<?php
/*
* Copyright 2019 Google LLC
*
* 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.
*/
namespace Google\Auth;
use DateTime;
use Exception;
use Firebase\JWT\ExpiredException;
use Firebase\JWT\JWT;
use Firebase\JWT\Key;
use Firebase\JWT\SignatureInvalidException;
use Google\Auth\Cache\MemoryCacheItemPool;
use Google\Auth\HttpHandler\HttpClientCache;
use Google\Auth\HttpHandler\HttpHandlerFactory;
use GuzzleHttp\Psr7\Request;
use GuzzleHttp\Psr7\Utils;
use InvalidArgumentException;
use phpseclib\Crypt\RSA;
use phpseclib\Math\BigInteger;
use Psr\Cache\CacheItemPoolInterface;
use RuntimeException;
use SimpleJWT\InvalidTokenException;
use SimpleJWT\JWT as SimpleJWT;
use SimpleJWT\Keys\KeyFactory;
use SimpleJWT\Keys\KeySet;
use UnexpectedValueException;
/**
* Wrapper around Google Access Tokens which provides convenience functions.
*
* @experimental
*/
class AccessToken
{
const FEDERATED_SIGNON_CERT_URL = 'https://www.googleapis.com/oauth2/v3/certs';
const IAP_CERT_URL = 'https://www.gstatic.com/iap/verify/public_key-jwk';
const IAP_ISSUER = 'https://cloud.google.com/iap';
const OAUTH2_ISSUER = 'accounts.google.com';
const OAUTH2_ISSUER_HTTPS = 'https://accounts.google.com';
const OAUTH2_REVOKE_URI = 'https://oauth2.googleapis.com/revoke';
/**
* @var callable
*/
private $httpHandler;
/**
* @var CacheItemPoolInterface
*/
private $cache;
/**
* @param callable $httpHandler [optional] An HTTP Handler to deliver PSR-7 requests.
* @param CacheItemPoolInterface $cache [optional] A PSR-6 compatible cache implementation.
*/
public function __construct(
callable $httpHandler = null,
CacheItemPoolInterface $cache = null
) {
$this->httpHandler = $httpHandler
?: HttpHandlerFactory::build(HttpClientCache::getHttpClient());
$this->cache = $cache ?: new MemoryCacheItemPool();
}
/**
* 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 $token The JSON Web Token to be verified.
* @param array<mixed> $options [optional] {
* Configuration options.
* @type string $audience The indended recipient of the token.
* @type string $issuer The intended issuer of the token.
* @type string $cacheKey The cache key of the cached certs. Defaults to
* the sha1 of $certsLocation if provided, otherwise is set to
* "federated_signon_certs_v3".
* @type string $certsLocation The location (remote or local) from which
* to retrieve certificates, if not cached. This value should only be
* provided in limited circumstances in which you are sure of the
* behavior.
* @type bool $throwException Whether the function should throw an
* exception if the verification fails. This is useful for
* determining the reason verification failed.
* }
* @return array<mixed>|false the token payload, if successful, or false if not.
* @throws InvalidArgumentException If certs could not be retrieved from a local file.
* @throws InvalidArgumentException If received certs are in an invalid format.
* @throws InvalidArgumentException If the cert alg is not supported.
* @throws RuntimeException If certs could not be retrieved from a remote location.
* @throws UnexpectedValueException If the token issuer does not match.
* @throws UnexpectedValueException If the token audience does not match.
*/
public function verify($token, array $options = [])
{
$audience = isset($options['audience'])
? $options['audience']
: null;
$issuer = isset($options['issuer'])
? $options['issuer']
: null;
$certsLocation = isset($options['certsLocation'])
? $options['certsLocation']
: self::FEDERATED_SIGNON_CERT_URL;
$cacheKey = isset($options['cacheKey'])
? $options['cacheKey']
: $this->getCacheKeyFromCertLocation($certsLocation);
$throwException = isset($options['throwException'])
? $options['throwException']
: false; // for backwards compatibility
// Check signature against each available cert.
$certs = $this->getCerts($certsLocation, $cacheKey, $options);
$alg = $this->determineAlg($certs);
if (!in_array($alg, ['RS256', 'ES256'])) {
throw new InvalidArgumentException(
'unrecognized "alg" in certs, expected ES256 or RS256'
);
}
try {
if ($alg == 'RS256') {
return $this->verifyRs256($token, $certs, $audience, $issuer);
}
return $this->verifyEs256($token, $certs, $audience, $issuer);
} catch (ExpiredException $e) { // firebase/php-jwt 5+
} catch (SignatureInvalidException $e) { // firebase/php-jwt 5+
} catch (InvalidTokenException $e) { // simplejwt
} catch (InvalidArgumentException $e) {
} catch (UnexpectedValueException $e) {
}
if ($throwException) {
throw $e;
}
return false;
}
/**
* Identifies the expected algorithm to verify by looking at the "alg" key
* of the provided certs.
