tls-devicer

Developed by Gateway Corporate Solutions

TLS Intelligence Middleware for the FP-Devicer Intelligence Suite.

Passively collect and match JA4 fingerprints, TLS extensions, cipher order, HTTP/2 settings, and header consistency to strengthen device identity.

Part of the FP-Devicer family — invisible to clients and extremely hard to spoof.

Important: tls-devicer does not derive JA4 itself. It consumes JA4 or related TLS signals from headers injected by an upstream edge such as Cloudflare, HAProxy with custom logic, Envoy filters, or another TLS terminator that can compute and forward them.

Usage

tls-devicer is designed to integrate seamlessly with FP-Devicer by use of the registerWith helper. This works best when your reverse proxy injects JA4 and TLS headers.

import { createInMemoryAdapter, DeviceManager } from "devicer.js";
import { TlsManager } from "tls-devicer";

const deviceManager = new DeviceManager(createInMemoryAdapter());
const tlsManager = new TlsManager({
	licenseKey: process.env.DEVICER_LICENSE_KEY,
});

tlsManager.registerWith(deviceManager);

app.post("/identify", async (req, res) => {
	const result = await deviceManager.identify(req.body, {
		tlsProfile: {
			ja4: req.headers["x-ja4"],
			extensions: req.headers["x-tls-extensions"]?.split(","),
			http2Settings: req.headers["x-http2-settings"],
		},
	});
});

Recommended Setup (Nginx w/ CloudFlare)

Stock nginx cannot generate JA4 or expose ClientHello extension lists through variables. That means the following variables do not exist in standard nginx:

• $ssl_client_hello_ja4
• $ssl_client_hello_extensions
• a request variable for the client's raw HTTP/2 SETTINGS frame

Use nginx as a pass-through layer for headers that were already added by an upstream edge.

Cloudflare to nginx to app

tls-devicer accepts cf-ja4 directly, but many applications prefer normalizing that to x-ja4 before it reaches Node.

This method requires a Cloudflare Enterprise subscription.

server {
	listen 443 ssl http2;
	server_name example.com;

	ssl_certificate /etc/letsencrypt/live/example/fullchain.pem;
	ssl_certificate_key /etc/letsencrypt/live/example/privkey.pem;

	location / {
		proxy_pass http://127.0.0.1:3000;

		proxy_set_header Host $host;
		proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
		proxy_set_header X-Forwarded-Proto $scheme;

		# Cloudflare-managed JA4 header forwarded to your app.
		proxy_set_header X-JA4 $http_cf_ja4;

		# Optional JA3 alias if your upstream provides it.
		proxy_set_header X-JA3 $http_cf_ja3_fingerprint;
	}
}

In your application, either consume x-ja4 as shown above or pass the raw Cloudflare header through unchanged. tls-devicer supports both x-ja4 and cf-ja4.

If nginx is your TLS edge

If nginx is the first TLS terminator, you have two realistic options:

1. Use another edge or extension that computes JA4 and injects it before the request reaches your app.
2. Run tls-devicer without JA4 and rely on the signals nginx can actually expose, such as header order and selected TLS metadata available from other headers.

For plain nginx, do not expect native JA4, raw extension-order, or client HTTP/2 SETTINGS extraction.

Documentation

This project uses typedoc and autodeploys via GitHub Pages. You can view the generated documentation here.

Installation

You can install ip-devicer and tls-devicer alongside FP-Devicer with

npm install devicer.js ip-devicer tls-devicer

You can also install the meta-package for the entire Devicer Intelligence Suite with

npm install @gatewaycorporate/devicer-intel

License

Published under the Business Source License 1.1 (BSL-1.1)

• Free for dev/testing/personal use
• Production use requires a paid license from Polar.sh
• Free tier has device count limits and basic features only
• Pro tier can operate on a single server and has no device count limits
• Enterprise can operate on any number of servers and has no device count limits

Pass the key in the constructor to remove restrictions

Obtaining a Key

tls-devicer uses polar.js for key verification. You can obtain a key for dual use of this library and ip-devicer by purchasing one here