Viel neues
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Sven Steinert
192
qa-tool/htdocs/oidc/phpseclib/Math/BinaryField.php
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192
qa-tool/htdocs/oidc/phpseclib/Math/BinaryField.php
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<?php
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/**
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* Binary Finite Fields
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*
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* Utilizes the factory design pattern
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*
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* PHP version 5 and 7
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*
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* @author Jim Wigginton <terrafrost@php.net>
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* @copyright 2017 Jim Wigginton
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* @license http://www.opensource.org/licenses/mit-license.html MIT License
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*/
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declare(strict_types=1);
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namespace phpseclib3\Math;
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use phpseclib3\Common\Functions\Strings;
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use phpseclib3\Exception\OutOfBoundsException;
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use phpseclib3\Math\BinaryField\Integer;
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use phpseclib3\Math\Common\FiniteField;
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/**
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* Binary Finite Fields
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*
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* @author Jim Wigginton <terrafrost@php.net>
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*/
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class BinaryField extends FiniteField
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{
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/**
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* Instance Counter
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*
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* @var int
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*/
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private static $instanceCounter = 0;
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/**
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* Keeps track of current instance
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*
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* @var int
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*/
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protected $instanceID;
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/** @var BigInteger */
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private $randomMax;
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/**
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* Default constructor
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*/
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public function __construct(...$indices)
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{
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$m = array_shift($indices);
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if ($m > 571) {
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/* sect571r1 and sect571k1 are the largest binary curves that https://www.secg.org/sec2-v2.pdf defines
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altho theoretically there may be legit reasons to use binary finite fields with larger degrees
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imposing a limit on the maximum size is both reasonable and precedented. in particular,
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http://tools.ietf.org/html/rfc4253#section-6.1 (The Secure Shell (SSH) Transport Layer Protocol) says
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"implementations SHOULD check that the packet length is reasonable in order for the implementation to
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avoid denial of service and/or buffer overflow attacks" */
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throw new OutOfBoundsException('Degrees larger than 571 are not supported');
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}
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$val = str_repeat('0', $m) . '1';
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foreach ($indices as $index) {
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$val[$index] = '1';
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}
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$modulo = static::base2ToBase256(strrev($val));
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$mStart = 2 * $m - 2;
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$t = (int) ceil($m / 8);
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$finalMask = chr((1 << ($m % 8)) - 1);
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if ($finalMask == "\0") {
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$finalMask = "\xFF";
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}
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$bitLen = $mStart + 1;
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$pad = (int) ceil($bitLen / 8);
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$h = $bitLen & 7;
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$h = $h ? 8 - $h : 0;
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$r = rtrim(substr($val, 0, -1), '0');
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$u = [static::base2ToBase256(strrev($r))];
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for ($i = 1; $i < 8; $i++) {
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$u[] = static::base2ToBase256(strrev(str_repeat('0', $i) . $r));
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}
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// implements algorithm 2.40 (in section 2.3.5) in "Guide to Elliptic Curve Cryptography"
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// with W = 8
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$reduce = function ($c) use ($u, $mStart, $m, $t, $finalMask, $pad, $h) {
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$c = str_pad($c, $pad, "\0", STR_PAD_LEFT);
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for ($i = $mStart; $i >= $m;) {
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$g = $h >> 3;
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$mask = $h & 7;
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$mask = $mask ? 1 << (7 - $mask) : 0x80;
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for (; $mask > 0; $mask >>= 1, $i--, $h++) {
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if (ord($c[$g]) & $mask) {
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$temp = $i - $m;
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$j = $temp >> 3;
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$k = $temp & 7;
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$t1 = $j ? substr($c, 0, -$j) : $c;
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$length = strlen($t1);
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if ($length) {
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$t2 = str_pad($u[$k], $length, "\0", STR_PAD_LEFT);
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$temp = $t1 ^ $t2;
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$c = $j ? substr_replace($c, $temp, 0, $length) : $temp;
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}
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}
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}
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}
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$c = substr($c, -$t);
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if (strlen($c) == $t) {
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$c[0] = $c[0] & $finalMask;
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}
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return ltrim($c, "\0");
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};
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$this->instanceID = self::$instanceCounter++;
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Integer::setModulo($this->instanceID, $modulo);
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Integer::setRecurringModuloFunction($this->instanceID, $reduce);
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$this->randomMax = new BigInteger($modulo, 2);
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}
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/**
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* Returns an instance of a dynamically generated PrimeFieldInteger class
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*
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* @param BigInteger|string $num
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*/
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public function newInteger($num): Integer
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{
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return new Integer($this->instanceID, $num instanceof BigInteger ? $num->toBytes() : $num);
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}
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/**
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* Returns an integer on the finite field between one and the prime modulo
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*/
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public function randomInteger(): Integer
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{
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static $one;
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if (!isset($one)) {
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$one = new BigInteger(1);
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}
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return new Integer($this->instanceID, BigInteger::randomRange($one, $this->randomMax)->toBytes());
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}
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/**
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* Returns the length of the modulo in bytes
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*/
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public function getLengthInBytes(): int
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{
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return strlen(Integer::getModulo($this->instanceID));
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}
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/**
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* Returns the length of the modulo in bits
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*/
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public function getLength(): int
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{
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return strlen(Integer::getModulo($this->instanceID)) << 3;
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}
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/**
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* Converts a base-2 string to a base-256 string
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*/
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public static function base2ToBase256(string $x, ?int $size = null): string
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{
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$str = Strings::bits2bin($x);
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$pad = strlen($x) >> 3;
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if (strlen($x) & 3) {
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$pad++;
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}
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$str = str_pad($str, $pad, "\0", STR_PAD_LEFT);
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if (isset($size)) {
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$str = str_pad($str, $size, "\0", STR_PAD_LEFT);
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}
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return $str;
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}
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/**
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* Converts a base-256 string to a base-2 string
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*/
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public static function base256ToBase2(string $x): string
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{
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if (function_exists('gmp_import')) {
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return gmp_strval(gmp_import($x), 2);
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}
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return Strings::bin2bits($x);
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}
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}
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