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<?php
namespace Firebase\JWT;
use \DomainException;
use \InvalidArgumentException;
use \UnexpectedValueException;
use \DateTime;
/**
* JSON Web Token implementation, based on this spec:
* http://tools.ietf.org/html/draft-ietf-oauth-json-web-token-06
*
* PHP version 5
*
* @category Authentication
* @package Authentication_JWT
* @author Neuman Vong <neuman@twilio.com>
* @author Anant Narayanan <anant@php.net>
* @license http://opensource.org/licenses/BSD-3-Clause 3-clause BSD
* @link https://github.com/firebase/php-jwt
*/
class JWT
{
/**
* When checking nbf, iat or expiration times,
* we want to provide some extra leeway time to
* account for clock skew.
*/
public static $leeway = 0;
/**
* Allow the current timestamp to be specified.
* Useful for fixing a value within unit testing.
*
* Will default to PHP time() value if null.
*/
public static $timestamp = null;
public static $supported_algs = array(
'HS256' => array('hash_hmac', 'SHA256'),
'HS512' => array('hash_hmac', 'SHA512'),
'HS384' => array('hash_hmac', 'SHA384'),
'RS256' => array('openssl', 'SHA256'),
);
/**
* Decodes a JWT string into a PHP object.
*
* @param string $jwt The JWT
* @param string|array $key The key, or map of keys.
* If the algorithm used is asymmetric, this is the public key
* @param array $allowed_algs List of supported verification algorithms
* Supported algorithms are 'HS256', 'HS384', 'HS512' and 'RS256'
*
* @return object The JWT's payload as a PHP object
*
* @throws UnexpectedValueException Provided JWT was invalid
* @throws SignatureInvalidException Provided JWT was invalid because the signature verification failed
* @throws BeforeValidException Provided JWT is trying to be used before it's eligible as defined by 'nbf'
* @throws BeforeValidException Provided JWT is trying to be used before it's been created as defined by 'iat'
* @throws ExpiredException Provided JWT has since expired, as defined by the 'exp' claim
*
* @uses jsonDecode
* @uses urlsafeB64Decode
*/
public static function decode($jwt, $key, $allowed_algs = array())
{
$timestamp = is_null(static::$timestamp) ? time() : static::$timestamp;
if (empty($key)) {
throw new InvalidArgumentException('Key may not be empty');
}
if (!is_array($allowed_algs)) {
throw new InvalidArgumentException('Algorithm not allowed');
}
$tks = explode('.', $jwt);
if (count($tks) != 3) {
throw new UnexpectedValueException('Wrong number of segments');
}
list($headb64, $bodyb64, $cryptob64) = $tks;
if (null === ($header = static::jsonDecode(static::urlsafeB64Decode($headb64)))) {
throw new UnexpectedValueException('Invalid header encoding');
}
if (null === $payload = static::jsonDecode(static::urlsafeB64Decode($bodyb64))) {
throw new UnexpectedValueException('Invalid claims encoding');
}
$sig = static::urlsafeB64Decode($cryptob64);
if (empty($header->alg)) {
throw new UnexpectedValueException('Empty algorithm');
}
if (empty(static::$supported_algs[$header->alg])) {
throw new UnexpectedValueException('Algorithm not supported');
}
if (!in_array($header->alg, $allowed_algs)) {
throw new UnexpectedValueException('Algorithm not allowed');
}
if (is_array($key) || $key instanceof \ArrayAccess) {
if (isset($header->kid)) {
$key = $key[$header->kid];
} else {
throw new UnexpectedValueException('"kid" empty, unable to lookup correct key');
}
}
// Check the signature
if (!static::verify("$headb64.$bodyb64", $sig, $key, $header->alg)) {
throw new SignatureInvalidException('Signature verification failed');
}
// Check if the nbf if it is defined. This is the time that the
// token can actually be used. If it's not yet that time, abort.
if (isset($payload->nbf) && $payload->nbf > ($timestamp + static::$leeway)) {
throw new BeforeValidException(
'Cannot handle token prior to ' . date(DateTime::ISO8601, $payload->nbf)
);
}
// Check that this token has been created before 'now'. This prevents
// using tokens that have been created for later use (and haven't
// correctly used the nbf claim).
if (isset($payload->iat) && $payload->iat > ($timestamp + static::$leeway)) {
throw new BeforeValidException(
'Cannot handle token prior to ' . date(DateTime::ISO8601, $payload->iat)
);
}
// Check if this token has expired.
if (isset($payload->exp) && ($timestamp - static::$leeway) >= $payload->exp) {
throw new ExpiredException('Expired token');
}
return $payload;
}
/**
* Converts and signs a PHP object or array into a JWT string.
*
* @param object|array $payload PHP object or array
* @param string $key The secret key.
* If the algorithm used is asymmetric, this is the private key
* @param string $alg The signing algorithm.
* Supported algorithms are 'HS256', 'HS384', 'HS512' and 'RS256'
* @param mixed $keyId
* @param array $head An array with header elements to attach
*
* @return string A signed JWT
*
* @uses jsonEncode
* @uses urlsafeB64Encode
*/
public static function encode($payload, $key, $alg = 'HS256', $keyId = null, $head = null)
{
$header = array('typ' => 'JWT', 'alg' => $alg);
if ($keyId !== null) {
$header['kid'] = $keyId;
}
if ( isset($head) && is_array($head) ) {
$header = array_merge($head, $header);
}
$segments = array();
$segments[] = static::urlsafeB64Encode(static::jsonEncode($header));
$segments[] = static::urlsafeB64Encode(static::jsonEncode($payload));
$signing_input = implode('.', $segments);
$signature = static::sign($signing_input, $key, $alg);
$segments[] = static::urlsafeB64Encode($signature);
return implode('.', $segments);
}
/**
* Sign a string with a given key and algorithm.
