Hi there! Website hacks and data breaches seem to be happening increasingly often these days. As an online business, you want to ensure your web applications are locked down tight against the rising threats targeting the modern web.
Implementing basic security headers provides an invaluable layer of protection. According to recent reports, over 70% of web traffic is now encrypted, yet many sites still do not utilize headers like CSP and HSTS. Attackers exploit this oversight to carry out SQL injection, cross-site scripting, and other common attacks.
Don‘t let your websites remain vulnerable! In this comprehensive guide, you‘ll learn how to leverage Cloudflare Workers to rapidly deploy essential security headers across your domains.
Understanding Today‘s Threat Landscape
The volume and sophistication of cyberattacks targeting web apps continues rising dramatically each year. Vulnerable headers are increasingly being used as an attack vector to infiltrate networks and steal data.
OWASP lists insecure headers in the top ten most critical web application vulnerabilities. Flaws like missing CSP policies and enabling outdated SSL protocols account for the majority of website hacks. Hospitality, retail, and healthcare sectors tend to have the most vulnerabilities.
The 2022 Cyberthreat Defense Report confirms this trend, reporting a 55% increase in cyberattacks, with 75% targeting application layers. F5 Labs research found 60% of apps still disable basic headers like HSTS.
By implementing headers like CSP and Feature-Policy, you can eliminate entire classes of threats looking to break in through cross-site scripting, injection attacks, clickingjacking and more. Let‘s look at how Cloudflare Workers makes that simple.
Understanding Cloudflare Workers
Cloudflare Workers provides serverless computing at the edge of Cloudflare‘s global network, across 250+ cities worldwide. This means the scripts you write run on infrastructure extremely close to your end users.
Unlike traditional web servers, Workers scales automatically without provisioning infrastructure. Your code handles requests as they come in, manipulates them, and sends back responses – allowing you to control what headers get set.
Other options like configuring headers in Apache or Nginx work for simple cases, but require rebuilding configurations across nodes. With Workers, you write the logic once and it applies instantly across Cloudflare‘s edge to all your traffic.
This makes Workers an extremely fast, flexible way to implement security headers at scale. Now let‘s explore the headers you need to know about.
Must-Have Security Headers
The Open Web Application Security Project (OWASP) provides excellent reference material detailing which headers you should implement to start properly securing your web apps.
These headers mitigate the most common vulnerabilities by enforcing good protocol usage, increasing browser protections, allowing only approved content sources, and controlling resource access.
Content-Security-Policy (CSP)
CSP is the front line of defense against dangerous cross-site scripting attacks. It restricts where browsers can load resources from, preventing untrusted sources.
For example, inline JavaScript can enable XSS attacks by running malicious code. By setting a policy like:
Content-Security-Policy: script-src ‘self‘; object-src ‘none‘We prevent inline scripts and object resource loading by default. Any whitelisting happens explicitly through the source directive values. This stops injection attacks in their tracks!
CSP can block a wide array of resource types – scripts, stylesheets, images, fonts, and more. Tuning the directives to precisely your app‘s needs is key for both security and functionality.
HTTP Strict Transport Security (HSTS)
HSTS handles enforcing HTTPS connectivity and TLS versions. For example:
Strict-Transport-Security: max-age=31536000; includeSubDomainsThis requires clients to use HTTPS for all requests to this domain and subdomains, for the next year (31536000 seconds). It also prevents HTTP redirects that could bypass TLS, and enables preloading in supporting browsers.
These protections mitigate weaknesses like insecure redirects, cookie hijacking, malware injection, and eavesdropping threats.
X-Frame-Options
Clickjacking remains another serious concern – hackers embed invisible iframes layered over legitimate pages to trick users into clicking elements they can‘t even see.
The X-Frame-Options header prevents this by disabling page rendering in iframes unauthorized domains. DENY blocks framing altogether, while SAMEORIGIN allows framing within your domain.
X-XSS-Protection
Inline code detection and filtering provided by browsers remains the first line of defense against reflected cross-site scripting attacks:
X-XSS-Protection: 1; mode=blockThis header configures the filter to block entire pages if XSS payloads are detected. The protection isn‘t flawless, but reduces exposure dramatically.
You should also sanitize untrusted inputs and safely encode outputs in your application code itself when displaying data from users.
Additional Headers
Beyond the core OWASP recommended headers, there are a few other useful ones:
X-Content-Type-Options – Stops MIME-sniffing attacks targeting response payloads by lying about content types.
Referrer-Policy – Govern information disclosure through limiting what referrer data sends cross-origin.
Feature-Policy – Selectively enables and disables browser features with granular origin-based controls. Can mitigate entire categories of threats related to insecure features.
Clear-Site-Data – Allows explicitly clearing browser cache/storage for sensitive apps like banking where leakage between sessions is unacceptable.
Now that you understand the immense value properly configured headers provide, let‘s get into how you can leverage Cloudflare Workers to deploy them with ease.
Implementing Security Headers with Workers
The Workers serverless platform makes it simple to intercept requests and inject new response headers before returning content to visitors.
Let‘s inspect a simplified script:
addEventListener("fetch", event => {
// Define header policies
const securityHeaders = {
"Content-Security-Policy": "default-src ‘self‘",
"Strict-Transport-Security": "max-age=31536000"
}
event.respondWith(
handleRequest(event) //Intercept
)
})
/**
* Fetch content from origin
* Assign security headers
* Return response
**/
async function handleRequest(event) {
const response = fetch(event.request)
const headers = new Headers(response.headers)
Object.assign(headers, securityHeaders)
return new Response(response.body, {
headers
})
}This demonstrates fetching the content from origin servers first, then combining the security headers with the response headers before sending back to the client.
You can easily set up individual header values like sources allowed in CSP. Additional logic can sanitize vulnerable headers, check content types, restrict by paths, and much more.
Now that you understand the basics, let‘s go over deploying such a script.
Deploying Your Security Worker
Cloudflare provides an excellent online editor to write Workers code quickly. Follow these steps:
- Navigate to Workers in your Cloudflare account sidebar
- Click the Create a Service button
- Give the service a name
- Paste in the header manipulation code above
- Customize headers and values for your sites
- Click Save and Deploy!
You can also upload existing scripts written externally. I recommend starting simple and tweaking one site/path at a time:
The editor allows updating code easily down the line. Adding routes during deployment restricts the headers to certain paths until you verify functionality.
And that‘s all there is to it! Cloudflare will activate the Worker across its servers around the world, applying security headers to traffic for your chosen sites.
Inspecting Headers for Issues
Once properly deployed, requests should return responses with the new headers inserted:
$ curl -I https://example.com
HTTP/2 200
Content-Security-Policy: default-src ‘self‘
Strict-Transport-Security: max-age=31536000
X-Content-Type-Options: nosniffI recommend running tests with Postman, cURL, or your browser‘s developer tools to validate presence and functionality of all headers. For example in Chrome:
Sometimes a certain header may get stripped depending on cache settings. Monitoring header delivery ensures full coverage. Services like Mozilla Observatory grade your total implementation.
With the power of Workers, you can dynamically tweak headers targeting specific paths and origins. As you enhance application security further, take advantage of Workers KV secure storage for managing dynamic policies at the edge.
Closing Thoughts
Implementing basic security headers is a quick win to significantly expand defenses. Cloudflare Workers removes complexity out of deploying robust header-based protection for your web applications.
I encourage all of you to reference the OWASP Secure Headers guide, start with the Foundational policies, customize to your application architecture, and progressively strengthen safeguards.
Let me know if you have any other questions! I‘m always happy to help fellow developers reinforce their application security posture against modern threats. Stay safe out there!
