dsh-kubectl-guard

A DeepSeek Harness policy plugin that gates kubectl by kubeconfig context.

Irreversible verbs against a non-local cluster are denied outright. Recoverable writes ask first. Reads and local clusters are untouched.

It registers no tools of its own — it inspects the command argument of shell tool calls, so it covers whatever the agent runs.

Install

Requires pnpm, which dsh plugin shells out to.

From npm:

dsh plugin --profile web add dsh-kubectl-guard

From source, if you want to hack on it:

git clone https://github.com/gengwg/dsh-kubectl-guard
cd dsh-kubectl-guard
dsh plugin --profile web add "$PWD"

Either way, activate it in ~/.dsh/profiles/<profile>/cordis.patch.yml:

- insert:
    - id: kubectl-guard
      name: dsh-kubectl-guard

Restart dsh to load it. Installing prints declares no dsh.bundle — installed as a plain dependency; that is expected, since this is a plugin activated by the patch entry above rather than a profile bundle.

Examples

Nothing to invoke. Ask the agent to do its normal work; the guard sits in the tool pipeline and inspects the shell command before it runs.

Blocked, with the cluster name replaced by a per-session pseudonym:

> delete the stuck nginx pod

Error: kubectl-guard: 'delete' is irreversible and ctx#4be1 is not a local
cluster. Denied.

Asked, so you approve it in the UI before it runs:

> roll out the new deployment

kubectl-guard: 'apply' writes to ctx#4be1, which is not a local cluster.
[approve] [deny]

Untouched, because reads are not gated:

> what pods are failing in kube-system?

kubectl get pods -n kube-system --field-selector=status.phase!=Running
NAME         READY   STATUS             RESTARTS
api-7d9f8c   0/1     CrashLoopBackOff   14

Untouched, because the context is local:

> wipe the test namespace on my kind cluster

kubectl --context kind-dev delete ns test
namespace "test" deleted

Dry runs are reads, so they pass and give the agent a way to show you a change before asking for it:

kubectl apply --dry-run=server -f deploy.yaml     # allowed
kubectl apply -f deploy.yaml                      # asks

Turn the guard off for one session without editing config:

dsh web --patch <(echo '- id: kubectl-guard
  disabled: true')

Behavior

Command	Non-local context	Local context
get, describe, logs, top	allow	allow
auth can-i	allow	allow
auth reconcile	ask	allow
apply, patch, scale, exec	ask	allow
delete, drain, evict	deny	allow
scale --replicas=0	deny	allow
apply --prune	deny	allow
replace --force	deny	allow
apply --dry-run=server	allow	allow

A context is local only if it matches localContexts. Everything else, including a kubeconfig that cannot be read, is treated as production.

The context is resolved the way the shell would resolve it: an explicit --context wins, then --kubeconfig, then a KUBECONFIG= assignment written inline on the same command line, then the ambient environment. That last case matters -- without it, KUBECONFIG=/path/to/prod kubectl delete ... would be judged against whatever your shell happened to point at.

Config

config:
  localContexts: [minikube, 'kind-*', docker-desktop]
  binaries: [kubectl, k]
  guardedTools: [bash, pwsh]
  showContextNames: false

showContextNames is off by default: blocked-command messages go to the model, and therefore to the LLM provider. With it off the model sees a stable per-session pseudonym like ctx#4be1 instead of your cluster's name.

Failing closed

A gate that can be talked around is worse than none. Anything unparseable — sh -c, command substitution, an unterminated quote — is treated as a mutation: denied if the text contains an irreversible verb, asked otherwise. An unknown verb asks rather than allows.

What this is not

This gates a cooperative agent, not an adversary. It reads the command string the agent asked to run, so anything that hides the binary name from that string defeats it by construction -- $KUBECTL delete ... with the name only in the environment, a shell alias resolved at runtime, a base64 round-trip.

Indirection that still contains the literal name is caught: K=kubectl; $K delete pod foo is denied, because any $ expansion alongside a mention of a guarded binary makes the command opaque, and opaque plus an irreversible verb is a denial. But treat the guard as a seatbelt against a confused agent, not a sandbox against a hostile one. If you need the stronger property, take the credential away rather than filtering the command.

Limitations

• Only kubectl. helm, argocd and flux are not covered; the verb table is data, so adding them is an edit to src/verbs.js.
• current-context is read with a line-anchored regex, not a YAML parser. Unreadable or unmatched means production, so the failure direction is safe.
• The pseudonym salt is per-process: ids are stable within a session, not across restarts.
• Guards are synchronous, so the deny path does no I/O beyond a cached readFileSync.

Test

npm test

MIT.