/**
* Validates $signature for document $document with public key $this->_public_key
* or $public_key and hash function $this->_hash_func or $hash_func.
*
* @param string $document document, signature of which must be validated
* @param string $signature signature, which must be validated
* @param object $public_key public key (object of Crypt_RSA_Key class)
* @param string $hash_func hash function, which will be used during validating signature
* @return mixed
* true, if signature of document is valid
* false, if signature of document is invalid
* null on error
*
* @access public
*/
function validateSign($document, $signature, $public_key = null, $hash_func = null)
{
// check public key
if (is_null($public_key)) {
$public_key = $this->_public_key;
} elseif (!Crypt_RSA_Key::isValid($public_key)) {
$obj = PEAR::raiseError('invalid public key. It must be an object of Crypt_RSA_Key class', CRYPT_RSA_ERROR_WRONG_KEY);
$this->pushError($obj);
return null;
}
if ($public_key->getKeyType() != 'public') {
$obj = PEAR::raiseError('validating key must be public', CRYPT_RSA_ERROR_NEED_PUB_KEY);
$this->pushError($obj);
return null;
}
// check hash_func
if (is_null($hash_func)) {
$hash_func = $this->_hash_func;
}
if (!function_exists($hash_func)) {
$obj = PEAR::raiseError('cannot find hash function with name [' . $hash_func . ']', CRYPT_RSA_ERROR_WRONG_HASH_FUNC);
$this->pushError($obj);
return null;
}
return $hash_func($document) == $this->decrypt($signature, $public_key);
}
