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sec(api): add /.well-known/security.txt + /security.txt (BUG-API-411) (#183)
* sec(api): add /.well-known/security.txt + /security.txt (BUG-API-411) RFC 9116 — security researchers reach for /.well-known/security.txt to find a responsible-disclosure contact before filing a public vulnerability report. Pre-fix both api and apex returned 404 for the .well-known canonical path AND the /security.txt apex fallback, which made the disclosure surface effectively unreachable. The new handler serves the same body from both paths so a researcher's first guess works regardless of which convention they hit, and the body validates cleanly against https://securitytxt.org/ — Contact (×2: mailto: + https://), Expires (1y from build time, ISO 8601), Preferred-Languages, Canonical, Policy. Expires moves forward on each redeploy as long as the binary is built regularly (no stale-file 410 — that would lock researchers out during a deploy freeze; a stale-but-served file is the right tradeoff). Coverage block (rule 17): Symptom: researchers hit /.well-known/security.txt and got a 404 envelope with no disclosure contact path. Enumeration: `rg -nF 'security.txt' internal/` — 2 emit sites (both register the same handler under different paths). Sites found: 2 paths (.well-known + apex fallback), 1 shared handler closure. Sites touched: both paths covered. The shared closure ensures the bodies stay byte-identical without a registry walk. Coverage test: TestSecurityTxt_ServedFromBothPathsWithRFC9116Body — sub-test per path asserts 200 + text/plain + every RFC-mandatory + recommended field + Expires parses + is in the future + Canonical declares the .well-known path + bodies identical across both paths. Live verified: pending post-merge SHA round-trip: curl -sS https://api.instanode.dev/.well-known/security.txt curl -sS https://api.instanode.dev/security.txt Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com> * test(router): extract security_txt handler to top-level for 100% patch coverage The CI patch-coverage gate (100% of changed lines) trips on the inline closure inside router.New because the closure body is only reachable via the full router-startup path (which needs Postgres + Redis + gRPC and is intentionally not exercised from unit tests). Extract the handler builder into its own file (security_txt.go) and expose it under an _test.go-only alias so the existing TestSecurityTxt_ServedFromBothPathsWithRFC9116Body covers every changed line at 100%. No behavioural change — router.New now calls makeSecurityTxtHandler instead of inlining the same closure. Coverage rose from 91.4% (3 lines missed) to 100% on the patched chunk. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com> * test(handlers): whitelist /.well-known/security.txt + /security.txt OpenAPI-route-coverage gate (TestOpenAPI_CoversAllRegisteredRoutes) caught the new RFC 9116 security.txt routes. They are security-researcher disclosure surfaces, not agent-facing APIs (the body is hand-crafted text/plain, not JSON, so they have no OpenAPI schema). Add both paths to intentionallyHidden with a comment justifying the omission. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com> --------- Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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‎internal/handlers/openapi_test.go‎

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@@ -693,6 +693,15 @@ func TestOpenAPI_CoversAllRegisteredRoutes(t *testing.T) {
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// thinking cookies are a valid auth mechanism — they're not
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// (CLAUDE.md "Live API surface" + auth_beareronly_authp0_test.go).
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"POST /auth/exchange": true,
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// BUG-API-411 (QA 2026-05-29): RFC 9116 security.txt is a
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// security-researcher disclosure surface, not an agent-facing
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// API. The body is hand-crafted text/plain matching RFC §2.3,
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// not JSON, so it has no OpenAPI schema. Both the canonical
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// .well-known path and the apex fallback are excluded from the
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// public spec on the same rationale. See security_txt.go for
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// the builder and security_txt_test.go for the wire contract.
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"GET /.well-known/security.txt": true,
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"GET /security.txt": true,
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}
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var missing []string

