php - Dynamic PayPal button generation - isn't it very insecure?

Question

I am just wondering here.. Aren't the PayPal buttons that are dynamically created, very unsecure, and easily "hackable"?

Like so:

<form name="_xclick" target="paypal" action="https://www.paypal.com" method="post">
<input type="hidden" name="cmd" value="_cart">
<input type="hidden" name="business" value="[email protected]">
<input type="hidden" name="currency_code" value="USD">
<input type="hidden" name="item_name" value="HTML book">
<input type="hidden" name="amount" value="24.99">
<input type="image" src="http://www.paypal.com/en_US/i/btn/btn_cart_LG.gif" border="0" name="submit" alt="Make payments with PayPal - it's fast, free and secure!">
<input type="hidden" name="add" value="1">
</form> 

Changing the price of the product is straight forward when you can modify the code with, say, FireBug.

The reason I am asking, is because I might/will start developing an E-Commerce kinda system, where the products can be added in that system, without doing it in PayPal.

Answer 1

You should use the PayPal Button API such as below:

$sendPayData = array(
    "METHOD" => "BMCreateButton",
    "VERSION" => "65.2",
    "USER" => "username",
    "PWD" => "password",
    "SIGNATURE" => "abcdefg",
    "BUTTONCODE" => "ENCRYPTED",
    "BUTTONTYPE" => "BUYNOW",
    "BUTTONSUBTYPE" => "SERVICES",
    "BUTTONCOUNTRY" => "GB",
    "BUTTONIMAGE" => "reg",
    "BUYNOWTEXT" => "BUYNOW",
    "L_BUTTONVAR1" => "item_number=$invoiceNumber",
    "L_BUTTONVAR2" => "item_name=$invoiceType",
    "L_BUTTONVAR3" => "amount=$invoiceTotal",
    "L_BUTTONVAR4" => "currency_code=GBP",
    "L_BUTTONVAR5" => "no_shipping=1",
    "L_BUTTONVAR6" => "no_note=1",
    "L_BUTTONVAR7" => "notify_url=http://www.abc.co.uk/paypal/ipn.php",
    "L_BUTTONVAR8" => "cancel_return=http://www.abc.co.uk/paypal/thanks",
    "L_BUTTONVAR9" => "return=http://www.abc.co.uk/paypal/return.php"
);

You can then send that with cURL to their API

$curl = curl_init();
curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, false);
curl_setopt($curl, CURLOPT_URL, 'https://api-3t.paypal.com/nvp?'.http_build_query($sendPayData));
$nvpPayReturn = curl_exec($curl);
curl_close($curl);

To then generate a encrypted HTML button that cannot be edited

<form action="https://www.paypal.com/cgi-bin/webscr" method="post"> 
<input type="hidden" name="cmd" value="_s-xclick"> 
<input type="hidden" name="encrypted" value="-----BEGIN PKCS7-----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-----END PKCS7-----
">
<input type="image" src="https://www.paypal.com/en_US/i/btn/btn_paynow_LG.gif" border="0" name="submit" alt="PayPal - The safer, easier way to pay online."> 
<img alt="" border="0" src="https://www.paypal.com/en_GB/i/scr/pixel.gif" width="1" height="1"> 

These links should help you with the button options:

https://cms.paypal.com/us/cgi-bin/?cmd=_render-content&content_ID=developer/e_howto_api_nvp_BMCreateButton

https://cms.paypal.com/us/cgi-bin/?cmd=_render-content&content_ID=developer/e_howto_api_ButtonMgrAPIIntro