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<?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\HttpHandler\HttpHandlerFactory;
use GuzzleHttp\Exception\ClientException;
use GuzzleHttp\Exception\RequestException;
use GuzzleHttp\Exception\ServerException;
use GuzzleHttp\Psr7\Request;
/**
* 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
{
const cacheKey = 'GOOGLE_AUTH_PHP_GCE';
/**
* 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 header whose presence indicates GCE presence.
*/
const FLAVOR_HEADER = 'Metadata-Flavor';
/**
* 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;
/**
* The full uri for accessing the default token.
*
* @return string
*/
public static function getTokenUri()
{
$base = 'http://' . self::METADATA_IP . '/computeMetadata/';
return $base . self::TOKEN_URI_PATH;
}
/**
* Determines if this an App Engine Flexible instance, by accessing the
* GAE_VM environment variable.
*
* @return true if this an App Engine Flexible Instance, false otherwise
*/
public static function onAppEngineFlexible()
{
return isset($_SERVER['GAE_VM']) && 'true' === $_SERVER['GAE_VM'];
}
/**
* 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 true if this a GCEInstance false otherwise
*/
public static function onGce(callable $httpHandler = null)
{
if (is_null($httpHandler)) {
$httpHandler = HttpHandlerFactory::build();
}
$checkUri = 'http://' . self::METADATA_IP;
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),
['timeout' => 0.3]
);
return $resp->getHeaderLine(self::FLAVOR_HEADER) == 'Google';
} catch (ClientException $e) {
return false;
} catch (ServerException $e) {
return false;
} catch (RequestException $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 the response
*
* @throws \Exception
*/
public function fetchAuthToken(callable $httpHandler = null)
{
if (is_null($httpHandler)) {
$httpHandler = HttpHandlerFactory::build();
}
if (!$this->hasCheckedOnGce) {
$this->isOnGce = self::onGce($httpHandler);
}
if (!$this->isOnGce) {
return array(); // return an empty array with no access token
}
$resp = $httpHandler(
new Request(
'GET',
self::getTokenUri(),
[self::FLAVOR_HEADER => 'Google']
)
);
$body = (string)$resp->getBody();
// Assume it's JSON; if it's not throw an exception
if (null === $json = json_decode($body, true)) {
throw new \Exception('Invalid JSON response');
}
// store this so we can retrieve it later
$this->lastReceivedToken = $json;
$this->lastReceivedToken['expires_at'] = time() + $json['expires_in'];
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;
}
}
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