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<?php
namespace Aws\Credentials;
use Aws\Configuration\ConfigurationResolver;
use Aws\Exception\CredentialsException;
use Aws\Exception\InvalidJsonException;
use Aws\Sdk;
use GuzzleHttp\Exception\TransferException;
use GuzzleHttp\Promise;
use GuzzleHttp\Psr7\Request;
use GuzzleHttp\Promise\PromiseInterface;
use Psr\Http\Message\ResponseInterface;
/**
* Credential provider that provides credentials from the EC2 metadata service.
*/
class InstanceProfileProvider
{
const CRED_PATH = 'meta-data/iam/security-credentials/';
const TOKEN_PATH = 'api/token';
const ENV_DISABLE = 'AWS_EC2_METADATA_DISABLED';
const ENV_TIMEOUT = 'AWS_METADATA_SERVICE_TIMEOUT';
const ENV_RETRIES = 'AWS_METADATA_SERVICE_NUM_ATTEMPTS';
const CFG_EC2_METADATA_V1_DISABLED = 'ec2_metadata_v1_disabled';
const CFG_EC2_METADATA_SERVICE_ENDPOINT = 'ec2_metadata_service_endpoint';
const CFG_EC2_METADATA_SERVICE_ENDPOINT_MODE = 'ec2_metadata_service_endpoint_mode';
const DEFAULT_TIMEOUT = 1.0;
const DEFAULT_RETRIES = 3;
const DEFAULT_TOKEN_TTL_SECONDS = 21600;
const DEFAULT_AWS_EC2_METADATA_V1_DISABLED = false;
const ENDPOINT_MODE_IPv4 = 'IPv4';
const ENDPOINT_MODE_IPv6 = 'IPv6';
const DEFAULT_METADATA_SERVICE_IPv4_ENDPOINT = 'http://169.254.169.254';
const DEFAULT_METADATA_SERVICE_IPv6_ENDPOINT = 'http://[fd00:ec2::254]';
/** @var string */
private $profile;
/** @var callable */
private $client;
/** @var int */
private $retries;
/** @var int */
private $attempts;
/** @var float|mixed */
private $timeout;
/** @var bool */
private $secureMode = true;
/** @var bool|null */
private $ec2MetadataV1Disabled;
/** @var string */
private $endpoint;
/** @var string */
private $endpointMode;
/**
* The constructor accepts the following options:
*
* - timeout: Connection timeout, in seconds.
* - profile: Optional EC2 profile name, if known.
* - retries: Optional number of retries to be attempted.
* - ec2_metadata_v1_disabled: Optional for disabling the fallback to IMDSv1.
* - endpoint: Optional for overriding the default endpoint to be used for fetching credentials.
* The value must contain a valid URI scheme. If the URI scheme is not https, it must
* resolve to a loopback address.
* - endpoint_mode: Optional for overriding the default endpoint mode (IPv4|IPv6) to be used for
* resolving the default endpoint.
*
* @param array $config Configuration options.
*/
public function __construct(array $config = [])
{
$this->timeout = (float) getenv(self::ENV_TIMEOUT) ?: ($config['timeout'] ?? self::DEFAULT_TIMEOUT);
$this->profile = $config['profile'] ?? null;
$this->retries = (int) getenv(self::ENV_RETRIES) ?: ($config['retries'] ?? self::DEFAULT_RETRIES);
$this->client = $config['client'] ?? \Aws\default_http_handler();
$this->ec2MetadataV1Disabled = $config[self::CFG_EC2_METADATA_V1_DISABLED] ?? null;
$this->endpoint = $config[self::CFG_EC2_METADATA_SERVICE_ENDPOINT] ?? null;
if (!empty($this->endpoint) && !$this->isValidEndpoint($this->endpoint)) {
throw new \InvalidArgumentException('The provided URI "' . $this->endpoint . '" is invalid, or contains an unsupported host');
}
$this->endpointMode = $config[self::CFG_EC2_METADATA_SERVICE_ENDPOINT_MODE] ?? null;
}
/**
* Loads instance profile credentials.