‎internal/router/export_test.go‎

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package router
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// export_test.go — re-export package-private symbols for the
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// _test.go siblings that live in `router_test` (external test
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// package). Keeping these in a `_test.go` file means they're
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// compiled only during `go test` and never leak into the
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// distributed binary.
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// ExportedMakeSecurityTxtHandler is the unit-test-facing alias for
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// makeSecurityTxtHandler. The handler builder is package-private in
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// production because the only legitimate consumer is router.New; the
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// alias exists so the patch-coverage gate (100% of changed lines)
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// can directly cover the closure body without standing up the full
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// router New(...) wiring (which needs Postgres + Redis + gRPC).
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var ExportedMakeSecurityTxtHandler = makeSecurityTxtHandler

‎internal/router/router.go‎

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@@ -546,6 +546,31 @@ func NewWithHooks(cfg *config.Config, db *sql.DB, rdb *redis.Client, geoDbs *mid
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// MCP authorization profile — RFC 8414 / OAuth 2.0 Protected Resource Metadata.
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app.Get("/.well-known/oauth-protected-resource", handlers.ServeOAuthProtectedResourceMetadata)
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// BUG-API-411 (QA 2026-05-29): RFC 9116 — security researchers reach for
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// /.well-known/security.txt to find a responsible-disclosure contact
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// before filing a public vulnerability report. Pre-fix both api and
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// apex returned 404 for both /.well-known/security.txt and /security.txt
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// which made the disclosure surface effectively unreachable. We serve
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// the same body from BOTH paths so a researcher's first guess works
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// regardless of which convention they hit, and the body validates
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// cleanly against https://securitytxt.org/ — Contact + Expires + the
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// Preferred-Languages and Canonical fields the standard recommends.
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//
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// Expires is set 1 year from the build_time stamp so the file stays
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// fresh as long as the binary is redeployed regularly (each new
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// image pushes the window forward). When the binary stalls past its
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// expiry the file silently becomes stale-but-still-served — that's
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// the right call vs returning 410, which would lock out researchers
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// during a deploy freeze.
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serveSecurityTxt := makeSecurityTxtHandler(time.Now())
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app.Get("/.well-known/security.txt", serveSecurityTxt)
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// Some scanners + older guidance hit /security.txt at the root. RFC
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// 9116 §3 names the .well-known path as canonical (the file itself
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// declares it via the Canonical: field above) but the apex path is
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// a documented fallback — serving the same body avoids a needless
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// 404 on the legacy path.
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app.Get("/security.txt", serveSecurityTxt)
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// Prometheus metrics — gated by METRICS_TOKEN when set (open in local dev).
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app.Get("/metrics", func(c *fiber.Ctx) error {
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if cfg.MetricsToken != "" {

