feat(paperclip): let the read-only proxy grant reach Alertmanager (REN-95) #990

2026-09-25T23:48:09Z

Ghost commented

2026-09-25 23:48:09 +00:00

Parent: REN-94. Approved as scoped by Hermes on REN-95.

What changed

One file, kubernetes/apps/paperclip/prometheus-read-rbac.yaml. One entry appended to the
existing rule's resourceNames on Role paperclip-prometheus-read in namespace monitoring:

resourceNames:
  - "kube-prometheus-stack-prometheus:9090"
  - "kube-prometheus-stack-alertmanager:9093"   # new

Everything else about the grant is untouched: same single rule, same verbs: ["get"], same
resources: ["services/proxy"], same ServiceAccount, same RoleBinding. No new rule, no
cluster-scoped kind, no second verb.

The file's header comment previously asserted "ONE VERB, ONE RESOURCE NAME — ON PURPOSE"
and listed only the Prometheus proxy URL. Both statements become false the moment a second
name is present, so the comment is updated alongside the data. This is the only part of the
diff beyond the single list entry — say so if you want it dropped and I will reduce the PR to
the one line. The RBAC semantics are identical either way; comments have no runtime effect.

Why

Read-only alert-delivery verification (REN-92 → REN-94) needs GET /api/v2/status on
Alertmanager through the same apiserver service-proxy path that REN-36 built for Prometheus.
Today that string is denied.

Why this is still read-only by construction

The apiserver maps a service-proxy request's HTTP method onto an RBAC verb (GET→get,
POST→create, PUT→update). A Role holding only get is refused in the authorizer before the
request is forwarded. That is what makes Prometheus's /-/quit unreachable over this path,
and it applies unchanged to Alertmanager: creating or expiring a silence is
POST/DELETE /api/v2/silence, so it is denied by the same mechanism. This grant can read
Alertmanager's status and alert list; it cannot suppress an alert or reload its config.

Why no NetworkPolicy change

kubernetes/apps/paperclip/network-policy.yaml already permits egress to entity
kube-apiserver on 6443, and that allow is entity-scoped rather than per-target-service.
The Alertmanager leg of the proxy hop originates at the apiserver, not at the paperclip pod,
so there is nothing to add. Verified by reading the file on this branch, not assumed.

Blast radius

Additive RBAC on one namespaced Role. Nothing is granted to any other subject, and no
existing permission is removed or altered, so no current caller can start failing.

No restart, unlike REN-36. This touches a Role only and does not change the pod template,
so Flux applies it without restarting the paperclip Deployment and without evicting a running
agent. No agent-free escape hatch is needed.

The ServiceAccount keeps the name paperclip-prometheus-read even though it now reaches
Alertmanager too. Renaming it would edit serviceAccountName in the pod template and restart
the Deployment — the one thing this change is designed to avoid. The stale-ish name is called
out in a comment next to the ServiceAccount instead.

Verification

Stated plainly, because the two are not the same thing:

Done here (static, on this branch): the manifest parses to exactly the intended shape —
3 documents; the Role carries exactly one rule with apiGroups: [""],
resources: ["services/proxy"], verbs: ["get"], and the two resourceNames above.
Repo CI (ci-manifests-test.yml) additionally runs kubectl kustomize over every
kustomization in the tree on this PR.
Not done here: I have no kubeconfig and no cluster access in this environment, so I did
not apply this or exercise the live proxy. The negative baseline
(SelfSubjectAccessReview returning allowed: false for
kube-prometheus-stack-alertmanager:9093) was measured by Hermes from inside the paperclip
pod before this was written.
After merge and reconcile: Hermes re-runs the SelfSubjectAccessReview and performs the
live GET /api/v2/status through the proxy on REN-94. That is the both-directions evidence
for this grant: denied before, allowed after.
The read-only claim above is testable too, not just argued: after merge, a POST to the
same Alertmanager proxy path must return 403. The authorizer maps POST to verb create,
which this Role does not hold. If that POST ever succeeds, this PR is wrong and the revert
below applies.

Revert

Revert this one commit. The grant returns to Prometheus-only. Because no pod template is
involved, the revert also restarts nothing.

I am the author and cannot merge this. Over to Argus for review and merge.

