MTLS with K6 does not work

Grafana k6 OSS Support
1

Hi Team,

Trying to make call to one endpoint using MTLS (private key and certificate) in K6 by following the standard documentation but it does not work.

How to replicate:

/*
This is a test JS file where a test has been written to test
MTLS with K6.

K6 Reference: https://grafana.com/docs/k6/latest/using-k6/protocols/ssl-tls/ssl-tls-client-certificates/
*/
import http from 'k6/http';
import encoding from 'k6/encoding';
import { check } from 'k6';

const url = 'https://mydomain/resource';

const CERT = `-----BEGIN CERTIFICATE-----
some certificate value
-----END CERTIFICATE-----`;
const KEY = `-----BEGIN PRIVATE KEY-----
private key for the certificate
-----END PRIVATE KEY-----`;


export const options = {
  tlsAuth: [
    {
      domains: ['mydomain'],
      //cert: open('cert.crt'),   // Tried cert providing from file
      //key: open('key.pem'),  // Tried private key providing from file
      cert: CERT,
      key: KEY,
    },
  ],
};

export default function () {
  let httpOptions = { 
    headers: { 
      'Content-Type': 'application/x-www-form-urlencoded',
    } 
  };

  let res = http.get(url, httpOptions);
  console.log(res.json());
}

OS: Windows 11
K6: k6.exe v1.0.0 (commit/41b4984b75, go1.24.2, windows/amd64)

The same REST resource has been tested with other clients like cURL, postman, Jmeter etc. It works everywhere except k6.

Please guide me if there is something missing here or there is bug in k6 injector.

Thanks,

2

Hello @siddhivinayaksk can you share response error from k6 console for further investigation.