*
* @param string $msg The message to sign
* @param string|resource $key The secret key
* @param string $alg The signing algorithm.
* Supported algorithms are 'HS256', 'HS384', 'HS512' and 'RS256'
*
* @return string An encrypted message
*
* @throws DomainException Unsupported algorithm was specified
*/
public static function sign($msg, $key, $alg = 'HS256')
{
if (empty(static::$supported_algs[$alg])) {
throw new DomainException('Algorithm not supported');
}
list($function, $algorithm) = static::$supported_algs[$alg];
switch($function) {
case 'hash_hmac':
return hash_hmac($algorithm, $msg, $key, true);
case 'openssl':
$signature = '';
$success = openssl_sign($msg, $signature, $key, $algorithm);
if (!$success) {
throw new DomainException("OpenSSL unable to sign data");
} else {
return $signature;
}
}
}
/**
* Verify a signature with the message, key and method. Not all methods
* are symmetric, so we must have a separate verify and sign method.
*
* @param string $msg The original message (header and body)
* @param string $signature The original signature
* @param string|resource $key For HS*, a string key works. for RS*, must be a resource of an openssl public key
* @param string $alg The algorithm
*
* @return bool
*
* @throws DomainException Invalid Algorithm or OpenSSL failure
*/
private static function verify($msg, $signature, $key, $alg)
{
if (empty(static::$supported_algs[$alg])) {
throw new DomainException('Algorithm not supported');
}
list($function, $algorithm) = static::$supported_algs[$alg];
switch($function) {
case 'openssl':
$success = openssl_verify($msg, $signature, $key, $algorithm);
if (!$success) {
throw new DomainException("OpenSSL unable to verify data: " . openssl_error_string());
} else {
return $signature;
}
case 'hash_hmac':
default:
$hash = hash_hmac($algorithm, $msg, $key, true);
if (function_exists('hash_equals')) {
return hash_equals($signature, $hash);
}
$len = min(static::safeStrlen($signature), static::safeStrlen($hash));
$status = 0;
for ($i = 0; $i < $len; $i++) {
$status |= (ord($signature[$i]) ^ ord($hash[$i]));
}
$status |= (static::safeStrlen($signature) ^ static::safeStrlen($hash));
return ($status === 0);
}
}
/**
* Decode a JSON string into a PHP object.
*
* @param string $input JSON string
*
* @return object Object representation of JSON string
*
* @throws DomainException Provided string was invalid JSON
*/
public static function jsonDecode($input)
{
if (version_compare(PHP_VERSION, '5.4.0', '>=') && !(defined('JSON_C_VERSION') && PHP_INT_SIZE > 4)) {
/** In PHP >=5.4.0, json_decode() accepts an options parameter, that allows you
* to specify that large ints (like Steam Transaction IDs) should be treated as
* strings, rather than the PHP default behaviour of converting them to floats.
*/
$obj = json_decode($input, false, 512, JSON_BIGINT_AS_STRING);
} else {
/** Not all servers will support that, however, so for older versions we must
* manually detect large ints in the JSON string and quote them (thus converting
*them to strings) before decoding, hence the preg_replace() call.
*/
$max_int_length = strlen((string) PHP_INT_MAX) - 1;
$json_without_bigints = preg_replace('/:\s*(-?\d{'.$max_int_length.',})/', ': "$1"', $input);
$obj = json_decode($json_without_bigints);
}
if (function_exists('json_last_error') && $errno = json_last_error()) {
static::handleJsonError($errno);
} elseif ($obj === null && $input !== 'null') {
throw new DomainException('Null result with non-null input');
}
return $obj;
}
/**
* Encode a PHP object into a JSON string.
*
* @param object|array $input A PHP object or array
*
* @return string JSON representation of the PHP object or array
*
* @throws DomainException Provided object could not be encoded to valid JSON
*/
public static function jsonEncode($input)
{
$json = json_encode($input);
if (function_exists('json_last_error') && $errno = json_last_error()) {
static::handleJsonError($errno);
} elseif ($json === 'null' && $input !== null) {
throw new DomainException('Null result with non-null input');
}
return $json;
}
/**
* Decode a string with URL-safe Base64.
*
* @param string $input A Base64 encoded string
*
* @return string A decoded string
*/
public static function urlsafeB64Decode($input)
{
$remainder = strlen($input) % 4;
if ($remainder) {
$padlen = 4 - $remainder;
$input .= str_repeat('=', $padlen);
}
return base64_decode(strtr($input, '-_', '+/'));
}
/**
* Encode a string with URL-safe Base64.
*
* @param string $input The string you want encoded
*
* @return string The base64 encode of what you passed in
*/
public static function urlsafeB64Encode($input)
{
return str_replace('=', '', strtr(base64_encode($input), '+/', '-_'));
}
/**
* Helper method to create a JSON error.
*
* @param int $errno An error number from json_last_error()
*
* @return void
*/
private static function handleJsonError($errno)
{
$messages = array(
JSON_ERROR_DEPTH => 'Maximum stack depth exceeded',
JSON_ERROR_CTRL_CHAR => 'Unexpected control character found',
JSON_ERROR_SYNTAX => 'Syntax error, malformed JSON'
);
throw new DomainException(
isset($messages[$errno])
? $messages[$errno]
: 'Unknown JSON error: ' . $errno
);
}
/**
* Get the number of bytes in cryptographic strings.
*
* @param string
*
* @return int
*/
private static function safeStrlen($str)
{
if (function_exists('mb_strlen')) {
return mb_strlen($str, '8bit');
}
return strlen($str);
}
}
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