Kubernetes Trusted Platform Module (TPM) using Device Plugin and Gatekeeper

Exposing the Trusted Platform Module (TPM) to a non-privleged kubernetes pod.

This allows an pod to interact directly with the TPM device /dev/tpm0 while the pod runs without privleged: true setting (which is dangerous).

Basically, we will use Kubernetes Generic Device Plugin to mount the device and also setup apply custom Pod-level security policies using Gatekeeper to limit privleged mode.

Gatekeeper will also only allow mounting the TPM event log from the host to each pod.

Essentially

• Device plugin runs as privleged DaemonSet in namespace: kube-system
• Device Plugin surfaces TPM access to each pod in namespace: ns1
• Gatekeeper prevents privleged access to namespace: ns1 (see Gatekeeper Privleged Containers)
• Gatekeeper allows hostPath mount to TPM Eventlog to namespace: ns1 (see GateKeeper Host Filesystem)

---

References

• Kubernetes Generic Device Plugin
• Apply custom Pod-level security policies using Gatekeeper
• Gatekeeper Pod Security Policy
• Pod Security Policies Deprecation
• Kubernetes Trusted Platform Module (TPM) DaemonSet
• Trusted Platform Module (TPM) recipes with tpm2_tools and go-tpm
• golang-jwt for Trusted Platform Module (TPM)
• TPM Credential Source for Google Cloud SDK
• TPM based TLS using Attested Keys

---

Setup

gcloud container clusters create cluster-1  \
     --region=us-central1 --machine-type=n2d-standard-2 \
     --enable-confidential-nodes    --enable-shielded-nodes \
     --shielded-secure-boot --shielded-integrity-monitoring \
     --num-nodes=1 --enable-network-policy 

# init gatekeeper
kubectl apply -f https://raw.githubusercontent.com/open-policy-agent/gatekeeper/master/deploy/gatekeeper.yaml

# init the device plugin and gatekeer configs
kubectl apply -f tpm-generic-device-plugin.yaml 

# create the deployment
## note, the pod you are deploying here is basically just tpm2_tools:
###  https://hub.docker.com/r/salrashid123/tpm2_tools

kubectl apply -f pod_manifest.yaml

## access the tpm
kubectl get po -n ns1

POD=$(kubectl get pod -n ns1 -l "app.kubernetes.io/name=tpm-client" -o jsonpath="{.items[0].metadata.name}")
echo $POD

kubectl exec  -it $POD --namespace ns1  -- tpm2_pcrread
  sha1:
    0 : 0x2AAB58E23EA5120D70A3EBCE56BD0E6D5E3035B7
    1 : 0xE3E9E1D9DEACD95B289BBBD3A1717A57AF7D211B
    2 : 0xB2A83B0EBF2F8374299A5B2BDFC31EA955AD7236
    3 : 0xB2A83B0EBF2F8374299A5B2BDFC31EA955AD7236

## read eventlog mounted at /root/binary_bios_measurements
kubectl exec  --namespace ns1 -it $POD   -- tpm2_eventlog /root/binary_bios_measurements

---