feat: blocked_networks config and extended SSRF ranges (closes #67 )

Add a blocked_networks config key: a list of CIDRs parsed with net/netip, added to (not replacing) the built-in SSRF blocklist. An invalid CIDR aborts startup naming the key and the offending value. Extend the built-in blocklist to CGNAT 100.64.0.0/10, IETF protocol assignments 192.0.0.0/24, benchmark 198.18.0.0/15, and NAT64 64:ff9b::/96, unmapping IPv4-mapped IPv6 so the IPv4 ranges are caught in both forms. Enforcement stays in the dial-time re-resolution (dialSSRFSafe), which now also consults the operator-supplied prefixes, so the DNS-rebinding window remains closed. Model: opus-4-8
test: failing tests for blocked_networks config and extended SSRF ranges
2026-09-21 18:30:53 +00:00 · 2026-09-21 18:30:53 +00:00
8 changed files with 12 additions and 418 deletions
@@ -39,14 +39,6 @@ exhaustion
  (IPv4-mapped forms covered); enforcement stays in the dial-time
  re-resolution so the DNS-rebinding window remains closed; documented in
  `README.md` and `config.example.yml`.
 - 2026-09-21 http.Server hardening (closes #92): added
  `HTTPReadHeaderTimeout` (10s, bounds the slowloris header dribble) and
  `HTTPIdleTimeout` (120s, bounds keep-alive reuse) alongside the
  existing timeouts and wired them onto the server; added a `LimitBody`
  middleware capping the two form POST bodies (`POST /`, `POST /generate`)
  at `MaxFormBytes` (1 MiB) and returning 413, applied ahead of the CSRF
  middleware so an oversized body is refused as 413 rather than being read
  as a missing CSRF token (403); left `WriteTimeout` at 60s unchanged
 - 2026-08-07 update golangci-lint to v2.12.2 with the canonical
  `.golangci.yml` (v2 schema, `default: all` minus six disabled
  linters, `lll` 88, tests included): bumped the pinned
@@ -1,45 +0,0 @@
 package handlers
 import (
 	"errors"
 	"net/http"
 )
 // MaxFormBytes bounds the request body accepted on the HTML form POST
 // routes (POST / and POST /generate). The forms carry a handful of short
 // fields, so 1 MiB is generous while making the bound explicit rather than
 // resting on ParseForm's incidental 10 MB cap.
 const MaxFormBytes = 1 << 20 // 1 MiB
 // LimitBody returns middleware that caps the request body on POST requests
 // at maxBytes and rejects an oversized body with 413 Request Entity Too
 // Large.
 //
 // It parses the form here, before the CSRF middleware reads the token from
 // it. The CSRF middleware reads the token with PostFormValue, which
 // swallows a parse error, so if the body were only capped there an
 // oversized body would read as a missing token and be refused as 403. By
 // parsing under the cap first, an oversized body is refused as 413. A
 // successful parse is cached on the request, so the CSRF check and the
 // handler reuse it rather than reading the body again.
 func (s *Handlers) LimitBody(maxBytes int64) func(http.Handler) http.Handler {
 	return func(next http.Handler) http.Handler {
 		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 			if r.Method == http.MethodPost {
 				r.Body = http.MaxBytesReader(w, r.Body, maxBytes)
 				err := r.ParseForm()
 				var tooLarge *http.MaxBytesError
 				if errors.As(err, &tooLarge) {
 					http.Error(w, "Request body too large",
 						http.StatusRequestEntityTooLarge)
 					return
 				}
 			}
 			next.ServeHTTP(w, r)
 		})
 	}
 }
@@ -1,177 +0,0 @@
 package handlers
 import (
 	"log/slog"
 	"net/http"
 	"net/url"
 	"strings"
 	"testing"
 	"github.com/go-chi/chi/v5"
 	"sneak.berlin/go/pixa/internal/config"
 	"sneak.berlin/go/pixa/internal/encurl"
 	"sneak.berlin/go/pixa/internal/session"
 )
 // Form field names and a throwaway source image URL for the body-limit
 // tests.
