refer to: http://wiki.vpslink.com/Configuring_vsftpd_for_secure_connections_%28TLS/SSL/SFTP%29
listen=YES anonymous_enable=NO local_enable=YES write_enable=YES dirmessage_enable=YES use_localtime=YES xferlog_enable=YES connect_from_port_20=YES chroot_local_user=YES secure_chroot_dir=/var/run/vsftpd/empty pam_service_name=vsftpd rsa_cert_file=/etc/ssl/private/vsftpd.pem rsa_private_key_file=/etc/ssl/private/vsftpd.pem ssl_enable=YES allow_anon_ssl=NO force_local_data_ssl=YES force_local_logins_ssl=YES ssl_tlsv1=YES ssl_sslv2=NO ssl_sslv3=NO require_ssl_reuse=NO ssl_ciphers=HIGH
