1 /* 2 * Copyright (c) 2009 Joshua Oreman <oremanj (at) rwcr.net>. 3 * 4 * This program is free software; you can redistribute it and/or 5 * modify it under the terms of the GNU General Public License as 6 * published by the Free Software Foundation; either version 2 of the 7 * License, or any later version. 8 * 9 * This program is distributed in the hope that it will be useful, but 10 * WITHOUT ANY WARRANTY; without even the implied warranty of 11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 12 * General Public License for more details. 13 * 14 * You should have received a copy of the GNU General Public License 15 * along with this program; if not, write to the Free Software 16 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. 17 */ 18 19 FILE_LICENCE ( GPL2_OR_LATER ); 20 21 /** @file 22 * 23 * Cryptographically strong random number generator 24 * 25 * Currently the cryptographic part is not implemented, and this just 26 * uses random(). 27 */ 28 29 #include <gpxe/crypto.h> 30 #include <stdlib.h> 31 32 /** 33 * Get cryptographically strong random bytes 34 * 35 * @v buf Buffer in which to store random bytes 36 * @v len Number of random bytes to generate 37 * 38 * @b WARNING: This function is currently underimplemented, and does 39 * not give numbers any stronger than random()! 40 */ 41 void get_random_bytes ( void *buf, size_t len ) 42 { 43 u8 *bufp = buf; 44 45 /* 46 * Somewhat arbitrarily, choose the 0x00FF0000-masked byte 47 * returned by random() as having good entropy. PRNGs often 48 * don't provide good entropy in lower bits, and the top byte 49 * might show a pattern because of sign issues. 50 */ 51 52 while ( len-- ) { 53 *bufp++ = ( random() >> 16 ) & 0xFF; 54 } 55 } 56
