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<?php
namespace Braintree;
/**
* Braintree WebhookNotificationGateway
* Manages Webhooks
*/
class WebhookNotificationGateway
{
private $config;
// phpcs:ignore PEAR.Commenting.FunctionComment.Missing
public function __construct($gateway)
{
$this->config = $gateway->config;
$this->config->assertHasAccessTokenOrKeys();
}
/**
* Parses a webhook from the Braintree API
*
* @param string $signature used to verify before parsing
* @param mixed $payload to be parsed
*
* @throws Exception\InvalidSignature
*
* @return WebhookNotification object
*/
public function parse($signature, $payload)
{
if (is_null($signature)) {
throw new Exception\InvalidSignature("signature cannot be null");
}
if (is_null($payload)) {
throw new Exception\InvalidSignature("payload cannot be null");
}
if (preg_match("/[^A-Za-z0-9+=\/\n]/", $payload) === 1) {
throw new Exception\InvalidSignature("payload contains illegal characters");
}
self::_validateSignature($signature, $payload);
$xml = base64_decode($payload);
$attributes = Xml::buildArrayFromXml($xml);
return WebhookNotification::factory($attributes['notification']);
}
/*
* Verify a webhook challenge
*
* @param object $challenge to be verified
*
* @throws Exception\InvalidChallenge
*
* @return string
*/
public function verify($challenge)
{
if (!preg_match('/^[a-f0-9]{20,32}$/', $challenge)) {
throw new Exception\InvalidChallenge("challenge contains non-hex characters");
}
$publicKey = $this->config->getPublicKey();
$digest = Digest::hexDigestSha1($this->config->getPrivateKey(), $challenge);
return "{$publicKey}|{$digest}";
}
private function _payloadMatches($signature, $payload)
{
$payloadSignature = Digest::hexDigestSha1($this->config->getPrivateKey(), $payload);
return Digest::secureCompare($signature, $payloadSignature);
}
private function _validateSignature($signatureString, $payload)
{
$signaturePairs = preg_split("/&/", $signatureString);
$signature = self::_matchingSignature($signaturePairs);
if (!$signature) {
throw new Exception\InvalidSignature("no matching public key");
}
if (!(self::_payloadMatches($signature, $payload) || self::_payloadMatches($signature, $payload . "\n"))) {
throw new Exception\InvalidSignature("signature does not match payload - one has been modified");
}
}
private function _matchingSignature($signaturePairs)
{
foreach ($signaturePairs as $pair) {
$components = preg_split("/\|/", $pair);
if ($components[0] == $this->config->getPublicKey()) {
return $components[1];
}
}
return null;
}
}