*
* @param array<mixed> $certs Certificate array according to the JWK spec (see
* https://tools.ietf.org/html/rfc7517).
* @return string The expected algorithm, such as "ES256" or "RS256".
*/
private function determineAlg(array $certs)
{
$alg = null;
foreach ($certs as $cert) {
if (empty($cert['alg'])) {
throw new InvalidArgumentException(
'certs expects "alg" to be set'
);
}
$alg = $alg ?: $cert['alg'];
if ($alg != $cert['alg']) {
throw new InvalidArgumentException(
'More than one alg detected in certs'
);
}
}
return $alg;
}
/**
* Verifies an ES256-signed JWT.
*
* @param string $token The JSON Web Token to be verified.
* @param array<mixed> $certs Certificate array according to the JWK spec (see
* https://tools.ietf.org/html/rfc7517).
* @param string|null $audience If set, returns false if the provided
* audience does not match the "aud" claim on the JWT.
* @param string|null $issuer If set, returns false if the provided
* issuer does not match the "iss" claim on the JWT.
* @return array<mixed> the token payload, if successful, or false if not.
*/
private function verifyEs256($token, array $certs, $audience = null, $issuer = null)
{
$this->checkSimpleJwt();
$jwkset = new KeySet();
foreach ($certs as $cert) {
$jwkset->add(KeyFactory::create($cert, 'php'));
}
// Validate the signature using the key set and ES256 algorithm.
$jwt = $this->callSimpleJwtDecode([$token, $jwkset, 'ES256']);
$payload = $jwt->getClaims();
if ($audience) {
if (!isset($payload['aud']) || $payload['aud'] != $audience) {
throw new UnexpectedValueException('Audience does not match');
}
}
// @see https://cloud.google.com/iap/docs/signed-headers-howto#verifying_the_jwt_payload
$issuer = $issuer ?: self::IAP_ISSUER;
if (!isset($payload['iss']) || $payload['iss'] !== $issuer) {
throw new UnexpectedValueException('Issuer does not match');
}
return $payload;
}
/**
* Verifies an RS256-signed JWT.
*
* @param string $token The JSON Web Token to be verified.
* @param array<mixed> $certs Certificate array according to the JWK spec (see
* https://tools.ietf.org/html/rfc7517).
* @param string|null $audience If set, returns false if the provided
* audience does not match the "aud" claim on the JWT.
* @param string|null $issuer If set, returns false if the provided
* issuer does not match the "iss" claim on the JWT.
* @return array<mixed> the token payload, if successful, or false if not.
*/
private function verifyRs256($token, array $certs, $audience = null, $issuer = null)
{
$this->checkAndInitializePhpsec();
$keys = [];
foreach ($certs as $cert) {
if (empty($cert['kid'])) {
throw new InvalidArgumentException(
'certs expects "kid" to be set'
);
}
if (empty($cert['n']) || empty($cert['e'])) {
throw new InvalidArgumentException(
'RSA certs expects "n" and "e" to be set'
);
}
$rsa = new RSA();
$rsa->loadKey([
'n' => new BigInteger($this->callJwtStatic('urlsafeB64Decode', [
$cert['n'],
]), 256),
'e' => new BigInteger($this->callJwtStatic('urlsafeB64Decode', [
$cert['e']
]), 256),
]);
// create an array of key IDs to certs for the JWT library
$keys[$cert['kid']] = new Key($rsa->getPublicKey(), 'RS256');
}
$payload = $this->callJwtStatic('decode', [
$token,
$keys,
]);
if ($audience) {
if (!property_exists($payload, 'aud') || $payload->aud != $audience) {
throw new UnexpectedValueException('Audience does not match');
}
}
// support HTTP and HTTPS issuers
// @see https://developers.google.com/identity/sign-in/web/backend-auth
$issuers = $issuer ? [$issuer] : [self::OAUTH2_ISSUER, self::OAUTH2_ISSUER_HTTPS];
if (!isset($payload->iss) || !in_array($payload->iss, $issuers)) {
throw new UnexpectedValueException('Issuer does not match');
}
return (array) $payload;
}
/**
* Revoke an OAuth2 access token or refresh token. This method will revoke the current access
* token, if a token isn't provided.
*
* @param string|array<mixed> $token The token (access token or a refresh token) that should be revoked.
* @param array<mixed> $options [optional] Configuration options.
* @return bool Returns True if the revocation was successful, otherwise False.
