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Annotation of qemu/roms/ipxe/src/crypto/crandom.c, revision 1.1.1.1

1.1       root        1: /*
                      2:  * Copyright (c) 2009 Joshua Oreman <[email protected]>.
                      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 <ipxe/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: }

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