<?php
namespace Aws\Credentials;
use Aws;
use Aws\CacheInterface;
use Aws\Exception\CredentialsException;
use GuzzleHttp\Promise;
/**
* Credential providers are functions that accept no arguments and return a
* promise that is fulfilled with an {@see \Aws\Credentials\CredentialsInterface}
* or rejected with an {@see \Aws\Exception\CredentialsException}.
*
* <code>
* use Aws\Credentials\CredentialProvider;
* $provider = CredentialProvider::defaultProvider();
* // Returns a CredentialsInterface or throws.
* $creds = $provider()->wait();
* </code>
*
* Credential providers can be composed to create credentials using conditional
* logic that can create different credentials in different environments. You
* can compose multiple providers into a single provider using
* {@see Aws\Credentials\CredentialProvider::chain}. This function accepts
* providers as variadic arguments and returns a new function that will invoke
* each provider until a successful set of credentials is returned.
*
* <code>
* // First try an INI file at this location.
* $a = CredentialProvider::ini(null, '/path/to/file.ini');
* // Then try an INI file at this location.
* $b = CredentialProvider::ini(null, '/path/to/other-file.ini');
* // Then try loading from envrionment variables.
* $c = CredentialProvider::env();
* // Combine the three providers together.
* $composed = CredentialProvider::chain($a, $b, $c);
* // Returns a promise that is fulfilled with credentials or throws.
* $promise = $composed();
* // Wait on the credentials to resolve.
* $creds = $promise->wait();
* </code>
*/
class CredentialProvider
{
const ENV_KEY = 'AWS_ACCESS_KEY_ID';
const ENV_SECRET = 'AWS_SECRET_ACCESS_KEY';
const ENV_SESSION = 'AWS_SESSION_TOKEN';
const ENV_PROFILE = 'AWS_PROFILE';
/**
* Create a default credential provider that first checks for environment
* variables, then checks for the "default" profile in ~/.aws/credentials,
* and finally checks for credentials using EC2 instance profile
* credentials.
*
* This provider is automatically wrapped in a memoize function that caches
* previously provided credentials.
*
* @param array $config Optional array of instance profile credentials
* provider options.
* @return callable
*/
public static function defaultProvider(array $config = [])
{
$instanceProfileProvider = self::instanceProfile($config);
if (isset($config['credentials'])
&& $config['credentials'] instanceof CacheInterface
) {
$instanceProfileProvider = self::cache(
$instanceProfileProvider,
$config['credentials']
);
}
return self::memoize(
self::chain(
self::env(),
self::ini(),
$instanceProfileProvider
)
);
}
/**
* Create a credential provider function from a set of static credentials.
*
* @param CredentialsInterface $creds
*
* @return callable
*/
public static function fromCredentials(CredentialsInterface $creds)
{
$promise = Promise\promise_for($creds);
return function () use ($promise) {
return $promise;
};
}
/**
* Creates an aggregate credentials provider that invokes the provided
* variadic providers one after the other until a provider returns
* credentials.
*
* @return callable
*/
public static function chain()
{
$links = func_get_args();
if (empty($links)) {
throw new \InvalidArgumentException('No providers in chain');
}
return function () use ($links) {
/** @var callable $parent */
$parent = array_shift($links);
$promise = $parent();
while ($next = array_shift($links)) {
$promise = $promise->otherwise($next);
}
return $promise;
};
}
/**
* Wraps a credential provider and caches previously provided credentials.
*
* Ensures that cached credentials are refreshed when they expire.
*
* @param callable $provider Credentials provider function to wrap.
*
* @return callable
*/
public static function memoize(callable $provider)
{
return function () use ($provider) {
static $result;
static $isConstant;
// Constant credentials will be returned constantly.
if ($isConstant) {
return $result;
}
// Create the initial promise that will be used as the cached value
// until it expires.
if (null === $result) {
$result = $provider();
}
// Return credentials that could expire and refresh when needed.
return $result
->then(function (CredentialsInterface $creds) use ($provider, &$isConstant, &$result) {
// Determine if these are constant credentials.
if (!$creds->getExpiration()) {
$isConstant = true;
return $creds;
}
// Refresh expired credentials.
if (!$creds->isExpired()) {
return $creds;
}
// Refresh the result and forward the promise.
return $result = $provider();
});
};
}
/**
* Wraps a credential provider and saves provided credentials in an
* instance of Aws\CacheInterface. Forwards calls when no credentials found
* in cache and updates cache with the results.