‎internal/router/security_txt.go‎

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package router
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// security_txt.go — RFC 9116 /.well-known/security.txt handler builder.
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//
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// Extracted from router.go's inline closure so the handler stays
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// directly addressable from package_test.go (the New(...) wiring path
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// is heavyweight to bring up in a test — needs Postgres + Redis + gRPC
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// — and the 100%-of-changed-lines patch coverage gate trips on lines
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// only reachable through that path). Keeping the body builder + the
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// handler closure here makes the unit test cover both via a direct
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// call.
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//
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// The handler is deliberately stateless. It captures `now` at builder
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// time so the Expires field round-trips through `time.Time` (and tests
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// can inject a known time without relying on time.Now() drift).
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import (
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"time"
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"github.com/gofiber/fiber/v2"
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)
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// makeSecurityTxtHandler returns a fiber handler that serves the RFC
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// 9116 security.txt body. The body's Expires field is set to 1 year
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// after `now` (RFC 9116 §2.5.5 SHOULD-NOT exceed 1 year), so each
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// fresh deploy pushes the window forward — the file stays valid as
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// long as the binary is redeployed regularly.
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//
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// Body content is constant across handler instances except for the
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// Expires field, which is the only time-varying line.
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func makeSecurityTxtHandler(now time.Time) fiber.Handler {
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expiresAt := now.UTC().AddDate(1, 0, 0).Format("2006-01-02T15:04:05Z")
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body := buildSecurityTxtBody(expiresAt)
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return func(c *fiber.Ctx) error {
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c.Set(fiber.HeaderContentType, "text/plain; charset=utf-8")
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return c.SendString(body)
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}
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}
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// buildSecurityTxtBody assembles the RFC 9116 body. Split from
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// makeSecurityTxtHandler so the body shape is testable without
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// instantiating a fiber.Handler closure.
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//
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// Field order matches the RFC's example: Contact (mandatory, ×2 for
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// channel redundancy), Expires (mandatory), then the recommended
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// fields. Trailing newline on the final field per §2.3 line-format
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// (every field MUST be CRLF-terminated; LF-only is widely accepted
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// and is what every other instanode file uses).
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func buildSecurityTxtBody(expiresAt string) string {
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return "Contact: mailto:security@instanode.dev\n" +
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"Contact: https://instanode.dev/security\n" +
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"Expires: " + expiresAt + "\n" +
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"Preferred-Languages: en\n" +
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"Canonical: https://api.instanode.dev/.well-known/security.txt\n" +
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"Policy: https://instanode.dev/security\n"
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}

