<?php
/*
* Copyright 2015 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.
*/
namespace Google\Auth\Credentials;
use Google\Auth\CredentialsLoader;
use Google\Auth\GetQuotaProjectInterface;
use Google\Auth\HttpHandler\HttpClientCache;
use Google\Auth\HttpHandler\HttpHandlerFactory;
use Google\Auth\Iam;
use Google\Auth\ProjectIdProviderInterface;
use Google\Auth\SignBlobInterface;
use GuzzleHttp\Exception\ClientException;
use GuzzleHttp\Exception\ConnectException;
use GuzzleHttp\Exception\RequestException;
use GuzzleHttp\Exception\ServerException;
use GuzzleHttp\Psr7\Request;
use InvalidArgumentException;
/**
* GCECredentials supports authorization on Google Compute Engine.
*
* It can be used to authorize requests using the AuthTokenMiddleware, but will
* only succeed if being run on GCE:
*
* use Google\Auth\Credentials\GCECredentials;
* use Google\Auth\Middleware\AuthTokenMiddleware;
* use GuzzleHttp\Client;
* use GuzzleHttp\HandlerStack;
*
* $gce = new GCECredentials();
* $middleware = new AuthTokenMiddleware($gce);
* $stack = HandlerStack::create();
* $stack->push($middleware);
*
* $client = new Client([
* 'handler' => $stack,
* 'base_uri' => 'https://www.googleapis.com/taskqueue/v1beta2/projects/',
* 'auth' => 'google_auth'
* ]);
*
* $res = $client->get('myproject/taskqueues/myqueue');
*/
class GCECredentials extends CredentialsLoader implements
SignBlobInterface,
ProjectIdProviderInterface,
GetQuotaProjectInterface
{
// phpcs:disable
const cacheKey = 'GOOGLE_AUTH_PHP_GCE';
// phpcs:enable
/**
* The metadata IP address on appengine instances.
*
* The IP is used instead of the domain 'metadata' to avoid slow responses
* when not on Compute Engine.
*/
const METADATA_IP = '169.254.169.254';
/**
* The metadata path of the default token.
*/
const TOKEN_URI_PATH = 'v1/instance/service-accounts/default/token';
/**
* The metadata path of the default id token.
*/
const ID_TOKEN_URI_PATH = 'v1/instance/service-accounts/default/identity';
/**
* The metadata path of the client ID.
*/
const CLIENT_ID_URI_PATH = 'v1/instance/service-accounts/default/email';
/**
* The metadata path of the project ID.
*/
const PROJECT_ID_URI_PATH = 'v1/project/project-id';
/**
* The header whose presence indicates GCE presence.
*/
const FLAVOR_HEADER = 'Metadata-Flavor';
/**
* Note: the explicit `timeout` and `tries` below is a workaround. The underlying
* issue is that resolving an unknown host on some networks will take
* 20-30 seconds; making this timeout short fixes the issue, but
* could lead to false negatives in the event that we are on GCE, but
* the metadata resolution was particularly slow. The latter case is
* "unlikely" since the expected 4-nines time is about 0.5 seconds.
* This allows us to limit the total ping maximum timeout to 1.5 seconds
* for developer desktop scenarios.
*/
const MAX_COMPUTE_PING_TRIES = 3;
const COMPUTE_PING_CONNECTION_TIMEOUT_S = 0.5;
/**
* Flag used to ensure that the onGCE test is only done once;.
*
* @var bool
*/
private $hasCheckedOnGce = false;
/**
* Flag that stores the value of the onGCE check.
*
* @var bool
*/
private $isOnGce = false;
/**
* Result of fetchAuthToken.
*/
protected $lastReceivedToken;
/**
* @var string|null
*/
private $clientName;
/**
* @var string|null
*/
private $projectId;
/**
* @var Iam|null
*/
private $iam;
/**
* @var string
*/
private $tokenUri;
/**
* @var string
*/
private $targetAudience;
/**
* @var string|null
*/
private $quotaProject;
/**
* @var string|null
*/
private $serviceAccountIdentity;
/**
* @param Iam $iam [optional] An IAM instance.
* @param string|array $scope [optional] the scope of the access request,
* expressed either as an array or as a space-delimited string.
* @param string $targetAudience [optional] The audience for the ID token.
* @param string $quotaProject [optional] Specifies a project to bill for access
* charges associated with the request.
* @param string $serviceAccountIdentity [optional] Specify a service
* account identity name to use instead of "default".
