Traefik v2
PHP

A Complete Guide to Securely Connecting Traefik v2 and PHP Using Mutual TLS

How to use TLS, client authentication, and CA certificates in Traefik v2 and PHP

Choose DIY vs smallstep-managed integration

Create a private key and request a certificate for your Traefik v2 server

Before you can teach your server to speak TLS, you will need a certificate issued by a trusted certificate authority (CA). If your organization already runs its own CA and you have a private key and certificate for your Traefik v2 server, along with your CA's root certificate, you can skip to the next step.

If your organization does not yet run its own internal CA, you can read more about creating and running a CA using the open source smallstep software here.

$ step ca certificate "myserver.internal.net" server.crt server.key

Your certificate and private key will be saved in server.crt and server.key respectively.

Request a copy of your CA root certificate, which will be used to make sure each application can trust certificates presented by other applications.

$ step ca root ca.crt

Your certificate will be saved in ca.crt.

Configure Traefik v2 to authenticate itself with its TLS certificate

We now want to instruct our Traefik v2 server to identify itself using the certificate issued in the last step and to force clients to connect over TLS.

In the dynamic configuration of Traefik specify the locations of the server's certificate and private key. The certificates will be automatically used when the domain in SNI requests matches the certificate domains.

This configuration applies to manually configured certificates. For automatic certificate renewal, check the section below.

## Dynamic configuration
[[tls.certificates]]
  certFile = "server.crt"
  keyFile = "server.key"

Traefik automatically selects the right certificates when the domain in SNI requests matches the certificate domains. To have one of the certificates be the default certificate - instead of the generated Traefik default certificate - for requests which don't match any certificate configured, you need to configure the default tls.stores.

## Dynamic configuration
[tls.stores]
  [tls.stores.default]
    [tls.stores.default.defaultCertificate]
      certFile = "server.crt"
      keyFile  = "server.key"

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Configure Traefik v2 to require clients to authenticate with a certificate issued by your CA

To tell Traefik v2 to use mutual TLS and not just one-way TLS, we must instruct it to require client authentication to ensure clients present a certificate from our CA when they connect.

Add or configure an existing TLS option to specify the location of your CA root certificate to use for authenticating client certificates.

## Dynamic configuration
[tls.options]
  [tls.options.mytlsoptions]
    [tls.options.mytlsoptions.clientAuth]
      caFiles = ["ca.crt"]
      clientAuthType = "RequireAndVerifyClientCert"

Then, when you add routers to your dynamic configuration for HTTPS traffic, you need to set tls and tls.options to enable client authentication:

## Dynamic configuration
[http]
  [http.routers]
    [http.routers.router1]
      ...
      [http.routers.router1.tls]
        options = "mytlsoptions"

That's it! Traefik v2 should now be able to receive TLS connections from clients who authenticate themselves using a certificate issued by your trusted CA.

Create a private key and request a certificate for your PHP client

Request a new certificate from your CA to represent your PHP client.

$ step ca certificate "myuser" client.crt client.key

Your certificate and private key will be saved in client.crt and client.key respectively.

Make a request from PHP using mutual TLS

Now, we need only to configure our PHP client to make authenticated requests using our certificate and private key. The CA root certificate will be used to verify that the client can trust the certificate presented by the server.

Pass your certificate, private key, and root CA certificate to the PHP cURL methods to authenticate your request over TLS.

<?php
// ...

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, 'https://myserver.internal.net:443');
curl_setopt($ch, CURLOPT_SSLVERSION, CURL_SSLVERSION_TLSv1_2);
curl_setopt($ch, CURLOPT_SSLCERT, 'client.crt');
curl_setopt($ch, CURLOPT_SSLKEY, 'client.key');
curl_setopt($ch, CURLOPT_CAINFO, 'ca.crt');
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$result = curl_exec($ch);
// do something with the result...

// ...
?>

Automate certificate renewal

By default, step-ca issues certificates with a 24 hour expiration. Short-lived certificates have many benefits but also require that you renew your certificates each day before they expire. How you renew certificates is often dependent on how you deploy your application. See the step-ca certificate lifecycle management docs for more information.

Let us know you're interested!

Smallstep is building Certificate Manager, a hosted certificate authority offering with integrations that make it easy to manage mututal TLS in technologies like Traefik v2 and PHP.

Certificate Manager is currently in early access (by request only). Please request an invitation and let us know you'd be interested in an integration with Traefik v2 and PHP.

Join Early Access

All documentation content from the Hello mTLS project is licensed under Creative Commons Attribution 4.0 International (CC BY 4.0).

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