Add SecurityHeadersFilter for hardened HTTP responses

Author: johanbriger

src/main/java/org/juv25d/App.java

@@ -1,16 +1,13 @@
 package org.juv25d;
 
-import org.juv25d.filter.IpFilter;
-import org.juv25d.filter.LoggingFilter;
-import org.juv25d.filter.RateLimitingFilter;
+import org.juv25d.filter.*;
 import org.juv25d.logging.ServerLogging;
 import org.juv25d.http.HttpParser;
 import org.juv25d.plugin.NotFoundPlugin; // New import
 import org.juv25d.plugin.StaticFilesPlugin;
 import org.juv25d.router.SimpleRouter; // New import
 import org.juv25d.util.ConfigLoader;
-import org.juv25d.filter.RedirectFilter;
-import org.juv25d.filter.RedirectRule;
+
 import java.util.List;
 
 import java.util.Set;
@@ -41,6 +38,8 @@ public static void main(String[] args) {
 
         pipeline.addGlobalFilter(new LoggingFilter(), 0);
 
+        pipeline.addGlobalFilter(new SecurityHeadersFilter(), 0);
+
         if (config.isRateLimitingEnabled()) {
             pipeline.addGlobalFilter(new RateLimitingFilter(
                 config.getRequestsPerMinute(),

src/main/java/org/juv25d/filter/SecurityHeadersFilter.java

@@ -0,0 +1,25 @@
+
+package org.juv25d.filter;
+
+import org.juv25d.http.HttpRequest;
+import org.juv25d.http.HttpResponse;
+import java.io.IOException;
+
+    /**
+     * Filter som lägger till säkerhetsheaders till varje HTTP-svar.
+     * Detta hjälper till att skydda mot attacker som Clickjacking och MIME-sniffing.
+     */
+    public class SecurityHeadersFilter implements Filter {
+
+        @Override
+        public void doFilter(HttpRequest req, HttpResponse res, FilterChain chain) throws IOException {
+            chain.doFilter(req, res);
+
+            res.setHeader("X-Content-Type-Options", "nosniff");
+            res.setHeader("X-Frame-Options", "DENY");
+            res.setHeader("X-XSS-Protection", "1; mode=block");
+            res.setHeader("Referrer-Policy", "no-referrer");
+        }
+    }
+
+