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<?php
declare(strict_types=1);
/*
* The MIT License (MIT)
*
* Copyright (c) 2014-2021 Spomky-Labs
*
* This software may be modified and distributed under the terms
* of the MIT license. See the LICENSE file for details.
*/
namespace Cose\Algorithm\Signature\ECDSA;
use function bin2hex;
use function dechex;
use function hexdec;
use InvalidArgumentException;
use function mb_strlen;
use function mb_substr;
use function str_pad;
use const STR_PAD_LEFT;
/**
* @internal
*/
final class ECSignature
{
private const ASN1_SEQUENCE = '30';
private const ASN1_INTEGER = '02';
private const ASN1_MAX_SINGLE_BYTE = 128;
private const ASN1_LENGTH_2BYTES = '81';
private const ASN1_BIG_INTEGER_LIMIT = '7f';
private const ASN1_NEGATIVE_INTEGER = '00';
private const BYTE_SIZE = 2;
public static function toAsn1(string $signature, int $length): string
{
$signature = bin2hex($signature);
if (self::octetLength($signature) !== $length) {
throw new InvalidArgumentException('Invalid signature length.');
}
$pointR = self::preparePositiveInteger(mb_substr($signature, 0, $length, '8bit'));
$pointS = self::preparePositiveInteger(mb_substr($signature, $length, null, '8bit'));
$lengthR = self::octetLength($pointR);
$lengthS = self::octetLength($pointS);
$totalLength = $lengthR + $lengthS + self::BYTE_SIZE + self::BYTE_SIZE;
$lengthPrefix = $totalLength > self::ASN1_MAX_SINGLE_BYTE ? self::ASN1_LENGTH_2BYTES : '';
$bin = hex2bin(
self::ASN1_SEQUENCE
.$lengthPrefix.dechex($totalLength)
.self::ASN1_INTEGER.dechex($lengthR).$pointR
.self::ASN1_INTEGER.dechex($lengthS).$pointS
);
if (false === $bin) {
throw new InvalidArgumentException('Unable to convert into ASN.1');
}
return $bin;
}
public static function fromAsn1(string $signature, int $length): string
{
$message = bin2hex($signature);
$position = 0;
if (self::ASN1_SEQUENCE !== self::readAsn1Content($message, $position, self::BYTE_SIZE)) {
throw new InvalidArgumentException('Invalid data. Should start with a sequence.');
}
// @phpstan-ignore-next-line
if (self::ASN1_LENGTH_2BYTES === self::readAsn1Content($message, $position, self::BYTE_SIZE)) {
$position += self::BYTE_SIZE;
}
$pointR = self::retrievePositiveInteger(self::readAsn1Integer($message, $position));
$pointS = self::retrievePositiveInteger(self::readAsn1Integer($message, $position));
$bin = hex2bin(str_pad($pointR, $length, '0', STR_PAD_LEFT).str_pad($pointS, $length, '0', STR_PAD_LEFT));
if (false === $bin) {
throw new InvalidArgumentException('Unable to convert from ASN.1');
}
return $bin;
}
private static function octetLength(string $data): int
{
return intdiv(mb_strlen($data, '8bit'), self::BYTE_SIZE);
}
private static function preparePositiveInteger(string $data): string
{
if (mb_substr($data, 0, self::BYTE_SIZE, '8bit') > self::ASN1_BIG_INTEGER_LIMIT) {
return self::ASN1_NEGATIVE_INTEGER.$data;
}
while (
self::ASN1_NEGATIVE_INTEGER === mb_substr($data, 0, self::BYTE_SIZE, '8bit')
&& mb_substr($data, 2, self::BYTE_SIZE, '8bit') <= self::ASN1_BIG_INTEGER_LIMIT
) {
$data = mb_substr($data, 2, null, '8bit');
}
return $data;
}
private static function readAsn1Content(string $message, int &$position, int $length): string
{
$content = mb_substr($message, $position, $length, '8bit');
$position += $length;
return $content;
}
private static function readAsn1Integer(string $message, int &$position): string
{
if (self::ASN1_INTEGER !== self::readAsn1Content($message, $position, self::BYTE_SIZE)) {
throw new InvalidArgumentException('Invalid data. Should contain an integer.');
}
$length = (int) hexdec(self::readAsn1Content($message, $position, self::BYTE_SIZE));
return self::readAsn1Content($message, $position, $length * self::BYTE_SIZE);
}
private static function retrievePositiveInteger(string $data): string
{
while (
self::ASN1_NEGATIVE_INTEGER === mb_substr($data, 0, self::BYTE_SIZE, '8bit')
&& mb_substr($data, 2, self::BYTE_SIZE, '8bit') > self::ASN1_BIG_INTEGER_LIMIT
) {
$data = mb_substr($data, 2, null, '8bit');
}
return $data;
}
}
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