How can I verify I'm using SSL to connect to mysql?

From the client, just run status. If this connection is using SSL, you'll get something interesting in the SSL row.

mysql> status
--------------
mysql  Ver 14.14 Distrib 5.5.30, for Linux (x86_64) using readline 5.1

Connection id:      12
Current database:
Current user:       [email protected]
SSL:            Cipher in use is DHE-RSA-AES256-SHA
Current pager:      stdout
Using outfile:      ''
Using delimiter:    ;
Server version:     5.5.30-log MySQL Community Server (GPL)
Protocol version:   10
Connection:     boston.hugskeep.wstudent.com via TCP/IP
Server characterset:    latin1
Db     characterset:    latin1
Client characterset:    utf8
Conn.  characterset:    utf8
TCP port:       3306
Uptime:         44 min 49 sec

Threads: 2  Questions: 16  Slow queries: 0  Opens: 34  Flush tables: 1  Open tables: 27  Queries per second avg: 0.005
--------------

mysql>

If this connection is not using SSL, you'll get:

SSL:            Not in use

You can also use:

mysql> SHOW STATUS LIKE 'Ssl_cipher';
+---------------+--------------------+
| Variable_name | Value              |
+---------------+--------------------+
| Ssl_cipher    | DHE-RSA-AES256-SHA |
+---------------+--------------------+
1 row in set (0.00 sec)

mysql>

But I think the first is more attractive, and sure easier to type.

This is applicable to mariadb mysql (haven't tried in pure mysql):

mysql -h xxx.xxx.xxx.xxx -u testuser --ssl

'--ssl' will tell you if ssl is enabled, without, it will say 'not in use'

Force SSL per user:

alter user 'my_user'@'%' REQUIRE SSL;
mysql> \s