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<?php
namespace Twilio\Jwt;
/**
* JSON Web Token implementation
*
* Minimum implementation used by Realtime auth, based on this spec:
* http://self-issued.info/docs/draft-jones-json-web-token-01.html.
*
* @author Neuman Vong <neuman@twilio.com>
*/
class JWT {
/**
* @param string $jwt The JWT
* @param string|null $key The secret key
* @param bool $verify Don't skip verification process
* @return object The JWT's payload as a PHP object
* @throws \DomainException
* @throws \UnexpectedValueException
*/
public static function decode($jwt, $key = null, $verify = true) {
$tks = explode('.', $jwt);
if (count($tks) != 3) {
throw new \UnexpectedValueException('Wrong number of segments');
}
list($headb64, $payloadb64, $cryptob64) = $tks;
if (null === ($header = self::jsonDecode(self::urlsafeB64Decode($headb64)))
) {
throw new \UnexpectedValueException('Invalid segment encoding');
}
if (null === $payload = self::jsonDecode(self::urlsafeB64Decode($payloadb64))
) {
throw new \UnexpectedValueException('Invalid segment encoding');
}
$sig = self::urlsafeB64Decode($cryptob64);
if ($verify) {
if (empty($header->alg)) {
throw new \DomainException('Empty algorithm');
}
if ($sig != self::sign("$headb64.$payloadb64", $key, $header->alg)) {
throw new \UnexpectedValueException('Signature verification failed');
}
}
return $payload;
}
/**
* @param object|array $payload PHP object or array
* @param string $key The secret key
* @param string $algo The signing algorithm
* @param array $additionalHeaders Additional keys/values to add to the header
*
* @return string A JWT
*/
public static function encode($payload, $key, $algo = 'HS256', $additionalHeaders = array()) {
$header = array('typ' => 'JWT', 'alg' => $algo);
$header = $header + $additionalHeaders;
$segments = array();
$segments[] = self::urlsafeB64Encode(self::jsonEncode($header));
$segments[] = self::urlsafeB64Encode(self::jsonEncode($payload));
$signing_input = implode('.', $segments);
$signature = self::sign($signing_input, $key, $algo);
$segments[] = self::urlsafeB64Encode($signature);
return implode('.', $segments);
}
/**
* @param string $msg The message to sign
* @param string $key The secret key
* @param string $method The signing algorithm
* @return string An encrypted message
* @throws \DomainException
*/
public static function sign($msg, $key, $method = 'HS256') {
$methods = array(
'HS256' => 'sha256',
'HS384' => 'sha384',
'HS512' => 'sha512',
);
if (empty($methods[$method])) {
throw new \DomainException('Algorithm not supported');
}
return hash_hmac($methods[$method], $msg, $key, true);
}
/**
* @param string $input JSON string
* @return object Object representation of JSON string
* @throws \DomainException
*/
public static function jsonDecode($input) {
$obj = json_decode($input);
if (function_exists('json_last_error') && $errno = json_last_error()) {
self::handleJsonError($errno);
} else if ($obj === null && $input !== 'null') {
throw new \DomainException('Null result with non-null input');
}
return $obj;
}
/**
* @param object|array $input A PHP object or array
* @return string JSON representation of the PHP object or array
* @throws \DomainException
*/
public static function jsonEncode($input) {
$json = json_encode($input);
if (function_exists('json_last_error') && $errno = json_last_error()) {
self::handleJsonError($errno);
} else if ($json === 'null' && $input !== null) {
throw new \DomainException('Null result with non-null input');
}
return $json;
}
/**
* @param string $input A base64 encoded string
*
* @return string A decoded string
*/
public static function urlsafeB64Decode($input) {
$padlen = 4 - strlen($input) % 4;
$input .= str_repeat('=', $padlen);
return base64_decode(strtr($input, '-_', '+/'));
}
/**
* @param string $input Anything really
*
* @return string The base64 encode of what you passed in
*/
public static function urlsafeB64Encode($input) {
return str_replace('=', '', strtr(base64_encode($input), '+/', '-_'));
}
/**
* @param int $errno An error number from json_last_error()
*
* @throws \DomainException
*/
private static function handleJsonError($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
);
}
}
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