chore(frontend): add CSP in next config (#85)

* Add security headers to frontend

* rm unsafe directives

* re-add unsafe directives, staging backend url

* fix json format

* add trailing comma

* chore(frontend): improve CSP per Next.js docs

* style(frontend): standardize quotes for upgrade-insecure-requests header

---------

Co-authored-by: Madhur Gupta <madhurgupta107@gmail.com>

Author: 0xflashboy

frontend/.env.example

@@ -3,4 +3,4 @@ NEXT_PUBLIC_EVENTS_WS_URL="wss://<SERVER_ADDR>:<SERVER_PORT>"
 
 # BlockVision Pro API key for Monad mainnet contract metadata lookups
 # Get your API key from https://docs.blockvision.org/
-BLOCKVISION_API_KEY="your-api-key-here"
+BLOCKVISION_API_KEY="your-api-key-here"

frontend/next.config.ts

@@ -1,5 +1,7 @@
 import type { NextConfig } from 'next'
 
+const isDev = process.env.NODE_ENV === 'development'
+
 const nextConfig: NextConfig = {
   images: {
     remotePatterns: [
@@ -10,6 +12,38 @@ const nextConfig: NextConfig = {
       },
     ],
   },
+  async headers() {
+    return [
+      {
+        source: '/(.*)',
+        headers: [
+          { key: 'X-Content-Type-Options', value: 'nosniff' },
+          { key: 'Referrer-Policy', value: 'strict-origin-when-cross-origin' },
+          {
+            key: 'Permissions-Policy',
+            value: 'geolocation=(), microphone=(), camera=()',
+          },
+          { key: 'X-Frame-Options', value: 'DENY' },
+          {
+            key: 'Content-Security-Policy',
+            value: [
+              "default-src 'self'",
+              `script-src 'self' 'unsafe-inline' https://va.vercel-scripts.com${isDev ? " 'unsafe-eval'" : ''}`,
+              "style-src 'self' 'unsafe-inline'",
+              "img-src 'self' data: https://raw.githubusercontent.com",
+              "font-src 'self'",
+              "connect-src 'self' wss://monode-mainnet.monadinfra.com wss://execution-events-backend-example.molandak.org",
+              "frame-ancestors 'none'",
+              "object-src 'none'",
+              "base-uri 'self'",
+              "form-action 'self'",
+              'upgrade-insecure-requests',
+            ].join('; '),
+          },
+        ],
+      },
+    ]
+  },
 }
 
 export default nextConfig