ipn.php

<?php
/* 2021: Paypal hosts arent neccesarily notify.paypal.com any longer.
if (gethostbyaddr($_SERVER['REMOTE_ADDR']) !== 'notify.paypal.com') {
	exit();
}
*/

function ip_in_range( $ip, $range ) {
    if ( strpos( $range, '/' ) === false ) {
        $range .= '/32';
    }
    // $range is in IP/CIDR format eg 127.0.0.1/24
    list( $range, $netmask ) = explode( '/', $range, 2 );
    $range_decimal = ip2long( $range );
    $ip_decimal = ip2long( $ip );
    $wildcard_decimal = pow( 2, ( 32 - $netmask ) ) - 1;
    $netmask_decimal = ~ $wildcard_decimal;
    return ( ( $ip_decimal & $netmask_decimal ) == ( $range_decimal & $netmask_decimal ) );
}

$paypal_ip_ranges = array(
    "173.0.81.65",
    "173.0.81.140",
    "64.4.240.0/21",
    "64.4.248.0/22",
    "66.211.168.0/22",
    "173.0.80.0/20",
    "91.243.72.0/23"
);

$verified = false;
for($i = 0; $i < count($paypal_ip_ranges); $i++) {
    if(ip_in_range($_SERVER["REMOTE_ADDR"], $paypal_ip_ranges[$i])) {
        $verified = true;
        break;
    }
}

if(!$verified) {
    exit();
}

// Require the functions to connect to database and fetch config values
require 'config.php';
require 'engine/database/connect.php';

// Fetch and sanitize POST and GET values
function getValue($value) {
	return (!empty($value)) ? sanitize($value) : false;
}
function sanitize($data) {
	return htmlentities(strip_tags(mysql_znote_escape_string($data)));
}

function VerifyPaypalIPN(array $IPN = null){
	if(empty($IPN)){
		$IPN = $_POST;
	}
	if(empty($IPN['verify_sign'])){
		return null;
	}
	$IPN['cmd'] = '_notify-validate';
	$PaypalHost = (empty($IPN['test_ipn']) ? 'www' : 'www.sandbox').'.paypal.com';
	$cURL = curl_init();
	curl_setopt($cURL, CURLOPT_SSL_VERIFYPEER, 1);
	curl_setopt($cURL, CURLOPT_SSL_VERIFYHOST, 2);
	curl_setopt($cURL, CURLOPT_SSLVERSION, 6);
	curl_setopt($cURL, CURLOPT_CAINFO, __DIR__ . '/engine/cert/cacert.pem');
	curl_setopt($cURL, CURLOPT_URL, "https://{$PaypalHost}/cgi-bin/webscr");
	curl_setopt($cURL, CURLOPT_ENCODING, 'gzip');
	curl_setopt($cURL, CURLOPT_BINARYTRANSFER, true);
	curl_setopt($cURL, CURLOPT_POST, true); // POST back
	curl_setopt($cURL, CURLOPT_POSTFIELDS, $IPN); // the $IPN
	curl_setopt($cURL, CURLOPT_HEADER, false);
	curl_setopt($cURL, CURLOPT_RETURNTRANSFER, true);
	curl_setopt($cURL, CURLOPT_FORBID_REUSE, true);
	curl_setopt($cURL, CURLOPT_FRESH_CONNECT, true);
	curl_setopt($cURL, CURLOPT_CONNECTTIMEOUT, 30);
	curl_setopt($cURL, CURLOPT_TIMEOUT, 60);
	curl_setopt($cURL, CURLINFO_HEADER_OUT, true);
	curl_setopt($cURL, CURLOPT_HTTPHEADER, array(
		'Connection: close',
		'Expect: ',
	));
	$Response = curl_exec($cURL);
	$Status = (int)curl_getinfo($cURL, CURLINFO_HTTP_CODE);
	curl_close($cURL);
	if(empty($Response) or !preg_match('~^(VERIFIED|INVALID)$~i', $Response = trim($Response)) or !$Status){
		return null;
	}
	if(intval($Status / 100) != 2){
		return false;
	}
	return !strcasecmp($Response, 'VERIFIED');
}

// Fetch paypal configurations
$paypal = $config['paypal'];
$prices = $config['paypal_prices'];

// Send an empty HTTP 204 OK response to acknowledge receipt of the notification
http_response_code(204);

// Build the required acknowledgement message out of the notification just received
$postdata = 'cmd=_notify-validate';
if(!empty($_POST)){
	$postdata.="&".http_build_query($_POST);
}
// Assign payment notification values to local variables
$item_name        = $_POST['item_name'];
$item_number      = $_POST['item_number'];
$payment_status   = $_POST['payment_status'];
$payment_amount   = $_POST['mc_gross'];
$payment_currency = $_POST['mc_currency'];
$txn_id           = getValue($_POST['txn_id']);
$receiver_email   = getValue($_POST['receiver_email']);
$payer_email      = getValue($_POST['payer_email']);
$custom           = (int)$_POST['custom'];

$connectedIp = $_SERVER['REMOTE_ADDR'];
mysql_insert("INSERT INTO `znote_paypal` VALUES ('0', '0', 'Connection from IP: $connectedIp', '0', '0', '0')");

$status = VerifyPaypalIPN();
if ($status) {
	// Check that the payment_status is Completed
	if ($payment_status == 'Completed') {


		// Check that txn_id has not been previously processed
		$txn_id_check = mysql_select_single("SELECT `txn_id` FROM `znote_paypal` WHERE `txn_id`='$txn_id'");
		if ($txn_id_check !== true) {
			// Check that receiver_email is your Primary PayPal email
			if ($receiver_email == $paypal['email']) {

				$status = true;
				$paidMoney = 0;
				$paidPoints = 0;

				foreach ($prices as $priceValue => $pointsValue) {
					if ($priceValue == $payment_amount) {
						$paidMoney = $priceValue;
						$paidPoints = $pointsValue;
					}
				}

				if ($paidMoney == 0) $status = false; // Wrong ammount of money
				if ($payment_currency != $paypal['currency']) $status = false; // Wrong currency

				// Verify that the user havent messed around with POST data
				if ($status) {
					// transaction log
					mysql_insert("INSERT INTO `znote_paypal` VALUES ('0', '$txn_id', '$payer_email', '$custom', '".$paidMoney."', '".$paidPoints."')");

					// Process payment
					$data = mysql_select_single("SELECT `points` AS `old_points` FROM `znote_accounts` WHERE `account_id`='$custom';");

					// Give points to user
					$new_points = $data['old_points'] + $paidPoints;
					mysql_update("UPDATE `znote_accounts` SET `points`='$new_points' WHERE `account_id`='$custom'");
				}
			}  else {
				$pmail = $paypal['email'];
				mysql_insert("INSERT INTO `znote_paypal` VALUES ('0', '$txn_id', 'ERROR: Wrong mail. Received: $receiver_email, configured: $pmail', '0', '0', '0')");
			}
		}
	}
} else {
	// Something is wrong
	mysql_insert("INSERT INTO `znote_paypal` VALUES ('0', '$txn_id', 'ERROR: Invalid data. $postdata', '0', '0', '0')");
}
?>