Achieving Secure Static Site Delivery with Cloudflare Pages

Cloudflare Pages is an excellent platform for hosting static sites. This article covers our actual deployment setup and security configuration using the _headers file.

Deployment Architecture: Why We Left Workers and Returned to Pages

Initially, we planned to use Cloudflare Workers for backend processing of the contact form. Workers allow server-side email sending and validation.

However, we encountered the following challenges during implementation:

• Build complexity: Serving Astro’s build output through Workers required additional configuration
• Debugging overhead: Behavioral differences between local wrangler dev and production
• Cache control: Pages integrates more naturally with Cloudflare’s CDN

Ultimately, we adopted ssgform.com as an external service for the contact form, completely eliminating server-side processing. This removed the need for Workers, allowing us to deploy as a pure static site on Pages.

Security Configuration with _headers

On Cloudflare Pages, you can specify HTTP response headers in the public/_headers file. Below is an excerpt of the configuration we actually use.

Content-Security-Policy (CSP)

CSP is a critical header for preventing cross-site scripting (XSS) attacks. It specifies allowed resource origins using a whitelist approach.

Content-Security-Policy: default-src 'self';
  script-src 'self' 'unsafe-inline' https://challenges.cloudflare.com https://pagead2.googlesyndication.com;
  style-src 'self' 'unsafe-inline';
  img-src 'self' https://wsrv.nl https://images.unsplash.com data:;
  connect-src 'self' https://challenges.cloudflare.com https://pagead2.googlesyndication.com;
  frame-src https://challenges.cloudflare.com https://googleads.g.doubleclick.net;
  form-action https://ssgform.com;

Key points:

• script-src: Allow Cloudflare Turnstile (challenges.cloudflare.com) and AdSense
• img-src: Allow the image proxy wsrv.nl and Unsplash
• form-action: Restrict form submissions to ssgform.com only
• frame-src: Allow Turnstile iframes and AdSense ad frames

Other Security Headers

X-Content-Type-Options: nosniff
X-Frame-Options: DENY
Referrer-Policy: strict-origin-when-cross-origin
Permissions-Policy: camera=(), microphone=(), geolocation=()

• X-Content-Type-Options: Prevent MIME sniffing
• X-Frame-Options: Prevent iframe embedding as a clickjacking countermeasure
• Referrer-Policy: Send only the origin for cross-origin requests
• Permissions-Policy: Disable unnecessary browser APIs (camera, microphone, geolocation)

Cache Control

We set long-term caching for static assets and shorter caching for HTML.

/_astro/*
  Cache-Control: public, max-age=31536000, immutable

/*.html
  Cache-Control: public, max-age=3600

Files in the _astro/ directory output by Astro include content hashes, making it safe to cache them for one year with immutable. HTML has a moderate update frequency, so we limit it to a one-hour cache.

Pages Deployment Configuration

Cloudflare Pages project settings are simple:

Once you connect a GitHub repository, pushes to the main branch trigger automatic deploys. Preview deployments are also auto-generated per PR, making reviews smoother.

Summary

The key is asking yourself: “Do I really need server-side processing?” By leveraging external services to eliminate Workers, both deployment and security management became simpler. CSP configuration via _headers takes some initial effort, but once written, it applies to all pages — making it a highly cost-effective security measure.