<?php
namespace Stripe;
abstract class WebhookSignature
{
const EXPECTED_SCHEME = 'v1';
/**
* Verifies the signature header sent by Stripe. Throws an
* Exception\SignatureVerificationException exception if the verification fails for
* any reason.
*
* @param string $payload the payload sent by Stripe
* @param string $header the contents of the signature header sent by
* Stripe
* @param string $secret secret used to generate the signature
* @param int $tolerance maximum difference allowed between the header's
* timestamp and the current time
*
* @throws Exception\SignatureVerificationException if the verification fails
*
* @return bool
*/
public static function verifyHeader($payload, $header, $secret, $tolerance = null)
{
// Extract timestamp and signatures from header
$timestamp = self::getTimestamp($header);
$signatures = self::getSignatures($header, self::EXPECTED_SCHEME);
if (-1 === $timestamp) {
throw Exception\SignatureVerificationException::factory(
'Unable to extract timestamp and signatures from header',
$payload,
$header
);
}
if (empty($signatures)) {
throw Exception\SignatureVerificationException::factory(
'No signatures found with expected scheme',
$payload,
$header
);
}
// Check if expected signature is found in list of signatures from
// header
$signedPayload = "{$timestamp}.{$payload}";
$expectedSignature = self::computeSignature($signedPayload, $secret);
$signatureFound = false;
foreach ($signatures as $signature) {
if (Util\Util::secureCompare($expectedSignature, $signature)) {
$signatureFound = true;
break;
}
}
if (!$signatureFound) {
throw Exception\SignatureVerificationException::factory(
'No signatures found matching the expected signature for payload',
$payload,
$header
);
}
// Check if timestamp is within tolerance
if (($tolerance > 0) && (\abs(\time() - $timestamp) > $tolerance)) {
throw Exception\SignatureVerificationException::factory(
'Timestamp outside the tolerance zone',
$payload,
$header
);
}
return true;
}
/**
* Extracts the timestamp in a signature header.
*
* @param string $header the signature header
*
* @return int the timestamp contained in the header, or -1 if no valid
* timestamp is found
*/
private static function getTimestamp($header)
{
$items = \explode(',', $header);
foreach ($items as $item) {
$itemParts = \explode('=', $item, 2);
if ('t' === $itemParts[0]) {
if (!\is_numeric($itemParts[1])) {
return -1;
}
return (int) ($itemParts[1]);
}
}
return -1;
}
/**
* Extracts the signatures matching a given scheme in a signature header.
*
* @param string $header the signature header
* @param string $scheme the signature scheme to look for
*
* @return array the list of signatures matching the provided scheme
*/
private static function getSignatures($header, $scheme)
{
$signatures = [];
$items = \explode(',', $header);
foreach ($items as $item) {
$itemParts = \explode('=', $item, 2);
if (\trim($itemParts[0]) === $scheme) {
$signatures[] = $itemParts[1];
}
}
return $signatures;
}
/**
* Computes the signature for a given payload and secret.
*
* The current scheme used by Stripe ("v1") is HMAC/SHA-256.
*
* @param string $payload the payload to sign
* @param string $secret the secret used to generate the signature
*
* @return string the signature as a string
*/
private static function computeSignature($payload, $secret)
{
return \hash_hmac('sha256', $payload, $secret);
}
}
About Section
NFC Pay was founded with a vision to transform the way people handle transactions. Our journey is defined by a commitment to innovation, security, and convenience. We strive to deliver seamless, user-friendly payment solutions that make everyday transactions effortless and secure. Our mission is to empower you to pay with ease and confidence, anytime, anywhere.
FAQ Section
Here are answers to some common questions about NFC Pay. We aim to provide clear and concise information to help you understand how our platform works and how it can benefit you. If you have any further inquiries, please don’t hesitate to contact our support team.
Download the app and sign up using your email or phone number, then complete the verification process.
Yes, we use advanced encryption and security protocols to protect your payment details.
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Go to the transfer section, select the recipient, enter the amount, and authorize the transfer.
Use the “Forgot PIN” feature in the app to reset it following the provided instructions.
Sign up for a merchant account through the app and follow the setup instructions to start accepting payments.
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