PayPal IPN leads to 502 Proxy Error - php

Question

I am using the IPN code sample (for PHP) available on Github. When running this code via the IPN simulator, there is a huge loading time and after a few minutes PayPal finally throws this error.
Proxy Error
The proxy server received an invalid response from an upstream server. The proxy server could not handle the request POST /webapps/developer/applications/ipn_simulator.
Reason: Error reading from remote server
Another user faced the same exact issue here. However, it seems his problem was due to the fact he was not using the good script.
My ipn.php file, when accessed directly in the browser does not throw any error. It looks as follows:
/* INITIALIZATION */
require_once $_SERVER['DOCUMENT_ROOT'] . '/lib/aes.php'; // AES lib
require_once $_SERVER['DOCUMENT_ROOT'] . '/lib/db.php'; // DB configuration
require_once $_SERVER['DOCUMENT_ROOT'] . '/lib/mandrill/src/Mandrill.php'; // Mandrill mailer lib
$UA = $_SERVER['HTTP_USER_AGENT']; // User-Agent
//$proxy = '<my IP>:443';
$ip = getenv('HTTP_CLIENT_IP')?:
getenv('HTTP_X_FORWARDED_FOR')?:
getenv('HTTP_X_FORWARDED')?:
getenv('HTTP_FORWARDED_FOR')?:
getenv('HTTP_FORWARDED')?:
getenv('REMOTE_ADDR'); // IP address
$paypal_business = '< MY PAYPAL ID >'; // My PayPal ID
$license_amount = array( 10 => 0,
25 => 1,
50 => 2); // Type of license wrt to amount paid
$license_types = array( 0 => 1,
1 => 5,
2 => 20); // Number of licenses wrt type of license
$license_names = array( 0 => 'Single',
1 => 'Group',
2 => 'Company'); // Name of license wrt type of license
$donated = false;
/* MAILER powered by Mandrill */
function GmSendMail($bdy, $sbj, $em) {
try {
$mandrill = new Mandrill('< MY API KEY >'); // Mandrill API Key
$message = array(
'html' => $bdy,
'subject' => $sbj,
'from_email' => 'mail#example.com',
'from_name' => 'Company',
'to' => array(
array(
'email' => $em,
'type' => 'to'
)
),
'headers' => array('Reply-To' => 'support#example.com'),
'important' => true,
'track_opens' => true,
'track_clicks' => null,
'auto_text' => null,
'auto_html' => true,
'inline_css' => null,
'url_strip_qs' => null,
'preserve_recipients' => null,
'view_content_link' => null,
'tracking_domain' => null,
'signing_domain' => 'example.com',
'return_path_domain' => null,
'merge' => true,
'tags' => array('license-activation'),
'metadata' => array('website' => 'example.com')
);
$async = false;
$ip_pool = 'Main Pool';
$result = $mandrill->messages->send($message, $async, $ip_pool);
//print_r($result);
} catch(Mandrill_Error $e) {
// Mandrill errors are thrown as exceptions
echo 'An unexpected error occurred: ' . get_class($e) . ' - ' . $e->getMessage();
// A mandrill error occurred: Mandrill_Unknown_Subaccount - No subaccount exists with the id 'customer-123'
throw $e;
}
}
/* PAYPAL IPN: CHECK PAYMENT HAS BEEN COMPLETED */
// CONFIG: Enable debug mode. This means we'll log requests into 'ipn.log' in the same directory.
// Especially useful if you encounter network errors or other intermittent problems with IPN (validation).
// Set this to 0 once you go live or don't require logging.
define("DEBUG", 1);
// Set to 0 once you're ready to go live
define("USE_SANDBOX", 1);
define("LOG_FILE", "./ipn.log");
// Read POST data
// reading posted data directly from $_POST causes serialization
// issues with array data in POST. Reading raw POST data from input stream instead.
