Harden HTTP defaults and proxy header trust.

Add explicit server timeout/header limits, require trusted proxy CIDRs when honoring forwarded IP headers, and document single-instance storage expectations.

Co-authored-by: Cursor <cursoragent@cursor.com>

README.md

@@ -28,6 +28,21 @@ All configuration is YAML.
 
 - `listen_addr`: address for the HTTP server (required).
   - Default: `:8080`
+- `read_header_timeout`: maximum time for reading request headers.
+  - Must be `> 0`
+  - Default: `5s`
+- `read_timeout`: maximum time for reading the full request.
+  - Must be `> 0`
+  - Default: `30s`
+- `write_timeout`: maximum time allowed for writing the response.
+  - Must be `> 0`
+  - Default: `30s`
+- `idle_timeout`: maximum keep-alive idle time between requests.
+  - Must be `> 0`
+  - Default: `120s`
+- `max_header_bytes`: max HTTP header size in bytes.
+  - Must be `> 0`
+  - Default: `1048576` (1 MiB)
 
 ### `limits`
 
@@ -64,7 +79,11 @@ All configuration is YAML.
   - Add trusted IPs/CIDRs for LAN/proxy clients (for example `192.168.1.0/24`)
   - Empty list means no allowlist restriction
 - `trust_proxy_headers`: if `true`, client IP extraction honors `X-Forwarded-For` then `X-Real-IP`.
+  - Only used when source IP matches `trusted_proxy_ips`.
   - Keep `false` unless behind a trusted reverse proxy that sets these headers.
+- `trusted_proxy_ips`: list of reverse-proxy IPs/CIDRs permitted to supply forwarded headers.
+  - Required when `trust_proxy_headers: true`
+  - Examples: `127.0.0.1`, `10.0.0.0/8`
 - `rate_limit.enabled`: enable per-IP token-bucket rate limiting on write route.
   - Default: `true`
 - `rate_limit.requests_per_minute`: steady refill rate per client IP.
@@ -103,3 +122,10 @@ If exposed beyond a trusted LAN, place a reverse proxy in front (Nginx, Caddy, T
 - Monitoring and log retention suitable for abuse triage.
 
 Recommended baseline: run behind a reverse proxy, keep low TTL and size limits, and use `allowed_ips` for write access whenever possible.
+
+## Storage Model
+
+Scratchbox storage is designed for a single process instance per `storage.data_dir`.
+
+- Do not run multiple scratchbox processes against the same data directory.
+- Metadata/index writes are process-local and are not coordinated with cross-process locking.

cmd/scratchbox/server.go

@@ -59,8 +59,13 @@ func run(configPath string) error {
 	go cleanupWorker.Start(ctx)
 
 	httpServer := &http.Server{
-		Addr:    cfg.Server.ListenAddr,
+		Addr:              cfg.Server.ListenAddr,
-		Handler: server.Routes(),
+		Handler:           server.Routes(),
+		ReadHeaderTimeout: cfg.Server.ReadHeaderTimeoutDur,
+		ReadTimeout:       cfg.Server.ReadTimeoutDur,
+		WriteTimeout:      cfg.Server.WriteTimeoutDur,
+		IdleTimeout:       cfg.Server.IdleTimeoutDur,
+		MaxHeaderBytes:    cfg.Server.MaxHeaderBytes,
 	}
 
 	go func() {

internal/config/config.go

@@ -15,6 +15,11 @@ import (
 
 const (
 	defaultListenAddr         = ":8080"
+	defaultReadHeaderTimeout  = "5s"
+	defaultReadTimeout        = "30s"
+	defaultWriteTimeout       = "30s"
+	defaultIdleTimeout        = "120s"
+	defaultMaxHeaderBytes     = 1 << 20
 	defaultMaxUploadSize      = "100MiB"
 	defaultTTL                = "1h"
 	defaultRawCacheMaxSize    = "200MiB"
@@ -36,7 +41,16 @@ type Config struct {
 }
 
