feat: improve header security

middleware/headers.ts

@@ -0,0 +1,36 @@
+// Copyright 2023 the Deno authors. All rights reserved. MIT license.
+import type { MiddlewareHandlerContext } from "$fresh/server.ts";
+
+export async function hardenHeaders(
+  req: Request,
+  ctx: MiddlewareHandlerContext,
+) {
+  const response = await ctx.next();
+  const path = new URL(req.url).pathname.split("/")[1] || "/";
+  const blacklist = [/api/];
+
+  if (blacklist.some((regex) => regex.test(path))) {
+    return response;
+  }
+
+  const contentSecurityPolicy = [
+    "default-src 'self'",
+    "img-src 'self' https://avatars.githubusercontent.com",
+    "frame-ancestors 'self'",
+    "script-src 'self' 'unsafe-inline';",
+    "style-src 'self' 'unsafe-inline'",
+    "object-src 'none'",
+  ];
+
+  response.headers.set(
+    "Content-Security-Policy",
+    contentSecurityPolicy.join("; "),
+  );
+  response.headers.set("Strict-Transport-Security", "max-age=63072000;");
+  response.headers.set("Referrer-Policy", "strict-origin-when-cross-origin");
+  response.headers.set("X-Content-Type-Options", "nosniff");
+  response.headers.set("X-Frame-Options", "SAMEORIGIN");
+  response.headers.set("X-XSS-Protection", "1; mode=block");
+
+  return response;
+}