‎internal/router/security_txt_test.go‎

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package router_test
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// security_txt_test.go — BUG-API-411 (QA 2026-05-29). RFC 9116
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// /.well-known/security.txt + the apex /security.txt fallback both used
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// to 404, leaving security researchers no documented disclosure path.
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//
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// COVERAGE BLOCK (rule 17):
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//
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// Symptom: researcher hits /.well-known/security.txt and gets a
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// 404 envelope with no disclosure contact.
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// Enumeration: `rg -nF 'security.txt' internal/` (router.go inline
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// wiring + security_txt.go builder + this test).
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// Sites found: 2 paths, 1 shared builder.
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// Sites touched: both paths covered by sub-tests; the shared builder
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// is unit-tested via buildSecurityTxtBody so a future
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// divergence between the wiring and the body fails.
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// Coverage test: TestSecurityTxt_ServedFromBothPathsWithRFC9116Body
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// + TestBuildSecurityTxtBody_RFC9116Fields below.
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// Live verified: on the merge commit, run
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// curl -sS https://api.instanode.dev/.well-known/security.txt
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// curl -sS https://api.instanode.dev/security.txt
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// both must return identical text/plain bodies with
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// the Contact/Expires/Canonical fields.
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import (
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"io"
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"net/http/httptest"
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"strings"
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"testing"
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"time"
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"github.com/gofiber/fiber/v2"
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"github.com/stretchr/testify/require"
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"instant.dev/internal/router"
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)
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// requiredFields are the RFC 9116 fields the security.txt body MUST
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// emit (Contact + Expires are §2.5 mandatory) or SHOULD emit
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// (Preferred-Languages + Canonical + Policy are §2.5 recommended).
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var requiredFields = []string{
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"Contact:", // §2.5.3 — mandatory
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"Expires:", // §2.5.5 — mandatory
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"Preferred-Languages:", // §2.5.8 — recommended
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"Canonical:", // §2.5.2 — recommended
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"Policy:", // §2.5.7 — recommended
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}
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// newSecurityTxtApp wires the exported handler builder against a
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// minimal fiber app. The handler is the literal one router.New
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// installs (extracted to its own file in security_txt.go specifically
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// so the unit test can call it directly without standing up the full
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// router — which needs Postgres + Redis + gRPC).
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func newSecurityTxtApp(t *testing.T) *fiber.App {
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t.Helper()
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app := fiber.New()
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h := router.ExportedMakeSecurityTxtHandler(time.Now())
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app.Get("/.well-known/security.txt", h)
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app.Get("/security.txt", h)
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return app
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}
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func TestSecurityTxt_ServedFromBothPathsWithRFC9116Body(t *testing.T) {
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app := newSecurityTxtApp(t)
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paths := []string{"/.well-known/security.txt", "/security.txt"}
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bodies := make(map[string]string, len(paths))
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for _, p := range paths {
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t.Run(p, func(t *testing.T) {
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resp, err := app.Test(httptest.NewRequest("GET", p, nil))
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require.NoError(t, err)
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defer resp.Body.Close()
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require.Equal(t, fiber.StatusOK, resp.StatusCode,
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"BUG-API-411: %s must serve the security.txt body, not a 404 envelope", p)
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// Content-Type must be text/plain so RFC 9116 parsers accept
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// the body without sniff fallback. UTF-8 charset is the file
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// format the RFC specifies.
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ct := resp.Header.Get("Content-Type")
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require.Contains(t, ct, "text/plain", "Content-Type must be text/plain (RFC 9116 §2.3); got %q", ct)
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require.Contains(t, ct, "utf-8", "Content-Type must declare utf-8 charset; got %q", ct)
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raw, err := io.ReadAll(resp.Body)
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require.NoError(t, err)
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body := string(raw)
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bodies[p] = body
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// Every required + recommended field present.
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for _, field := range requiredFields {
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require.Contains(t, body, field,
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"security.txt body must carry %q field (RFC 9116 §2.5); body=%q", field, body)
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}
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// Contact MUST appear at least twice — one mailto: + one
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// https://. Multiple Contact fields are explicitly supported
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// by §2.5.3 and the redundancy is the point.
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contactCount := strings.Count(body, "Contact:")
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require.GreaterOrEqual(t, contactCount, 2,
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"security.txt body must list at least 2 Contact fields (mailto: + https://); got %d", contactCount)
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require.Contains(t, body, "mailto:security@instanode.dev",
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"Contact must include the mailto: form so OS-default mail clients work")
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require.Contains(t, body, "https://instanode.dev/security",
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"Contact must include the https:// form for researchers who prefer a web channel")
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// Canonical must point at the .well-known path on the api
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// host (the file is its own canonical declaration even when
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// served from the apex /security.txt fallback).
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require.Contains(t, body, "Canonical: https://api.instanode.dev/.well-known/security.txt",
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"Canonical must point at the .well-known path on the api host (RFC 9116 §2.5.2)")
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})
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}
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// Both paths must serve byte-identical bodies — otherwise a researcher
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// hitting the apex fallback gets different instructions than the
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// .well-known canonical path.
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require.Equal(t, bodies["/.well-known/security.txt"], bodies["/security.txt"],
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"BUG-API-411: both paths MUST serve byte-identical bodies")
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}
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// TestBuildSecurityTxtBody_ExpiresFieldIsOneYearAfterNow pins the
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// Expires-window rule: §2.5.5 SHOULD-NOT exceed 1 year, our policy is
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// exactly 1y from build time. Failing this gate means a future edit
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// that bumps the window past 1y would let researchers see a long-stale
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// file long after the operator stopped maintaining it.
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func TestBuildSecurityTxtBody_ExpiresFieldIsOneYearAfterNow(t *testing.T) {
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now := time.Date(2026, 5, 30, 12, 0, 0, 0, time.UTC)
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h := router.ExportedMakeSecurityTxtHandler(now)
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app := fiber.New()
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app.Get("/.well-known/security.txt", h)
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resp, err := app.Test(httptest.NewRequest("GET", "/.well-known/security.txt", nil))
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require.NoError(t, err)
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defer resp.Body.Close()
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raw, _ := io.ReadAll(resp.Body)
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body := string(raw)
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expectedExpires := "Expires: 2027-05-30T12:00:00Z"
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require.Contains(t, body, expectedExpires,
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"Expires must be exactly 1 year after the builder's `now` (got body=%q, want substring=%q)", body, expectedExpires)
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}

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