Check our JA3 fingerprints against ja3.zone

Author: pimterry

test/test-util.ts

@@ -1,3 +1,5 @@
+import * as stream from 'stream';
+
 export type Deferred<T> = Promise<T> & {
     resolve(value: T): void,
     reject(e: Error): void
@@ -14,4 +16,14 @@ export function getDeferred<T>(): Deferred<T> {
     result.reject = rejectCallback!;
 
     return result;
+}
+
+export async function streamToBuffer(stream: stream.Readable): Promise<Buffer> {
+    const data: Buffer[] = [];
+    stream.on('data', (d) => data.push(d));
+
+    return new Promise((resolve, reject) => {
+        stream.on('end', () => resolve(Buffer.concat(data)));
+        stream.on('error', reject);
+    });
 }

test/test.spec.ts

@@ -4,7 +4,7 @@ import * as https from 'https';
 import { makeDestroyable, DestroyableServer } from 'destroyable-server';
 
 import { expect } from 'chai';
-import { getDeferred } from './test-util';
+import { getDeferred, streamToBuffer } from './test-util';
 
 import {
     getTlsFingerprintData,
@@ -89,4 +89,41 @@ describe("Read-TLS-Fingerprint", () => {
         ]);
     });
 
+    it("calculates the same fingerprint as ja3.zone", async () => {
+        server = makeDestroyable(new net.Server());
+
+        server.listen();
+        await new Promise((resolve) => server.on('listening', resolve));
+
+        let incomingSocketPromise = getDeferred<net.Socket>();
+        server.on('connection', (socket) => incomingSocketPromise.resolve(socket));
+
+        const port = (server.address() as net.AddressInfo).port;
+        https.request({
+            host: 'localhost',
+            port
+        }).on('error', () => {}); // Socket will fail, since server never responds, that's OK
+
+        const incomingSocket = await incomingSocketPromise;
+        const ourFingerprint = await getTlsFingerprintAsJa3(incomingSocket);
+
+        const remoteFingerprint = await new Promise((resolve, reject) => {
+            const response = https.get('https://check.ja3.zone/');
+            response.on('response', async (resp) => {
+                if (resp.statusCode !== 200) reject(new Error(`Unexpected ${resp.statusCode} from ja3.zon`));
+
+                try {
+                    const rawData = await streamToBuffer(resp);
+                    const data = JSON.parse(rawData.toString());
+                    resolve(data.hash);
+                } catch (e) {
+                    reject(e);
+                }
+            });
+            response.on('error', reject);
+        });
+
+        expect(ourFingerprint).to.equal(remoteFingerprint);
+    });
+
 });