I implemented a dynamic button "buy now" (not saved in my PayPal account) with IPN and it works fine (yeah!).
Now I have a doubt about his security, because if someone change with firebug (for example) the amount value, the transaction is valid for paypal also if my IPN listener says there is a problem with amount.
My question is "Can I encrypt the form with a php / codeigniter library?"
Because I tried to check amount in the IPN listener, but the transaction on paypal continue correctly and It isn't blocked from IPN.
Here, you find a part of my listener code:
private function isVerifiedIPN(){
$req = 'cmd=_notify-validate';
$posts = $this->input->post();
foreach ($posts as $key => $value){
$value = urlencode(stripslashes($value));
$req .= "&$key=$value";
}
if($this->config->item('SIMULATION'))
$url = $this->config->item('SIMULATION_URL');
else
$url = $this->config->item('PRODUCTION_URL');
if(!$this->isVerifiedAmmount() ||
!$this->isPrimaryPayPalEmail() ||
!$this->isNotProcessed()){
$req = '';
}
$header = "POST /cgi-bin/webscr HTTP/1.0
";
$header .= "Host: $url
"; //443
$header .= "Content-type: application/x-www-form-urlencoded
";
$header .= "Content-length: " . strlen($req) . "
";
$fp = fsockopen ("ssl://$url", 443, $errno, $errstr, 30);
if (!$fp)
{
$this->sendReport("Errore connessione socket");
return FALSE;
}
else
{
fputs ($fp, $header . $req);
while (!feof($fp))
{
$res = fgets ($fp, 1024);
if (strcmp($res, "VERIFIED") == 0)
{
// transizione valida
fclose ($fp);
return TRUE;
}
else if (strcmp ($res, "INVALID") == 0)
{
$this->sendReport('Transizione non valida');
fclose ($fp);
return FALSE;
}
}
}
}