Had the same question. Thankfully some other folks had proposed a reasonable solution here: https://core.trac.wordpress.org/ticket/28625. End-to-end, here's what I did to get SSL working:
1. Add the following to the wordpress wp-includes/wp-db.php file. (except the last 2 lines which are just for insertion point reference)
//ADDED per https://core.trac.wordpress.org/ticket/28625
// call set_ssl if mysql client flag set and settings available
if ( $client_flags & MYSQL_CLIENT_SSL ) {
$pack = array( $this->dbh );
$call_set = false;
foreach( array( 'MYSQL_SSL_KEY', 'MYSQL_SSL_CERT', 'MYSQL_SSL_CA',
'MYSQL_SSL_CAPATH', 'MYSQL_SSL_CIPHER' ) as $opt_key ) {
$pack[] = ( defined( $opt_key ) ) ? constant( $opt_key ) : null;
$call_set |= defined( $opt_key );
}
/* Now if anything was packed - unpack into the function.
* Note this doesn't check if paths exist, as per the PHP doc
* at http://www.php.net/manual/en/mysqli.ssl-set.php: "This
* function always returns TRUE value. If SSL setup is incorrect
* mysqli_real_connect() will return an error ..."
*/
if ( $call_set ) { // SSL added here!
call_user_func_array( 'mysqli_ssl_set', $pack );
}
}//END ADD - below is the point above which to insert this
if ( WP_DEBUG ) {
mysqli_real_connect( $this->dbh, $host, $this->dbuser, $this->dbpassword, null, $port, $socket, $client_flags );
2. Customize your wordpress wp-config.php file.
Add & customize the following lines in your wp-config.php file. You can test these from development/staging as well as production if you have multiple environments.
define('DB_HOST', 'rds-yourserver-abcdefghi9j.us-west-1.rds.amazonaws.com');
define('MYSQL_CLIENT_FLAGS', MYSQL_CLIENT_SSL);//This activates SSL mode
define('MYSQL_SSL_CA', '/file/path/to/your/aws/rds-combined-ca-bundle.pem');
Note that there are 5 available MYSQL_SSL* settings you could use in your config, per code in #1 above. My RDS connection works via SSL with just the _CA option.
3. Sanity test that your connection is encrypted.
Add a quick test file to show whether the current Wordpress connection is using SSL or not. Create a sample file like this one called test.php, and put in your wordpress root or somewhere web accessible. Don't forget to remove this file when done testing.
<?php
require( dirname( __FILE__ ) . '/wp-blog-header.php' ); //EDIT THIS PATH SO IT IS CORRECT FOR YOUR test.php file relative to the wp-blog-header.php file
global $wpdb;
$row = $wpdb->get_row( "SHOW STATUS LIKE 'Ssl_cipher'" );
var_dump($row);
/*
If you are connected over SSL this should output something like:
object(stdClass)#116 (2) { ["Variable_name"]=> string(10) "Ssl_cipher" ["Value"]=> string(10) "AES256-SHA" }
If you are NOT connected over SSL this should output something like:
object(stdClass)#116 (2) { ["Variable_name"]=> string(10) "Ssl_cipher" ["Value"]=> string(10) "" }
*/
?>
4. Deploy and test your connection
Deploy your changes & test.php file to your wordpress installation, and restart your web server as needed. I'm using apache, so I run
sudo apachectl restart
