Merge pull request 'fix(cloudflared): fsGroup so uid 65532 can read the 0440 credentials Secret' (#154) from fix/cloudflared-creds-permission into main

Reviewed-on: #154
Reviewed-by: Keith Jackson <[email protected]>

conformance/tests/l0-static/cloudflared-ingress-rules/chainsaw-test.yaml

@@ -39,7 +39,9 @@ spec:
         Parse platform/cloudflared/config.yaml with BASE_DOMAIN substituted, assert every rule's
         target against the Gateway Service derived from platform/gateway/gateway.yaml, assert the
         excluded hostnames 404 first, check the egress CiliumNetworkPolicy and the Flux wiring, and
-        run the evaluator on mutated configs to prove it is not vacuous.
+        run the evaluator on mutated configs to prove it is not vacuous; and assert the
+        credentials Secret volume is readable by the container's run-as uid/groups (fsGroup +
+        mode), self-tested by mutation.
       try:
         - script:
             content: bash ./check.sh

conformance/tests/l0-static/cloudflared-ingress-rules/check.sh

@@ -26,9 +26,19 @@
 #       (5) the Flux tier is ISOLATED: its own Kustomization, wait:false, not listed in
 #           platform/kustomization.yaml, nothing anywhere dependsOn it, and both overlays carry its
 #           SOPS decryption patch — so a missing or invalid credential can stall nothing else;
-#   AND (6) the rule evaluator is not vacuous: it is run against mutated copies of the real config
+#       (6) the rule evaluator is not vacuous: it is run against mutated copies of the real config
 #           (an API rule added, plex moved below the wildcard, the catch-all removed) and must
-#           flag each one.
+#           flag each one;
+#   AND (7) every Secret volume the container mounts — the tunnel credentials above all — is
+#           READABLE by the container's run-as identity, modelled the way the kubelet lays it out:
+#           files owned by uid 0, group-owned by fsGroup if set (else gid 0), with the item mode or
+#           defaultMode (API default 0644). The identity is the container securityContext over
+#           the pod's; the process's groups are runAsGroup + fsGroup + supplementalGroups. An
+#           unset runAsUser is a FAIL, not a pass: the image default cannot be read offline. The
+#           model is deliberately conservative — it does not credit the kubelet's habit of
+#           OR-ing group-read into fsGroup-owned volumes, so 0400+fsGroup fails here though it
+#           would work. Self-tested by mutation (fsGroup removed; mode 0400; runAsUser unset).
+#           This is the 2026-11-08 CrashLoop: runAsUser 65532, no fsGroup, 0440 root:root.
 #
 # NOT proven (static): that Cloudflare routes only the hostnames whose DNS points at the tunnel,
 # that the Gateway's certificate validates from cloudflared, or that Envoy enforces (4) — those are
@@ -236,6 +246,69 @@ check(dep["spec"]["template"]["metadata"]["labels"].get("homelab.keithjackson.de
 check(dep["spec"]["template"]["spec"].get("automountServiceAccountToken") is False,
       "(4) the pods mount no ServiceAccount token")
 
