Tighten Content Security Policy and enhance security headers #130
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Summary
Successfully tightened Content Security Policy to enhance XSS protection by removing
unsafe-evalandunsafe-inlinefrom production builds while maintaining development workflow compatibility.Changes Made
CSP Implementation
unsafe-evalfrom production: Only allowed in development mode for Hot Module Replacement (HMR)unsafe-inlinewith nonce-based approach: Implemented dynamic per-request nonce generation using cryptographic randomnessimg-srcandconnect-srcweb/middleware.tsfor per-request securitySecurity Improvements
frame-ancestors 'self',connect-srcrestrictions, and other security headers remain intactDocumentation
web/docs/CSP_SECURITY_IMPROVEMENTS.mdTesting
unsafe-evalandunsafe-inlinefor HMRTechnical Implementation
Buffer.from(crypto.randomUUID()).toString('base64')The changes are production-ready and provide significant security improvements without breaking existing functionality.
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Completed all remaining tasks! Here's what was done:
✅ Security Scan: Ran CodeQL analysis - no security issues detected
✅ Documentation: Created comprehensive documentation in
web/docs/CSP_SECURITY_IMPROVEMENTS.mdcovering:✅ README Update: Added Web Application Security section highlighting CSP improvements
Summary of Changes (commit
4484fc0):unsafe-evalfrom production CSP (kept for dev HMR)unsafe-inlinewith nonce-based approachAll acceptance criteria met:
The PR is now ready for review!
Pull request overview
This PR tightens the web app’s Content Security Policy by removing
unsafe-eval/unsafe-inlinefor production scripts and switching to a per-request nonce generated in Next.js middleware, while keeping development workflow compatibility.Changes:
next.config.mjstoweb/middleware.tsto support per-request nonces and environment-specific directives.getNonce()helper and pass the nonce into the Google Analyticsnext/scriptusages.web/docs/CSP_SECURITY_IMPROVEMENTS.md) and update the root README with a Web Application Security section.Reviewed changes
Copilot reviewed 9 out of 9 changed files in this pull request and generated 7 comments.
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getNonce()helper to read the per-request nonce from headers in Server Components.next/scripttags.💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.
@@ -59,3 +59,4 @@{/* Structured Data - JSON-LD scripts don't execute JavaScript, so they don't need nonces */}<scripttype="application/ld+json"dangerouslySetInnerHTML={{This inline JSON-LD
<script>is still an inline script from CSP’s perspective and may be blocked by the new productionscript-src(no'unsafe-inline') unless it includes the per-request nonce (or a hash). Consider adding the nonce attribute so structured data isn’t silently dropped and to avoid CSP violations.With the new production CSP (
script-srcwithout'unsafe-inline'), this inline<script type="application/ld+json">will still be treated as an inline script and is likely to be blocked unless it carries the per-request nonce (or a hash). The comment says nonces aren’t needed, but in practice you should addnonce={nonce}(or convert tonext/scriptwith nonce) to avoid CSP violations and structured data being dropped in production.@@ -71,3 +71,4 @@{/* Structured Data - JSON-LD scripts don't execute JavaScript, so they don't need nonces */}<scripttype="application/ld+json"dangerouslySetInnerHTML={{This inline JSON-LD
<script>will be subject to the tightened production CSP (script-srcwithout'unsafe-inline') and may be blocked without a nonce/hash. If you want the structured data to be delivered in production without CSP violations, add the request nonce to this script tag (or render it vianext/scriptwithnonce).@@ -0,0 +19,4 @@- Dynamic nonce generation in middleware for each request- Nonces are cryptographically random (base64-encoded UUID)- Next.js Script components automatically receive nonces- JSON-LD structured data scripts don't require nonces (type="application/ld+json")The doc claims JSON-LD
<script type="application/ld+json">blocks “don’t require nonces”. Withscript-srctightened to remove'unsafe-inline', these inline script tags can still be blocked unless they include a nonce or hash, which would prevent structured data from being applied and generate CSP violations. Consider updating the guidance to recommend adding the nonce/hash to JSON-LD scripts under the production policy.@@ -60,3 +82,2 @@},});For protected API routes (e.g.
/api/app/bind), this middleware redirects unauthenticated requests to/signin.fetch()calls will typically follow the redirect and return HTML with200, which will then failres.json()and also changes the API contract away from the existing401JSON responses returned by the route handlers. Consider returningNextResponse.json({ error: 'Unauthorized' }, { status: 401 })for/api/*requests (or excluding/apifrom the middleware matcher and letting the API handlers enforce auth).Buffer.from(...)is used to build the CSP nonce inside middleware. Next.js middleware runs in the Edge runtime where Node globals likeBufferare not available, so this will throw at runtime in production. Generate the nonce using Web Crypto APIs (e.g.,crypto.getRandomValues) and base64-encode without relying onBuffer.The middleware matcher now runs on all routes except a few static/internal paths, which includes
/api/*. That means every API response will also get this page-oriented middleware behavior (locale header/cookie and CSP header), and combined with the redirect logic above can alter API semantics. If CSP/locale are only intended for HTML pages, consider excluding/apiin the matcher.