*/
public function revoke($token, array $options = [])
{
if (is_array($token)) {
if (isset($token['refresh_token'])) {
$token = $token['refresh_token'];
} else {
$token = $token['access_token'];
}
}
$body = Utils::streamFor(http_build_query(['token' => $token]));
$request = new Request('POST', self::OAUTH2_REVOKE_URI, [
'Cache-Control' => 'no-store',
'Content-Type' => 'application/x-www-form-urlencoded',
], $body);
$httpHandler = $this->httpHandler;
$response = $httpHandler($request, $options);
return $response->getStatusCode() == 200;
}
/**
* 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.
*
* @param string $location The location from which to retrieve certs.
* @param string $cacheKey The key under which to cache the retrieved certs.
* @param array<mixed> $options [optional] Configuration options.
* @return array<mixed>
* @throws InvalidArgumentException If received certs are in an invalid format.
*/
private function getCerts($location, $cacheKey, array $options = [])
{
$cacheItem = $this->cache->getItem($cacheKey);
$certs = $cacheItem ? $cacheItem->get() : null; // @phpstan-ignore-line
$gotNewCerts = false;
if (!$certs) {
$certs = $this->retrieveCertsFromLocation($location, $options);
$gotNewCerts = true;
}
if (!isset($certs['keys'])) {
if ($location !== self::IAP_CERT_URL) {
throw new InvalidArgumentException(
'federated sign-on certs expects "keys" to be set'
);
}
throw new InvalidArgumentException(
'certs expects "keys" to be set'
);
}
// Push caching off until after verifying certs are in a valid format.
// Don't want to cache bad data.
if ($gotNewCerts) {
$cacheItem->expiresAt(new DateTime('+1 hour'));
$cacheItem->set($certs);
$this->cache->save($cacheItem);
}
return $certs['keys'];
}
/**
* Retrieve and cache a certificates file.
*
* @param string $url location
* @param array<mixed> $options [optional] Configuration options.
* @return array<mixed> certificates
* @throws InvalidArgumentException If certs could not be retrieved from a local file.
* @throws RuntimeException If certs could not be retrieved from a remote location.
*/
private function retrieveCertsFromLocation($url, array $options = [])
{
// If we're retrieving a local file, just grab it.
if (strpos($url, 'http') !== 0) {
if (!file_exists($url)) {
throw new InvalidArgumentException(sprintf(
'Failed to retrieve verification certificates from path: %s.',
$url
));
}
return json_decode((string) file_get_contents($url), true);
}
$httpHandler = $this->httpHandler;
$response = $httpHandler(new Request('GET', $url), $options);
if ($response->getStatusCode() == 200) {
return json_decode((string) $response->getBody(), true);
}
throw new RuntimeException(sprintf(
'Failed to retrieve verification certificates: "%s".',
$response->getBody()->getContents()
), $response->getStatusCode());
}
/**
* @return void
*/
private function checkAndInitializePhpsec()
{
// @codeCoverageIgnoreStart
if (!class_exists('phpseclib\Crypt\RSA')) {
throw new RuntimeException('Please require phpseclib/phpseclib v2 to use this utility.');
}
// @codeCoverageIgnoreEnd
$this->setPhpsecConstants();
}
/**
* @return void
*/
private function checkSimpleJwt()
{
// @codeCoverageIgnoreStart
if (!class_exists(SimpleJwt::class)) {
throw new RuntimeException('Please require kelvinmo/simplejwt ^0.2 to use this utility.');
}
// @codeCoverageIgnoreEnd
}
/**
* 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
* @codeCoverageIgnore
*
* @return void
*/
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', RSA::MODE_OPENSSL);
}
}
}
/**
* Provide a hook to mock calls to the JWT static methods.
*
* @param string $method
* @param array<mixed> $args
* @return mixed
*/
protected function callJwtStatic($method, array $args = [])
{
return call_user_func_array([JWT::class, $method], $args); // @phpstan-ignore-line
}
/**
* Provide a hook to mock calls to the JWT static methods.
*
* @param array<mixed> $args
* @return mixed
*/
protected function callSimpleJwtDecode(array $args = [])
{
return call_user_func_array([SimpleJwt::class, 'decode'], $args);
}
/**
* Generate a cache key based on the cert location using sha1 with the
* exception of using "federated_signon_certs_v3" to preserve BC.
*
* @param string $certsLocation
* @return string
*/
private function getCacheKeyFromCertLocation($certsLocation)
{
$key = $certsLocation === self::FEDERATED_SIGNON_CERT_URL
? 'federated_signon_certs_v3'
: sha1($certsLocation);
return 'google_auth_certs_cache|' . $key;
}
}