73 lines
2.2 KiB
PHP
73 lines
2.2 KiB
PHP
<?php
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/**
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* Generates entropy values based on strongest available methods
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* (mcrypt_create_iv(), openssl_random_pseudo_bytes(), /dev/urandom, COM.CAPICOM.Utilities.1, mt_rand()).
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* Chosen method depends on operating system and PHP version.
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*
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* @package framework
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* @subpackage security
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* @author Ingo Schommer
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*/
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class RandomGenerator {
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/**
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* Note: Returned values are not guaranteed to be crypto-safe,
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* depending on the used retrieval method.
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*
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* @return string Returns a random series of bytes
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*/
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function generateEntropy() {
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$isWin = preg_match('/WIN/', PHP_OS);
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// TODO Fails with "Could not gather sufficient random data" on IIS, temporarily disabled on windows
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if(!$isWin) {
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// mcrypt with urandom is only available on PHP 5.3 or newer
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if(version_compare(PHP_VERSION, '5.3.0', '>=') && function_exists('mcrypt_create_iv')) {
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$e = mcrypt_create_iv(64, MCRYPT_DEV_URANDOM);
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if($e !== false) return $e;
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}
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}
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// Fall back to SSL methods - may slow down execution by a few ms
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if (function_exists('openssl_random_pseudo_bytes')) {
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$e = openssl_random_pseudo_bytes(64, $strong);
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// Only return if strong algorithm was used
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if($strong) return $e;
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}
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// Read from the unix random number generator
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if(!$isWin && !ini_get('open_basedir') && is_readable('/dev/urandom') && ($h = fopen('/dev/urandom', 'rb'))) {
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$e = fread($h, 64);
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fclose($h);
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return $e;
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}
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// Warning: Both methods below are considered weak
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// try to read from the windows RNG
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if($isWin && class_exists('COM')) {
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try {
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$comObj = new COM('CAPICOM.Utilities.1');
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$e = base64_decode($comObj->GetRandom(64, 0));
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return $e;
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} catch (Exception $ex) {
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}
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}
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// Fallback to good old mt_rand()
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return uniqid(mt_rand(), true);
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}
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/**
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* Generates a hash suitable for manual session identifiers, CSRF tokens, etc.
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*
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* @param String $algorithm Any identifier listed in hash_algos() (Default: whirlpool)
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* If possible, choose a slow algorithm which complicates brute force attacks.
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* @return String Returned length will depend on the used $algorithm
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*/
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function generateHash($algorithm = 'whirlpool') {
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return hash($algorithm, $this->generateEntropy());
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}
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}
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