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/*
* Copyright (c) 2009 Joshua Oreman <oremanj@rwcr.net>.
*
* 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 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., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
FILE_LICENCE ( GPL2_OR_LATER );
/** @file
*
* Cryptographically strong random number generator
*
* Currently the cryptographic part is not implemented, and this just
* uses random().
*/
#include <gpxe/crypto.h>
#include <stdlib.h>
/**
* Get cryptographically strong random bytes
*
* @v buf Buffer in which to store random bytes
* @v len Number of random bytes to generate
*
* @b WARNING: This function is currently underimplemented, and does
* not give numbers any stronger than random()!
*/
void get_random_bytes ( void *buf, size_t len )
{
u8 *bufp = buf;
/*
* Somewhat arbitrarily, choose the 0x00FF0000-masked byte
* returned by random() as having good entropy. PRNGs often
* don't provide good entropy in lower bits, and the top byte
* might show a pattern because of sign issues.
*/
while ( len-- ) {
*bufp++ = ( random() >> 16 ) & 0xFF;
}
}
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