This is a 2 min read · Published on 27 Oct 2021

I'm obsessed with WebPageTest. It's such an amazing free resource and I use it to measure every project I build. When I first moved this website over to Cloudflare Pages (literally my first day at Cloudflare) I was sad to see it get a FAILING grade on WebPageTest.

It was getting A's across the board except for the security audit. Digging a bit deeper, it was unhappy that my site was missing a few important security headers.

WebPageTest Security Failing

WebPageTest Security Details Page

At the time, it wasn't super easy to add custom headers to a Cloudflare Pages project. It was definitely doable! But you needed to build a Cloudflare Worker to sit in front of the site and add response headers. That all changed today!

Cloudflare adds custom headers for Pages

Now you can simply add a _headers file to your Pages project and Cloudflare will add them to the responses!

So I went to my website, adding a _headers file in the root directory with the security headers in it and deployed!

Content-Security-Policy: default-src 'self'
X-Frame-Options: DENY
X-XSS-Protection: 1
X-Content-Type-Options: nosniff

I raced over to check my WebPageTest score and...

WebPageTest Security Failing

Dangit. I checked my _site directory and sure enough, there was no _headers file in there.

Adding the headers file to Eleventy

Then I remembered something about static assets on Eleventy. I did a quick search and found this lovely documentation page (their docs are so good) Passthrough file copy

So I added this line of code to my eleventy.js file:

eleventyConfig.addPassthroughCopy({ static: "/" })

Now, any files I stick in my /static/ directory will be directly copied over to the root of my _site folder on build! So /static/_headers becomes /_site/_headers when you run eleventy.

Deployed it again and BOOM, A+ city.

WebPageTest All A's

And then everything broke...

I was so pumped! I wrote this blog post and Tweeted it! But then when I went to view it, I noticed that my Tweet embeds weren't working. I looked in the console and my Google Fonts and inline scripts stopped working too!

Dang you, CSP!

Ok so I found this awesome website on content security policies and scraped together some allowed domains to get my Google Fonts and Twitter embeds working again.

Content-Security-Policy: default-src 'self';font-src;style-src 'self' 'sha256-5g0QXxO6NfvHJ6Uf5BK/hqQHtso8ZOdjlnbyKtYLvwc='; script-src 'self'; frame-src 'self'

But what about my sweet dark mode toggle which is some inline JavaScript?

It turns out you have three choices:

  1. Use a nonce
  2. Use the 'unsafe-inline' option
  3. Generate a SHA hash and allow that.

I like pain so I chose option #3. I minified all of my inline JS into a single line

<script>function toggle_light_mode(){"dark"==localStorage.getItem("theme")?(localStorage.setItem("theme","light"),document.documentElement.setAttribute("data-theme","light")):(localStorage.setItem("theme","dark"),document.documentElement.setAttribute("data-theme","dark"))}"dark"===localStorage.getItem("theme")?document.documentElement.setAttribute("data-theme","dark"):document.documentElement.setAttribute("data-theme","light");</script>

And then I ran

echo -n 'that single line of js above' | openssl sha256 -binary | openssl base64

And that generated a unique hash, 8ZCTxR11UEYhveA/O/iAlHa4qNfBXa9oH8mU57KOrps=.

Finally, I added sha256-that_hash_above to the script-src section of my _header file. So now it looks like

Content-Security-Policy: default-src 'self';font-src;style-src 'self' 'sha256-5g0QXxO6NfvHJ6Uf5BK/hqQHtso8ZOdjlnbyKtYLvwc='; script-src 'self' 'sha256-8ZCTxR11UEYhveA/O/iAlHa4qNfBXa9oH8mU57KOrps='; frame-src 'self'

I really need to get back to work 😅

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