+# (7) the credentials Secret is readable by the run-as identity
+def unreadable_secret_volumes(pod_spec):
+    """Return a description per Secret volume the containers mount but cannot read."""
+    bad = []
+    psc = pod_spec.get("securityContext") or {}
+    vols = {v["name"]: v for v in pod_spec.get("volumes") or [] if "secret" in v}
+    for c in (pod_spec.get("initContainers") or []) + (pod_spec.get("containers") or []):
+        csc = c.get("securityContext") or {}
+        uid = csc.get("runAsUser", psc.get("runAsUser"))
+        gid = csc.get("runAsGroup", psc.get("runAsGroup"))
+        fs_group = psc.get("fsGroup")
+        groups = {g for g in [gid, fs_group, *(psc.get("supplementalGroups") or [])]
+                  if g is not None}
+        for vm in c.get("volumeMounts") or []:
+            v = vols.get(vm["name"])
+            if v is None:
+                continue
+            sec = v["secret"]
+            if uid is None:
+                bad.append(f"container {c['name']} mounts Secret volume {vm['name']} but sets no "
+                           f"runAsUser (pod or container) — readability cannot be proven offline")
+                continue
+            default = sec.get("defaultMode", 0o644)
+            modes = [it.get("mode", default) for it in sec.get("items") or []] or [default]
+            owner_gid = fs_group if fs_group is not None else 0
+            for mode in modes:
+                readable = ((uid == 0 and mode & 0o400) or (owner_gid in groups and mode & 0o040)
+                            or mode & 0o004)
+                if not readable:
+                    bad.append(f"container {c['name']} (uid {uid}, groups {sorted(groups)}) cannot "
+                               f"read Secret volume {vm['name']} ({sec.get('secretName')}): files "
+                               f"are 0:{owner_gid} mode {mode:04o} — set pod fsGroup to a group "
+                               f"the container runs with, keeping 0440")
+    return bad
+
+
+pod_spec = dep["spec"]["template"]["spec"]
+creds_vol = [v for v in pod_spec.get("volumes") or []
+             if (v.get("secret") or {}).get("secretName") == "cloudflared-credentials"]
+check(len(creds_vol) == 1, "(7) the Deployment mounts Secret cloudflared-credentials as a volume")
+for v in unreadable_secret_volumes(pod_spec):
+    check(False, f"(7) {v}")
+sec_mutants = {}
+m = copy.deepcopy(pod_spec)
+m["securityContext"].pop("fsGroup", None)
+m["securityContext"].pop("supplementalGroups", None)
+sec_mutants["fsGroup removed"] = m
+m = copy.deepcopy(pod_spec)
+for v in m["volumes"]:
+    if "secret" in v:
+        v["secret"]["defaultMode"] = 0o400
+        for it in v["secret"].get("items") or []:
+            it["mode"] = 0o400
+sec_mutants["mode 0400"] = m
+m = copy.deepcopy(pod_spec)
+m["securityContext"].pop("runAsUser", None)
+for c in m["containers"]:
+    (c.get("securityContext") or {}).pop("runAsUser", None)
+sec_mutants["runAsUser unset"] = m
+for name, mut in sec_mutants.items():
+    check(unreadable_secret_volumes(mut),
+          f"(7) self-test: the readability model did NOT flag the mutant '{name}' — vacuous")
+
 if CHECKS < 25:
     FAILURES.append(f"only {CHECKS} assertions ran — the check degenerated")
 if FAILURES:

decisions/2026-11-08-cloudflared-creds-permission.md

@@ -0,0 +1,59 @@
+---
+date: 2026-11-08
+branch: fix/cloudflared-creds-permission
+title: cloudflared CrashLoop — credentials Secret unreadable by uid 65532; add fsGroup, pin it in L0
+---
+
+## What changed
+
+- **`platform/cloudflared/deployment.yaml`**: pod `securityContext.fsGroup: 65532`. Root cause of
+  the CrashLoop that followed #152/#153: the pod runs as `65532:65532` with no `fsGroup`, and the
+  Secret volume is `defaultMode: 0440`. The kubelet therefore laid `credentials.json` down as
+  `root:root 0440`, which uid 65532 (not owner, not in gid 0) cannot read. cloudflared logged
+  `couldn't read tunnel credentials ... permission denied`, then fell back to origin-cert lookup
+  and ended on the misleading `error parsing tunnel ID: Error locating origin cert`. With
+  `fsGroup` the files are group-owned by 65532, readable by the container and no other uid; the
+  mode stays 0440 (not loosened to 0444). Same fix as `platform/keycloak/client-secret-reconciler.yaml`.
+  Still non-root, `runAsNonRoot: true`, unchanged otherwise.
+- **`conformance/tests/l0-static/cloudflared-ingress-rules/check.sh`**: new assertion (7). For each
+  Secret volume a container mounts, it models kubelet ownership (uid 0, gid = fsGroup or 0, item
+  mode / defaultMode / API default 0644) against the container's effective runAsUser and its groups
+  (runAsGroup + fsGroup + supplementalGroups) and fails if the file is unreadable. An unset
+  runAsUser fails (image default is not knowable offline). Conservative: it does not credit the
+  kubelet OR-ing group-read into fsGroup volumes. Mutation self-test: fsGroup removed, mode 0400,
+  runAsUser unset must each be flagged. Chainsaw step description updated to match.
+- **`runbooks/cloudflare-tunnel.md`**: new first "likely cause" (permission denied on
+  credentials.json → the origin-cert error is a red herring) plus a "read the first error line"
+  note; causes renumbered. New section **Rotating the tunnel credential**: create a new tunnel,
+  swap the UUID and the encrypted credentials, merge, verify (new tunnel has two connectors, old
+  has none), then `cloudflared tunnel cleanup`/`delete <old>`.
+- NOT touched, on purpose: `tunnel:` in `config.yaml` and `cloudflared-credentials.sops.yaml`. The
+  operator is rotating the credential (it was exposed in a transcript) in a separate PR.
+
+## What I verified
+
+- Live (k3s-prod, read-only, 2026-11-08 ~21:38Z): Deployment pod securityContext is
+  `{"runAsGroup":65532,"runAsNonRoot":true,"runAsUser":65532,"seccompProfile":...}`, no
+  `fsGroup`; creds volume `defaultMode: 288` (= 0440). All three pods CrashLoopBackOff (38
+  restarts). Secret `cloudflared-credentials` has the one key `credentials.json` (key names only).
+- Pinned image `cloudflare/cloudflared@sha256:4955524a...` config (`skopeo inspect --config`):
+  `User: 65532:65532`, `Entrypoint: [cloudflared]`, `Cmd: [version]`.
+- The new assertion FAILS (rc 1) on the pre-fix deployment.yaml with
+  `container cloudflared (uid 65532, groups [65532]) cannot read Secret volume creds ... files are
+  0:0 mode 0440`, and PASSES (51 assertions) with the fix. All three mutants are flagged.
+- Kyverno admission policies under `platform/kyverno/admission/` that mention securityContext
+  fields are scoped to the conformance-trigger and pm-agent Jobs only; none constrains fsGroup here.
+- Toolbox gate: see the PR description for the rc and skipped stages.
+
+## What I did NOT verify
+
+- **That the pods actually become Ready after merge.** Not deployed by me; Flux applies it. The
+  file mode inside the running container was not observed (pods crash before an exec is possible,
+  and exec would be an operator action anyway). The readability claim rests on the kubelet's
+  documented fsGroup behaviour and the identical, working keycloak reconciler.
+- Whether the CURRENT credential is otherwise valid (UUID/TunnelID match, tunnel exists). Moot:
+  the operator is rotating it.
+- The rotation runbook section has not been executed; `cloudflared tunnel cleanup` / `delete`
+  syntax is from the CLI's documented commands, not run here.
+- The deployment comment says the image ENTRYPOINT is `cloudflared --no-autoupdate`; the pinned
+  image's ENTRYPOINT is plain `cloudflared`. Left unchanged (out of scope); flagged for follow-up.

