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<?php
/*
* Copyright 2008 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
use Firebase\JWT\ExpiredException as ExpiredExceptionV3;
use Firebase\JWT\SignatureInvalidException;
use GuzzleHttp\Client;
use GuzzleHttp\ClientInterface;
use Psr\Cache\CacheItemPoolInterface;
use Google\Auth\Cache\MemoryCacheItemPool;
use Stash\Driver\FileSystem;
use Stash\Pool;
/**
* Wrapper around Google Access Tokens which provides convenience functions
*
*/
class Google_AccessToken_Verify
{
const FEDERATED_SIGNON_CERT_URL = 'https://www.googleapis.com/oauth2/v3/certs';
const OAUTH2_ISSUER = 'accounts.google.com';
const OAUTH2_ISSUER_HTTPS = 'https://accounts.google.com';
/**
* @var GuzzleHttp\ClientInterface The http client
*/
private $http;
/**
* @var Psr\Cache\CacheItemPoolInterface cache class
*/
private $cache;
/**
* Instantiates the class, but does not initiate the login flow, leaving it
* to the discretion of the caller.
*/
public function __construct(
ClientInterface $http = null,
CacheItemPoolInterface $cache = null,
$jwt = null
) {
if (null === $http) {
$http = new Client();
}
if (null === $cache) {
$cache = new MemoryCacheItemPool;
}
$this->http = $http;
$this->cache = $cache;
$this->jwt = $jwt ?: $this->getJwtService();
}
/**
* Verifies an id token and returns the authenticated apiLoginTicket.
* Throws an exception if the id token is not valid.
* The audience parameter can be used to control which id tokens are
* accepted. By default, the id token must have been issued to this OAuth2 client.
*
* @param string $idToken the ID token in JWT format
* @param string $audience Optional. The audience to verify against JWt "aud"
* @return array the token payload, if successful
*/
public function verifyIdToken($idToken, $audience = null)
{
if (empty($idToken)) {
throw new LogicException('id_token cannot be null');
}
// set phpseclib constants if applicable
$this->setPhpsecConstants();
// Check signature
$certs = $this->getFederatedSignOnCerts();
foreach ($certs as $cert) {
$bigIntClass = $this->getBigIntClass();
$rsaClass = $this->getRsaClass();
$modulus = new $bigIntClass($this->jwt->urlsafeB64Decode($cert['n']), 256);
$exponent = new $bigIntClass($this->jwt->urlsafeB64Decode($cert['e']), 256);
$rsa = new $rsaClass();
$rsa->loadKey(array('n' => $modulus, 'e' => $exponent));
try {
$payload = $this->jwt->decode(
$idToken,
$rsa->getPublicKey(),
array('RS256')
);
if (property_exists($payload, 'aud')) {
if ($audience && $payload->aud != $audience) {
return false;
}
}
// support HTTP and HTTPS issuers
// @see https://developers.google.com/identity/sign-in/web/backend-auth
$issuers = array(self::OAUTH2_ISSUER, self::OAUTH2_ISSUER_HTTPS);
if (!isset($payload->iss) || !in_array($payload->iss, $issuers)) {
return false;
}
return (array) $payload;
} catch (ExpiredException $e) {
return false;
} catch (ExpiredExceptionV3 $e) {
return false;
} catch (SignatureInvalidException $e) {
// continue
} catch (DomainException $e) {
// continue
}
}
return false;
}
private function getCache()
{
return $this->cache;
}
/**
* Retrieve and cache a certificates file.
*
* @param $url string location
* @throws Google_Exception
* @return array certificates
*/
private function retrieveCertsFromLocation($url)
{
// If we're retrieving a local file, just grab it.
if (0 !== strpos($url, 'http')) {
if (!$file = file_get_contents($url)) {
throw new Google_Exception(
"Failed to retrieve verification certificates: '" .
$url . "'."
);
}
return json_decode($file, true);
}
$response = $this->http->get($url);
if ($response->getStatusCode() == 200) {
return json_decode((string) $response->getBody(), true);
}
throw new Google_Exception(
sprintf(
'Failed to retrieve verification certificates: "%s".',
$response->getBody()->getContents()
),
$response->getStatusCode()
);
}
// Gets federated sign-on certificates to use for verifying identity tokens.
// Returns certs as array structure, where keys are key ids, and values
// are PEM encoded certificates.
private function getFederatedSignOnCerts()
{
$certs = null;
if ($cache = $this->getCache()) {
$cacheItem = $cache->getItem('federated_signon_certs_v3');
$certs = $cacheItem->get();
}
if (!$certs) {
$certs = $this->retrieveCertsFromLocation(
self::FEDERATED_SIGNON_CERT_URL
);
if ($cache) {
$cacheItem->expiresAt(new DateTime('+1 hour'));
$cacheItem->set($certs);
$cache->save($cacheItem);
}
}
if (!isset($certs['keys'])) {
throw new InvalidArgumentException(
'federated sign-on certs expects "keys" to be set'
);
}
return $certs['keys'];
}
private function getJwtService()
{
$jwtClass = 'JWT';
if (class_exists('\Firebase\JWT\JWT')) {
$jwtClass = 'Firebase\JWT\JWT';
}
if (property_exists($jwtClass, 'leeway') && $jwtClass::$leeway < 1) {
// Ensures JWT leeway is at least 1
// @see https://github.com/google/google-api-php-client/issues/827
$jwtClass::$leeway = 1;
}
return new $jwtClass;
}
private function getRsaClass()
{
if (class_exists('phpseclib\Crypt\RSA')) {
return 'phpseclib\Crypt\RSA';
}
return 'Crypt_RSA';
}
private function getBigIntClass()
{
if (class_exists('phpseclib\Math\BigInteger')) {
return 'phpseclib\Math\BigInteger';
}
return 'Math_BigInteger';
}
private function getOpenSslConstant()
{
if (class_exists('phpseclib\Crypt\RSA')) {
return 'phpseclib\Crypt\RSA::MODE_OPENSSL';
}
if (class_exists('Crypt_RSA')) {
return 'CRYPT_RSA_MODE_OPENSSL';
}
throw new \Exception('Cannot find RSA class');
}
/**
* phpseclib calls "phpinfo" by default, which requires special
* whitelisting in the AppEngine VM environment. This function
* sets constants to bypass the need for phpseclib to check phpinfo
*
* @see phpseclib/Math/BigInteger
* @see https://github.com/GoogleCloudPlatform/getting-started-php/issues/85
*/
private function setPhpsecConstants()
{
if (filter_var(getenv('GAE_VM'), FILTER_VALIDATE_BOOLEAN)) {
if (!defined('MATH_BIGINTEGER_OPENSSL_ENABLED')) {
define('MATH_BIGINTEGER_OPENSSL_ENABLED', true);
}
if (!defined('CRYPT_RSA_MODE')) {
define('CRYPT_RSA_MODE', constant($this->getOpenSslConstant()));
}
}
}
}
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