 const (
 	sourceURLField = "url"
 	testSourceURL  = "https://example.com/a.jpg"
 )
 // newBodyLimitTestRouter mirrors the production wiring for the form POST
 // routes (see server.SetupRoutes): LimitBody sits in front of the CSRF
 // middleware, which sits in front of the handlers. maxBytes is the body
 // cap under test, so a test can trip the limit with a small body.
 func newBodyLimitTestRouter(
 	t *testing.T, maxBytes int64,
 ) (*Handlers, http.Handler) {
 	t.Helper()
 	cfg := &config.Config{SigningKey: testSigningKey, Debug: true}
 	sessMgr, err := session.NewManager(testSigningKey)
 	if err != nil {
 		t.Fatalf("session.NewManager() error = %v", err)
 	}
 	encGen, err := encurl.NewGenerator(testSigningKey)
 	if err != nil {
 		t.Fatalf("encurl.NewGenerator() error = %v", err)
 	}
 	protect, err := newCSRFProtect(testSigningKey, cfg.Debug)
 	if err != nil {
 		t.Fatalf("newCSRFProtect() error = %v", err)
 	}
 	h := &Handlers{
 		log:         slog.New(slog.DiscardHandler),
 		config:      cfg,
 		sessMgr:     sessMgr,
 		encGen:      encGen,
 		csrfProtect: protect,
 	}
 	r := chi.NewRouter()
 	r.Group(func(r chi.Router) {
 		r.Use(h.LimitBody(maxBytes))
 		r.Use(h.CSRF())
 		r.Get("/", h.HandleRoot())
 		r.Post("/", h.HandleRoot())
 		r.Post("/generate", h.HandleGenerateURL())
 	})
 	return h, r
 }
 // TestOversizedLoginPostRejectedBeforeCSRF is the core regression: an
 // oversized POST / carrying an otherwise valid CSRF cookie and token must
 // be rejected with 413. If the body limit ran after CSRF, the truncated
 // body would read as a missing token and return 403; if it ran after the
 // handler, a valid token would return 303. Getting 413 proves the limit
 // fires before CSRF parses the form.
 func TestOversizedLoginPostRejectedBeforeCSRF(t *testing.T) {
 	t.Parallel()
 	_, srv := newBodyLimitTestRouter(t, 16)
 	cookies, token := csrfCredentials(t, srv, nil)
 	rec := postForm(srv, "/", cookies, url.Values{
 		loginKeyField:  {testSigningKey},
 		csrfTokenField: {token},
 	})
 	if rec.Code != http.StatusRequestEntityTooLarge {
 		t.Errorf("oversized POST / status = %d, want %d",
 			rec.Code, http.StatusRequestEntityTooLarge)
 	}
 }
 // TestOversizedGeneratePostRejectedBeforeCSRF is the same regression for
 // POST /generate, which also parses a form behind CSRF.
 func TestOversizedGeneratePostRejectedBeforeCSRF(t *testing.T) {
 	t.Parallel()
 	h, srv := newBodyLimitTestRouter(t, 16)
 	sessionCookie := newSessionCookie(t, h)
 	cookies, token := csrfCredentials(t, srv, []*http.Cookie{sessionCookie})
 	cookies = append(cookies, sessionCookie)
 	rec := postForm(srv, "/generate", cookies, url.Values{
 		sourceURLField: {testSourceURL},
 		csrfTokenField: {token},
 	})
 	if rec.Code != http.StatusRequestEntityTooLarge {
 		t.Errorf("oversized POST /generate status = %d, want %d",
 			rec.Code, http.StatusRequestEntityTooLarge)
 	}
 }
 // TestWithinLimitLoginPostSucceeds verifies the limit does not disturb a
 // normal request: under the production cap, a valid login still parses and
 // establishes a session (303). This guards against the body limit
 // consuming or corrupting the form the CSRF check and handler depend on.