platform/cloudflared/deployment.yaml

@@ -47,6 +47,14 @@ spec:
         # The image is distroless `nonroot` (65532).
         runAsUser: 65532
         runAsGroup: 65532
+        # fsGroup makes the kubelet GROUP-own the Secret volume's files to 65532. Without it they
+        # are root:root, and defaultMode 0440 (below) is unreadable to uid 65532 — every replica
+        # CrashLooped on "couldn't read tunnel credentials ... permission denied" (2026-11-08),
+        # which cloudflared then misreports as "Error locating origin cert". Same lesson as
+        # platform/keycloak/client-secret-reconciler.yaml. fsGroup + 0440 keeps the credential
+        # unreadable to any other uid rather than relaxing it to world-readable 0444.
+        # Pinned by the L0 check cloudflared-ingress-rules, assertion (7).
+        fsGroup: 65532
         seccompProfile:
           type: RuntimeDefault
       topologySpreadConstraints:
@@ -121,6 +129,8 @@ spec:
           secret:
             # cloudflared-credentials.sops.yaml — the tunnel credentials JSON, by name only.
             secretName: cloudflared-credentials
+            # 0440, owner root, group fsGroup 65532 (pod securityContext) — readable by the
+            # container user through its group, by nobody else.
             defaultMode: 0440
 ---
 # One replica may be disrupted at a time — enough for kured's one-node-at-a-time drain to

runbooks/cloudflare-tunnel.md

@@ -63,23 +63,36 @@ patch is missing; see causes below.
 