*
* @return PromiseInterface
*/
public function __invoke($previousCredentials = null)
{
$this->attempts = 0;
return Promise\Coroutine::of(function () use ($previousCredentials) {
// Retrieve token or switch out of secure mode
$token = null;
while ($this->secureMode && is_null($token)) {
try {
$token = (yield $this->request(
self::TOKEN_PATH,
'PUT',
[
'x-aws-ec2-metadata-token-ttl-seconds' => self::DEFAULT_TOKEN_TTL_SECONDS
]
));
} catch (TransferException $e) {
if ($this->getExceptionStatusCode($e) === 500
&& $previousCredentials instanceof Credentials
) {
goto generateCredentials;
} elseif ($this->shouldFallbackToIMDSv1()
&& (!method_exists($e, 'getResponse')
|| empty($e->getResponse())
|| !in_array(
$e->getResponse()->getStatusCode(),
[400, 500, 502, 503, 504]
))
) {
$this->secureMode = false;
} else {
$this->handleRetryableException(
$e,
[],
$this->createErrorMessage(
'Error retrieving metadata token'
)
);
}
}
$this->attempts++;
}
// Set token header only for secure mode
$headers = [];
if ($this->secureMode) {
$headers = [
'x-aws-ec2-metadata-token' => $token
];
}
// Retrieve profile
while (!$this->profile) {
try {
$this->profile = (yield $this->request(
self::CRED_PATH,
'GET',
$headers
));
} catch (TransferException $e) {
// 401 indicates insecure flow not supported, switch to
// attempting secure mode for subsequent calls
if (!empty($this->getExceptionStatusCode($e))
&& $this->getExceptionStatusCode($e) === 401
) {
$this->secureMode = true;
}
$this->handleRetryableException(
$e,
[ 'blacklist' => [401, 403] ],
$this->createErrorMessage($e->getMessage())
);
}
$this->attempts++;
}
// Retrieve credentials
$result = null;
while ($result == null) {
try {
$json = (yield $this->request(
self::CRED_PATH . $this->profile,
'GET',
$headers
));
$result = $this->decodeResult($json);
} catch (InvalidJsonException $e) {
$this->handleRetryableException(
$e,
[ 'blacklist' => [401, 403] ],
$this->createErrorMessage(
'Invalid JSON response, retries exhausted'
)
);
} catch (TransferException $e) {
// 401 indicates insecure flow not supported, switch to
// attempting secure mode for subsequent calls
if (($this->getExceptionStatusCode($e) === 500
|| strpos($e->getMessage(), "cURL error 28") !== false)
&& $previousCredentials instanceof Credentials
) {
goto generateCredentials;
} elseif (!empty($this->getExceptionStatusCode($e))
&& $this->getExceptionStatusCode($e) === 401
) {
$this->secureMode = true;
}
$this->handleRetryableException(
$e,
[ 'blacklist' => [401, 403] ],
$this->createErrorMessage($e->getMessage())
);
}
$this->attempts++;
}
generateCredentials:
if (!isset($result)) {
$credentials = $previousCredentials;
} else {
$credentials = new Credentials(
$result['AccessKeyId'],
$result['SecretAccessKey'],
$result['Token'],
strtotime($result['Expiration'])
);
}
if ($credentials->isExpired()) {
$credentials->extendExpiration();
}
yield $credentials;
});
}
/**
* @param string $url
* @param string $method
* @param array $headers
* @return PromiseInterface Returns a promise that is fulfilled with the
* body of the response as a string.
*/
private function request($url, $method = 'GET', $headers = [])
{
$disabled = getenv(self::ENV_DISABLE) ?: false;
if (strcasecmp($disabled, 'true') === 0) {
throw new CredentialsException(
$this->createErrorMessage('EC2 metadata service access disabled')
);
}
$fn = $this->client;
$request = new Request($method, $this->resolveEndpoint() . $url);
$userAgent = 'aws-sdk-php/' . Sdk::VERSION;
if (defined('HHVM_VERSION')) {
$userAgent .= ' HHVM/' . HHVM_VERSION;
}
$userAgent .= ' ' . \Aws\default_user_agent();
$request = $request->withHeader('User-Agent', $userAgent);
foreach ($headers as $key => $value) {
$request = $request->withHeader($key, $value);
}
return $fn($request, ['timeout' => $this->timeout])
->then(function (ResponseInterface $response) {
return (string) $response->getBody();
})->otherwise(function (array $reason) {
$reason = $reason['exception'];
if ($reason instanceof TransferException) {
throw $reason;
}
$msg = $reason->getMessage();
throw new CredentialsException(
$this->createErrorMessage($msg)
);
});
}
private function handleRetryableException(
\Exception $e,
$retryOptions,
$message
) {
$isRetryable = true;
if (!empty($status = $this->getExceptionStatusCode($e))
&& isset($retryOptions['blacklist'])
&& in_array($status, $retryOptions['blacklist'])
) {
$isRetryable = false;
}
if ($isRetryable && $this->attempts < $this->retries) {
sleep((int) pow(1.2, $this->attempts));
} else {
throw new CredentialsException($message);
}
}
private function getExceptionStatusCode(\Exception $e)
{
if (method_exists($e, 'getResponse')
&& !empty($e->getResponse())
) {
return $e->getResponse()->getStatusCode();
}
return null;
}
private function createErrorMessage($previous)
{
return "Error retrieving credentials from the instance profile "
. "metadata service. ({$previous})";
}
private function decodeResult($response)
{
$result = json_decode($response, true);
if (json_last_error() > 0) {
throw new InvalidJsonException();
}
if ($result['Code'] !== 'Success') {
throw new CredentialsException('Unexpected instance profile '
. 'response code: ' . $result['Code']);
}
return $result;
}
/**
* This functions checks for whether we should fall back to IMDSv1 or not.