 type ServerConfig struct {
-	ListenAddr string `yaml:"listen_addr" comment:"Address to bind the HTTP server to."`
+	ListenAddr           string        `yaml:"listen_addr" comment:"Address to bind the HTTP server to."`
+	ReadHeaderTimeout    string        `yaml:"read_header_timeout" comment:"Maximum duration for reading request headers (for slowloris protection). Must be > 0."`
+	ReadTimeout          string        `yaml:"read_timeout" comment:"Maximum duration for reading the full request, including body. Must be > 0."`
+	WriteTimeout         string        `yaml:"write_timeout" comment:"Maximum duration before timing out writes of a response. Must be > 0."`
+	IdleTimeout          string        `yaml:"idle_timeout" comment:"Maximum amount of time to wait for the next request when keep-alives are enabled. Must be > 0."`
+	MaxHeaderBytes       int           `yaml:"max_header_bytes" comment:"Maximum size of request headers in bytes. Must be > 0."`
+	ReadHeaderTimeoutDur time.Duration `yaml:"-"`
+	ReadTimeoutDur       time.Duration `yaml:"-"`
+	WriteTimeoutDur      time.Duration `yaml:"-"`
+	IdleTimeoutDur       time.Duration `yaml:"-"`
 }
 
 type LimitsConfig struct {
@@ -56,10 +70,12 @@ type StorageConfig struct {
 }
 
 type SecurityConfig struct {
-	AllowedIPs        []string        `yaml:"allowed_ips" comment:"Allowlist for POST /api/scratch as IPs or CIDRs (examples: 127.0.0.1, 192.168.1.0/24). Keep 127.0.0.1 for local access; add trusted ranges as needed. Empty means unrestricted."`
+	AllowedIPs           []string        `yaml:"allowed_ips" comment:"Allowlist for POST /api/scratch as IPs or CIDRs (examples: 127.0.0.1, 192.168.1.0/24). Keep 127.0.0.1 for local access; add trusted ranges as needed. Empty means unrestricted."`
-	TrustProxyHeaders bool            `yaml:"trust_proxy_headers" comment:"Honor X-Forwarded-For / X-Real-IP when true (trusted proxy only)."`
+	TrustProxyHeaders    bool            `yaml:"trust_proxy_headers" comment:"Honor X-Forwarded-For / X-Real-IP only when request source IP matches security.trusted_proxy_ips."`
-	RateLimit         RateLimitConfig `yaml:"rate_limit" comment:"Per-client token bucket on POST /api/scratch."`
+	TrustedProxyIPs      []string        `yaml:"trusted_proxy_ips" comment:"IPs/CIDRs of reverse proxies allowed to supply forwarded client IP headers. Required when trust_proxy_headers is true."`
-	AllowedPrefixes   []netip.Prefix  `yaml:"-"`
+	RateLimit            RateLimitConfig `yaml:"rate_limit" comment:"Per-client token bucket on POST /api/scratch."`
+	AllowedPrefixes      []netip.Prefix  `yaml:"-"`
+	TrustedProxyPrefixes []netip.Prefix  `yaml:"-"`
 }
 
