MySQL Client

Using Mutual TLS on the Client Side with MySQL Client

How to use TLS, client authentication, and CA certificates in MySQL Client

Create a private key and request a certificate for your MySQL Client client

Before you can teach your client 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 MySQL Client client, 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 client name for the actual name / DNS name of your MySQL Client client).

Since you're using MySQL Client, which requires RSA keys, we'll pass the --kty=RSA flag to let step know to generate RSA keys instead of the default EC type.

$ step ca certificate --kty=RSA "myuser" client.crt client.key

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

Open a connection from MySQL Client using mutual TLS

Now, we need only to configure our MySQL Client 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.

For additional security, step certificates are signed by an intermediate CA by default rather than the root CA. The intermediate certificate is bundled into your server.crt certificate (configured on the server side).

Unfortunately, MySQL has an outstanding bug that prevents it from being able to read the intermediate certificate out of server.crt. So, we'll have to instead bundle that intermediate CA certificate together with the root CA certificate we saved previously (ca.crt) so that our MySQL client can read it and verify the server certificate was signed by your intermediate CA.

$ step certificate bundle $(step path)/certs/intermediate_ca.crt ca.crt ca-bundle.crt

Pass your certificate, private key, and the CA bundle to your MySQL client to authenticate your connection over TLS. The SSL mode VERIFY_IDENTITY instructs MySQL to verify that the name in our server certificate matches the hostname for the connection, which offers the tightest security.

$ mysql -h -P 443 -u myuser -p --ssl-mode=VERIFY_IDENTITY --ssl-cert=client.crt --ssl-key=client.key --ssl-ca=ca-bundle.crt

It's also possible to configure those arguments in the [client] section of your my.cnf file to be used on every connection:


# ...

# ...

Then, they can be dropped from the CLI client command.

$ mysql -h -P 443 -u myuser -p

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.

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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