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File: src/Hex.php

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File: src/Hex.php
Role: Class source
Content type: text/plain
Description: Class source
Class: PHP Constant Time String Encoding
Encode text without leaking context information
Author: By
Last change:
Date: 3 years ago
Size: 5,239 bytes
 

Contents

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<?php
declare(strict_types=1);
namespace
ParagonIE\ConstantTime;

/**
 * Copyright (c) 2016 - 2018 Paragon Initiative Enterprises.
 * Copyright (c) 2014 Steve "Sc00bz" Thomas (steve at tobtu dot com)
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

/**
 * Class Hex
 * @package ParagonIE\ConstantTime
 */
abstract class Hex implements EncoderInterface
{
   
/**
     * Convert a binary string into a hexadecimal string without cache-timing
     * leaks
     *
     * @param string $binString (raw binary)
     * @return string
     * @throws \TypeError
     */
   
public static function encode(string $binString): string
   
{
       
/** @var string $hex */
       
$hex = '';
       
$len = Binary::safeStrlen($binString);
        for (
$i = 0; $i < $len; ++$i) {
           
/** @var array<int, int> $chunk */
           
$chunk = \unpack('C', Binary::safeSubstr($binString, $i, 1));
           
/** @var int $c */
           
$c = $chunk[1] & 0xf;
           
/** @var int $b */
           
$b = $chunk[1] >> 4;

           
$hex .= pack(
               
'CC',
                (
87 + $b + ((($b - 10) >> 8) & ~38)),
                (
87 + $c + ((($c - 10) >> 8) & ~38))
            );
        }
        return
$hex;
    }

   
/**
     * Convert a binary string into a hexadecimal string without cache-timing
     * leaks, returning uppercase letters (as per RFC 4648)
     *
     * @param string $binString (raw binary)
     * @return string
     * @throws \TypeError
     */
   
public static function encodeUpper(string $binString): string
   
{
       
/** @var string $hex */
       
$hex = '';
       
/** @var int $len */
       
$len = Binary::safeStrlen($binString);

        for (
$i = 0; $i < $len; ++$i) {
           
/** @var array<int, int> $chunk */
           
$chunk = \unpack('C', Binary::safeSubstr($binString, $i, 2));
           
/** @var int $c */
           
$c = $chunk[1] & 0xf;
           
/** @var int $b */
           
$b = $chunk[1] >> 4;

           
$hex .= pack(
               
'CC',
                (
55 + $b + ((($b - 10) >> 8) & ~6)),
                (
55 + $c + ((($c - 10) >> 8) & ~6))
            );
        }
        return
$hex;
    }

   
/**
     * Convert a hexadecimal string into a binary string without cache-timing
     * leaks
     *
     * @param string $hexString
     * @param bool $strictPadding
     * @return string (raw binary)
     * @throws \RangeException
     */
   
public static function decode(string $hexString, bool $strictPadding = false): string
   
{
       
/** @var int $hex_pos */
       
$hex_pos = 0;
       
/** @var string $bin */
       
$bin = '';
       
/** @var int $c_acc */
       
$c_acc = 0;
       
/** @var int $hex_len */
       
$hex_len = Binary::safeStrlen($hexString);
       
/** @var int $state */
       
$state = 0;
        if ((
$hex_len & 1) !== 0) {
            if (
$strictPadding) {
                throw new \
RangeException(
                   
'Expected an even number of hexadecimal characters'
               
);
            } else {
               
$hexString = '0' . $hexString;
                ++
$hex_len;
            }
        }

       
/** @var array<int, ing> $chunk */
       
$chunk = \unpack('C*', $hexString);
        while (
$hex_pos < $hex_len) {
            ++
$hex_pos;
           
/** @var int $c */
           
$c = $chunk[$hex_pos];
           
/** @var int $c_num */
           
$c_num = $c ^ 48;
           
/** @var int $c_num0 */
           
$c_num0 = ($c_num - 10) >> 8;
           
/** @var int $c_alpha */
           
$c_alpha = ($c & ~32) - 55;
           
/** @var int $c_alpha0 */
           
$c_alpha0 = (($c_alpha - 10) ^ ($c_alpha - 16)) >> 8;

            if ((
$c_num0 | $c_alpha0) === 0) {
                throw new \
RangeException(
                   
'hexEncode() only expects hexadecimal characters'
               
);
            }
           
/** @var int $c_val */
           
$c_val = ($c_num0 & $c_num) | ($c_alpha & $c_alpha0);
            if (
$state === 0) {
               
$c_acc = $c_val * 16;
            } else {
               
$bin .= \pack('C', $c_acc | $c_val);
            }
           
$state ^= 1;
        }
        return
$bin;
    }
}

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