 type RateLimitConfig struct {
@@ -93,7 +109,12 @@ func Default() Config {
 func defaults() Config {
 	return Config{
 		Server: ServerConfig{
-			ListenAddr: defaultListenAddr,
+			ListenAddr:        defaultListenAddr,
+			ReadHeaderTimeout: defaultReadHeaderTimeout,
+			ReadTimeout:       defaultReadTimeout,
+			WriteTimeout:      defaultWriteTimeout,
+			IdleTimeout:       defaultIdleTimeout,
+			MaxHeaderBytes:    defaultMaxHeaderBytes,
 		},
 		Limits: LimitsConfig{
 			MaxUploadSize:      defaultMaxUploadSize,
@@ -122,6 +143,45 @@ func (c *Config) Validate() error {
 	if strings.TrimSpace(c.Server.ListenAddr) == "" {
 		return errors.New("server.listen_addr is required")
 	}
+	readHeaderTimeout, err := time.ParseDuration(strings.TrimSpace(c.Server.ReadHeaderTimeout))
+	if err != nil {
+		return fmt.Errorf("server.read_header_timeout invalid: %w", err)
+	}
+	if readHeaderTimeout <= 0 {
+		return errors.New("server.read_header_timeout must be > 0")
+	}
+	c.Server.ReadHeaderTimeoutDur = readHeaderTimeout
+
+	readTimeout, err := time.ParseDuration(strings.TrimSpace(c.Server.ReadTimeout))
+	if err != nil {
+		return fmt.Errorf("server.read_timeout invalid: %w", err)
+	}
+	if readTimeout <= 0 {
+		return errors.New("server.read_timeout must be > 0")
+	}
+	c.Server.ReadTimeoutDur = readTimeout
+
+	writeTimeout, err := time.ParseDuration(strings.TrimSpace(c.Server.WriteTimeout))
+	if err != nil {
+		return fmt.Errorf("server.write_timeout invalid: %w", err)
+	}
+	if writeTimeout <= 0 {
+		return errors.New("server.write_timeout must be > 0")
+	}
+	c.Server.WriteTimeoutDur = writeTimeout
+
+	idleTimeout, err := time.ParseDuration(strings.TrimSpace(c.Server.IdleTimeout))
+	if err != nil {
+		return fmt.Errorf("server.idle_timeout invalid: %w", err)
+	}
+	if idleTimeout <= 0 {
+		return errors.New("server.idle_timeout must be > 0")
+	}
+	c.Server.IdleTimeoutDur = idleTimeout
+
+	if c.Server.MaxHeaderBytes <= 0 {
+		return errors.New("server.max_header_bytes must be > 0")
+	}
 
 	sizeBytes, err := parseHumanSize(c.Limits.MaxUploadSize)
 	if err != nil {
@@ -168,6 +228,14 @@ func (c *Config) Validate() error {
 		return fmt.Errorf("security.allowed_ips invalid: %w", err)
 	}
 	c.Security.AllowedPrefixes = prefixes
+	trustedProxyPrefixes, err := parseAllowedPrefixes(c.Security.TrustedProxyIPs)
+	if err != nil {
+		return fmt.Errorf("security.trusted_proxy_ips invalid: %w", err)
+	}
+	c.Security.TrustedProxyPrefixes = trustedProxyPrefixes
+	if c.Security.TrustProxyHeaders && len(c.Security.TrustedProxyPrefixes) == 0 {
+		return errors.New("security.trusted_proxy_ips is required when security.trust_proxy_headers is true")
+	}
 
 	if c.Security.RateLimit.RequestsPerMinute <= 0 {
 		return errors.New("security.rate_limit.requests_per_minute must be > 0")

