I received a dreaded "cURL error: Unknown SSL protocol error in connection to secure.authorize.net:443" when setting up the Authorize.net payment gateway for use in a Drupal Ubercart store recently. Oh noes! Here's how I fixed it.
Find the module ubercart > payment > uc_authorizenet
On line 558 (your mileage may vary) I added:
curl_setopt($ch, CURLOPT_SSLVERSION, 3); // Force SSLv3 to fix Unknown SSL Protocol error
Goodbye sweet, sweet error. I barely knew ye.
C. M., President/CEO Bordercross Enterprises, LLC
I will definitely be working with John in the future. He is a true professional who is dedicated to delivering high-quality work. I enjoyed working with him and appreciate his attention to detail and his communication skills. I highly recommend him to others.