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");
            }
            $data = \Aws\parse_ini_file($filename, true, INI_SCANNER_RAW);
            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']
                )
            );
        };
    }