17.3.8 Setting Up Replication to Use Encrypted Connections

To use an encrypted connection for the transfer of the binary log required during replication, both the source and the replica servers must support encrypted network connections. If either server does not support encrypted connections (because it has not been compiled or configured for them), replication through an encrypted connection is not possible.

Setting up encrypted connections for replication is similar to doing so for client/server connections. You must obtain (or create) a suitable security certificate that you can use on the source, and a similar certificate (from the same certificate authority) on each replica. You must also obtain suitable key files.

For more information on setting up a server and client for encrypted connections, see Section 6.3.1, “Configuring MySQL to Use Encrypted Connections”.

To enable encrypted connections on the source, you must create or obtain suitable certificate and key files, and then add the following configuration parameters to the source's configuration within the [mysqld] section of the source's my.cnf file, changing the file names as necessary:

[mysqld]
ssl_ca=cacert.pem
ssl_cert=server-cert.pem
ssl_key=server-key.pem

The paths to the files may be relative or absolute; we recommend that you always use complete paths for this purpose.

The configuration parameters are as follows:

ssl_ca: The path name of the Certificate Authority (CA) certificate file. (--ssl-capath is similar but specifies the path name of a directory of CA certificate files.)
ssl_cert: The path name of the server public key certificate file. This certificate can be sent to the client and authenticated against the CA certificate that it has.
ssl_key: The path name of the server private key file.

On the replica, there are two ways to specify the information required for connecting using encryption to the source. You can either name the replica certificate and key files in the [client] section of the replica's my.cnf file, or you can explicitly specify that information using the CHANGE MASTER TO statement:

To name the replica certificate and key files using an option file, add the following lines to the [client] section of the replica's my.cnf file, changing the file names as necessary:
```
[client]
ssl-ca=cacert.pem
ssl-cert=client-cert.pem
ssl-key=client-key.pem
```
Restart the replica server, using the --skip-slave-start option to prevent the replica from connecting to the source. Use CHANGE MASTER TO to specify the source configuration, using the MASTER_SSL option to connect using encryption:
```
mysql> CHANGE MASTER TO
    -> MASTER_HOST='source_hostname',
    -> MASTER_USER='replicate',
    -> MASTER_PASSWORD='password',
    -> MASTER_SSL=1;
```

To specify the certificate and key names using the CHANGE MASTER TO statement, append the appropriate MASTER_SSL_xxx options:

mysql> CHANGE MASTER TO
    -> MASTER_HOST='source_hostname',
    -> MASTER_USER='replicate',
    -> MASTER_PASSWORD='password',
    -> MASTER_SSL=1,
    -> MASTER_SSL_CA = 'ca_file_name',
    -> MASTER_SSL_CAPATH = 'ca_directory_name',
    -> MASTER_SSL_CERT = 'cert_file_name',
    -> MASTER_SSL_KEY = 'key_file_name';

After the source information has been updated, start the replication process:

mysql> START SLAVE;

You can use the SHOW SLAVE STATUS statement to confirm that an encrypted connection was established successfully.

For more information on the CHANGE MASTER TO statement, see Section 13.4.2.1, “CHANGE MASTER TO Statement”.

If you want to enforce the use of encrypted connections during replication, create a user with the REPLICATION SLAVE privilege and use the REQUIRE SSL option for that user. For example:

mysql> CREATE USER 'repl'@'%.example.com' IDENTIFIED BY 'password';
mysql> GRANT REPLICATION SLAVE ON *.*
    -> TO 'repl'@'%.example.com' REQUIRE SSL;

If the account already exists, you can add REQUIRE SSL to it with this statement:

mysql> GRANT USAGE ON *.*
    -> TO 'repl'@'%.example.com' REQUIRE SSL;