/**
* Decodes a JWT string into a PHP object.
*
* @param string $jwt The JWT
* @param string|array|null $key The key, or map of keys.
* If the algorithm used is asymmetric, this is the public key
* @param array $allowed_algs List of supported verification algorithms
* Supported algorithms are 'HS256', 'HS384', 'HS512' and 'RS256'
*
* @return object The JWT's payload as a PHP object
*
* @throws DomainException Algorithm was not provided
* @throws UnexpectedValueException Provided JWT was invalid
* @throws SignatureInvalidException Provided JWT was invalid because the signature verification failed
* @throws BeforeValidException Provided JWT is trying to be used before it's eligible as defined by 'nbf'
* @throws BeforeValidException Provided JWT is trying to be used before it's been created as defined by 'iat'
* @throws ExpiredException Provided JWT has since expired, as defined by the 'exp' claim
*
* @uses jsonDecode
* @uses urlsafeB64Decode
*/
public static function decode($jwt, $key, $allowed_algs = array())
{
// 检查密钥
if (empty($key)) {
throw new InvalidArgumentException('Key may not be empty');
// 500 设置错误
}
// 检查服务器算法
if (!is_array($allowed_algs)) {
throw new InvalidArgumentException('alg算法设置错误');
// 500 设置错误
}
// 分解成数组
$tks = explode('.', $jwt);
if (count($tks) != 3) {
throw new UnexpectedValueException('Wrong number of segments');
// 4XX JWT无效
}
// 头解码
list($headb64, $bodyb64, $cryptob64) = $tks;
if (null === ($header = JWT::jsonDecode(JWT::urlsafeB64Decode($headb64)))) {
throw new UnexpectedValueException('Invalid header encoding');
// 4XX JWT无效
}
// 体解码
if (null === ($payload = JWT::jsonDecode(JWT::urlsafeB64Decode($bodyb64)))) {
throw new UnexpectedValueException('Invalid claims encoding');
// 4XX JWT无效
}
$sig = JWT::urlsafeB64Decode($cryptob64);
// 检查算法
if (empty($header->alg)) {
throw new DomainException('Empty algorithm');
// 4XX JWT无效
}
if (empty(self::$supported_algs[$header->alg])) {
throw new DomainException('Algorithm not supported');
// 4XX JWT无效
}
if (!is_array($allowed_algs) || !in_array($header->alg, $allowed_algs)) {
throw new DomainException('Algorithm not allowed');
// 500 或 4xx
}
// 检查密钥数组
if (is_array($key) || $key instanceof \ArrayAccess) {
if (isset($header->kid)) {
$key = $key[$header->kid];
} else {
throw new DomainException('"kid" empty, unable to lookup correct key');
// 500 或 4XX
}
}
// Check the signature
// 验证密钥
if (!JWT::verify("{$headb64}.{$bodyb64}", $sig, $key, $header->alg)) {
throw new SignatureInvalidException('Signature verification failed');
// 4XX JWT无效
}
// Check if the nbf if it is defined. This is the time that the
// token can actually be used. If it's not yet that time, abort.
// 检查nbf(不能在这之前使用)
if (isset($payload->nbf) && $payload->nbf > time() + self::$leeway) {
throw new BeforeValidException('Cannot handle token prior to ' . date(DateTime::ISO8601, $payload->nbf));
}
// Check that this token has been created before 'now'. This prevents
// using tokens that have been created for later use (and haven't
// correctly used the nbf claim).
// 检查时钟偏移（创建后的JWT在$leeway秒内不能使用）
if (isset($payload->iat) && $payload->iat > time() + self::$leeway) {
throw new BeforeValidException('Cannot handle token prior to ' . date(DateTime::ISO8601, $payload->iat));
}
// 检查JWT是否过期， 以服务器设置为先
$exp = isset($payload->exp) ? $payload->exp : 7 * 24 * 60 * 60;
$exp = config('jwt.claims.exp') ? config('jwt.claims.exp') : $exp;
if (isset($payload->iat) && $payload->iat + $exp < time()) {
throw new ExpiredException('Expired token');
}
return $payload;
}