internal/config/config_test.go

@@ -22,6 +22,21 @@ func TestValidateAppliesDefaultsAndParsedFields(t *testing.T) {
 	if cfg.Limits.MaxUploadSizeBytes != 100*1024*1024 {
 		t.Fatalf("MaxUploadSizeBytes = %d, want %d", cfg.Limits.MaxUploadSizeBytes, int64(100*1024*1024))
 	}
+	if cfg.Server.ReadHeaderTimeoutDur != 5*time.Second {
+		t.Fatalf("ReadHeaderTimeoutDur = %s, want 5s", cfg.Server.ReadHeaderTimeoutDur)
+	}
+	if cfg.Server.ReadTimeoutDur != 30*time.Second {
+		t.Fatalf("ReadTimeoutDur = %s, want 30s", cfg.Server.ReadTimeoutDur)
+	}
+	if cfg.Server.WriteTimeoutDur != 30*time.Second {
+		t.Fatalf("WriteTimeoutDur = %s, want 30s", cfg.Server.WriteTimeoutDur)
+	}
+	if cfg.Server.IdleTimeoutDur != 120*time.Second {
+		t.Fatalf("IdleTimeoutDur = %s, want 120s", cfg.Server.IdleTimeoutDur)
+	}
+	if cfg.Server.MaxHeaderBytes != 1<<20 {
+		t.Fatalf("MaxHeaderBytes = %d, want %d", cfg.Server.MaxHeaderBytes, 1<<20)
+	}
 	if cfg.Limits.DefaultTTLDuration != time.Hour {
 		t.Fatalf("DefaultTTLDuration = %s, want 1h", cfg.Limits.DefaultTTLDuration)
 	}
@@ -51,6 +66,11 @@ func TestLoadParsesConfiguredFields(t *testing.T) {
 	content := `
 server:
   listen_addr: "127.0.0.1:9090"
+  read_header_timeout: "4s"
+  read_timeout: "25s"
+  write_timeout: "35s"
+  idle_timeout: "90s"
+  max_header_bytes: 2097152
 limits:
   max_upload_size: "2MiB"
   default_ttl: "2h"
@@ -64,6 +84,8 @@ security:
     - "127.0.0.1"
     - "10.0.0.0/8"
   trust_proxy_headers: true
+  trusted_proxy_ips:
+    - "10.0.0.0/8"
   rate_limit:
     enabled: true
     requests_per_minute: 12
@@ -81,6 +103,21 @@ security:
 	if cfg.Server.ListenAddr != "127.0.0.1:9090" {
 		t.Fatalf("ListenAddr = %q, want %q", cfg.Server.ListenAddr, "127.0.0.1:9090")
 	}
+	if cfg.Server.ReadHeaderTimeoutDur != 4*time.Second {
+		t.Fatalf("ReadHeaderTimeoutDur = %s, want 4s", cfg.Server.ReadHeaderTimeoutDur)
+	}
+	if cfg.Server.ReadTimeoutDur != 25*time.Second {
+		t.Fatalf("ReadTimeoutDur = %s, want 25s", cfg.Server.ReadTimeoutDur)
+	}
+	if cfg.Server.WriteTimeoutDur != 35*time.Second {
+		t.Fatalf("WriteTimeoutDur = %s, want 35s", cfg.Server.WriteTimeoutDur)
+	}
+	if cfg.Server.IdleTimeoutDur != 90*time.Second {
+		t.Fatalf("IdleTimeoutDur = %s, want 90s", cfg.Server.IdleTimeoutDur)
+	}
+	if cfg.Server.MaxHeaderBytes != 2*1024*1024 {
+		t.Fatalf("MaxHeaderBytes = %d, want %d", cfg.Server.MaxHeaderBytes, 2*1024*1024)
+	}
 	if cfg.Limits.MaxUploadSizeBytes != 2*1024*1024 {
 		t.Fatalf("MaxUploadSizeBytes = %d, want %d", cfg.Limits.MaxUploadSizeBytes, int64(2*1024*1024))
 	}
@@ -105,6 +142,9 @@ security:
 	if len(cfg.Security.AllowedPrefixes) != 2 {
 		t.Fatalf("AllowedPrefixes len = %d, want 2", len(cfg.Security.AllowedPrefixes))
 	}
+	if len(cfg.Security.TrustedProxyPrefixes) != 1 {
+		t.Fatalf("TrustedProxyPrefixes len = %d, want 1", len(cfg.Security.TrustedProxyPrefixes))
+	}
 }
 
 func TestValidateRejectsInvalidValues(t *testing.T) {
@@ -129,6 +169,41 @@ func TestValidateRejectsInvalidValues(t *testing.T) {
 			},
 			wantErr: "limits.max_upload_size",
 		},
+		{
+			name: "invalid read header timeout",
+			mutate: func(cfg *Config) {
+				cfg.Server.ReadHeaderTimeout = "bogus"
+			},
+			wantErr: "server.read_header_timeout",
+		},
+		{
+			name: "invalid read timeout",
+			mutate: func(cfg *Config) {
+				cfg.Server.ReadTimeout = "bogus"
+			},
+			wantErr: "server.read_timeout",
+		},
+		{
+			name: "invalid write timeout",
+			mutate: func(cfg *Config) {
+				cfg.Server.WriteTimeout = "bogus"
+			},
+			wantErr: "server.write_timeout",
+		},
+		{
+			name: "invalid idle timeout",
+			mutate: func(cfg *Config) {
+				cfg.Server.IdleTimeout = "bogus"
+			},
+			wantErr: "server.idle_timeout",
+		},
+		{
+			name: "invalid max header bytes",
+			mutate: func(cfg *Config) {
+				cfg.Server.MaxHeaderBytes = 0
+			},
+			wantErr: "server.max_header_bytes",
+		},
 		{
 			name: "invalid ttl parse",
 			mutate: func(cfg *Config) {
@@ -164,6 +239,21 @@ func TestValidateRejectsInvalidValues(t *testing.T) {
 			},
 			wantErr: "security.allowed_ips",
 		},
+		{
+			name: "invalid trusted proxy entry",
+			mutate: func(cfg *Config) {
+				cfg.Security.TrustedProxyIPs = []string{"not-an-ip"}
+			},
+			wantErr: "security.trusted_proxy_ips",
+		},
+		{
+			name: "trust proxy headers requires trusted proxies",
+			mutate: func(cfg *Config) {
+				cfg.Security.TrustProxyHeaders = true
+				cfg.Security.TrustedProxyIPs = nil
+			},
+			wantErr: "security.trusted_proxy_ips is required",
+		},
 		{
 			name: "invalid rate limit burst",
 			mutate: func(cfg *Config) {