$raw_post_data = file_get_contents('php://input');
$raw_post_array = explode('&', $raw_post_data);
$myPost = array();
foreach ($raw_post_array as $keyval) {
$keyval = explode ('=', $keyval);
if (count($keyval) == 2)
$myPost[$keyval[0]] = urldecode($keyval[1]);
}
// read the post from PayPal system and add 'cmd'
$req = 'cmd=_notify-validate';
if(function_exists('get_magic_quotes_gpc')) {
$get_magic_quotes_exists = true;
}
foreach ($myPost as $key => $value) {
if($get_magic_quotes_exists == true && get_magic_quotes_gpc() == 1) {
$value = urlencode(stripslashes($value));
} else {
$value = urlencode($value);
}
$req .= "&$key=$value";
}
// Post IPN data back to PayPal to validate the IPN data is genuine
// Without this step anyone can fake IPN data
if(USE_SANDBOX == true) {
$paypal_url = "https://www.sandbox.paypal.com/cgi-bin/webscr";
} else {
$paypal_url = "https://www.paypal.com/cgi-bin/webscr";
}
$ch = curl_init($paypal_url);
if ($ch == FALSE) {
return FALSE;
}
curl_setopt($ch, CURLOPT_HTTP_VERSION, CURL_HTTP_VERSION_1_1);
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_RETURNTRANSFER,1);
curl_setopt($ch, CURLOPT_POSTFIELDS, $req);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 1);
curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 2);
curl_setopt($ch, CURLOPT_FORBID_REUSE, 1);
if(DEBUG == true) {
curl_setopt($ch, CURLOPT_HEADER, 1);
curl_setopt($ch, CURLINFO_HEADER_OUT, 1);
}
// CONFIG: Optional proxy configuration
//curl_setopt($ch, CURLOPT_PROXY, $proxy);
//curl_setopt($ch, CURLOPT_HTTPPROXYTUNNEL, 1);
// Set TCP timeout to 30 seconds
curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 30);
curl_setopt($ch, CURLOPT_HTTPHEADER, array('Connection: Close'));
// CONFIG: Please download 'cacert.pem' from "http://curl.haxx.se/docs/caextract.html" and set the directory path
// of the certificate as shown below. Ensure the file is readable by the webserver.
// This is mandatory for some environments.
$cert = __DIR__ . "/lib/cacert.pem";
curl_setopt($ch, CURLOPT_CAINFO, $cert);
$res = curl_exec($ch);
if (curl_errno($ch) != 0) // cURL error
{
if(DEBUG == true) {
error_log(date('[Y-m-d H:i e] '). "Can't connect to PayPal to validate IPN message: " . curl_error($ch) . PHP_EOL, 3, LOG_FILE);
}
curl_close($ch);
exit;
} else {
// Log the entire HTTP response if debug is switched on.
if(DEBUG == true) {
error_log(date('[Y-m-d H:i e] '). "HTTP request of validation request:". curl_getinfo($ch, CURLINFO_HEADER_OUT) ." for IPN payload: $req" . PHP_EOL, 3, LOG_FILE);
error_log(date('[Y-m-d H:i e] '). "HTTP response of validation request: $res" . PHP_EOL, 3, LOG_FILE);
// Split response headers and payload
list($headers, $res) = explode("\r\n\r\n", $res, 2);
}
curl_close($ch);
}
// Inspect IPN validation result and act accordingly
if (strcmp ($res, "VERIFIED") == 0) {
//if (preg_match("!(VERIFIED)\s*\Z!",$res)) {
$payment_status = $_POST['payment_status'];
$payment_amount = $_POST['mc_gross'];
$payment_date = $_POST['payment_date'];
$txn_id = $_POST['txn_id'];
$receiver_business = $_POST['business'];
$payer_email = $_POST['payer_email'];
$email_hash = sha1($payer_email, TRUE);
$user_id = $_POST['custom'];
// Retrieve license information
$license = $license_amount[$payment_amount];
$nblic = $license_types[$license] - 1;
$name_license = $license_names[$license];
// Confirmation email variables
$subject_paypal = 'Premium License [' . $name_license . ']';