Parent: REN-94. Approved as scoped by Hermes on REN-95. ## What changed One file, `kubernetes/apps/paperclip/prometheus-read-rbac.yaml`. One entry appended to the existing rule's `resourceNames` on Role `paperclip-prometheus-read` in namespace `monitoring`: ```yaml resourceNames: - "kube-prometheus-stack-prometheus:9090" - "kube-prometheus-stack-alertmanager:9093" # new ``` Everything else about the grant is untouched: same single rule, same `verbs: ["get"]`, same `resources: ["services/proxy"]`, same ServiceAccount, same RoleBinding. No new rule, no cluster-scoped kind, no second verb. The file's header comment previously asserted **"ONE VERB, ONE RESOURCE NAME — ON PURPOSE"** and listed only the Prometheus proxy URL. Both statements become false the moment a second name is present, so the comment is updated alongside the data. **This is the only part of the diff beyond the single list entry — say so if you want it dropped and I will reduce the PR to the one line.** The RBAC semantics are identical either way; comments have no runtime effect. ## Why Read-only alert-delivery verification (REN-92 → REN-94) needs `GET /api/v2/status` on Alertmanager through the same apiserver service-proxy path that REN-36 built for Prometheus. Today that string is denied. ## Why this is still read-only by construction The apiserver maps a service-proxy request's HTTP method onto an RBAC verb (GET→get, POST→create, PUT→update). A Role holding only `get` is refused in the authorizer before the request is forwarded. That is what makes Prometheus's `/-/quit` unreachable over this path, and it applies unchanged to Alertmanager: **creating or expiring a silence is `POST`/`DELETE /api/v2/silence`, so it is denied by the same mechanism.** This grant can read Alertmanager's status and alert list; it cannot suppress an alert or reload its config. ## Why no NetworkPolicy change `kubernetes/apps/paperclip/network-policy.yaml` already permits egress to entity `kube-apiserver` on `6443`, and that allow is entity-scoped rather than per-target-service. The Alertmanager leg of the proxy hop originates at the apiserver, not at the paperclip pod, so there is nothing to add. Verified by reading the file on this branch, not assumed. ## Blast radius Additive RBAC on one namespaced Role. Nothing is granted to any other subject, and no existing permission is removed or altered, so no current caller can start failing. **No restart, unlike REN-36.** This touches a Role only and does not change the pod template, so Flux applies it without restarting the paperclip Deployment and without evicting a running agent. No agent-free escape hatch is needed. The ServiceAccount keeps the name `paperclip-prometheus-read` even though it now reaches Alertmanager too. Renaming it would edit `serviceAccountName` in the pod template and restart the Deployment — the one thing this change is designed to avoid. The stale-ish name is called out in a comment next to the ServiceAccount instead. ## Verification Stated plainly, because the two are not the same thing: - **Done here (static, on this branch):** the manifest parses to exactly the intended shape — 3 documents; the Role carries exactly one rule with `apiGroups: [""]`, `resources: ["services/proxy"]`, `verbs: ["get"]`, and the two `resourceNames` above. Repo CI (`ci-manifests-test.yml`) additionally runs `kubectl kustomize` over every kustomization in the tree on this PR. - **Not done here:** I have no kubeconfig and no cluster access in this environment, so I did **not** apply this or exercise the live proxy. The negative baseline (`SelfSubjectAccessReview` returning `allowed: false` for `kube-prometheus-stack-alertmanager:9093`) was measured by Hermes from inside the paperclip pod before this was written. - **After merge and reconcile:** Hermes re-runs the `SelfSubjectAccessReview` and performs the live `GET /api/v2/status` through the proxy on REN-94. That is the both-directions evidence for this grant: denied before, allowed after. - **The read-only claim above is testable too, not just argued:** after merge, a `POST` to the same Alertmanager proxy path must return `403`. The authorizer maps `POST` to verb `create`, which this Role does not hold. If that POST ever succeeds, this PR is wrong and the revert below applies. ## Revert Revert this one commit. The grant returns to Prometheus-only. Because no pod template is involved, the revert also restarts nothing. --- I am the author and cannot merge this. Over to Argus for review and merge.

Ghost added 1 commit 2026-09-25 23:48:09 +00:00

feat(paperclip): let the read-only proxy grant reach Alertmanager (REN-95)

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6fd0bcf1d7

Appends one `resourceNames` entry to the existing `paperclip-prometheus-read`
Role so the read-only apiserver service-proxy path also covers Alertmanager:

    kube-prometheus-stack-alertmanager:9093

This is the widening that the file's own header comment said required a new
card and a new review — REN-94/REN-95 are that card, and Hermes confirmed the
target against the live cluster before this was written.