*/
public function __construct(
Iam $iam = null,
$scope = null,
$targetAudience = null,
$quotaProject = null,
$serviceAccountIdentity = null
) {
$this->iam = $iam;
if ($scope && $targetAudience) {
throw new InvalidArgumentException(
'Scope and targetAudience cannot both be supplied'
);
}
$tokenUri = self::getTokenUri($serviceAccountIdentity);
if ($scope) {
if (is_string($scope)) {
$scope = explode(' ', $scope);
}
$scope = implode(',', $scope);
$tokenUri = $tokenUri . '?scopes=' . $scope;
} elseif ($targetAudience) {
$tokenUri = self::getIdTokenUri($serviceAccountIdentity);
$tokenUri = $tokenUri . '?audience=' . $targetAudience;
$this->targetAudience = $targetAudience;
}
$this->tokenUri = $tokenUri;
$this->quotaProject = $quotaProject;
$this->serviceAccountIdentity = $serviceAccountIdentity;
}
/**
* The full uri for accessing the default token.
*
* @param string $serviceAccountIdentity [optional] Specify a service
* account identity name to use instead of "default".
* @return string
*/
public static function getTokenUri($serviceAccountIdentity = null)
{
$base = 'http://' . self::METADATA_IP . '/computeMetadata/';
$base .= self::TOKEN_URI_PATH;
if ($serviceAccountIdentity) {
return str_replace(
'/default/',
'/' . $serviceAccountIdentity . '/',
$base
);
}
return $base;
}
/**
* The full uri for accessing the default service account.
*
* @param string $serviceAccountIdentity [optional] Specify a service
* account identity name to use instead of "default".
* @return string
*/
public static function getClientNameUri($serviceAccountIdentity = null)
{
$base = 'http://' . self::METADATA_IP . '/computeMetadata/';
$base .= self::CLIENT_ID_URI_PATH;
if ($serviceAccountIdentity) {
return str_replace(
'/default/',
'/' . $serviceAccountIdentity . '/',
$base
);
}
return $base;
}
/**
* The full uri for accesesing the default identity token.
*
* @param string $serviceAccountIdentity [optional] Specify a service
* account identity name to use instead of "default".
* @return string
*/
private static function getIdTokenUri($serviceAccountIdentity = null)
{
$base = 'http://' . self::METADATA_IP . '/computeMetadata/';
$base .= self::ID_TOKEN_URI_PATH;
if ($serviceAccountIdentity) {
return str_replace(
'/default/',
'/' . $serviceAccountIdentity . '/',
$base
);
}
return $base;
}
/**
* The full uri for accessing the default project ID.
*
* @return string
*/
private static function getProjectIdUri()
{
$base = 'http://' . self::METADATA_IP . '/computeMetadata/';
return $base . self::PROJECT_ID_URI_PATH;
}
/**
* Determines if this an App Engine Flexible instance, by accessing the
* GAE_INSTANCE environment variable.
*
* @return bool true if this an App Engine Flexible Instance, false otherwise
*/
public static function onAppEngineFlexible()
{
return substr(getenv('GAE_INSTANCE'), 0, 4) === 'aef-';
}
/**
* Determines if this a GCE instance, by accessing the expected metadata
* host.
* If $httpHandler is not specified a the default HttpHandler is used.
*
* @param callable $httpHandler callback which delivers psr7 request
* @return bool True if this a GCEInstance, false otherwise
*/
public static function onGce(callable $httpHandler = null)
{
$httpHandler = $httpHandler
?: HttpHandlerFactory::build(HttpClientCache::getHttpClient());
$checkUri = 'http://' . self::METADATA_IP;
for ($i = 1; $i <= self::MAX_COMPUTE_PING_TRIES; $i++) {
try {
// Comment from: oauth2client/client.py
//
// Note: the explicit `timeout` below is a workaround. The underlying
// issue is that resolving an unknown host on some networks will take
// 20-30 seconds; making this timeout short fixes the issue, but
// could lead to false negatives in the event that we are on GCE, but
// the metadata resolution was particularly slow. The latter case is
// "unlikely".
$resp = $httpHandler(
new Request(
'GET',
$checkUri,
[self::FLAVOR_HEADER => 'Google']
),
['timeout' => self::COMPUTE_PING_CONNECTION_TIMEOUT_S]
);
return $resp->getHeaderLine(self::FLAVOR_HEADER) == 'Google';
} catch (ClientException $e) {
} catch (ServerException $e) {
} catch (RequestException $e) {
} catch (ConnectException $e) {
}
}
return false;
}
/**
* Implements FetchAuthTokenInterface#fetchAuthToken.
*
* Fetches the auth tokens from the GCE metadata host if it is available.
* If $httpHandler is not specified a the default HttpHandler is used.
*
* @param callable $httpHandler callback which delivers psr7 request
*
* @return array A set of auth related metadata, based on the token type.
