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[crypto] Add a placeholder for a proper random number generator
Currently it just calls random(). Signed-off-by: Marty Connor <mdc@etherboot.org>
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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. | ||
*/ | ||
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FILE_LICENCE ( GPL2_OR_LATER ); | ||
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/** @file | ||
* | ||
* Cryptographically strong random number generator | ||
* | ||
* Currently the cryptographic part is not implemented, and this just | ||
* uses random(). | ||
*/ | ||
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#include <gpxe/crypto.h> | ||
#include <stdlib.h> | ||
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/** | ||
* 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; | ||
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/* | ||
* 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. | ||
*/ | ||
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while ( len-- ) { | ||
*bufp++ = ( random() >> 16 ) & 0xFF; | ||
} | ||
} |
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