PayPal IPN verification

Question

I have an IPN which is sending the messages correctly to my file, I have confirmed that I am receiving them, first here's my code:

echo "test";
// Response from Paypal

// read the post from PayPal system and add 'cmd'
$req = 'cmd=_notify-validate';
foreach ($_POST as $key => $value) {
    $value = urlencode(stripslashes($value));
    $value = preg_replace('/(.*[^%^0^D])(%0A)(.*)/i','${1}%0D%0A${3}',$value);// IPN fix
    $req .= "&$key=$value";
}

// assign posted variables to local variables
$data['item_name']          = $_POST['item_name'];
$data['item_number']        = $_POST['item_number'];
$data['payment_status']     = $_POST['payment_status'];
$data['payment_amount']     = $_POST['mc_gross'];
$data['payment_currency']   = $_POST['mc_currency'];
$data['txn_id']             = $_POST['txn_id'];
$data['receiver_email']     = $_POST['receiver_email'];
$data['payer_email']        = $_POST['payer_email'];
$data['custom']             = $_POST['custom'];

// post back to PayPal system to validate
$header  = "POST /cgi-bin/webscr HTTP/1.1\r\n";
$header .= "Host: www.sanbox.paypal.com\r\n";
$header .= "Accept: */*\r\n";
$header .= "Connection: Close\r\n";
$header .= "Content-Length: " . strlen($req) . "\r\n";
$header .= "Content-Type: application/x-www-form-urlencoded\r\n";
$header .= "\r\n";

$fp = fsockopen ('ssl://www.sandbox.paypal.com', 443, $errno, $errstr, 30); 
if ($fp === FALSE) {
exit("Could not open socket");
}else{
if (!$fp) {
    echo "Error code: 200";
}else{

    fputs ($fp, $header . $req);
$res = stream_get_contents($fp, 2048);
echo "test2";
$res = trim($res);
        if (strcmp($res, "VERIFIED") == 0){
        echo "test3";
            // Used for debugging
            //@mail("[email protected]", "PAYPAL DEBUGGING", "Verified Response<br />data = <pre>".print_r($post, true)."</pre>");

            // Validate payment (Check unique txnid & correct price)
            $valid_txnid = check_txnid($data['txn_id']);
            $valid_price = check_price($data['payment_amount'], $data['item_number']);
            // PAYMENT VALIDATED & VERIFIED!
            if($valid_txnid && $valid_price){
                $orderid = updatePayments($data);       
                if($orderid){       
                   echo "thanks for your payment!";
                   $lel = mysqli_query($con,"UPDATE stats SET stats.bankedgold = 10000 WHERE stats.id = $id4");
                    // Payment has been made & successfully inserted into the Database                              
                }else{                          
                    echo "Error code: 100";
                    // E-mail admin or alert user
                }
            }else{
                echo "Error code: 130";
                // Payment made but data has been changed
                // E-mail admin or alert user
            }                       

        }else if (strcmp ($res, "INVALID") == 0) {
             echo "Error code: 170";
            // PAYMENT INVALID & INVESTIGATE MANUALY! 
            // E-mail admin or alert user

            // Used for debugging
            //@mail("[email protected]", "PAYPAL DEBUGGING", "Invalid     Response<br />data = <pre>".print_r($post, true)."</pre>");
        }       
    echo strcmp($res,"VERIFIED" == 0);      
fclose ($fp);
}   

}
}

Now, a var_dump of $res gives:

HTTP/1.1 200 OK
Date: Mon, 02 Mar 2015 11:24:35 GMT 
Server: Apache X-Frame-  
Options: SAMEORIGIN 
Set-Cookie: <REDACTED_FOR_PRIVACY>
Set-Cookie: navcmd=_notify-validate; domain=.paypal.com; path=/; Secure; HttpOnly 
Set-Cookie: navlns=0.0; expires=Wed, 01-Mar-2017 11:24:35 GMT; domain=.paypal.com; path=/; Secure; HttpOnly
Set-Cookie: Apache=10.72.108.11.1425295475397401; path=/; expires=Wed, 22-Feb-45 11:24:35 GMT
Vary: Accept-Encoding,User-Agent Connection: close 
Set-Cookie: <REDACTED_FOR_PRIVACY>
Set-Cookie: X-PP-SILOVER=; Expires=Thu, 01 Jan 1970 00:00:01 GMT    
Set-Cookie: Apache=10.72.128.11.1425295475383817; path=/; expires=Wed, 22-Feb-45 11:24:35 GMT
Strict-Transport-Security: max-age=14400 
Transfer-Encoding: chunked 
Content-Type: text/html; charset=UTF-8 8

VERIFIED 0

But I need it to say just VERIFIED or INVALID so I can determine what to do from there.

A simple fix for me would be to add "strpos" and just see if it contains the words but I want to verify with you experts that it would be a good fix?

Niet the Dark Absol Niet the Dark Absol · Accepted Answer · 2015-03-02T12:15:09

PayPal has started using HTTP/1.1 to send its responses. This means, among other things, that you get Transfer-Encoding: chunked in the response.

The chunked encoding requires parsing. Typically it will look like this:

8
VERIFIED

0

Translated, this gives "chunk of length 8 = VERIFIED || chunk of length 0 = end of stream"

If you can't parse this response, you can try to force PayPal to not use chunked encoding by specifying HTTP/1.0 in your validation response. Alternatively, use a better library like cURL to do the parsing for you - PayPal's demo IPN code was written for a very old version of PHP, or at least one with no extensions enabled. It seems like the programmer was ignorant of the http_build_query function to properly encode the $req verification data, which is just sad really. You'd think PayPal could afford competent developers _^*ahem* but anyway... Personally I "solved" it by just reading the Content-Length header - all the responses that PayPal can send here have different lengths. Sort of cheating, but it worked.

Hope this helps :)

PayPal IPN verification

2 Answers