/**
* Decodes a serialised JWT.
*
* @param string $token the serialised JWT
* @param SimpleJWT\Keys\KeySet $keys the key set containing the key to verify the
* JWT's signature
* @param string $expected_alg the expected value of the `alg` parameter, which
* should be agreed between the parties out-of-band
* @param string $kid the ID of the key to use to verify the signature. If null, this
* is automatically retrieved
* @param bool|array $skip_validation an array of headers or claims that
* should be ignored as part of the validation process (e.g. if expired tokens
* are to be accepted), or false if all validation
* is to be performed.
* @param string $format the JWT serialisation format
* @return JWT the decoded JWT
* @throws InvalidTokenException if the token is invalid for any reason
*/
public static function decode($token, $keys, $expected_alg, $kid = null, $skip_validation = array(), $format = self::COMPACT_FORMAT)
{
if ($skip_validation === false) {
$skip_validation = array();
}
switch ($format) {
case self::COMPACT_FORMAT:
$parts = explode('.', $token, 3);
if (count($parts) != 3) {
throw new InvalidTokenException('Cannot decode compact serialisation', InvalidTokenException::TOKEN_PARSE_ERROR);
}
list($protected, $payload, $signature) = $parts;
break;
case self::JSON_FORMAT:
$obj = json_decode($token, true);
if ($obj == null) {
throw new InvalidTokenException('Cannot decode JSON', InvalidTokenException::TOKEN_PARSE_ERROR);
}
$payload = $obj['payload'];
if (isset($obj['signatures'])) {
foreach ($obj['signatures'] as $signature_obj) {
if (isset($signature_obj['header']['kid'])) {
$target_kid = $signature_obj['header']['kid'];
if ($target_kid == $kid || $keys->getById($target_kid) != null) {
$unprotected = $signature_obj['header'];
$protected = $signature_obj['protected'];
$signature = $signature_obj['signature'];
break;
}
}
throw new InvalidTokenException('Cannot find verifiable signature', InvalidTokenException::TOKEN_PARSE_ERROR);
}
} else {
$unprotected = $obj['header'];
$protected = $obj['protected'];
$signature = $obj['signature'];
}
break;
default:
throw new \InvalidArgumentException('Incorrect format');
}
$headers = json_decode(Util::base64url_decode($protected), true);
if ($headers == null) {
throw new InvalidTokenException('Cannot decode header', InvalidTokenException::TOKEN_PARSE_ERROR);
}
// Process crit
if (isset($headers['crit'])) {
foreach ($headers['crit'] as $critical) {
if (!in_array($critical, array('nbf', 'exp', 'alg', 'kid'))) {
throw new InvalidTokenException('Critical header not supported: ' . $critical, InvalidTokenException::UNSUPPORTED_ERROR);
}
}
}
if (isset($unprotected)) {
$headers = array_merge($headers, $unprotected);
}
$claims = json_decode(Util::base64url_decode($payload), true);
if ($claims == null) {
throw new InvalidTokenException('Cannot decode claims', InvalidTokenException::TOKEN_PARSE_ERROR);
}
// Check signatures
if ($headers['alg'] != $expected_alg) {
throw new InvalidTokenException('Unexpected algorithm', InvalidTokenException::SIGNATURE_VERIFICATION_ERROR);
}
$signer = AlgorithmFactory::create($expected_alg);
$signing_input = $protected . '.' . $payload;
try {
if (isset($headers['kid'])) {
$kid = $headers['kid'];
}
$result = $signer->verify($signature, $signing_input, $keys, $kid);
} catch (KeyException $e) {
throw new InvalidTokenException($e->getMessage(), InvalidTokenException::SIGNATURE_VERIFICATION_ERROR, $e);
} catch (CryptException $e) {
throw new InvalidTokenException($e->getMessage(), InvalidTokenException::SIGNATURE_VERIFICATION_ERROR, $e);
}
if (!$result) {
throw new InvalidTokenException('Incorrect signature', InvalidTokenException::SIGNATURE_VERIFICATION_ERROR);
}
// Check time, etc
$time = time();
if (isset($claims['nbf']) && !in_array('nbf', $skip_validation)) {
if ($time < $claims['nbf'] - self::$TIME_ALLOWANCE) {
throw new InvalidTokenException('Too early due to nbf claim', InvalidTokenException::TOO_EARLY_ERROR, null, $claims['nbf']);
}
}
if (isset($claims['exp']) && !in_array('exp', $skip_validation)) {
if ($time > $claims['exp'] + self::$TIME_ALLOWANCE) {
throw new InvalidTokenException('Too late due to exp claim', InvalidTokenException::TOO_LATE_ERROR, null, $claims['exp']);
}
}
return new JWT($headers, $claims);
}
/**
* Decrypts a JWE.
