Here is the default connection string in db-core.php:
$dbh = new PDO(
'mysql:host='.MF_DB_HOST.';dbname='.MF_DB_NAME,
MF_DB_USER,
MF_DB_PASSWORD,
array(PDO::MYSQL_ATTR_USE_BUFFERED_QUERY => true)
);
Here is how you need to connect when using SSL/TLS ( http://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/CHAP_MySQL.html#MySQL.Concepts.SSLSupport ):
$dbh = new PDO(
'mysql:host='.MF_DB_HOST.';dbname='.MF_DB_NAME,
MF_DB_USER,
MF_DB_PASSWORD,
array(
PDO::MYSQL_ATTR_USE_BUFFERED_QUERY => true,
PDO::MYSQL_ATTR_SSL_CA =>'../../rds-combined-ca-bundle.pem'
)
);