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This is a boilerplate for using the GreyNoise API as an enrichment within a Cloudflare Worker.

How it works

  1. Client makes a request to the Worker webservice
  2. Using the Workers Request object, we extract the incoming request client IP
  3. We look up that client IP on GreyNoise
  4. Based on the GreyNoise classification, we return a different response.

In this example, there are three responses:

GreyNoise classification Response Function What it does
malicious maliciousResponse() Responds with a 301 redirect to an ASCII Rick Roll (thanks @ryancdotorg)
benign benignResponse() Responds with 200 with plaintext message stating your benign-ness
Everything else normalResponse() Responds with 200 and welcomes you :)

Why have you done this?

One of the best features of the Workers platform is the speed. Since the serverless Workers are deployed globally on Cloudflare's edge, there are some serious speed gains compared to running a webservice on a VPS somewhere.

Cloudflare WAF can handle most of your problems. But what if you wanted to do a very targeted lookup against a service you trust? This project is an example of how you might do that with GreyNoise, which is doing cool work annotating web traffic.

How much slower is it?

The benchmarks are OK. For regular humans browing the web, its almost negligble. I'd be dissappointed with any page load 10x slower than without the enrichment lookup.

Test Case Speed Client Location Performance Grade Link
Without enrichment API lookup 57 ms San Francisco 🟢 A pingdom test
With enrichment API lookup 383 ms San Francisco 🟢 A pingdom test
Without enrichment API lookup 76 ms Frankfurt N/A URLscan
With enrichment API lookup 444 ms Frankfurt N/A URLscan

Running locally in development mode

The best development experience for running locally is with miniflare, which does an excellent job simulating the Workers platform.

To do this, just run

miniflare index.js -w

This will run the default wrangler.toml, which is a template. To run a specific wrangler.toml that is perhaps filled with secrets like your GreyNoise API token and your Cloudflare ID info, you can specify a specific wrangler.toml by running something like this:

miniflare -c .secrets/wrangler.toml index.js -w

To simulate the environment variable GREYNOISE_API_KEY you will also need to pass it as a command line arg:

miniflare -c .secrets/wrangler.toml index.js -w --binding GREYNOISE_API_KEY=<your GreyNoise API key>

To route a tunnel to your localhost development runtime you could even use something like cloudflared or ngrok to better simulate web traffic.


Once you have your wrangler.toml filled out, you can publish your worker with the wrangler CLI.

wrangler publish

though if you sourced your wrangler.toml in a directory like .secrets, you would run this:

wrangler publish -c .secrets/wrangler.toml

Using this as a template

You would be able to do this

wrangler generate project_name

However this command looks for the master branch rather than the main branch. Go bother the wrangler devs if this annoys you too.