Quick question about PayPal IPN Security
Posted
by Alix Axel
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Published on 2010-05-18T10:55:24Z
Indexed on
2010/05/18
11:00 UTC
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PayPal IPN sends a POST request with a variable number of fields to the notify URL, in order to confirm that the POST request is legit we need to resubmit the same request along with a additional cmd=_notify-validate field to PayPal, which then replies SUCCESS or FAILURE.
My question is, why do we need to resend the request to PayPal? Wouldn't something like this work?
if (preg_match('~^(?:.+[.])?paypal[.]com$~i', gethostbyaddr($_SERVER['REQUEST_ADDR'])) > 0)
{
// request came from PayPal, it's legit.
}
Iff we can trust the server to correctly resolve IPs, I assume we can trust PayPal POST requests, no?
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