Anso f03c9dc7b6 fix(webhooks): address Codex review of PR #1177 (#1181) ...

* fix(webhooks): close HMAC timing oracle on trigger reject paths

The trigger handler in PR #1177 returned a uniform 404 for every
unauthenticated rejection, but only the wrong-signature path computed
an HMAC over the request body. The other reject paths (unknown id,
disabled webhook, non-paid tier, missing X-Webhook-Signature header,
missing rawBody) short-circuited before any HMAC work. Repeated
near-rate-limit probes with a large attacker-controlled body could
distinguish a valid-and-enabled paid webhook id from the other reject
cases through response latency.

WebhookService.validateSignature is now constant-time over every input
shape: it always runs crypto.createHmac and crypto.timingSafeEqual
against fixed-length 32-byte buffers regardless of whether the
signature is missing, has the wrong prefix, is malformed hex, or is
the wrong length. The trigger handler calls it unconditionally before
any reject branch fires, using a stable per-process decoy secret
(WebhookService.getDecoySecret) when the webhook does not exist and an
empty buffer when the request has no body. Response timing now depends
only on the size of the request body, which the attacker already
controls and which reveals nothing webhook-specific.

Six new tests pin the behaviour: validateSignature is observed firing
on the unknown-id and missing-signature paths through a spy assertion,
and four direct-call tests confirm validateSignature returns false
without throwing for empty, wrong-prefix, malformed-hex, and
wrong-length signatures.

* fix(safe-log): redact Basic auth and lowercase Windows drive letters

The redactSensitiveText helper now covers two cases the prior chain
missed:

* Authorization: Basic <base64> previously left the base64 payload
  intact. The existing key/value regex caught only the literal word
  Basic before stopping at the space. A new Basic\s+[A-Za-z0-9+/=]+
  replacement runs before the key/value regex so the credential is
  scrubbed first.
* Windows homedir paths like c:\Users\<user>\... with a lowercase
  drive letter previously slipped through because the regex required
  [A-Z]. Changed to [A-Za-z] so both letter cases are covered.

Two new tests pin both fixes.

* docs(webhooks): document 429, fix shared schema, comply with D27/D31

* Trigger endpoint declares the 429 response that webhookTriggerLimiter
  can return (500 requests per minute per source IP); both
  docs/openapi.yaml and the response table in docs/features/webhooks.mdx
  carry the new row, and a new troubleshooting accordion explains the
  shared-NAT scenario.
* Shared Webhook schema in docs/openapi.yaml extends the action enum to
  include git-pull and documents the node_id property. The GET list
  endpoint returns these fields; the prior schema would have failed
  validation for any git-pull row.
* docs/features/webhooks.mdx:7 rewritten from a customer-side role
  enumeration ("non-admins on a paid tier can view the list but cannot
  manage it") to a single requirement statement ("Webhooks require a
  Skipper or Admiral license. Managing webhooks is admin-only.") per
  CLAUDE.md D27/D31; the prior phrasing was customer-side fence-spec.
* Two em dashes in webhook description strings I had touched in the
  prior OpenAPI sync commit replaced with semicolons per D18.

2026-05-23 16:03:48 -04:00

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