From 73fc21b6a84effa487f4f1fc0c1c21832eb6660e Mon Sep 17 00:00:00 2001
From: sneak <sneak@sneak.berlin>
Date: Mon, 21 Sep 2026 18:16:20 +0000
Subject: [PATCH 1/2] test: assert HSTS, CSP, and Permissions-Policy headers

Failing test for the three security headers required before 1.0
(issue #91). Implementation follows in the next commit.

Model: opus-4-8
---
 .../middleware/middleware_internal_test.go    | 55 +++++++++++++++++++
 1 file changed, 55 insertions(+)

diff --git a/internal/middleware/middleware_internal_test.go b/internal/middleware/middleware_internal_test.go
index ac3f128..9992a60 100644
--- a/internal/middleware/middleware_internal_test.go
+++ b/internal/middleware/middleware_internal_test.go
@@ -56,6 +56,61 @@ 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()
 
-- 
2.54.0


From 3afce4838349b3ef8eadac8623d83abc2139b9b9 Mon Sep 17 00:00:00 2001
From: sneak <sneak@sneak.berlin>
Date: Mon, 21 Sep 2026 18:16:20 +0000
Subject: [PATCH 2/2] feat: add HSTS, CSP, and Permissions-Policy security
 headers (closes #91)

SecurityHeaders() now also sets Strict-Transport-Security,
Content-Security-Policy, and Permissions-Policy.

HSTS is emitted unconditionally: browsers ignore it over plaintext
(RFC 6797 section 8.1), so it never lies about the connection and no
forwarded-proto header need be trusted.

The CSP baseline is default-src 'self' with frame-ancestors 'none' as
the primary clickjacking control. script-src and style-src carry
'unsafe-inline' because the generator template has inline onclick
handlers and the bundled Tailwind asset injects a runtime <style>
element; removing that need is a template change beyond this issue.

Permissions-Policy denies browser features pixa does not use.

Model: opus-4-8
---
 internal/middleware/middleware.go | 37 +++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/internal/middleware/middleware.go b/internal/middleware/middleware.go
index 754ebd1..00d59f7 100644
--- a/internal/middleware/middleware.go
+++ b/internal/middleware/middleware.go
@@ -21,6 +21,33 @@ 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
@@ -164,6 +191,16 @@ 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)
 		})
 	}
-- 
2.54.0