internal/http/handlers.go

@@ -44,10 +44,10 @@ func (s *Server) Routes() http.Handler {
 
 	writeHandler := http.HandlerFunc(s.createScratch)
 	middlewares := make([]func(http.Handler) http.Handler, 0, 2)
-	middlewares = append(middlewares, AllowlistMiddleware(s.cfg.Security.AllowedPrefixes, s.cfg.Security.TrustProxyHeaders, s.logger))
+	middlewares = append(middlewares, AllowlistMiddleware(s.cfg.Security.AllowedPrefixes, s.cfg.Security.TrustProxyHeaders, s.cfg.Security.TrustedProxyPrefixes, s.logger))
 	if s.cfg.Security.RateLimit.Enabled {
 		limiter := NewRateLimiter(s.cfg.Security.RateLimit.RequestsPerMinute, s.cfg.Security.RateLimit.Burst)
-		middlewares = append(middlewares, RateLimitMiddleware(limiter, s.cfg.Security.TrustProxyHeaders))
+		middlewares = append(middlewares, RateLimitMiddleware(limiter, s.cfg.Security.TrustProxyHeaders, s.cfg.Security.TrustedProxyPrefixes))
 	}
 	mux.Handle("POST /api/scratch", Chain(writeHandler, middlewares...))
 
@@ -298,7 +298,7 @@ func (s *Server) isUploadAllowedForRequest(r *http.Request) bool {
 		return true
 	}
 
-	clientIP, ok := extractClientIP(r, s.cfg.Security.TrustProxyHeaders)
+	clientIP, ok := extractClientIP(r, s.cfg.Security.TrustProxyHeaders, s.cfg.Security.TrustedProxyPrefixes)
 	if !ok {
 		return false
 	}

internal/http/middleware.go

@@ -59,14 +59,14 @@ func (r *RateLimiter) Allow(ip string) bool {
 	return v.limiter.Allow()
 }
 
-func AllowlistMiddleware(allowed []netip.Prefix, trustProxyHeaders bool, logger *log.Logger) func(http.Handler) http.Handler {
+func AllowlistMiddleware(allowed []netip.Prefix, trustProxyHeaders bool, trustedProxies []netip.Prefix, logger *log.Logger) func(http.Handler) http.Handler {
 	return func(next http.Handler) http.Handler {
 		if len(allowed) == 0 {
 			return next
 		}
 
 		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-			clientIP, ok := extractClientIP(r, trustProxyHeaders)
+			clientIP, ok := extractClientIP(r, trustProxyHeaders, trustedProxies)
 			if !ok {
 				http.Error(w, "unable to determine client ip", http.StatusForbidden)
 				return
@@ -85,10 +85,10 @@ func AllowlistMiddleware(allowed []netip.Prefix, trustProxyHeaders bool, logger
 	}
 }
 
-func RateLimitMiddleware(limiter *RateLimiter, trustProxyHeaders bool) func(http.Handler) http.Handler {
+func RateLimitMiddleware(limiter *RateLimiter, trustProxyHeaders bool, trustedProxies []netip.Prefix) func(http.Handler) http.Handler {
 	return func(next http.Handler) http.Handler {
 		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-			clientIP, ok := extractClientIP(r, trustProxyHeaders)
+			clientIP, ok := extractClientIP(r, trustProxyHeaders, trustedProxies)
 			if !ok {
 				http.Error(w, "unable to determine client ip", http.StatusTooManyRequests)
 				return
@@ -115,8 +115,13 @@ func Chain(handler http.Handler, middlewares ...func(http.Handler) http.Handler)
 	return wrapped
 }
 
