/**
* EMSA-PSS-VERIFY.
*
* @param string $m
* @param string $em
* @param int $emBits
* @param \Jose\Util\Hash $hash
*
* @return bool
*/
private static function verifyEMSAPSS($m, $em, $emBits, Hash $hash)
{
$emLen = $emBits + 1 >> 3;
$sLen = $hash->getLength();
$mHash = $hash->hash($m);
Assertion::greaterThan($emLen, $hash->getLength() + $sLen + 2);
Assertion::eq($em[mb_strlen($em, '8bit') - 1], chr(0xbc));
$maskedDB = mb_substr($em, 0, -$hash->getLength() - 1, '8bit');
$h = mb_substr($em, -$hash->getLength() - 1, $hash->getLength(), '8bit');
$temp = chr(0xff << ($emBits & 7));
Assertion::eq(~$maskedDB[0] & $temp, $temp);
$dbMask = self::getMGF1($h, $emLen - $hash->getLength() - 1, $hash);
$db = $maskedDB ^ $dbMask;
$db[0] = ~chr(0xff << ($emBits & 7)) & $db[0];
$temp = $emLen - $hash->getLength() - $sLen - 2;
Assertion::eq(mb_substr($db, 0, $temp, '8bit'), str_repeat(chr(0), $temp));
Assertion::eq(ord($db[$temp]), 1);
$salt = mb_substr($db, $temp + 1, null, '8bit');
// should be $sLen long
$m2 = "" . $mHash . $salt;
$h2 = $hash->hash($m2);
return hash_equals($h, $h2);
}
