Workers – One-click Cloudflare Access for Workers

You can now enable Cloudflare Access for your workers.dev and Preview URLs in a single click.

Access allows you to limit access to your Workers to specific users or groups. You can limit access to yourself, your teammates, your organization, or anyone else you specify in your Access policy.

To enable Cloudflare Access:

1. In the Cloudflare dashboard, go to the Workers & Pages page.

   Go to Workers & Pages

2. In Overview, select your Worker.

3. Go to Settings > Domains & Routes.

4. For workers.dev or Preview URLs, click Enable Cloudflare Access.

5. Optionally, to configure the Access application, click Manage Cloudflare Access. There, you can change the email addresses you want to authorize. View Access policies to learn about configuring alternate rules.

To fully secure your application, it is important that you validate the JWT that Cloudflare Access adds to the Cf-Access-Jwt-Assertion header on the incoming request.

The following code will validate the JWT using the jose NPM package:

import { jwtVerify, createRemoteJWKSet } from "jose";

export default {
  async fetch(request, env, ctx) {
    // Get the JWT from the request headers
    const token = request.headers.get("cf-access-jwt-assertion");

    // Check if token exists
    if (!token) {
      return new Response("Missing required CF Access JWT", {
        status: 403,
        headers: { "Content-Type": "text/plain" },
      });
    }

    try {
      // Create JWKS from your team domain
      const JWKS = createRemoteJWKSet(
        new URL(`${env.TEAM_DOMAIN}/cdn-cgi/access/certs`),
      );

      // Verify the JWT
      const { payload } = await jwtVerify(token, JWKS, {
        issuer: env.TEAM_DOMAIN,
        audience: env.POLICY_AUD,
      });

      // Token is valid, proceed with your application logic
      return new Response(`Hello ${payload.email || "authenticated user"}!`, {
        headers: { "Content-Type": "text/plain" },
      });
    } catch (error) {
      // Token verification failed
      return new Response(`Invalid token: ${error.message}`, {
        status: 403,
        headers: { "Content-Type": "text/plain" },
      });
    }
  },
};

Required environment variables

Add these environment variables to your Worker:

• POLICY_AUD: Your application’s AUD tag
• TEAM_DOMAIN: https://<your-team-name>.cloudflareaccess.com

Both of these appear in the modal that appears when you enable Cloudflare Access.

You can set these variables by adding them to your Worker’s Wrangler configuration file, or via the Cloudflare dashboard under Workers & Pages > your-worker > Settings > Environment Variables.

Source: Cloudflare

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