-func extractClientIP(r *http.Request, trustProxyHeaders bool) (netip.Addr, bool) {
+func extractClientIP(r *http.Request, trustProxyHeaders bool, trustedProxies []netip.Prefix) (netip.Addr, bool) {
-	if trustProxyHeaders {
+	remoteIP, ok := remoteIPFromRequest(r)
+	if !ok {
+		return netip.Addr{}, false
+	}
+
+	if trustProxyHeaders && isTrustedProxy(remoteIP, trustedProxies) {
 		if xff := strings.TrimSpace(r.Header.Get("X-Forwarded-For")); xff != "" {
 			parts := strings.Split(xff, ",")
 			if len(parts) > 0 {
@@ -131,7 +136,10 @@ func extractClientIP(r *http.Request, trustProxyHeaders bool) (netip.Addr, bool)
 			}
 		}
 	}
+	return remoteIP, true
+}
 
+func remoteIPFromRequest(r *http.Request) (netip.Addr, bool) {
 	host, _, err := net.SplitHostPort(strings.TrimSpace(r.RemoteAddr))
 	if err != nil {
 		if ip, parseErr := netip.ParseAddr(strings.TrimSpace(r.RemoteAddr)); parseErr == nil {
@@ -146,6 +154,15 @@ func extractClientIP(r *http.Request, trustProxyHeaders bool) (netip.Addr, bool)
 	return ip, true
 }
 
+func isTrustedProxy(remoteIP netip.Addr, trusted []netip.Prefix) bool {
+	for _, prefix := range trusted {
+		if prefix.Contains(remoteIP) {
+			return true
+		}
+	}
+	return false
+}
+
 func writeJSON(w http.ResponseWriter, status int, payload any) {
 	w.Header().Set("Content-Type", "application/json")
 	w.WriteHeader(status)

internal/http/middleware_test.go

@@ -17,7 +17,7 @@ func TestAllowlistMiddlewareDeniesAndAllowsByIP(t *testing.T) {
 
 	logger := log.New(io.Discard, "", 0)
 	allowed := []netip.Prefix{netip.MustParsePrefix("10.0.0.0/8")}
-	mw := AllowlistMiddleware(allowed, false, logger)
+	mw := AllowlistMiddleware(allowed, false, nil, logger)
 
 	next := http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
 		w.WriteHeader(http.StatusNoContent)
@@ -46,7 +46,8 @@ func TestAllowlistMiddlewareHonorsProxyHeaderWhenTrusted(t *testing.T) {
 
 	logger := log.New(io.Discard, "", 0)
 	allowed := []netip.Prefix{netip.MustParsePrefix("203.0.113.5/32")}
-	mw := AllowlistMiddleware(allowed, true, logger)
+	trustedProxies := []netip.Prefix{netip.MustParsePrefix("10.0.0.0/8")}
+	mw := AllowlistMiddleware(allowed, true, trustedProxies, logger)
 	handler := mw(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
 		w.WriteHeader(http.StatusNoContent)
 	}))
@@ -66,7 +67,7 @@ func TestRateLimitMiddlewareKeysByClientIP(t *testing.T) {
 	t.Parallel()
 
 	limiter := NewRateLimiter(60, 1)
-	handler := RateLimitMiddleware(limiter, false)(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+	handler := RateLimitMiddleware(limiter, false, nil)(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
 		w.WriteHeader(http.StatusNoContent)
 	}))
 
@@ -98,7 +99,7 @@ func TestRateLimitMiddlewareKeysByClientIP(t *testing.T) {
 func TestAllowlistMiddlewareNoRestrictionsReturnsNext(t *testing.T) {
 	t.Parallel()
 
