Navigating Access Challenges in Kubernetes-Based Infrastructure
Sep 19
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Teleport

Workload Attestation

Version 16.x
Preview

Teleport Workload Identity is currently in Preview. This means that some features may be missing. We're actively looking for design partners to help us shape the future of Workload Identity and would love to hear your feedback.

Workload Attestation is the process completed by tbot to assert the identity of a workload that has connected to the Workload API and requested certificates. The information gathered during attestation is used to decide which, if any, SPIFFE IDs should be encoded into an SVID and issued to the workload.

Workload Attestors are the individual components that perform this attestation. They use the process ID of the workload to gather information about the workload from platform-specific APIs. For example, the Kubernetes Workload Attestor queries the local Kubelet API to determine which Kubernetes pod the process belongs to.

The result of the attestation process is known as attestation metadata. This attestation metadata is referred to by the rules you configured for tbot's Workload API service. For example, you may state that only workloads running in a specific Kubernetes namespace should be issued a specific SPIFFE ID.

Additionally, this metadata is included in the log messages output by tbot when it issues an SVID. This allows you to audit the issuance of SVIDs and understand why a specific SPIFFE ID was issued to a workload.

Unix

The Unix Workload Attestor is the most basic attestor and allows you to restrict the issuance of SVIDs to specific Unix processes based on a range of criteria.

Attestation Metadata

The following metadata is produced by the Unix Workload Attestor and is available to be used when configuring rules for tbot's Workload API service:

FieldDescription
unix.attestedIndicates that the workload has been attested by the Unix Workload Attestor.
unix.pidThe process ID of the attested workload.
unix.uidThe effective user ID of the attested workload.
unix.gidThe effective primary group ID of the attested workload.

Kubernetes

The Kubernetes Workload Attestor allows you to restrict the issuance of SVIDs to specific Kubernetes workloads based on a range of criteria.

It works by first determining the pod ID for a given process ID and then by querying the local kubelet API for details about that pod.

Attestation Metadata

The following metadata is produced by the Kubernetes Workload Attestor and is available to be used when configuring rules for tbot's Workload API service:

FieldDescription
kubernetes.attestedIndicates that the workload has been attested by the Kubernetes Workload Attestor.
kubernetes.namespaceThe namespace of the Kubernetes Pod.
kubernetes.service_accountThe service account of the Kubernetes Pod.
kubernetes.pod_nameThe name of the Kubernetes Pod.

Deployment Guidance

To use Kubernetes Workload Attestation, tbot must be deployed as a daemon set. This is because the unix domain socket can only be accessed by pods on the same node as the agent. Additionally, the daemon set must have the hostPID property set to true to allow the agent to access information about processes within other containers.

The daemon set must also have a service account assigned that allows it to query the Kubelet API. This is an example role with the required RBAC:

kind: ClusterRole
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: tbot
rules:
  - resources: ["pods","nodes","nodes/proxy"]
    apiGroups: [""]
    verbs: ["get"]

Mapping the Workload API Unix domain socket into the containers of workloads can be done in two ways:

  • Directly configuring a hostPath volume for the tbot daemonset and workloads which will need to connect to it.
  • Using spiffe-csi-driver.

Example manifests for required Kubernetes resources:

kind: ClusterRole
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: tbot
rules:
  - resources: ["pods","nodes","nodes/proxy"]
    apiGroups: [""]
    verbs: ["get"]
---
kind: ClusterRoleBinding
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: tbot
subjects:
  - kind: ServiceAccount
    name: tbot
    namespace: default
roleRef:
  kind: ClusterRole
  name: tbot
  apiGroup: rbac.authorization.k8s.io
---
apiVersion: v1
kind: ServiceAccount
metadata:
  name: tbot
  namespace: default
---
apiVersion: v1
kind: ConfigMap
metadata:
  name: tbot-config
  namespace: default
data:
  tbot.yaml: |
    version: v2
    onboarding:
      join_method: kubernetes
      # replace with the name of a join token you have created.
      token: example-token
    storage:
      type: memory
    # ensure this is configured to the address of your Teleport Proxy Service.
    proxy_server: example.teleport.sh:443
    services:
      - type: spiffe-workload-api
        listen: unix:///run/tbot/sockets/workload.sock
        attestor:
          kubernetes:
            enabled: true
            kubelet:
              # skip verification of the Kubelet API certificate as this is not
              # usually issued by the cluster CA.
              skip_verify: true
        # replace the svid entries with the SPIFFE IDs that you wish to issue,
        # using the `rules` blocks to restrict these to specific Kubernetes
        # workloads.
        svids:
          - path: /my-service
            rules:
              - kubernetes:
                  namespace: default
                  service_account: example-sa
---
apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: tbot
spec:
  selector:
      matchLabels:
        app: tbot
  template:
    metadata:
      labels:
        app: tbot
    spec:
      securityContext:
        runAsUser: 0
        runAsGroup: 0
      hostPID: true
      containers:
        - name: tbot
          image: public.ecr.aws/gravitational/tbot-distroless:16.3.0
          imagePullPolicy: IfNotPresent
          securityContext:
            privileged: true
          args:
            - start
            - -c
            - /config/tbot.yaml
            - --log-format
            - json
          volumeMounts:
            - mountPath: /config
              name: config
            - mountPath: /var/run/secrets/tokens
              name: join-sa-token
            - name: tbot-sockets
              mountPath: /run/tbot/sockets
              readOnly: false
          env:
            - name: TELEPORT_NODE_NAME
              valueFrom:
                fieldRef:
                  fieldPath: spec.nodeName
            - name: KUBERNETES_TOKEN_PATH
              value: /var/run/secrets/tokens/join-sa-token
      serviceAccountName: tbot
      volumes:
        - name: tbot-sockets
          hostPath:
            path: /run/tbot/sockets
            type: DirectoryOrCreate
        - name: config
          configMap:
            name: tbot-config
        - name: join-sa-token
          projected:
            sources:
              - serviceAccountToken:
                  path: join-sa-token
                  # 600 seconds is the minimum that Kubernetes supports. We
                  # recommend this value is used.
                  expirationSeconds: 600
                  # `example.teleport.sh` must be replaced with the name of
                  # your Teleport cluster.
                  audience: example.teleport.sh

Next steps