 func TestWithinLimitLoginPostSucceeds(t *testing.T) {
 	t.Parallel()
 	_, srv := newBodyLimitTestRouter(t, MaxFormBytes)
 	cookies, token := csrfCredentials(t, srv, nil)
 	rec := postForm(srv, "/", cookies, url.Values{
 		loginKeyField:  {testSigningKey},
 		csrfTokenField: {token},
 	})
 	if rec.Code != http.StatusSeeOther {
 		t.Fatalf("within-limit POST / status = %d, want %d",
 			rec.Code, http.StatusSeeOther)
 	}
 	var authed bool
 	for _, c := range rec.Result().Cookies() {
 		if c.Name == session.CookieName && c.Value != "" {
 			authed = true
 		}
 	}
 	if !authed {
 		t.Error("within-limit valid login did not set a session cookie")
 	}
 }
 // TestWithinLimitGeneratePostSucceeds is the same non-regression check for
 // POST /generate.
 func TestWithinLimitGeneratePostSucceeds(t *testing.T) {
 	t.Parallel()
 	h, srv := newBodyLimitTestRouter(t, MaxFormBytes)
 	sessionCookie := newSessionCookie(t, h)
 	cookies, token := csrfCredentials(t, srv, []*http.Cookie{sessionCookie})
 	cookies = append(cookies, sessionCookie)
 	rec := postForm(srv, "/generate", cookies, url.Values{
 		sourceURLField: {testSourceURL},
 		"format":       {"jpeg"},
 		csrfTokenField: {token},
 	})
 	if rec.Code != http.StatusOK {
 		t.Fatalf("within-limit POST /generate status = %d, want %d",
 			rec.Code, http.StatusOK)
 	}
 	if !strings.Contains(rec.Body.String(), "/v1/e/") {
 		t.Error("within-limit generate response did not contain a generated URL")
 	}
 }
@@ -21,33 +21,6 @@ import (
 // CORSMaxAgeSeconds is the max age for CORS preflight cache (24 hours).
 const CORSMaxAgeSeconds = 86400
 // HSTSValue is the Strict-Transport-Security header value: one year with
 // includeSubDomains. Emitted unconditionally even though pixa listens plain
 // HTTP behind a TLS-terminating proxy; browsers ignore an HSTS header received
 // over plaintext (RFC 6797 section 8.1), so it never lies about the connection,
 // and emitting it here avoids trusting a forwarded-proto header.
 const HSTSValue = "max-age=31536000; includeSubDomains"
 // ContentSecurityPolicyValue is the Content-Security-Policy header value.
 // default-src 'self' is the baseline and frame-ancestors 'none' is the primary
 // clickjacking control. 'unsafe-inline' is required in script-src and style-src
 // because the served templates carry inline onclick handlers (generator page)
 // and the bundled Tailwind asset injects a runtime <style> element; dropping it
 // needs template changes outside this issue's scope.
 const ContentSecurityPolicyValue = "default-src 'self'; " +
 	"script-src 'self' 'unsafe-inline'; " +
 	"style-src 'self' 'unsafe-inline'; " +
 	"object-src 'none'; " +
 	"base-uri 'self'; " +
 	"form-action 'self'; " +
 	"frame-ancestors 'none'"
 // PermissionsPolicyValue is the Permissions-Policy header value. Every listed
 // feature is denied because pixa uses none of them.
 const PermissionsPolicyValue = "accelerometer=(), autoplay=(), camera=(), " +
 	"display-capture=(), geolocation=(), gyroscope=(), magnetometer=(), " +
 	"microphone=(), payment=(), usb=()"
 // Params defines dependencies for Middleware.