$body_paypal = '<p>Dear user.</p>';
if ( $payment_status == 'Completed' && $receiver_business == strtolower($paypal_business) ) {
/* DB interactions and checks */
$check = mysql_query("SELECT * FROM `premium` WHERE `id` = '$email_hash'");
/* 1) User already exists: Update DB */
if (mysql_num_rows($check) === 1) {
$row = mysql_fetch_assoc($check);
$transaction_id = $row['pa'];
if ($txn_id == $transaction_id) {
$donated = true;
die('Premium license already activated.');
} else {
$licenses_left = $row['la'];
$current_key = $row['k'];
$newnblic = $licenses_left + $nblic;
// UPDATE DB
mysql_query("UPDATE `premium` SET `lt` = '$license', `la` = '$newnblic', `t` = '$payment_date', `pa` = '$txn_id' WHERE `id` = '$email_hash' ");
// SEND EMAIL CONFIRMATION
GmSendMail($body_paypal, $subject_paypal, $payer_email);
}
/* 2) This is a NEW entry: Insert into DB
*/
} else {
// CREATE ENTRY INTO DB
mysql_query("INSERT INTO `premium` VALUES('$email_hash','$license','$nblic','$payment_date','$txn_id')");
// SEND EMAIL CONFIRMATION
GmSendMail($body_paypal, $subject_paypal, $payer_email);
}
}
if(DEBUG == true) {
error_log(date('[Y-m-d H:i e] '). "Verified IPN: $req ". PHP_EOL, 3, LOG_FILE);
}
} else if (strcmp ($res, "INVALID") == 0) {
// log for manual investigation
// Add business logic here which deals with invalid IPN messages
if(DEBUG == true) {
error_log(date('[Y-m-d H:i e] '). "Invalid IPN: $req" . PHP_EOL, 3, LOG_FILE);
}
}
The ipn.log file, when accessed directly from the browser reads:
[2014-02-15 11:53 America/Denver] HTTP request of validation request:POST /cgi-bin/webscr HTTP/1.1
Host: www.sandbox.paypal.com
Accept: */*
Connection: Close
Content-Length: 20
Content-Type: application/x-www-form-urlencoded
for IPN payload: cmd=_notify-validate
[2014-02-15 11:53 America/Denver] HTTP response of validation request: HTTP/1.1 200 OK
Date: Sat, 15 Feb 2014 18:53:08 GMT
Server: Apache
X-Frame-Options: SAMEORIGIN
Set-Cookie: < Cookie Hash >; domain=.paypal.com; path=/; Secure; HttpOnly
Set-Cookie: cookie_check=yes; expires=Tue, 13-Feb-2024 18:53:08 GMT; domain=.paypal.com; path=/; Secure; HttpOnly
Set-Cookie: navcmd=_notify-validate; domain=.paypal.com; path=/; Secure; HttpOnly
Set-Cookie: navlns=0.0; expires=Mon, 15-Feb-2016 18:53:08 GMT; domain=.paypal.com; path=/; Secure; HttpOnly
Set-Cookie: Apache=10.72.109.11.1392490388263396; path=/; expires=Mon, 08-Feb-44 18:53:08 GMT
Connection: close
Set-Cookie: X-PP-SILOVER=name%3DSANDBOX3.WEB.1%26silo_version%3D880%26app%3Dslingshot%26TIME%3D2495086418; domain=.paypal.com; path=/; Secure; HttpOnly
Set-Cookie: X-PP-SILOVER=; Expires=Thu, 01 Jan 1970 00:00:01 GMT
Set-Cookie: Apache=10.72.128.11.1392490388253446; path=/; expires=Mon, 08-Feb-44 18:53:08 GMT
Vary: Accept-Encoding
Strict-Transport-Security: max-age=14400
Transfer-Encoding: chunked
Content-Type: text/html; charset=UTF-8
INVALID
[2014-02-15 11:53 America/Denver] Invalid IPN: cmd=_notify-validate
For information, ipn.php is hosted on a subdomain with https enabled, .htaccess is clean and does not block any proxy. PHP 5.4 is used. I'm on a shared server with a dedicated IP.
I tried to uncomment the following lines in ipn.php:
// CONFIG: Optional proxy configuration
curl_setopt($ch, CURLOPT_PROXY, $proxy);
curl_setopt($ch, CURLOPT_HTTPPROXYTUNNEL, 1);
with one time:
$proxy = 'mydedicatedIP:80';
another time:
$proxy = 'mydedicatedIP:443';
Without any success. Any help welcome !