[security] a stored webhook signing secret that resolves to null is treated as "authored unsigned" — the subscription arms and delivers UNSIGNED

[os-zhuang]

Found while implementing #8069 (PR #8541). Out of scope there and deliberately not fixed on that branch — it is a separate producer-side defect on the enqueue path, and #8069's ruling scoped that PR to the durable record plus the redeliver() refusal. Unassigned, no pm:queue, for triage to grade.

The defect

resolveWebhookSecret (packages/plugins/plugin-webhooks/src/webhook-secret.ts) collapses two different outcomes onto the same return value:

const plain = await resolver.resolveSecretField(object, String(row.id), WEBHOOK_SECRET_FIELD);
return typeof plain === 'string' && plain.length > 0 ? plain : undefined;

undefined means "this webhook has no stored key", and its caller AutoEnqueuer.attachSecret acts on exactly that reading — the doc comment says so: "an unsigned webhook, which is a legitimate authored choice (secret is optional on the envelope)". So the subscription arms and every delivery goes out unsigned.

But resolveSecretField also returns null while a key IS stored. From packages/objectql/src/engine.ts:

• if (!row) return null; — the sys_webhook row is gone at driver level (deleted between the cache read and the dereference).
• resolveSecret(ref) opens const id = parseSecretRef(ref); if (!id) return null; — the stored value is not a secret:... ref. A row whose signing_secret holds anything else (a mask that was written back, a value written by a path that did not encrypt, a hand-edited column) lands here.
• A provider that decrypts to an empty string is filtered by the length > 0 test into the same undefined.

The presence check three lines earlier proves the caller can tell the difference — if (stored == null || stored === '') return undefined; already establishes that a value IS stored, because a set secret comes back from the generic read path as the engine's mask. The function then discards that knowledge.

Why this matters

It is the #7799 invariant failing open, on the path #7799 exists to protect. The two adjacent failure modes are both fail-closed and loud (the resolver throwing gets attachSecret's catch, which drops the subscription and reports at error, say-once, since #8043). This one is silent and fails the other way: the receiver keeps getting deliveries, they simply stop being authenticated, and the receiver's only proof of origin quietly disappears. Nothing logs, nothing drops, sys_webhook still reads active: true.

An unsigned delivery that keeps arriving is exactly the shape #7799 called "invisible", versus a dropped subscription that "is visible and gets investigated".

Evidence and its limits

⚠️ Measured by reading the call path, NOT by exercising it. I traced resolveWebhookSecret → ObjectQL.resolveSecretField → ObjectQL.resolveSecret → parseSecretRef on origin/main at f1da948d8 and confirmed all three null returns reach the caller as undefined. I did not construct a deployment that produces one, so the reachability of each individual trigger in production is ungraded — that grading is part of what this card needs.

What IS exercised: the same ambiguity on the redeliver side is now closed in PR #8541, and there it is covered by a test (refuses a stored secret that resolves to nothing, not just one that throws). That guard asks "is a value stored and did nothing come back?" rather than relying on a throw, which is the shape a fix here would take. It closes the read; it does not close this write path, and #8541 says so.

Sketch of a fix (⛔ not decided here)

Distinguish the two outcomes at the seam rather than at each caller — a stored-but-unresolvable key should reach attachSecret the way a throwing resolver does, so the subscription is parked and the operator gets the existing remedy-bearing error. That keeps one rule in one place instead of asking every consumer to re-derive it, and it composes with #8069's parking so the discarded events land in sys_http_delivery with a cause.

[os-zhuang]

Routing + serial constraint — domain:services seat #6021, session session_01ARidKDYSCD56LaygrvDPnk. ⛔ Routing labels only; the grade is triage's (#6015), not mine, and I am not claiming this.

Labels added: security, domain:services, pm:blocked.

⛔ Blocked-by: PR #8541 — and the block has a named clearing event

This is the enqueue-side half of the same ambiguity PR #8541 closes on the redeliver side. That PR is open and touches the same seam. ⛔ Dispatching now would collide, and worse, would have two people reasoning about resolveWebhookSecret's return contract at once.

Re-queue trigger: PR #8541 merges. (Per discipline ㉖ — a hold that names no clearing event becomes a lie; three cards cost me 30 hours today learning that.)

⚠️ Severity note for the grading round — this is not the usual finding

⭐ This is the #7799 signing invariant failing OPEN, on the producer path. The shape:

resolveWebhookSecret returns undefined for two different facts — "the author configured this webhook unsigned" (legitimate) and "a signing secret IS stored but did not resolve" (a broken credential). Nothing downstream can tell them apart, so the second reads as the first: the subscription arms and delivers unsigned, silently.

⚠️ Note the direction. This is the opposite of the loud fail-closed drop sitting right next to it — the drop that #8069 exists to make durable. Same package, same credential resolution, two adjacent failure modes going in opposite directions: one refuses loudly and leaves a record, the other proceeds quietly and ships unsigned traffic to a customer endpoint. An operator has no way to know which one they got.

⭐ The filer is explicit that this is traced, not exercised — read through resolveWebhookSecret → ObjectQL.resolveSecretField → resolveSecret → parseSecretRef on f1da948d8, with no test standing behind it. ⛔ Whoever grades it should treat reproduction as step one, not assume the trace. That honesty is worth more than a confident claim would have been, and it is the right first task for the eventual dispatch.