 type Params struct {
 	fx.In
@@ -191,16 +164,6 @@ func (s *Middleware) SecurityHeaders() func(http.Handler) http.Handler {
 			// Disable XSS filtering (modern browsers don't need it, can cause issues)
 			w.Header().Set("X-XSS-Protection", "0")
 			// Force HTTPS on future visits (ignored by browsers over plaintext)
 			w.Header().Set("Strict-Transport-Security", HSTSValue)
 			// Restrict content sources; frame-ancestors is the primary
 			// clickjacking control, X-Frame-Options the legacy fallback
 			w.Header().Set("Content-Security-Policy", ContentSecurityPolicyValue)
 			// Deny browser features pixa does not use
 			w.Header().Set("Permissions-Policy", PermissionsPolicyValue)
 			next.ServeHTTP(w, r)
 		})
 	}
@@ -56,61 +56,6 @@ func TestSecurityHeaders(t *testing.T) {
 	}
 }
 func TestSecurityHeaders_PolicyHeaders(t *testing.T) {
 	t.Parallel()
 	cfg := &config.Config{}
 	mw := &Middleware{
 		log:    slog.Default(),
 		config: cfg,
 	}
 	testHandler := http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
 		w.WriteHeader(http.StatusOK)
 	})
 	handler := mw.SecurityHeaders()(testHandler)
 	req := httptest.NewRequestWithContext(t.Context(), http.MethodGet, "/test", nil)
 	rec := httptest.NewRecorder()
 	handler.ServeHTTP(rec, req)
 	tests := []struct {
 		header string
 		want   string
 	}{
 		{"Strict-Transport-Security", "max-age=31536000; includeSubDomains"},
 		{
 			"Content-Security-Policy",
 			"default-src 'self'; " +
 				"script-src 'self' 'unsafe-inline'; " +
 				"style-src 'self' 'unsafe-inline'; " +
 				"object-src 'none'; " +
 				"base-uri 'self'; " +
 				"form-action 'self'; " +
 				"frame-ancestors 'none'",
 		},
 		{
 			"Permissions-Policy",
 			"accelerometer=(), autoplay=(), camera=(), " +
 				"display-capture=(), geolocation=(), gyroscope=(), " +
 				"magnetometer=(), microphone=(), payment=(), usb=()",
 		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.header, func(t *testing.T) {
 			t.Parallel()
 			got := rec.Header().Get(tt.header)
 			if got != tt.want {
 				t.Errorf("%s = %q, want %q", tt.header, got, tt.want)
 			}
 		})
 	}
 }
 func TestSecurityHeaders_PreservesExistingHeaders(t *testing.T) {
 	t.Parallel()
@@ -10,39 +10,23 @@ import (
 // HTTP server configuration constants.
 const (
 	HTTPReadTimeout    = 30 * time.Second
 	// HTTPReadHeaderTimeout bounds the request-header read on its own,
 	// short, so a slowloris client dribbling headers is dropped well
 	// before it ties up a connection for the whole ReadTimeout window.
 	HTTPReadHeaderTimeout = 10 * time.Second
 	HTTPWriteTimeout   = 60 * time.Second
 	// HTTPIdleTimeout bounds how long an idle keep-alive connection is
 	// held open, so idle connections cannot accumulate without limit on a
 	// service targeting high concurrency.
 	HTTPIdleTimeout    = 120 * time.Second
 	HTTPMaxHeaderBytes = 8 << 10 // 8KB
 )
-// newHTTPServer builds the http.Server with the hardening timeouts and
+func (s *Server) serveUntilShutdown() {
-// limits applied. It is separate from serveUntilShutdown so the
+	listenAddr := fmt.Sprintf(":%d", s.config.Port)
-// configuration can be asserted in a test without binding a listener.
