ dn ]
CN = nfd-master

[ alt_names ]
DNS.1 = nfd-master
DNS.2 = nfd-master.node-feature-discovery.svc.cluster.local
DNS.3 = localhost

openssl req -new -newkey rsa:4096 -keyout nfd-master.key -nodes -out nfd-master.csr -config nfd-master.conf

Create certificates for nfd-worker and nfd-topology-updater

cat <<EOF > nfd-worker.conf
.include nfd-common.conf

[ dn ]
CN = nfd-worker

[ alt_names ]
DNS.1 = nfd-worker
DNS.2 = nfd-worker.node-feature-discovery.svc.cluster.local

# Config for topology updater is identical except for the DN and alt_names
sed -e 's/worker/topology-updater/g' < nfd-worker.conf > nfd-topology-updater.conf

openssl req -new -newkey rsa:4096 -keyout nfd-worker.key -nodes -out nfd-worker.csr -config nfd-worker.conf
openssl req -new -newkey rsa:4096 -keyout nfd-topology-updater.key -nodes -out nfd-topology-updater.csr -config nfd-topology-updater.conf

Now, sign the certificates with the CA created earlier.

for cert in nfd-master nfd-worker nfd-topology-updater; do
  echo signing $cert
  openssl x509 -req -in $cert.csr -CA ca.crt -CAkey ca.key \
    -CAcreateserial -out $cert.crt -days 10000 \
    -extensions v3_ext -extfile $cert.conf

Finally, turn these certificates into secrets.

for cert in nfd-master nfd-worker nfd-topology-updater; do
  echo creating secret for $cert in node-feature-discovery namespace
  cat <<EOF | kubectl create -n node-feature-discovery -f -
apiVersion: v1
kind: Secret
  name: ${cert}-cert
  ca.crt: $( cat ca.crt | base64 -w 0 )
  tls.crt: $( cat $cert.crt | base64 -w 0 )
  tls.key: $( cat $cert.key | base64 -w 0 )