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 Go server, along with your CA's root certificate, you can skip to the next step.
To request a certificate from your CA using the step
CLI, bootstrap your CA with step ca bootstrap
and run the following command (sub the server name for the actual name / DNS name of your Go server).
$ 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
.
We now want to instruct our Go server to identify itself using the certificate issued in the last step and to force clients to connect over TLS.
In your server's Go file, we pass the server's certificate and private key into Go's convenient API to launch a HTTPS listener.
// ...
http.ListenAndServeTLS(":9443", "server.crt", "server.key", nil)
// ...
To tell Go 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.
In your server's Go file, we pass a TLS stack configuration into the server initalization. The configuration enables strict client certificate verification against all trusted root certificates in the CA pool we create. Finally, we call the server's API to create a HTTPS listener using its own certificate and private key for client-side verification.
// ...
caCert, _ := ioutil.ReadFile("ca.crt")
caCertPool := x509.NewCertPool()
caCertPool.AppendCertsFromPEM(caCert)
tlsConfig := &tls.Config{
ClientCAs: caCertPool,
ClientAuth: tls.RequireAndVerifyClientCert,
}
tlsConfig.BuildNameToCertificate()
server := &http.Server{
Addr: ":9443",
TLSConfig: tlsConfig,
}
server.ListenAndServeTLS("server.crt", "server.key")
// ...
That's it! Go should now be able to receive TLS connections from clients who authenticate themselves using a certificate issued by your trusted CA.
Request a new certificate from your CA to represent your Curl client.
$ step ca certificate "myuser" client.crt client.key
Your certificate and private key will be saved in client.crt
and client.key
respectively.
Now, we need only to configure our Curl 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 curl
to authenticate your request over TLS.
$ curl --cert client.crt --key client.key --cacert ca.crt https://myserver.internal.net:9443
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.
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