* If $ec2MetadataV1Disabled is null then we will try to resolve this value from
* the following sources:
* - From environment: "AWS_EC2_METADATA_V1_DISABLED".
* - From config file: aws_ec2_metadata_v1_disabled
* - Defaulted to false
*
* @return bool
*/
private function shouldFallbackToIMDSv1(): bool
{
$isImdsV1Disabled = \Aws\boolean_value($this->ec2MetadataV1Disabled)
?? \Aws\boolean_value(
ConfigurationResolver::resolve(
self::CFG_EC2_METADATA_V1_DISABLED,
self::DEFAULT_AWS_EC2_METADATA_V1_DISABLED,
'bool',
['use_aws_shared_config_files' => true]
)
)
?? self::DEFAULT_AWS_EC2_METADATA_V1_DISABLED;
return !$isImdsV1Disabled;
}
/**
* Resolves the metadata service endpoint. If the endpoint is not provided
* or configured then, the default endpoint, based on the endpoint mode resolved,
* will be used.
* Example: if endpoint_mode is resolved to be IPv4 and the endpoint is not provided
* then, the endpoint to be used will be http://169.254.169.254.
*
* @return string
*/
private function resolveEndpoint(): string
{
$endpoint = $this->endpoint;
if (is_null($endpoint)) {
$endpoint = ConfigurationResolver::resolve(
self::CFG_EC2_METADATA_SERVICE_ENDPOINT,
$this->getDefaultEndpoint(),
'string',
['use_aws_shared_config_files' => true]
);
}
if (!$this->isValidEndpoint($endpoint)) {
throw new CredentialsException('The provided URI "' . $endpoint . '" is invalid, or contains an unsupported host');
}
if (substr($endpoint, strlen($endpoint) - 1) !== '/') {
$endpoint = $endpoint . '/';
}
return $endpoint . 'latest/';
}
/**
* Resolves the default metadata service endpoint.
* If endpoint_mode is resolved as IPv4 then:
* - endpoint = http://169.254.169.254
* If endpoint_mode is resolved as IPv6 then:
* - endpoint = http://[fd00:ec2::254]
*
* @return string
*/
private function getDefaultEndpoint(): string
{
$endpointMode = $this->resolveEndpointMode();
switch ($endpointMode) {
case self::ENDPOINT_MODE_IPv4:
return self::DEFAULT_METADATA_SERVICE_IPv4_ENDPOINT;
case self::ENDPOINT_MODE_IPv6:
return self::DEFAULT_METADATA_SERVICE_IPv6_ENDPOINT;
}
throw new CredentialsException("Invalid endpoint mode '$endpointMode' resolved");
}
/**
* Resolves the endpoint mode to be considered when resolving the default
* metadata service endpoint.
*
* @return string
*/
private function resolveEndpointMode(): string
{
$endpointMode = $this->endpointMode;
if (is_null($endpointMode)) {
$endpointMode = ConfigurationResolver::resolve(
self::CFG_EC2_METADATA_SERVICE_ENDPOINT_MODE,
self::ENDPOINT_MODE_IPv4,
'string',
['use_aws_shared_config_files' => true]
);
}
return $endpointMode;
}
/**
* This method checks for whether a provide URI is valid.
* @param string $uri this parameter is the uri to do the validation against to.
*
* @return string|null
*/
private function isValidEndpoint(
$uri
): bool
{
// We make sure first the provided uri is a valid URL
$isValidURL = filter_var($uri, FILTER_VALIDATE_URL) !== false;
if (!$isValidURL) {
return false;
}
// We make sure that if is a no secure host then it must be a loop back address.
$parsedUri = parse_url($uri);
if ($parsedUri['scheme'] !== 'https') {
$host = trim($parsedUri['host'], '[]');
return CredentialsUtils::isLoopBackAddress(gethostbyname($host))
|| in_array(
$uri,
[self::DEFAULT_METADATA_SERVICE_IPv4_ENDPOINT, self::DEFAULT_METADATA_SERVICE_IPv6_ENDPOINT]
);
}
return true;
}
}