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<?php
/**
* A cryptographic random generator class used for generating secret keys
*
* This is based in part on Drupal code as well as what we used in our own code
* prior to introduction of this class.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
* http://www.gnu.org/copyleft/gpl.html
*
* @author Daniel Friesen
* @file
*/
class MWCryptRand {
/**
* Generate a run of cryptographically random data and return
* it in hexadecimal string format.
*
* @param int $chars The number of hex chars of random data to generate
* @return string Hexadecimal random data
*/
public static function generateHex( $chars ) {
// hex strings are 2x the length of raw binary so we divide the length in half
// odd numbers will result in a .5 that leads the generate() being 1 character
// short, so we use ceil() to ensure that we always have enough bytes
$bytes = ceil( $chars / 2 );
// Generate the data and then convert it to a hex string
$hex = bin2hex( random_bytes( $bytes ) );
// A bit of paranoia here, the caller asked for a specific length of string
// here, and it's possible (eg when given an odd number) that we may actually
// have at least 1 char more than they asked for. Just in case they made this
// call intending to insert it into a database that does truncation we don't
// want to give them too much and end up with their database and their live
// code having two different values because part of what we gave them is truncated
// hence, we strip out any run of characters longer than what we were asked for.
return substr( $hex, 0, $chars );
}
}
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