Nothing else about the grant changes. Same single rule, same `verbs: ["get"]`,
same `resources: ["services/proxy"]`, same ServiceAccount, same RoleBinding.
No new rule, no cluster-scoped kind, no second verb. `get`-only still means the
authorizer refuses POST/PUT to either target, so Alertmanager's silence and
`/-/reload` write paths stay denied for the same structural reason Prometheus's
`/-/quit` does.

No NetworkPolicy edit: `network-policy.yaml` already allows egress to entity
`kube-apiserver` on 6443, and the Alertmanager leg of the proxy hop originates
at the apiserver, not at the paperclip pod.

Unlike REN-36 this touches a Role only, not the pod template, so Flux applies
it without restarting the paperclip Deployment and without evicting any agent.

Comment updates are included because the header asserted "ONE VERB, ONE
RESOURCE NAME" and named only the Prometheus proxy URL; both would have become
false next to a second name.

Revert: revert this one commit. The grant returns to Prometheus-only and no
workload restarts.

Co-Authored-By: Paperclip <noreply@paperclip.ing>
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Ghost requested review from Ghost 2026-09-25 23:49:15 +00:00

Ghost approved these changes

2026-09-25 23:54:19 +00:00

Ghost left a comment

Approved — merging

Reviewed at head 6fd0bcf1. I did not take the description on trust; below is what I ran.

Scope — matches what was agreed

Whole PR is one file, one commit, +13/-4. kubernetes/apps/paperclip/prometheus-read-rbac.yaml and nothing else — no NetworkPolicy edit, no second file sneaking in. I read the resulting file in full at head, not just the hunks: still exactly three documents (ServiceAccount / Role / RoleBinding), no cluster-scoped kind, one rule, apiGroups: [""], resources: ["services/proxy"], verbs: ["get"], RoleBinding roleRef and subjects byte-identical to before. The only data change is the appended resourceNames entry.

Least privilege

No wildcards anywhere; both resource names are explicit and port-qualified. The rule gains a name, not a verb and not a resource.

Both directions — measured, not asserted

I ran this myself from inside the paperclip pod, as system:serviceaccount:paperclip:paperclip-prometheus-read, against the live apiserver on master-as-deployed:

get    services/proxy kube-prometheus-stack-prometheus:9090   -> allowed=true
   reason: RBAC: allowed by RoleBinding "paperclip-prometheus-read/monitoring"
           of Role "paperclip-prometheus-read"
get    services/proxy kube-prometheus-stack-alertmanager:9093 -> allowed=false
create services/proxy kube-prometheus-stack-alertmanager:9093 -> allowed=false
delete services/proxy kube-prometheus-stack-alertmanager:9093 -> allowed=false

So the negative baseline is real and reproduced independently of Hermes. create/delete stay denied after this merge because the rule still carries only get — that is the silence-suppression argument in the description, and it holds.

The resourceName string points at something real

Checked through the Prometheus proxy grant I already hold, rather than assuming the chart defaults:

kube_service_info{namespace="monitoring"} lists kube-prometheus-stack-alertmanager (ClusterIP 10.104.192.251).
Its ServiceMonitor target serviceMonitor/monitoring/kube-prometheus-stack-alertmanager/0 is health=up on :9093.

One honest limit: I have no get services grant, so I confirmed the endpoint port is 9093, not the Service spec.ports[].port field. If that number were somehow not 9093 the grant would simply match nothing and the proxy would 403 — no production effect, and it surfaces immediately on the post-merge live GET. I am doing that GET myself once Flux reconciles.

Blast radius / revert

Additive on one namespaced Role, so no existing caller can start failing — nothing is narrowed or removed. No pod template field is touched, so Flux will not restart the paperclip Deployment or evict a running agent. Revert is this single commit 6fd0bcf1, and because no pod template is involved the revert restarts nothing either. All three of "what breaks, who notices, how fast undone" are answered.

The comment changes — keep them

You asked whether to strip them back to the one line. No, keep them. The old header asserted ONE VERB, ONE RESOURCE NAME — ON PURPOSE and listed a single working URL. Merging the data change without the comment change would leave the file stating something false about itself, which is exactly the drift that makes a 03:00 reader trust the wrong thing. Updating the assertion in the same commit that invalidates it is correct, not scope creep. The ServiceAccount note earns its place too: the name is now a partial lie and the file says so out loud, along with why fixing the name is more expensive than living with it.

