Pin the body cap's order in every page route group (closes #93)

Follow-ups from an August review of the body cap, each checked against the current tree. One route test now requires an oversized POST, with no session and no CSRF token, to be refused with 413 before CSRF runs, in every page route group with a POST route and in /settings/, so moving a group's body cap after CSRF fails it. The three test router helpers build the server through New with a lifecycle that is never started, so no field is set by hand. The middleware test comment names runMaxBodySize, and the MaxBodySize doc comment says methods other than POST, PUT and PATCH pass uncapped on purpose. The README item was already settled.

Model: opus-5-5

internal/middleware/middleware.go

@@ -600,7 +600,10 @@ func bodyLimitedMethod(method string) bool {
 }
 
 // MaxBodySize returns middleware that limits the size of
-// POST/PUT/PATCH request bodies to maxBytes. It must be registered
+// POST/PUT/PATCH request bodies to maxBytes. A request with any other
+// method passes through uncapped, deliberately: no route behind it
+// reads a body on GET, HEAD or DELETE. A handler that starts to needs
+// its method added to bodyLimitedMethod first. It must be registered
 // before any middleware that parses the body — notably CSRF, which
 // calls r.PostFormValue — so that form parsing happens under this
 // cap rather than net/http's 10 MB default.

internal/middleware/middleware_test.go

@@ -730,10 +730,8 @@ func TestNoCache_SetsHeaders(t *testing.T) {
 
 const testBodyLimit int64 = 64
 
-// maxBodySizeHandler wraps a sentinel handler in MaxBodySize with
-// testBodyLimit. The sentinel records whether it ran and how much of
-// the body it managed to read, so tests can distinguish "never
-// reached" from "reached but truncated".
+// maxBodySizeResult is what runMaxBodySize's sentinel handler saw,
+// together with the response.
 type maxBodySizeResult struct {
 	called   bool
 	read     int
@@ -741,6 +739,10 @@ type maxBodySizeResult struct {
 	response *httptest.ResponseRecorder
 }
 
+// runMaxBodySize wraps a sentinel handler in MaxBodySize with
+// testBodyLimit and serves req through it. The sentinel records
+// whether it ran and how much of the body it managed to read, so
+// tests can distinguish "never reached" from "reached but truncated".
 func runMaxBodySize(
 	t *testing.T,
 	req *http.Request,

internal/server/error_page_test.go

@@ -191,7 +191,7 @@ func TestErrorPage_PanicOnAdminPage(t *testing.T) {
 
 	w := serve(
 		server.NewRouterWithPageProbeForTest(
-			env.log.Get(), env.cfg, env.mw, env.hnd,
+			t, env.log, env.cfg, env.mw, env.hnd,
 			true, panicProbeHandler,
 		),
 		server.PageProbePattern,
@@ -200,7 +200,7 @@ func TestErrorPage_PanicOnAdminPage(t *testing.T) {
 
 	w = serve(
 		server.NewRouterWithProbeForTest(
-			env.log.Get(), env.cfg, env.mw, env.hnd,
+			t, env.log, env.cfg, env.mw, env.hnd,
 			true, panicProbeHandler,
 		),
 		server.ProbePattern,

internal/server/export_test.go

@@ -1,13 +1,16 @@
 package server
 
 import (
-	"log/slog"
 	"net/http"
+	"testing"
 
 	"github.com/getsentry/sentry-go"
 	"github.com/go-chi/chi"
+	"github.com/stretchr/testify/require"
+	"go.uber.org/fx/fxtest"
 	"sneak.berlin/go/webhooker/internal/config"
 	"sneak.berlin/go/webhooker/internal/handlers"
+	"sneak.berlin/go/webhooker/internal/logger"
 	"sneak.berlin/go/webhooker/internal/middleware"
 )
 
@@ -34,23 +37,45 @@ func SentryClientOptionsForTest(
 	return sentryClientOptions(dsn, release)
 }
 
+// newServerForTest builds a Server through New, as the application
+// does, on a lifecycle that is never started: the hooks New adds to
+// it never run, so nothing listens.
+func newServerForTest(
+	t *testing.T,
+	log *logger.Logger,
+	cfg *config.Config,
+	mw *middleware.Middleware,
+	h *handlers.Handlers,
+) *Server {
+	t.Helper()
+
+	s, err := New(fxtest.NewLifecycle(t), ServerParams{
+		Logger:     log,
+		Config:     cfg,
+		Middleware: mw,
+		Handlers:   h,
+	})
+	require.NoError(t, err)
+
+	return s
+}
+
 // NewRouterForTest builds the real route tree via SetupRoutes with
-// the supplied middleware and handlers, bypassing the fx lifecycle
-// and the HTTP listener. Tests use it so that route-group middleware
-// registration order is exercised exactly as it ships, rather than
-// against a hand-rebuilt chain that could drift from routes.go.
+// the supplied middleware and handlers, on a Server from New whose
+// lifecycle is never started, so no HTTP listener runs. Tests use it
+// so that route-group middleware registration order is exercised
+// exactly as it ships, rather than against a hand-rebuilt chain that
+// could drift from routes.go.
 func NewRouterForTest(
-	log *slog.Logger,
+	t *testing.T,
+	log *logger.Logger,
 	cfg *config.Config,
 	mw *middleware.Middleware,
 	h *handlers.Handlers,
 ) http.Handler {
-	s := &Server{
-		log:    log,
-		mw:     mw,
-		h:      h,
-		params: ServerParams{Config: cfg},
-	}
+	t.Helper()
+
+	s := newServerForTest(t, log, cfg, mw, h)
 	s.SetupRoutes()
 