-	handler := AllowlistMiddleware(nil, false, log.New(io.Discard, "", 0))(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+	handler := AllowlistMiddleware(nil, false, nil, log.New(io.Discard, "", 0))(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
 		w.WriteHeader(http.StatusAccepted)
 	}))
 	req := httptest.NewRequest(http.MethodPost, "/api/scratch", nil)
@@ -115,7 +116,7 @@ func TestAllowlistMiddlewareRejectsUnknownClientIP(t *testing.T) {
 
 	logger := log.New(io.Discard, "", 0)
 	allowed := []netip.Prefix{netip.MustParsePrefix("10.0.0.0/8")}
-	handler := AllowlistMiddleware(allowed, false, logger)(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+	handler := AllowlistMiddleware(allowed, false, nil, logger)(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
 		w.WriteHeader(http.StatusNoContent)
 	}))
 	req := httptest.NewRequest(http.MethodPost, "/api/scratch", nil)
@@ -131,7 +132,7 @@ func TestRateLimitMiddlewareUnknownIP(t *testing.T) {
 	t.Parallel()
 
 	limiter := NewRateLimiter(60, 1)
-	handler := RateLimitMiddleware(limiter, false)(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+	handler := RateLimitMiddleware(limiter, false, nil)(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
 		w.WriteHeader(http.StatusNoContent)
 	}))
 	req := httptest.NewRequest(http.MethodPost, "/api/scratch", nil)
@@ -147,7 +148,7 @@ func TestRateLimitMiddleware429PayloadAndRetryHeader(t *testing.T) {
 	t.Parallel()
 
 	limiter := NewRateLimiter(1, 1)
-	handler := RateLimitMiddleware(limiter, false)(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+	handler := RateLimitMiddleware(limiter, false, nil)(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
 		w.WriteHeader(http.StatusNoContent)
 	}))
 	req1 := httptest.NewRequest(http.MethodPost, "/api/scratch", nil)
@@ -195,7 +196,7 @@ func TestExtractClientIPFallbacks(t *testing.T) {
 
 	req := httptest.NewRequest(http.MethodGet, "/", nil)
 	req.RemoteAddr = "203.0.113.9"
-	ip, ok := extractClientIP(req, false)
+	ip, ok := extractClientIP(req, false, nil)
 	if !ok || ip.String() != "203.0.113.9" {
 		t.Fatalf("extract direct ip = (%v,%v), want (203.0.113.9,true)", ip, ok)
 	}
@@ -204,14 +205,26 @@ func TestExtractClientIPFallbacks(t *testing.T) {
 	req2.RemoteAddr = "192.0.2.50:8080"
 	req2.Header.Set("X-Forwarded-For", "bad,198.51.100.1")
 	req2.Header.Set("X-Real-IP", "198.51.100.5")
-	ip2, ok2 := extractClientIP(req2, true)
+	ip2, ok2 := extractClientIP(req2, true, []netip.Prefix{netip.MustParsePrefix("192.0.2.0/24")})
 	if !ok2 || ip2.String() != "198.51.100.5" {
 		t.Fatalf("extract x-real-ip = (%v,%v), want (198.51.100.5,true)", ip2, ok2)
 	}
 
 	req3 := httptest.NewRequest(http.MethodGet, "/", nil)
 	req3.RemoteAddr = "still-not-an-ip"
-	if _, ok3 := extractClientIP(req3, false); ok3 {
+	if _, ok3 := extractClientIP(req3, false, nil); ok3 {
 		t.Fatalf("extractClientIP() ok = true, want false")
 	}
 }
+
+func TestExtractClientIPIgnoresHeadersFromUntrustedProxy(t *testing.T) {
+	t.Parallel()
+
+	req := httptest.NewRequest(http.MethodGet, "/", nil)
+	req.RemoteAddr = "203.0.113.10:8080"
+	req.Header.Set("X-Forwarded-For", "198.51.100.5")
+	ip, ok := extractClientIP(req, true, []netip.Prefix{netip.MustParsePrefix("10.0.0.0/8")})
+	if !ok || ip.String() != "203.0.113.10" {
+		t.Fatalf("extractClientIP() = (%v,%v), want (203.0.113.10,true)", ip, ok)
+	}
+}