Phase 3 audits returned one BLOCKER and one SPEC-VIOLATION plus two
should-fix items; all cleared in-phase per the no-rot rule.
BLOCKER — template.html double-escaped JS-context interpolations.
Go's html/template auto-escapes {{.X}} in <script> string-literal
position via its built-in jsstrescaper. Piping through the explicit
`| js` (JSEscaper) re-ran the escaper, producing `\\u003D` /
`\\u0026` on the wire (double backslash). JS parses `\\u003D` as a
literal backslash followed by "u003D" text rather than `=`, so any
realistic destination URL — e.g.
https://news.example.com/article?utm_source=newsletter&utm_medium=email
— was corrupted into
https://news.example.com/article?utm_source=newsletter&utm_medium=email
before being passed to window.location.replace. The unit tests
previously missed it because every test destination was an
escape-free string. Fix: drop `| js` from both JS-context actions
in template.html; the contextual auto-escaper alone produces single-
backslash `=` which JS correctly decodes. Spec §9.2 line 1031
and 1038 (and the explanatory paragraph 1045) are factually wrong
about `| js` being a custom template func — it is `JSEscaper`, and
adding it on top of the built-in contextual JS string escaper is
pure double-escape harm. Spec docs (local-only, not committed)
amended accordingly. Added
TestTrigger_DestinationRoundtripsThroughJSStringDecode as a
regression guard against re-introducing the pipeline.
SPEC-VIOLATION — nil-token Trigger returned `404 + "Not Found"`,
breaking spec §8.5 ("token not found | 200, ... deliberately do NOT
404") and §8.5 line 964 ("/c/* endpoints never return JSON errors").
A 404 on a non-existent token ID lets scanners enumerate which IDs
are real. Fix: nil-token branch now renders the same template with a
benign decoy destination ("/") and returns 200 + text/html with the
full CSP override and cache headers. Response is byte-shape
indistinguishable from a valid-token response except for the
destination URL embedded in the script. Added
TestTrigger_TokenNotFound_HasSameResponseShapeAsValidToken to
assert the indistinguishability invariant. The `(nil event, &resp,
nil error)` return shape from the handoff anti-relitigation is
preserved.
SHOULD-FIX S1 — extractDestination now allowlists `http://` and
`https://` (case-insensitive) and returns the new
ErrInvalidDestinationScheme sentinel otherwise. The noscript
meta-refresh sits in an HTML-attribute context where html/template
does NOT recognize `url=...` as a URL context, so `javascript:`,
`data:`, `file:`, `vbscript:` and scheme-relative `//example.com`
would otherwise render verbatim and follow on JS-disabled clients.
Phase 9's `validate:"url"` on input is necessary but not sufficient
(the validator's `url` tag accepts any scheme). Added
TestGenerate_RejectsDangerousDestinationSchemes (8 cases) and
TestGenerate_AcceptsHTTPAndHTTPSSchemes (4 case-variants).
SHOULD-FIX S3 — fingerprint handler now silently 204s on any
Content-Type that does not start with "application/json". The
embedded template is the only legitimate caller and always sends
JSON; this rejects adversarial probes before the MaxBytesReader
read. Added
TestFingerprintHandler_WrongContentType_Returns204AndDoesNotTouchEvent.
SHOULD-FIX S4 — added integration tests for the oversize-body cap
(128 KiB body returns 204, Extra untouched) and the empty-token-id
guard (`/c//fingerprint`); the latter accepts chi's natural routing
behavior alongside the in-handler 204.
Non-functional cleanups: extracted shared template-render path
into renderWith / renderResponse / renderDecoyResponse to keep the
nil-token + happy-path bodies definitionally identical;
ErrMissingDestination and ErrInvalidDestinationScheme exported so
callers (and tests) can ErrorIs them; TestGenerate_RejectsMissing*
tightened to use require.ErrorIs(tc.wantErr) instead of bare
require.Error.
Pre-rollup gate (go build / vet / test -race unit+integration /
golangci-lint) is clean.
a46fa4465e