public function decryptAndVerify($ciphertext, $tag, $cek, $additional, $iv)
{
$params = self::$alg_params[$this->getAlg()];
if (strlen($cek) != $this->getCEKSize() / 8) {
throw new CryptException('Incorrect key length');
}
$iv = Util::base64url_decode($iv);
if (strlen($iv) != $this->getIVSize() / 8) {
throw new CryptException('Incorrect IV length');
}
list($mac_key, $enc_key) = str_split($cek, (int) (strlen($cek) / 2));
$al = Util::packInt64(strlen($additional) * 8);
$e = Util::base64url_decode($ciphertext);
$m = hash_hmac($params['hash'], $additional . $iv . $e . $al, $mac_key, true);
$t = substr($m, 0, $params['tag']);
if (!Util::secure_compare(Util::base64url_decode($tag), $t)) {
throw new CryptException('Authentication tag does not match');
}
$plaintext = openssl_decrypt($e, $params['cipher'], $enc_key, OPENSSL_RAW_DATA, $iv);
return $plaintext;
}
public function verify($signature, $data, $keys, $kid = null)
{
$compare = $this->sign($data, $keys, $kid);
return Util::secure_compare($signature, $compare);
}
/**
* Decodes a message using EME-OAEP.
*
* @param string $message the message to decode
* @param int $key_length the length of the RSA key in octets
* @param string $hash the hash algorithm - must be one supported by `hash_algos()`
* @param string $label the label
* @return string the decoded message
* @throws CryptException if an error occurred in the decoding
* @see https://tools.ietf.org/html/rfc3447
*/
protected final function oaep_decode($encoded, $key_length, $hash = 'sha1', $label = '')
{
$lHash = hash($hash, $label, true);
$Y = ord($encoded[0]);
$maskedSeed = substr($encoded, 1, strlen($lHash));
$maskedDB = substr($encoded, strlen($lHash) + 1);
$seedMask = $this->mgf1($maskedDB, strlen($lHash), $hash);
$seed = $maskedSeed ^ $seedMask;
$dbMask = $this->mgf1($seed, $key_length - strlen($lHash) - 1, $hash);
$DB = $maskedDB ^ $dbMask;
$lHash2 = substr($DB, 0, strlen($lHash));
if (!Util::secure_compare($lHash, $lHash2)) {
throw new CryptException('OAEP decoding error');
}
$PSM = substr($DB, strlen($lHash));
$PSM = ltrim($PSM, "");
if (substr($PSM, 0, 1) != "") {
throw new CryptException('OAEP decoding error');
}
return substr($PSM, 1);
}