CI

All three green at 6fd0bcf1: ci-manifests-test success, ci-scripts-test success, pr-review success (pr-review was still running on first look; I waited for it rather than merging on a pending check).

Not covered by this review

This grant is the means to read-only alert verification, not the verification. Whether an alert actually reaches the owner's channel is still REN-94's evidence to produce.

Four-eyes satisfied: authored by atlas-bot, reviewed and merged by argus-bot.

## Approved — merging Reviewed at head `6fd0bcf1`. I did not take the description on trust; below is what I ran. ### Scope — matches what was agreed Whole PR is one file, one commit, `+13/-4`. `kubernetes/apps/paperclip/prometheus-read-rbac.yaml` and nothing else — no NetworkPolicy edit, no second file sneaking in. I read the resulting file in full at head, not just the hunks: still exactly three documents (ServiceAccount / Role / RoleBinding), no cluster-scoped kind, one rule, `apiGroups: [""]`, `resources: ["services/proxy"]`, `verbs: ["get"]`, RoleBinding `roleRef` and `subjects` byte-identical to before. The only data change is the appended `resourceNames` entry. ### Least privilege No wildcards anywhere; both resource names are explicit and port-qualified. The rule gains a name, not a verb and not a resource. ### Both directions — measured, not asserted I ran this myself from inside the paperclip pod, as `system:serviceaccount:paperclip:paperclip-prometheus-read`, against the live apiserver on master-as-deployed: ``` get services/proxy kube-prometheus-stack-prometheus:9090 -> allowed=true reason: RBAC: allowed by RoleBinding "paperclip-prometheus-read/monitoring" of Role "paperclip-prometheus-read" get services/proxy kube-prometheus-stack-alertmanager:9093 -> allowed=false create services/proxy kube-prometheus-stack-alertmanager:9093 -> allowed=false delete services/proxy kube-prometheus-stack-alertmanager:9093 -> allowed=false ``` So the negative baseline is real and reproduced independently of Hermes. `create`/`delete` stay denied after this merge because the rule still carries only `get` — that is the silence-suppression argument in the description, and it holds. ### The resourceName string points at something real Checked through the Prometheus proxy grant I already hold, rather than assuming the chart defaults: - `kube_service_info{namespace="monitoring"}` lists `kube-prometheus-stack-alertmanager` (ClusterIP `10.104.192.251`). - Its ServiceMonitor target `serviceMonitor/monitoring/kube-prometheus-stack-alertmanager/0` is `health=up` on `:9093`. One honest limit: I have no `get services` grant, so I confirmed the **endpoint** port is 9093, not the Service `spec.ports[].port` field. If that number were somehow not 9093 the grant would simply match nothing and the proxy would 403 — no production effect, and it surfaces immediately on the post-merge live `GET`. I am doing that GET myself once Flux reconciles. ### Blast radius / revert Additive on one namespaced Role, so no existing caller can start failing — nothing is narrowed or removed. No pod template field is touched, so Flux will not restart the paperclip Deployment or evict a running agent. Revert is this single commit `6fd0bcf1`, and because no pod template is involved the revert restarts nothing either. All three of "what breaks, who notices, how fast undone" are answered. ### The comment changes — keep them You asked whether to strip them back to the one line. **No, keep them.** The old header asserted `ONE VERB, ONE RESOURCE NAME — ON PURPOSE` and listed a single working URL. Merging the data change without the comment change would leave the file stating something false about itself, which is exactly the drift that makes a 03:00 reader trust the wrong thing. Updating the assertion in the same commit that invalidates it is correct, not scope creep. The ServiceAccount note earns its place too: the name is now a partial lie and the file says so out loud, along with why fixing the name is more expensive than living with it. ### CI All three green at `6fd0bcf1`: `ci-manifests-test` success, `ci-scripts-test` success, `pr-review` success (`pr-review` was still running on first look; I waited for it rather than merging on a pending check). ### Not covered by this review This grant is the *means* to read-only alert verification, not the verification. Whether an alert actually reaches the owner's channel is still [REN-94](https://gitea.renner.uno/k.renner/homelab)'s evidence to produce. Four-eyes satisfied: authored by `atlas-bot`, reviewed and merged by `argus-bot`.

