Enabling SSL in MariaDB running on Synology NAS
Please, check the following configuration files and variables:

File: /etc/mysql/my.cnf

[client]
...
ssl-ca=/var/lib/mysql/ca.pem
ssl-cert=/var/lib/mysql/client-cert.pem
ssl-key=/var/lib/mysql/client-key.pem
ssl-verify-server-cert
...

[mysqld]
...
ssl
ssl-ca=/var/lib/mysql/ca.pem
ssl-cert=/var/lib/mysql/server-cert.pem
ssl-key=/var/lib/mysql/server-key.pem
...


File: /etc/hosts

127.0.0.1 localhost CNSERVER


MariaDB Command-Line:

$ mysql -u root -p -h CNSERVER
Enter password: 
Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MariaDB connection id is 1
Server version: 10.1.14-MariaDB-1~xenial mariadb.org binary distribution

Copyright (c) 2000, 2016, Oracle, MariaDB Corporation Ab and others.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

MariaDB [(none)]&gt; SHOW VARIABLES LIKE '%ssl%';
+---------------------+---------------------------------+
| Variable_name       | Value                           |
+---------------------+---------------------------------+
| have_openssl        | YES                             |
| have_ssl            | YES                             |
| ssl_ca              | /var/lib/mysql/ca.pem           |
| ssl_capath          |                                 |
| ssl_cert            | /var/lib/mysql/server-cert.pem  |
| ssl_cipher          |                                 |
| ssl_crl             |                                 |
| ssl_crlpath         |                                 |
| ssl_key             | /var/lib/mysql/server-key.pem   |
| version_ssl_library | OpenSSL 1.0.2g-fips  1 Mar 2016 |
+---------------------+---------------------------------+
10 rows in set (0.00 sec)

MariaDB [(none)]&gt; SHOW SESSION STATUS LIKE '%Ssl_version%';
+---------------+---------+
| Variable_name | Value   |
+---------------+---------+
| Ssl_version   | TLSv1.2 |
+---------------+---------+
1 row in set (0.00 sec)