+	s.httpServer = &http.Server{
-func (s *Server) newHTTPServer() *http.Server {
+		Addr:           listenAddr,
 	return &http.Server{
 		Addr:              fmt.Sprintf(":%d", s.config.Port),
 		ReadTimeout:    HTTPReadTimeout,
 		ReadHeaderTimeout: HTTPReadHeaderTimeout,
 		WriteTimeout:   HTTPWriteTimeout,
 		IdleTimeout:       HTTPIdleTimeout,
 		MaxHeaderBytes: HTTPMaxHeaderBytes,
 		Handler:        s,
 	}
 }
 func (s *Server) serveUntilShutdown() {
 	s.httpServer = s.newHTTPServer()
 	s.SetupRoutes()
-	s.log.Info("http begin listen", "listenaddr", s.httpServer.Addr)
+	s.log.Info("http begin listen", "listenaddr", listenAddr)
 	err := s.httpServer.ListenAndServe()
 	if err != nil && !errors.Is(err, http.ErrServerClosed) {
@@ -1,65 +0,0 @@
 package server
 import (
 	"testing"
 	"time"
 	"sneak.berlin/go/pixa/internal/config"
 )
 // TestNewHTTPServerTimeouts verifies that the constructed http.Server
 // carries every hardening timeout wired onto it, including the slowloris
 // defense (ReadHeaderTimeout) and the keep-alive bound (IdleTimeout). This
 // guards against a field being defined but never set on the server, so
 // each assertion compares the server field to its constant.
 func TestNewHTTPServerTimeouts(t *testing.T) {
 	t.Parallel()
 	s := &Server{config: &config.Config{Port: 8080}}
 	srv := s.newHTTPServer()
 	fields := []struct {
 		name string
 		got  time.Duration
 		want time.Duration
 	}{
 		{"ReadTimeout", srv.ReadTimeout, HTTPReadTimeout},
 		{"ReadHeaderTimeout", srv.ReadHeaderTimeout, HTTPReadHeaderTimeout},
 		{"WriteTimeout", srv.WriteTimeout, HTTPWriteTimeout},
 		{"IdleTimeout", srv.IdleTimeout, HTTPIdleTimeout},
 	}
 	for _, f := range fields {
 		if f.got != f.want {
 			t.Errorf("%s = %v, want %v", f.name, f.got, f.want)
 		}
 	}
 	if srv.MaxHeaderBytes != HTTPMaxHeaderBytes {
 		t.Errorf("MaxHeaderBytes = %d, want %d",
 			srv.MaxHeaderBytes, HTTPMaxHeaderBytes)
 	}
 	if srv.Handler != s {
 		t.Error("Handler is not the server")
 	}
 }
 // TestHardeningTimeoutValues pins the intent behind the two new timeouts
 // without hard-coding brittle exact durations: the header-read phase is
 // bounded strictly shorter than the whole-request read (the slowloris
 // dribble), and idle keep-alive connections are bounded rather than held
 // open forever.
 func TestHardeningTimeoutValues(t *testing.T) {
 	t.Parallel()
 	if HTTPReadHeaderTimeout <= 0 || HTTPReadHeaderTimeout > HTTPReadTimeout {
 		t.Errorf("ReadHeaderTimeout = %v, want positive and <= ReadTimeout %v",
 			HTTPReadHeaderTimeout, HTTPReadTimeout)
 	}
 	if HTTPIdleTimeout <= 0 {
 		t.Errorf("IdleTimeout = %v, want positive bound", HTTPIdleTimeout)
 	}
 }
@@ -8,7 +8,6 @@ import (
 	"github.com/go-chi/chi/v5/middleware"
 	"github.com/prometheus/client_golang/prometheus/promhttp"
 	"sneak.berlin/go/pixa/internal/handlers"
 	"sneak.berlin/go/pixa/internal/static"
 )
@@ -47,10 +46,8 @@ func (s *Server) SetupRoutes() {
 	// Login/generator UI. The form routes carry CSRF protection; the
 	// token cookie is independent of the session cookie, so it also
-	// covers the login POST, where no session exists yet. LimitBody caps
+	// covers the login POST, where no session exists yet.
 	// the POST body ahead of CSRF, which reads its token from that body.
 	s.router.Group(func(r chi.Router) {
 		r.Use(s.h.LimitBody(handlers.MaxFormBytes))
 		r.Use(s.h.CSRF())
 		r.Get("/", s.h.HandleRoot())
 		r.Post("/", s.h.HandleRoot())