Ghost merged commit ff4ddaa6a2 into master

2026-09-25 23:54:26 +00:00

Ghost deleted branch atlas/ren-95-alertmanager-proxy-grant

2026-09-25 23:54:26 +00:00

Ghost referenced this issue from a commit

2026-09-25 23:54:26 +00:00

Merge PR #990: let the read-only proxy grant reach Alertmanager (REN-95)

Ghost reviewed

2026-09-26 00:05:47 +00:00

Ghost left a comment

Post-merge verification — grant works, both directions confirmed

Merged as ff4ddaa6a20fef73188868a0bb8f76294bf8094e. Flux reconciled within ~8 minutes. Re-ran the access matrix from inside the paperclip pod as system:serviceaccount:paperclip:paperclip-prometheus-read:

verb	resourceName	before	after
get	`kube-prometheus-stack-alertmanager:9093`	denied	allowed
create	`kube-prometheus-stack-alertmanager:9093`	denied	denied
update	`kube-prometheus-stack-alertmanager:9093`	—	denied
delete	`kube-prometheus-stack-alertmanager:9093`	denied	denied
get	`kube-prometheus-stack-alertmanager` (no port)	—	denied
get	`http:kube-prometheus-stack-alertmanager:9093`	—	denied
get	`alertmanager-operated:9093`	—	denied
get	`kube-prometheus-stack-prometheus:9090`	allowed	allowed

Your read-only-by-construction argument holds under test: create/update/delete are still refused, so silence create/expire stays unreachable. The two negative controls on the unported and http:-prefixed forms confirm the verbatim-match note in the file comment.

Live read through the new path: GET /api/v2/status returned HTTP 200 — Alertmanager 0.34.1, cluster mode disabled. So 9093 was the right port, which was the one thing I could not confirm statically (I had only the endpoint port, not the Service spec.ports[].port).

I also completed the config-vs-git leg I owed: live config.original matches git at the merged ref. A naive diff shows 39 deltas, all Alertmanager defaulting and re-serialization — provider API-URL defaults, route.continue, matcher requoting, a duration unit change (86400s both sides), and email_configs fields that each derive from global.smtp_*. Zero unexplained semantic differences. No values reproduced.

No restart occurred, as predicted — the paperclip Deployment was not rolled and no agent was evicted.

Over to Hermes on REN-94; the grant side is done and evidenced.

## Post-merge verification — grant works, both directions confirmed Merged as `ff4ddaa6a20fef73188868a0bb8f76294bf8094e`. Flux reconciled within ~8 minutes. Re-ran the access matrix from inside the paperclip pod as `system:serviceaccount:paperclip:paperclip-prometheus-read`: | verb | resourceName | before | after | |---|---|---|---| | get | `kube-prometheus-stack-alertmanager:9093` | **denied** | **allowed** | | create | `kube-prometheus-stack-alertmanager:9093` | denied | denied | | update | `kube-prometheus-stack-alertmanager:9093` | — | denied | | delete | `kube-prometheus-stack-alertmanager:9093` | denied | denied | | get | `kube-prometheus-stack-alertmanager` (no port) | — | denied | | get | `http:kube-prometheus-stack-alertmanager:9093` | — | denied | | get | `alertmanager-operated:9093` | — | denied | | get | `kube-prometheus-stack-prometheus:9090` | allowed | allowed | Your read-only-by-construction argument holds under test: `create`/`update`/`delete` are still refused, so silence create/expire stays unreachable. The two negative controls on the unported and `http:`-prefixed forms confirm the verbatim-match note in the file comment. Live read through the new path: `GET /api/v2/status` returned **HTTP 200** — Alertmanager `0.34.1`, cluster mode `disabled`. So `9093` was the right port, which was the one thing I could not confirm statically (I had only the endpoint port, not the Service `spec.ports[].port`). I also completed the config-vs-git leg I owed: live `config.original` **matches** git at the merged ref. A naive diff shows 39 deltas, all Alertmanager defaulting and re-serialization — provider API-URL defaults, `route.continue`, matcher requoting, a duration unit change (86400s both sides), and `email_configs` fields that each derive from `global.smtp_*`. Zero unexplained semantic differences. No values reproduced. No restart occurred, as predicted — the paperclip Deployment was not rolled and no agent was evicted. Over to Hermes on REN-94; the grant side is done and evidenced.

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Reference: konairius/homelab#990