 	return s.router
@@ -83,19 +108,17 @@ const ProbePattern = "/probe"
 // option and the recoverer registered outside it is the thing a test
 // has to be able to pin.
 func NewRouterWithProbeForTest(
-	log *slog.Logger,
+	t *testing.T,
+	log *logger.Logger,
 	cfg *config.Config,
 	mw *middleware.Middleware,
 	h *handlers.Handlers,
 	sentryEnabled bool,
 	probe http.HandlerFunc,
 ) http.Handler {
-	s := &Server{
-		log:    log,
-		mw:     mw,
-		h:      h,
-		params: ServerParams{Config: cfg},
-	}
+	t.Helper()
+
+	s := newServerForTest(t, log, cfg, mw, h)
 	s.sentryEnabled.Store(sentryEnabled)
 	s.SetupRoutes()
 	s.router.Handle(ProbePattern, probe)
@@ -113,19 +136,17 @@ const PageProbePattern = "/pages/probe"
 // it, so the probe runs behind that group's own middleware exactly as
 // the group's real routes do.
 func NewRouterWithPageProbeForTest(
-	log *slog.Logger,
+	t *testing.T,
+	log *logger.Logger,
 	cfg *config.Config,
 	mw *middleware.Middleware,
 	h *handlers.Handlers,
 	sentryEnabled bool,
 	probe http.HandlerFunc,
 ) http.Handler {
-	s := &Server{
-		log:    log,
-		mw:     mw,
-		h:      h,
-		params: ServerParams{Config: cfg},
-	}
+	t.Helper()
+
+	s := newServerForTest(t, log, cfg, mw, h)
 	s.sentryEnabled.Store(sentryEnabled)
 	s.SetupRoutes()
 

internal/server/recoverer_test.go

@@ -199,7 +199,7 @@ func TestPanicProbeChild(t *testing.T) {
 	env := newTestEnv(t)
 
 	router := server.NewRouterWithProbeForTest(
-		env.log.Get(), env.cfg, env.mw, env.hnd,
+		t, env.log, env.cfg, env.mw, env.hnd,
 		false, panicProbeHandler,
 	)
 
@@ -253,7 +253,7 @@ func TestSentryStillSeesAPanic(t *testing.T) {
 	require.NoError(t, err)
 
 	router := server.NewRouterWithProbeForTest(
-		env.log.Get(), env.cfg, env.mw, env.hnd,
+		t, env.log, env.cfg, env.mw, env.hnd,
 		true, panicProbeHandler,
 	)
 

internal/server/response_controller_test.go

@@ -67,11 +67,11 @@ func TestResponseControllerThroughProductionRouter(t *testing.T) {
 
 			routers := map[string]http.Handler{
 				server.ProbePattern: server.NewRouterWithProbeForTest(
-					env.log.Get(), env.cfg, env.mw, env.hnd,
+					t, env.log, env.cfg, env.mw, env.hnd,
 					tc.sentryEnabled, probe,
 				),
 				server.PageProbePattern: server.NewRouterWithPageProbeForTest(
-					env.log.Get(), env.cfg, env.mw, env.hnd,
+					t, env.log, env.cfg, env.mw, env.hnd,
 					tc.sentryEnabled, probe,
 				),
 			}

internal/server/routes_test.go

@@ -136,7 +136,7 @@ func newTestEnvWithConfig(
 	t.Cleanup(app.RequireStop)
 
 	return &testEnv{
-		router: server.NewRouterForTest(log.Get(), cfg, mw, hnd),
+		router: server.NewRouterForTest(t, log, cfg, mw, hnd),
 		sess:   sess,
 		db:     db,
 		dbMgr:  dbMgr,
@@ -531,6 +531,48 @@ func TestStaticServesOnlyGetAndHead(t *testing.T) {
 	}
 }
 
+// --- every page route group ---
+
+// TestPageRouteGroups_OversizeBody_RejectedBeforeCSRF pins the body
+// cap ahead of CSRF and RequireAuth in every page route group. The
+// requests carry no session and no CSRF token, so if either ran first
+// the answer would be a 403 or a redirect to the login page rather
+// than 413, and CSRF would issue its cookie (see
+// TestPagesLogin_UnderLimit_NoToken_CSRFRejects). /settings has no
+// POST route, but its group's middleware runs before the method is
+// matched, so a POST there still reaches CSRF's form parsing if the
+// cap moves after it. The user and webhook in the paths need not
+// exist: nothing after the cap runs.
+func TestPageRouteGroups_OversizeBody_RejectedBeforeCSRF(
+	t *testing.T,
+) {
+	t.Parallel()
+
+	env := newTestEnv(t)
+
+	form := url.Values{}
+	form.Set("name", oversizeValue())
+
+	for _, path := range []string{
+		"/pages/login",
+		"/user/nobody/password",
+		"/settings/",
+		"/hooks/new",
+		"/hook/nonexistent/edit",
+	} {
+		w := env.post(path, form, nil)
+
+		assert.Equal(
+			t, http.StatusRequestEntityTooLarge, w.Code, path,
+		)
+		assert.False(
+			t, csrfCookieSet(w),
+			"CSRF middleware must not run for an oversized body to %s",
+			path,
+		)
+	}
+}
+
 // --- /pages group ---
 
 // TestPagesLogin_OversizeBody_RejectedBeforeCSRF proves the cap runs
@@ -1610,7 +1652,7 @@ func TestTwoMetricsRoutersInOneProcess(t *testing.T) {
 	)
 	third := &testEnv{
 		router: server.NewRouterForTest(
-			first.log.Get(), first.cfg, first.mw, first.hnd,
+			t, first.log, first.cfg, first.mw, first.hnd,
 		),
 	}