Magento – form post – getURL secure (HTTPS / SSL)

There is a function just for that, called shouldUrlBeSecure located in app/code/core/Mage/Core/Model/Config.php on line 1477.

Here is the complete function:

/**
 * Check whether given path should be secure according to configuration security requirements for URL
 * "Secure" should not be confused with https protocol, it is about web/secure/*_url settings usage only
 *
 * @param string $url
 * @return bool
 */
public function shouldUrlBeSecure($url)
{
    if (!Mage::getStoreConfigFlag(Mage_Core_Model_Store::XML_PATH_SECURE_IN_FRONTEND)) {
        return false;
    }

    if (!isset($this->_secureUrlCache[$url])) {
        $this->_secureUrlCache[$url] = false;
        $secureUrls = $this->getNode('frontend/secure_url');
        foreach ($secureUrls->children() as $match) {
            if (strpos($url, (string)$match) === 0) {
                $this->_secureUrlCache[$url] = true;
                break;
            }
        }
    }

    return $this->_secureUrlCache[$url];
}

To see which URLs should be secure you can add a simple Mage::log($secureUrls) inside the if statement. This is what my log entry looked like:

2014-02-12T11:55:26+00:00 DEBUG (7): Mage_Core_Model_Config_Element Object
(
    [install] => /install/wizard/checkSecureHost
    [customer] => /customer/
    [sales] => /sales/
    [authorizenet_paygate] => /paygate/authorizenet_payment
    [checkout_onepage] => /checkout/onepage
    [checkout_multishipping] => /checkout/multishipping
    [paypal_express] => /paypal/express
    [paypal_standard] => /paypal/standard
    [paypal_express_callbackshippingoptions] => paypal/express/callbackshippingoptions
    [googlecheckout_redirect] => /googlecheckout/redirect/
    [googlecheckout_beacon] => /googlecheckout/api/beacon/
    [googlecheckout_api] => /googlecheckout/api/
    [review_customer] => /review/customer/
    [tag_customer] => /tag/customer/
    [wishlist] => /wishlist/
    [paypaluk_express] => /paypaluk/express
    [rss_catalog_review] => /rss/catalog/review
    [rss_order_new] => /rss/order/new
    [rss_catalog_notifystock] => /rss/catalog/notifystock
    [centinel] => /centinel/
    [newsletter_manage] => /newsletter/manage/
    [downloadable] => /downloadable/customer/
    [downloadable_download] => /downloadable/download/
    [ogone_api] => /ogone/api
    [persistent_onepage_register] => /persistent/index/saveMethod
    [checkout_cart] => /checkout/cart
    [storecredit_info] => /storecredit/info/
    [giftcard_customer] => /giftcard/customer/
    [enterprise_pbridge_pbridge] => /enterprise_pbridge/pbridge/
    [invitation] => /invitation/
)

Now to figure out how Magento switches HTTP to HTTPS I think you would most likely have dive into the Zend framework in the lib inside lib/Zend/Http/* because it contains files of most interest. Well, anyway hope this helped. Good luck!

I wouldn't recommend you to use the ".htaccess" method to force your Magento store to use HTTPS.

What you can do instead is just to change both your Secure and Unsecure Base URL to HTTPS and make sure to remove the ".htaccess" redirect rules.

With both the Secure and Unsecure Base URL with HTTPS, the buttons generated should be running HTTPS as well unless they are hard coded somehow (not likely).