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JWT.php
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JWT.php
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<?php
/**
* Implements JWT encoding and decoding as per http://tools.ietf.org/html/draft-ietf-oauth-json-web-token-06
* Encoding algorithm based on http://code.google.com/p/google-api-php-client
* Decoding algorithm based on https://github.com/luciferous/jwt
* @author Francis Chuang <francis.chuang@gmail.com>
*/
class JWT
{
public static function encode($payload, $key, $algo = 'HS256')
{
$header = array('typ' => 'JWT', 'alg' => $algo);
$segments = array(
JWT::urlsafeB64Encode(json_encode($header)),
JWT::urlsafeB64Encode(json_encode($payload))
);
$signing_input = implode('.', $segments);
$signature = JWT::sign($signing_input, $key, $algo);
$segments[] = JWT::urlsafeB64Encode($signature);
return implode('.', $segments);
}
public static function decode($jwt, $key = null, $algo = null)
{
$tks = explode('.', $jwt);
if (count($tks) != 3) {
throw new Exception('Wrong number of segments');
}
list($headb64, $payloadb64, $cryptob64) = $tks;
if (null === ($header = json_decode(JWT::urlsafeB64Decode($headb64)))) {
throw new Exception('Invalid segment encoding');
}
if (null === $payload = json_decode(JWT::urlsafeB64Decode($payloadb64))) {
throw new Exception('Invalid segment encoding');
}
$sig = JWT::urlsafeB64Decode($cryptob64);
if (isset($key)) {
if (empty($header->alg)) {
throw new DomainException('Empty algorithm');
}
if (!JWT::verifySignature($sig, "$headb64.$payloadb64", $key, $algo)) {
throw new UnexpectedValueException('Signature verification failed');
}
}
return $payload;
}
private static function verifySignature($signature, $input, $key, $algo)
{
switch ($algo) {
case'HS256':
case'HS384':
case'HS512':
return JWT::sign($input, $key, $algo) === $signature;
case 'RS256':
return (boolean) openssl_verify($input, $signature, $key, OPENSSL_ALGO_SHA256);
case 'RS384':
return (boolean) openssl_verify($input, $signature, $key, OPENSSL_ALGO_SHA384);
case 'RS512':
return (boolean) openssl_verify($input, $signature, $key, OPENSSL_ALGO_SHA512);
default:
throw new Exception("Unsupported or invalid signing algorithm.");
}
}
private static function sign($input, $key, $algo)
{
switch ($algo) {
case 'HS256':
return hash_hmac('sha256', $input, $key, true);
case 'HS384':
return hash_hmac('sha384', $input, $key, true);
case 'HS512':
return hash_hmac('sha512', $input, $key, true);
case 'RS256':
return JWT::generateRSASignature($input, $key, OPENSSL_ALGO_SHA256);
case 'RS384':
return JWT::generateRSASignature($input, $key, OPENSSL_ALGO_SHA384);
case 'RS512':
return JWT::generateRSASignature($input, $key, OPENSSL_ALGO_SHA512);
default:
throw new Exception("Unsupported or invalid signing algorithm.");
}
}
private static function generateRSASignature($input, $key, $algo)
{
if (!openssl_sign($input, $signature, $key, $algo)) {
throw new Exception("Unable to sign data.");
}
return $signature;
}
private static function urlSafeB64Encode($data)
{
$b64 = base64_encode($data);
$b64 = str_replace(array('+', '/', '\r', '\n', '='),
array('-', '_'),
$b64);
return $b64;
}
private static function urlSafeB64Decode($b64)
{
$b64 = str_replace(array('-', '_'),
array('+', '/'),
$b64);
return base64_decode($b64);
}
}