*
* @param string $token the serialised JWE
* @param SimpleJWT\Keys\KeySet $keys the key set containing the key to verify the
* JWT's signature
* @param string $expected_alg the expected value of the `alg` parameter, which
* should be agreed between the parties out-of-band
* @param string $format the JWE serialisation format
* @return JWE the decrypted JWE
* @throws InvalidTokenException if the token is invalid for any reason
*/
public static function decrypt($token, $keys, $expected_alg, $format = self::COMPACT_FORMAT)
{
switch ($format) {
case self::COMPACT_FORMAT:
$parts = explode('.', $token, 5);
if (count($parts) != 5) {
throw new InvalidTokenException('Cannot decode compact serialisation', InvalidTokenException::TOKEN_PARSE_ERROR);
}
list($protected, $encrypted_key, $iv, $ciphertext, $tag) = $parts;
break;
case self::JSON_FORMAT:
$obj = json_decode($token, true);
if ($obj == null) {
throw new InvalidTokenException('Cannot decode JSON', InvalidTokenException::TOKEN_PARSE_ERROR);
}
$protected = $obj['protected'];
$unprotected = $obj['unprotected'];
$iv = $obj['iv'];
$ciphertext = $obj['ciphertext'];
$tag = $obj['tag'];
if (isset($obj['recipients'])) {
foreach ($obj['recipients'] as $recipient) {
if (isset($recipient_obj['header']['kid'])) {
$target_kid = $recipient_obj['header']['kid'];
if ($keys->getById($target_kid) != null) {
$unprotected = isset($unprotected) ? array_merge($unprotected, $recipient_obj['header']) : $recipient_obj['header'];
$encrypted_key = $recipient_obj['encrypted_key'];
break;
}
}
throw new InvalidTokenException('Cannot find verifiable signature', InvalidTokenException::TOKEN_PARSE_ERROR);
}
} else {
$unprotected = isset($unprotected) ? array_merge($unprotected, $obj['header']) : $obj['header'];
$encrypted_key = $obj['encrypted_key'];
}
break;
default:
throw new \InvalidArgumentException('Incorrect format');
}
$headers = json_decode(Util::base64url_decode($protected), true);
if ($headers == null) {
throw new InvalidTokenException('Cannot decode header', InvalidTokenException::TOKEN_PARSE_ERROR);
}
if (isset($unprotected)) {
$headers = array_merge($headers, $unprotected);
}
// Process crit
if (isset($headers['crit'])) {
foreach ($headers['crit'] as $critical) {
if (!in_array($critical, array('alg', 'enc', 'kid', 'zip'))) {
throw new InvalidTokenException('Critical header not supported: ' . $critical, InvalidTokenException::UNSUPPORTED_ERROR);
}
}
}
if (!isset($headers['alg'])) {
throw new InvalidTokenException('alg parameter missing', InvalidTokenException::TOKEN_PARSE_ERROR);
}
if (!isset($headers['enc'])) {
throw new InvalidTokenException('enc parameter missing', InvalidTokenException::TOKEN_PARSE_ERROR);
}
if ($headers['alg'] != $expected_alg) {
throw new InvalidTokenException('Unexpected algorithm', InvalidTokenException::DECRYPTION_ERROR);
}
$key_enc = AlgorithmFactory::create($headers['alg']);
$content_enc = AlgorithmFactory::create($headers['enc']);
if ($key_enc instanceof KeyDerivationAlgorithm) {
try {
$agreed_key = $key_enc->deriveKey($keys, $headers, $kid);
} catch (KeyException $e) {
throw new InvalidTokenException($e->getMessage(), InvalidTokenException::DECRYPTION_ERROR, $e);
} catch (CryptException $e) {
throw new InvalidTokenException($e->getMessage(), InvalidTokenException::DECRYPTION_ERROR, $e);
}
if ($key_enc instanceof KeyEncryptionAlgorithm) {
// Key agreement with wrapping
$keys->add(new SymmetricKey(array('kty' => SymmetricKey::KTY, 'alg' => $this->headers['alg'], 'k' => Util::base64url_encode($agreed_key), 'kid' => '#key-agreement-with-wrapping'), 'php'));
$kid = '#key-agreement-with-wrapping';
} else {
// Direct key agreement or direct encryption
$cek = $agreed_key;
if ($encrypted_key != '') {
throw new InvalidTokenException('encrypted key should be empty', InvalidTokenException::TOKEN_PARSE_ERROR);
}
}
}
if (!isset($cek) && $key_enc instanceof KeyEncryptionAlgorithm) {
try {
if (!isset($kid)) {
$kid = isset($headers['kid']) ? $headers['kid'] : null;
}
$cek = $key_enc->decryptKey($encrypted_key, $keys, $headers, $kid);
} catch (KeyException $e) {
throw new InvalidTokenException($e->getMessage(), InvalidTokenException::DECRYPTION_ERROR, $e);
} catch (CryptException $e) {
throw new InvalidTokenException($e->getMessage(), InvalidTokenException::DECRYPTION_ERROR, $e);
}
}
if (!$cek) {
throw new InvalidTokenException('alg parameter incorrect', InvalidTokenException::TOKEN_PARSE_ERROR);
}
try {
$plaintext = $content_enc->decryptAndVerify($ciphertext, $tag, $cek, $protected, $iv);
if (isset($headers['zip'])) {
switch ($headers['zip']) {
case 'DEF':
$plaintext = gzinflate($plaintext);
break;
default:
throw new InvalidTokenException('Unsupported zip header:' . $headers['zip'], InvalidTokenException::UNSUPPORTED_ERROR);
}
}
} catch (CryptException $e) {
throw new InvalidTokenException($e->getMessage(), InvalidTokenException::DECRYPTION_ERROR, $e);
}
return new JWE($headers, $plaintext);
}