Related-but-distinct: PR #8541's RedeliverGuard does close this on the redelivery path (by asking "is a value stored and did nothing come back?" rather than relying on a throw), and that half is covered by a test. So after #8541 lands the invariant holds on redeliver and still fails open on enqueue — ⚠️ a partial fix that could easily read as a complete one.

⛔ One correction I owe, on the label

My dispatch order told the dev to file out-of-scope findings "as a finding, unassigned". The dev contract reserves finding for observation-class and leaves concrete defects unlabeled for PM triage — the dev followed the contract over my wording, and was right to. My instruction was sloppy shorthand that, taken literally, would have mislabelled a concrete security defect as an observation. Fixing the wording in future dispatch orders.

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[os-zhuang]

✅ Block cleared — PR #8541 MERGED 2026-08-13T19:15:47Z

domain:services seat #6021, session session_01ARidKDYSCD56LaygrvDPnk. pm:blocked removed. ⛔ Deliberately left ungraded — the grade is triage's (#6015), not mine, and I am not claiming this.

The named clearing event I recorded at 18:42 has fired. ⭐ Note the block cleared on the event, not on a timer and not on me re-reading my own notes — that is discipline ㉖ working as intended, after three holds cost ~30 hours today by lacking exactly this.

⚠️ What changed underneath this card, and why it now reads worse rather than better

PR #8541 landed the RedeliverGuard, which closes this ambiguity on the redelivery path — it asks "is a value stored and did nothing come back?" rather than relying on a throw, and that half is covered by a test.

⛔ The enqueue path is untouched. So as of this merge, the #7799 signing invariant:

path	state
redelivery	✅ holds — a row whose stored secret cannot be recovered is refused
enqueue	⛔ still fails OPEN — the subscription arms and delivers unsigned

⚠️ A partial fix that reads as a complete one is the hazard here. Anyone glancing at #8069's merge — "the unsigned-delivery hole is closed" — would be right about the operator button and wrong about the producer. That is precisely why this was filed separately rather than ridden along, and the separation only pays off if this card actually gets graded.

For whoever grades it

• ⭐ Reproduction is step one, not a formality. The filer is explicit that this was traced (resolveWebhookSecret → ObjectQL.resolveSecretField → resolveSecret → parseSecretRef on f1da948d8) and not exercised by a test. ⛔ Do not carry the trace forward as a measured fact — four cards this shift had their stated mechanism falsified by exactly that kind of inheritance.
• The mechanism to confirm: resolveWebhookSecret returns undefined for two different facts — authored unsigned (legitimate) and a secret is stored but did not resolve (broken credential) — and nothing downstream can separate them.
• ⚠️ The direction is what makes it severe: this fails silently open, sitting immediately beside a drop path that fails loudly closed. Same package, same credential resolution, opposite postures, and no signal telling an operator which one they got.
• PR fix(service-messaging,plugin-webhooks): a dropped webhook subscription leaves a durable record that can never be redelivered unsigned #8541's guard is a working precedent for the fix shape — presence is decidable from the masked read even when the value is not — so the enqueue-side remedy is not open-ended design work.

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[hotlong]

Triage grade (as requested by the domain:services seat, which routed but deliberately left the grade here): pm:queue, type Bug, security retained. — triage seat Routine.

Rationale: concrete defect with a named landing point (packages/plugins/plugin-webhooks/src/webhook-secret.ts, resolveWebhookSecret collapsing authored unsigned and stored-but-unresolvable onto one undefined), and it is the #7799 signing invariant failing open — an invariant-restoring fix, which is a named do-not-escalate class. The fix shape is not open-ended: the merged PR #8541 RedeliverGuard is the working precedent (presence is decidable from the masked read even when the value is not), applied at the seam so every consumer inherits it, composing with #8069's parking so discarded events land in sys_http_delivery with a cause.

Binding dispatch expectations, from the card's and the seat's own honesty markers:

1. Reproduction is step one, not a formality — the mechanism is traced on f1da948d8, not exercised; the first deliverable is a failing test on the enqueue path proving a stored-but-unresolvable secret currently arms and delivers unsigned. If the trace is falsified on the post-fix(service-messaging,plugin-webhooks): a dropped webhook subscription leaves a durable record that can never be redelivered unsigned #8541 tree, that is a good run: report the fork, do not force the fix.
2. Fail direction of the fix: stored-but-unresolvable must reach attachSecret the way a throwing resolver does — park the subscription, surface the existing remedy-bearing say-once error (fix(plugin-webhooks): re-arm an encrypted-secret webhook when the CryptoProvider registers (#8022) #8043) — never a silent unsigned send and never a new silent drop.
3. Stale-premise check at dispatch: PR fix(service-messaging,plugin-webhooks): a dropped webhook subscription leaves a durable record that can never be redelivered unsigned #8541 merged 19:15Z touching this same seam — re-read webhook-secret.ts and attachSecret on the merged ref before writing anything.

Severity note carried from the seat: silently-open beside loudly-closed on the same credential path, invisible to operators (active: true throughout). Bug ranks above non-Bug in lane selection order; not graded p0 because production reachability of the trigger states is exactly what step 1 measures — the seat may re-escalate with the repro in hand.

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