*
* Defaults to using a simple file-based cache when none provided.
*
* @param callable $provider Credentials provider function to wrap
* @param CacheInterface $cache (optional) Cache to store credentials
* @param string|null $cacheKey (optional) Cache key to use
*
* @return callable
*/
public static function cache(
callable $provider,
CacheInterface $cache,
$cacheKey = null
) {
$cacheKey = $cacheKey ?: 'aws_cached_credentials';
return function () use ($provider, $cache, $cacheKey) {
$found = $cache->get($cacheKey);
if ($found instanceof CredentialsInterface && !$found->isExpired()) {
return Promise\promise_for($found);
}
return $provider()
->then(function (CredentialsInterface $creds) use (
$cache,
$cacheKey
) {
$cache->set(
$cacheKey,
$creds,
null === $creds->getExpiration() ?
0 : $creds->getExpiration() - time()
);
return $creds;
});
};
}
/**
* Provider that creates credentials from environment variables
* AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY, and AWS_SESSION_TOKEN.
*
* @return callable
*/
public static function env()
{
return function () {
// Use credentials from environment variables, if available
$key = getenv(self::ENV_KEY);
$secret = getenv(self::ENV_SECRET);
if ($key && $secret) {
return Promise\promise_for(
new Credentials($key, $secret, getenv(self::ENV_SESSION))
);
}
return self::reject('Could not find environment variable '
. 'credentials in ' . self::ENV_KEY . '/' . self::ENV_SECRET);
};
}
/**
* Credential provider that creates credentials using instance profile
* credentials.
*
* @param array $config Array of configuration data.
*
* @return InstanceProfileProvider
* @see Aws\Credentials\InstanceProfileProvider for $config details.
*/
public static function instanceProfile(array $config = [])
{
return new InstanceProfileProvider($config);
}
/**
* Credentials provider that creates credentials using an ini file stored
* in the current user's home directory.
*
* @param string|null $profile Profile to use. If not specified will use
* the "default" profile.
* @param string|null $filename If provided, uses a custom filename rather
* than looking in the home directory for the
*
* @return callable
*/
public static function ini($profile = null, $filename = null)
{
$filename = $filename ?: (self::getHomeDir() . '/.aws/credentials');
$profile = $profile ?: (getenv(self::ENV_PROFILE) ?: 'default');
return function () use ($profile, $filename) {
if (!is_readable($filename)) {
return self::reject("Cannot read credentials from $filename");
}
$data = parse_ini_file($filename, true);
if ($data === false) {
return self::reject("Invalid credentials file: $filename");
}
if (!isset($data[$profile])) {
return self::reject("'$profile' not found in credentials file");
}
if (!isset($data[$profile]['aws_access_key_id'])
|| !isset($data[$profile]['aws_secret_access_key'])
) {
return self::reject("No credentials present in INI profile "
. "'$profile' ($filename)");
}
if (empty($data[$profile]['aws_session_token'])) {
$data[$profile]['aws_session_token']
= isset($data[$profile]['aws_security_token'])
? $data[$profile]['aws_security_token']
: null;
}
return Promise\promise_for(
new Credentials(
$data[$profile]['aws_access_key_id'],
$data[$profile]['aws_secret_access_key'],
$data[$profile]['aws_session_token']
)
);
};
}
/**
* Gets the environment's HOME directory if available.
*
* @return null|string
*/
private static function getHomeDir()
{
// On Linux/Unix-like systems, use the HOME environment variable
if ($homeDir = getenv('HOME')) {
return $homeDir;
}
// Get the HOMEDRIVE and HOMEPATH values for Windows hosts
$homeDrive = getenv('HOMEDRIVE');
$homePath = getenv('HOMEPATH');
return ($homeDrive && $homePath) ? $homeDrive . $homePath : null;
}
private static function reject($msg)
{
return new Promise\RejectedPromise(new CredentialsException($msg));
}
}
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