 ## Likely causes, most likely first
 
-1. **The tunnel has not been enrolled yet** (Phase 1, steps 1-5 below not done). Logs show an
-   error about the tunnel `REPLACE-ME-TUNNEL-UUID` or a missing origin certificate. Do steps 1-5.
-2. **UUID and credentials disagree** — `config.yaml` `tunnel:` is not the `TunnelID` in the
+**Read the FIRST error line, not the last.** When cloudflared cannot use the credentials file it
+falls back to looking for an origin certificate, and the error it ends on —
+`Cannot determine default origin certificate path` / `error parsing tunnel ID: Error locating
+origin cert` — is a **red herring** whatever the real cause was. The credentials file is the
+whole of what this Deployment needs; no `cert.pem` ever belongs in the pod.
+
+1. **`permission denied` on `credentials.json` → the "origin cert" error is a red herring.** Logs:
+   `couldn't read tunnel credentials from /etc/cloudflared/creds/credentials.json: permission
+   denied`, then the origin-cert lines. The container (uid 65532) cannot read the Secret file:
+   the pod `securityContext.fsGroup: 65532` is missing, so the 0440 file is `root:root`. Fix it in
+   git (`platform/cloudflared/deployment.yaml`); the L0 check `cloudflared-ingress-rules`,
+   assertion (7), should already have refused that. Do NOT loosen `defaultMode` to 0444. (This is
+   what CrashLooped every replica on 2026-11-08.)
+2. **The tunnel has not been enrolled yet** (Phase 1, steps 1-5 below not done). Logs show an
+   error about the tunnel `REPLACE-ME-TUNNEL-UUID` (and the origin-cert red herring). Do steps 1-5.
+3. **UUID and credentials disagree** — `config.yaml` `tunnel:` is not the `TunnelID` in the
    credentials JSON. Logs: authentication / "tunnel not found". Check with step 4's verify command.
-3. **Credentials still encrypted in the cluster** — the `cloudflared` decryption patch is missing
+4. **Credentials still encrypted in the cluster** — the `cloudflared` decryption patch is missing
    from `clusters/prod/kustomization.yaml`. The L0 check guards this, so this means someone bypassed
    it.
-4. **Egress blocked** — a policy change, or the edge moved off 7844. Look for drops:
+5. **Egress blocked** — a policy change, or the edge moved off 7844. Look for drops:
    ```
    infra/devcontainer/dev.sh run bash -c \
      'kubectl --context k3s-prod -n kube-system exec ds/cilium -c cilium-agent -- \
         hubble observe --verdict DROPPED --from-namespace cloudflared --last 100 -o compact'
    ```
    (`ds/cilium` picks one node's agent; repeat per node if empty.)
-5. **The tunnel was deleted or its secret rotated in Cloudflare** — `cloudflared tunnel list`
+6. **The tunnel was deleted or its secret rotated in Cloudflare** — `cloudflared tunnel list`
    (step 2's podman form) no longer shows it. Re-enrol with steps 2-5.
-6. **`CloudflaredReplicasDegraded` only**: one replica cannot schedule (the spread is hard, one per
+7. **`CloudflaredReplicasDegraded` only**: one replica cannot schedule (the spread is hard, one per
    node — a cordoned node during a kured reboot is normal and clears) or an image pull failed.
 
 ## When to escalate or stop
@@ -270,6 +283,42 @@ disappears with the pod on the next rollout.)
 Finally **delete the `tunnel-canary` CNAME** in the dashboard and confirm it is gone:
 `dig +short tunnel-canary.home.keithjackson.dev @1.1.1.1` returns nothing.
 
+## Rotating the tunnel credential
+
+Do this whenever the credentials JSON (`TunnelSecret`) or `cert.pem` may have been exposed — a
+transcript, a log, a screen share. A tunnel's secret cannot be changed in place from this
+workflow, so rotation is **a new tunnel**: the old credential stays valid until the old tunnel
+is deleted, which is why the last step is not optional.
+
+1. **Create the new tunnel** (*Enrolling*, step 2's `cf` helper; `cf tunnel login` again if
+   `cert.pem` is not to hand). Use a NEW name — the old one is still taken:
+   ```
+   cf tunnel list                       # note the OLD tunnel's id and name
+   cf tunnel create --credentials-file /root/.cloudflared/tunnel.json home-k3s-2
+   ```
+2. **Swap the UUID** in your own worktree, on a new branch (CLAUDE.md §0):
+   ```
+   OLD=$(sed -n 's/^tunnel: //p' platform/cloudflared/config.yaml)
+   sed -i "s/^tunnel: ${OLD}$/tunnel: <NEW UUID>/" platform/cloudflared/config.yaml
+   ```
+3. **Swap the encrypted credentials** with *Enrolling* step 4 — the same `sops set`, then the
+   same `ok`-only verify, which now checks the JSON's `TunnelID` against the NEW UUID. Never
+   `sops -d` to the terminal.
+4. **Merge** — gate, PR, `/approve-override` by the operator (it touches `**/*.sops.yaml`), merge.
+   Flux rolls the Deployment because the content-hashed ConfigMap changed.
+5. **Verify** with *Enrolling* step 6: both replicas Ready, `Registered tunnel connection` in
+   each replica's log, `cf tunnel info home-k3s-2` lists two connectors, and
+   `cf tunnel info <old name>` lists **none**.
+6. **Only then delete the old tunnel**, which revokes the exposed credential:
+   ```
+   cf tunnel cleanup <old name>   # drops any stale connector records first
+   cf tunnel delete <old name>
+   cf tunnel list                 # the old tunnel is gone
+   ```
+   After the Phase 2 DNS flip, records point at `<UUID>.cfargotunnel.com`: confirm external-dns
+   has repointed every record to the NEW UUID before deleting, or those hostnames go dark.
+   Then replace `tunnel.json`/`cert.pem` in the password manager and delete them from disk.
+
 ## Rollback
 
 - **Phase 1 (no DNS on the tunnel):** revert the PR. Flux prunes the `cloudflared` namespace and