*
* Access tokens have the following keys:
* - access_token (string)
* - expires_in (int)
* - token_type (string)
* ID tokens have the following keys:
* - id_token (string)
*
* @throws \Exception
*/
public function fetchAuthToken(callable $httpHandler = null)
{
$httpHandler = $httpHandler
?: HttpHandlerFactory::build(HttpClientCache::getHttpClient());
if (!$this->hasCheckedOnGce) {
$this->isOnGce = self::onGce($httpHandler);
$this->hasCheckedOnGce = true;
}
if (!$this->isOnGce) {
return array(); // return an empty array with no access token
}
$response = $this->getFromMetadata($httpHandler, $this->tokenUri);
if ($this->targetAudience) {
return ['id_token' => $response];
}
if (null === $json = json_decode($response, true)) {
throw new \Exception('Invalid JSON response');
}
$json['expires_at'] = time() + $json['expires_in'];
// store this so we can retrieve it later
$this->lastReceivedToken = $json;
return $json;
}
/**
* @return string
*/
public function getCacheKey()
{
return self::cacheKey;
}
/**
* @return array|null
*/
public function getLastReceivedToken()
{
if ($this->lastReceivedToken) {
return [
'access_token' => $this->lastReceivedToken['access_token'],
'expires_at' => $this->lastReceivedToken['expires_at'],
];
}
return null;
}
/**
* Get the client name from GCE metadata.
*
* Subsequent calls will return a cached value.
*
* @param callable $httpHandler callback which delivers psr7 request
* @return string
*/
public function getClientName(callable $httpHandler = null)
{
if ($this->clientName) {
return $this->clientName;
}
$httpHandler = $httpHandler
?: HttpHandlerFactory::build(HttpClientCache::getHttpClient());
if (!$this->hasCheckedOnGce) {
$this->isOnGce = self::onGce($httpHandler);
$this->hasCheckedOnGce = true;
}
if (!$this->isOnGce) {
return '';
}
$this->clientName = $this->getFromMetadata(
$httpHandler,
self::getClientNameUri($this->serviceAccountIdentity)
);
return $this->clientName;
}
/**
* Sign a string using the default service account private key.
*
* This implementation uses IAM's signBlob API.
*
* @see https://cloud.google.com/iam/credentials/reference/rest/v1/projects.serviceAccounts/signBlob SignBlob
*
* @param string $stringToSign The string to sign.
* @param bool $forceOpenSsl [optional] Does not apply to this credentials
* type.
* @param string $accessToken The access token to use to sign the blob. If
* provided, saves a call to the metadata server for a new access
* token. **Defaults to** `null`.
* @return string
*/
public function signBlob($stringToSign, $forceOpenSsl = false, $accessToken = null)
{
$httpHandler = HttpHandlerFactory::build(HttpClientCache::getHttpClient());
// Providing a signer is useful for testing, but it's undocumented
// because it's not something a user would generally need to do.
$signer = $this->iam ?: new Iam($httpHandler);
$email = $this->getClientName($httpHandler);
if (is_null($accessToken)) {
$previousToken = $this->getLastReceivedToken();
$accessToken = $previousToken
? $previousToken['access_token']
: $this->fetchAuthToken($httpHandler)['access_token'];
}
return $signer->signBlob($email, $accessToken, $stringToSign);
}
/**
* Fetch the default Project ID from compute engine.
*
* Returns null if called outside GCE.
*
* @param callable $httpHandler Callback which delivers psr7 request
* @return string|null
*/
public function getProjectId(callable $httpHandler = null)
{
if ($this->projectId) {
return $this->projectId;
}
$httpHandler = $httpHandler
?: HttpHandlerFactory::build(HttpClientCache::getHttpClient());
if (!$this->hasCheckedOnGce) {
$this->isOnGce = self::onGce($httpHandler);
$this->hasCheckedOnGce = true;
}
if (!$this->isOnGce) {
return null;
}
$this->projectId = $this->getFromMetadata($httpHandler, self::getProjectIdUri());
return $this->projectId;
}
/**
* Fetch the value of a GCE metadata server URI.
*
* @param callable $httpHandler An HTTP Handler to deliver PSR7 requests.
* @param string $uri The metadata URI.
* @return string
*/
private function getFromMetadata(callable $httpHandler, $uri)
{
$resp = $httpHandler(
new Request(
'GET',
$uri,
[self::FLAVOR_HEADER => 'Google']
)
);
return (string) $resp->getBody();
}
/**
* Get the quota project used for this API request
*
* @return string|null
*/
public function getQuotaProject()
{
return $this->quotaProject;
}
}